 Section 1 of Grey's Anatomy Part 5. This is a LibriVox recording. All LibriVox recordings are in the public domain. For more information or to volunteer, please visit LibriVox.org. Recorded by Larianne Walden. Anatomy of the Human Body Part 5 by Henry Gray. Splanknology. Under this heading are included the respiratory, digestive, and urogenital organs and the ductless glands. The Respiratory Apparatus. Apparatus Respiratorius Respiratory System. The respiratory apparatus consists of the larynx, trachea, bronchi, lungs, and pluri. Development. The rudiment of the respiratory organs appears as a median longitudinal groove in the ventral wall of the pharynx. The groove deepens and its lips fuse to form a septum which grows from below upward and converts the groove into a tube, the laryngeotracheal tube, the cephalic end of which opens into the pharynx by a slit-like aperture formed by the persistent anterior part of the groove. The tube is aligned by endoderm from which the epithelial lining of the respiratory tract is developed. The cephalic part of the tube becomes the larynx and its next succeeding part, the trachea, while from its caudal end to lateral outgrowth, the right and left lung buds arise and from them the bronchi and lungs are developed. The first rudiment of the larynx consists of two arytenoid swellings which appear, one on either side of the cephalic end of the laryngeotracheal groove, and are continuous in front of the groove with a transverse ridge, fercula of hiss, which lies between the ventral ends of the third brachial arches and from which the epiglottis is subsequently developed. After the separation of the trachea from the esophagus, the arytenoid swellings come into contact with one another and with the back of the epiglottis and the entrance to the larynx assumes the form of a T-shaped cleft, the margins of the cleft adhere to one another and the laryngeal entrance is for a time occluded. The mesodermal wall of the tube becomes condensed to form the cartilages of the larynx and trachea. The arytenoid swellings are differentiated into the arytenoid and corniculate cartilages and the folds joining them to the epiglottis form the ariepiglottic folds in which the cuneiform cartilages are developed as derivatives of the epiglottis. The thyroid cartilage appears as two lateral plates, each condrified from two centers and united in the mid-ventral line by membrane in which an additional center of condrification develops. The cricoid cartilage arises from two cartilaginous centers which soon unite ventrally and gradually extend and ultimately fuse on the dorsal aspect of the tube. J. Ernest Frazier has made an important investigation on the development of the larynx and the following are his main conclusions. The opening of the pulmonary diverticulum lies between the two fifth arch masses and behind a central mass in the middle line. The proximal end of the diverticulum is compressed between the fifth arch masses. The fifth arch is joined by the fourth to form a lateral mass on each side of the opening and these lateral masses grow forward and overlap the central mass and so form a secondary transverse cavity which is really a part of the cavity of the pharynx. The two parts of the cavity of the larynx are separated in the adult by a line drawn back along the vocal fold and then upward along the border of the arytenoid eminence to the inter-arytenoid notch. The arytenoid and cricoid are developed in the fifth arch mass. The thyroid is primarily a fourth arch derivative and if it has a fifth arch element this is a later addition. The epiglottis is derived from the central mass and has a third arch element in its oral and upper aspect. The arch value of the central mass is doubtful. The right and left lung buds grow out behind the ducts of QVA and are at first symmetrical but their ends soon become lobulated three lobules appearing on the right and two on the left. These subdivisions are the early indications of the corresponding lobes of the lungs. The buds undergo further subdivision and ramification and ultimately end in minute expanded extremities, the infundibular of the lung. After the sixth month the air sacs began to make their appearance on the infundibular in the form of minute pouches. The pulmonary arteries are derived from the sixth aortic arches. During the course of their development the lungs migrate in a caudal direction so that by the time of birth the bifurcation of the trachea is opposite the fourth thoracic vertebra. As the lungs grow they project into that part of the selum which will ultimately form the pleural cavities and the superficial layer of the mesoderm enveloping the lung rudiment expands on the growing lung and is converted into the pulmonary pleura. End of section 1 The larynx, Part 1 The larynx or organ of voice is placed at the upper part of the air passage. It is situated between the trachea and the root of the tongue at the upper and four part of the neck where it presents a considerable projection in the middle line. It forms the lower part of the anterior wall of the pharynx and is covered behind by the mucous lining of that cavity. On either side of it lie the great vessels of the neck. Its vertical extent corresponds to the fourth, fifth and sixth cervical vertebrae but it is placed somewhat higher in the female and also during childhood. Simmington found that in infants between 6 and 12 months of age the tip of the epiglottis was a little above the level of the fibrocartilage between the odontoid process and body of the axis and that between infancy and adult life the larynx descends for a distance equal to two vertebral bodies and two intervertebral fibrocartilages. According to SAPI the average measurements of the adult larynx are as follows length in males 44 millimeters in females 36 millimeters transverse diameter in males 43 millimeters in females 41 millimeters anteroposterior diameter in males 36 millimeters in females 26 millimeters circumference in males 136 millimeters in females 112 millimeters until puberty the larynx of the male differs little in size from that of the female in the female its increase after puberty is only slight in the male it undergoes considerable increase all the cartilages are enlarged and the thyroid cartilage becomes prominent in the middle line of the neck while the length of the rheumoglottidus is nearly doubled the larynx is broad above where it presents the form of a triangular box flattened behind and at the sides bounded in front by a prominent vertical ridge below it is narrow and cylindrical it is composed of cartilages which are connected together by ligaments and moved by numerous muscles it is lined by mucous membrane continuous above with that of the pharynx and below with that of the trachea the cartilages of the larynx cartilaginus laryngis are nine in number one single and three paired as follows thyroid, cricoid, two arytenoid, two carniculate, two cuneiform, epiglottis the thyroid cartilage cartilagothiroidea is the largest cartilage of the larynx it consists of two laminy the interior borders of which are fused with each other at an acute angle in the middle line of the neck and form a subcutaneous projection named the laryngeal prominence, pomum adami this prominence is most distinct at its upper part and is larger in the male than in the female immediately above it the laminy are separated by a V-shaped notch the superior thyroid notch the laminy are irregularly quadrilateral in shape posterior angles are prolonged into processes termed the superior and inferior cornoa the outer surface of each lamina presents an oblique line which runs downward and forward from the superior thyroid tubercle situated near the root of the superior corno to the inferior thyroid tubercle on the lower border this line gives attachment to the sternothyroidius, thyroid hyodias and constrictor pharyngeus inferior the inner surface is smooth above and behind it is slightly concave and covered by mucus membrane in front in the angle formed by the junction of the laminy are attached the stem of the epiglottis the ventricular and vocal ligaments the thyroid arytenoidy, thyroid epiglottici and vocalis muscles and the thyroid epiglottic ligament the upper border is concave behind and convex in front it gives attachment to the corresponding half of the hyothyroid membrane the lower border is concave behind and nearly straight in front the two parts being separated by the inferior thyroid tubercle a small part of it in and near the middle line is connected to the cricoid cartilage by the middle cricothyroid ligament the posterior border, thick and rounded receives the insertions of the stylopharyngeus and the pharyngopalatinas it ends above in the superior corno and below in the inferior corno the superior corno is long and narrow directed upward, backward and medialward and ends in a conical extremity which gives attachment to the lateral hyothyroid ligament the inferior corno is short and thick it is directed downward with a slight inclination forward and medialward and presents on the medial side of its tip a small oval articular facet for articulation with the side of the cricoid cartilage during infancy the laminy of the thyroid cartilage are joined to each other by a narrow lozen-shaped strip named the intrathyroid cartilage this strip extends from the upper to the lower border of the cartilage in the middle line and is distinguished from the laminy by being more transparent and more flexible the cricoid cartilage, cartilago cricoidia is smaller but thicker and stronger than the thyroid and forms the lower and posterior parts of the wall of the larynx it consists of two parts a posterior, quadrate lamina and a narrow anterior arch one fourth or one fifth of the depth of the lamina the lamina, lamina cartilaginus cricoidia posterior portion is deep and broad and measures from above downward about two or three centimeters on its posterior surface in the middle line is a vertical ridge to the lower part of which are attached the longitudinal fibers of the esophagus and on either side of this a broad depression for the cricoaritnoidius posterior the arch, archus cartilaginus cricoidia anterior portion is narrow and convex and measures vertically from five to seven millimeters it affords attachment externally in front and at the sides to the cricothyrode and behind to the part of the constrictor pharyngeus inferior on either side at the junction of the lamina with the arch is a small round articular surface for articulation with the inferior cornu of the thyroid cartilage the lower border of the cricoid cartilage is horizontal and connected to the highest ring of the trachea by the cricotrachea ligament the upper border runs obliquely upward and backward owing to the great depth of the lamina it gives attachment in front to the middle cricothyroid ligament at the side to the conus elasticus and the cricoaritnoidilateralis behind it presents in the middle a shallow notch and on either side of this is a smooth oval convex surface directed upward and lateral word for articulation with the base of an aritnoid cartilage the inner surface of the cricoid cartilage is smooth and lined by mucus membrane the aritnoid cartilages cartilagines aritnoidiae are two in number and situated at the upper border of the lamina of the cricoid cartilage at the back of the larynx each is pyramidal in form and has three surfaces a base and an apex the posterior surface is a triangular smooth concave and gives attachment to the aritnoid oblicus and transversus the anterolateral surface is somewhat convex and rough on it near the apex of the cartilage is a rounded elevation caliculus from which a ridge crista arcuata curves at first backward and then downward and forward to the vocal process the lower part of this crest intervenes between two depressions or fove in upper triangular and a lower oblong in shape the latter gives attachment to the vocalis muscle the medial surface is narrow, smooth, and flattened covered by mucus membrane and forms the lateral boundary of the inter cartilaginous part of the rheumaglottidus the base of each cartilage is broad and on it is a concave smooth surface for articulation with the cricoid cartilage its lateral angle is short, rounded, and prominent it projects backward and lateral word and is termed the muscular process it gives insertion to the cricoirritnoidus posterior behind and to the cricoirritnoidus lateralus in front its anterior angle, also prominent but more pointed projects horizontally forward it gives attachment to the vocal ligament and is called the vocal process the apex of each cartilage is pointed, curved backward and medial word and surmounted by a small conical cartilaginous nodule the corniculate cartilage the corniculate cartilages, cartilaginous corniculare cartilages of Santorini are two small conical nodules consisting of yellow elastic cartilage which articulate with the summits of the rheuritnoid cartilages and serve to prolong them backward and medial word they are situated in the posterior parts of the areopaglottic folds of mucus membrane and are sometimes fused with the rheuritnoid cartilages the cuneiform cartilages, cartilaginous cuneiformis cartilages of Riesberg are two small elongated pieces of yellow elastic cartilage placed one on either side in the areopaglottic fold where they give rise to small whitish elevations on the surface of the mucus membrane just in front of the rheuritnoid cartilages the epiglottis cartilago epiglottica is a thin lamina of fibrocartilage of a yellowish color shaped like a leaf and projecting obliquely upward behind the root of the tongue in front of the entrance to the larynx the free extremity is broad and rounded the attached part or stem is long, narrow and connected by the thyroepiglottic ligament to the angle farmed by the two laminae of the thyroid cartilage a short distance below the superior thyroid notch the lower part of its anterior surface is connected to the upper border of the body of the hyoid bone by an elastic ligamentous band, the hyoepiglottic ligament the anterior or lingual surface is curved forward and covered on its upper free part by mucus membrane which is reflected onto the sides and root of the tongue forming a median and two lateral glasoepiglottic folds the lateral folds are partly attached to the wall of the pharynx the depressions between the epiglottis and the root of the tongue on either side of the median fold are named the velicule the lower part of the anterior surface lies behind the hyoid bone the hyothyroid membrane and upper part of the thyroid cartilage but is separated from these structures by a mass of fatty tissue the posterior or laryngeal surface is smooth concave from side to side, concavo convex from above downward its lower part projects backward as an elevation, the tubercle or cushion when the mucus membrane is removed the surface of the cartilage is seen to be indented by a number of small pits in which mucus glands are lodged to its sides the are epiglottic folds are attached structure, the corniculate and cuneiform cartilages the epiglottis and the apices of the uritinoids at first consist of hyaline cartilage but later elastic fibers are deposited in the matrix converting them into yellow fibrocartilage which shows little tendency to calcification the thyroid, cricoid and the greater part of the uritinoids consist of hyaline cartilage and become more or less ossified as age advances ossification commences about the 25th year in the thyroid cartilage and somewhat later in the cricoid and uritinoids by the 65th year these cartilages may be completely converted into bone ligaments the ligaments of the larynx are extrinsic that is, those connecting the thyroid cartilage and epiglottis with the hyoid bone and the cricoid cartilage with the trachea and intrinsic, those which connect the several cartilages of the larynx to each other extrinsic ligaments the ligaments connecting the thyroid cartilage with the hyoid bone are the hyothyroid membrane and the middle and two lateral hyothyroid ligaments the hyothyroid membrane, membrana hyothyroidia thyrohyoid membrane is a broad fibroelastic layer attached below to the upper border of the thyroid cartilage and to the front of its superior cornu and above to the upper margin of the posterior surface of the body and greater cornoa of the hyoid bone thus passing behind the posterior surface of the body of the hyoid and being separated from it by a mucus bursa which facilitates the upward movement of the larynx during the clutition its middle thicker part is termed the middle hyothyroid ligament ligamentum hyothyroidium medium middle thyrohyoid ligament its lateral thinner portions are pierced by the superior laryngeal vessels and the internal branch of the superior laryngeal nerve its interior surface is in relation with the thyrohyoidius, sternohyoidius, and omohyoidius and with the body of the hyoid bone the lateral hyothyroid ligament, ligamentum hyothyroidium laterale lateral thyroid hyoid ligament is a round elastic cord which forms the posterior border of the hyothyroid membrane and passes between the tip of the superior cornoa of the thyroid cartilage and the extremity of the greater cornoa of the hyoid bone a small cartilaginous nodule, cartilagro trititia sometimes bony is frequently found in it the epiglottis is connected with the hyoid bone by an elastic band, the hyoepiglottic ligament ligamentum hyoepiglotticum which extends from the interior surface of the epiglottis to the upper border of the body of the hyoid bone the glassoepiglottic folds of mucous membrane may also be considered as extrinsic ligaments of the epiglottis the cricotracheal ligament, ligamentum cricotracheale connects the cricoid cartilage with the first ring of the trachea it resembles the fibrous membrane which connects the cartilaginous rings of the trachea to each other intrinsic ligaments beneath the mucous membrane of the larynx is a broad sheet of fibrous tissue containing many elastic fibers and termed the elastic membrane of the larynx it is subdivided on either side by the interval between the ventricular and vocal ligaments the upper portion extends between the arytenoid cartilage and the epiglottis and is often poorly defined the lower part is a well-marked membrane forming with its fellow of the opposite side, the conus elasticus which connects the thyroid, cricoid and arytenoid cartilages to one another in addition, the joints between the individual cartilages are provided with ligaments the conus elasticus, cricothyroid membrane is composed mainly of yellow elastic tissue it consists of an anterior and two lateral portions the anterior part, or middle cricothyroid ligament ligamentum cricothyroidium medium central part of cricothyroid membrane is thick and strong, narrow above and broad below it connects together the front parts of the contiguous margins of the thyroid and cricoid cartilages it is overlapped on either side by the cricothyroidius but between these is subcontaneous it is crossed horizontally by a small anastomotic arterial arch formed by the junction of the two cricothyroid arteries branches of which pierce it the lateral portions are thinner and lie close under the mucous membrane of the larynx they extend from the superior border of the cricoid cartilage to the inferior margin of the vocal ligaments with which they are continuous these ligaments may therefore be regarded as the free borders of the lateral portions of the conus elasticus and extend from the vocal processes of the arytenoid cartilages to the angle of the thyroid cartilage about midway between its upper and lower borders an articular capsule strengthened posteriorly by a well marked fibrous band encloses the articulation of the inferior cornu of the thyroid with the cricoid cartilage on either side each arytenoid cartilage is connected to the cricoid by a capsule and a posterior cricoaritnoid ligament the capsule, capsular articularis cricoaritnoidia is thin and loose and is attached to the margins of the articular surfaces the posterior cricoaritnoid ligament ligamentum cricoaritnoidium posterius extends from the cricoid to the medial and back part of the base of the arytenoid the thyroepaglottic ligament ligamentum thyroepaglotticum is a long slender elastic cord which connects the stem of the epiglottis with the angle of the thyroid cartilage immediately beneath the superior thyroid notch above the attachment of the ventricular ligaments movements the articulation between the inferior cornu of the thyroid cartilage and the cricoid cartilage on either side is a diarthrodial one and permits a rotatory and gliding movements the rotatory movement is one in which the cricoid cartilage rotates upon the inferior cornoa of the thyroid cartilage around an axis passing transversely through both joints the gliding movement consists in a limited shifting of the cricoid on the thyroid in different directions the articulation between the arytenoid cartilages and the cricoid is also a diarthrodial one and permits of two varieties of movement one is a rotation of the arytenoid on a vertical axis whereby the vocal process is moved lateral word or medial word and the rheumaglottis increased or diminished the other is a gliding movement and allows the arytenoid cartilages to approach or receive from each other from the direction and slope of the articular surfaces lateral gliding is accompanied by a forward and downward movement the two movements of gliding and rotation are associated the medial gliding being connected with medial word rotation and the lateral gliding with lateral word rotation the posterior crico-arytenoid ligaments limit the forward movement of the arytenoid cartilages on the cricoid end of section 2 read by Veronica Jenkins in Ottawa Illinois section 3 of Grey's Anatomy Part 5 this is a LibriVox recording all LibriVox recordings are in the public domain for more information or to volunteer please visit LibriVox.org Anatomy of the Human Body Part 5 by Henry Gray The Larynx Part 2 Interior of the Larynx The cavity of the larynx, Cobham laryngous extends from the laryngeal entrance to the lower border of the cricoid cartilage where it is continuous with that of the trachea it is divided into two parts by the projection of the vocal folds between which is a narrow triangular fissure or chink the rheumaglottidus the portion of the cavity of the larynx above the vocal folds is called the vestibule it is wide and triangular in shape its base or anterior wall presenting however about its center the backward projection of the tubercle of the epiglottis it contains the ventricular folds and between these and the vocal folds are the ventricles of the larynx the portion below the vocal folds is at first of an elliptical form but lower down it widens out assumes a circular form and is continuous with the tube of the trachea the difference of the larynx is a triangular opening wide in front, narrow behind and sloping obliquely downward and backward it is bounded in front by the epiglottis behind by the apices of the uritinoid cartilages the corniculate cartilages and the intrauritinoid notch and on either side by a fold of mucous membrane enclosing ligamentus and muscular fibers stretched between the side of the epiglottis and the apex of the uritinoid cartilage this is the area epiglottic fold on the posterior part of the margin of which the cuneiform cartilage forms a more or less distinct widish prominence the cuneiform tubercle the ventricular folds pleike ventricularis superior or false vocal cords are two thick folds of mucous membrane each enclosing a narrow band of fibrous tissue the ventricular ligament which is attached in front to the angle of the thyroid cartilage immediately below the attachment of the epiglottis and behind to the anterolateral surface of the uritinoid cartilage a short distance above the vocal process the lower border of this ligament enclosed in mucous membrane forms a free crescentic margin which constitutes the upper boundary of the ventricle of the larynx the vocal folds pleike vocalis inferior or true vocal cords are concerned in the production of sound and enclose two strong bands named the vocal ligaments ligamenta vocalis inferior thyroid uritinoid each ligament consists of a band of yellow elastic tissue attached in front to the angle of the thyroid cartilage and behind to the vocal process of the uritinoid its lower border is continuous with the thin lateral part of the conus elasticus its upper border forms the lower boundary of the ventricle of the larynx laterally the vocalis muscle lies parallel with it it is covered medially by mucous membrane which is extremely thin and closely adherent to its surface the ventricle of the larynx ventriculus laryngis morgagni laryngeal sinus is a fusiform fossa situated between the ventricular and vocal folds on either side and extending nearly their entire length the fossa is bounded above by the free crescentic edge of the ventricular fold below by the straight margin of the vocal fold laterally by the mucous membrane covering the corresponding thyroid noidius the anterior part of the ventricle leads up by a narrow opening into a sequel pouch of mucous membrane of variable size called the appendix the appendix of the laryngeal ventricle appendix ventriculi laryngeus laryngeal saccule is a membranous sac placed between the ventricular fold and the inner surface of the thyroid cartilage occasionally extending as far as its upper border or even higher it is conical in form and curved slightly backward on the surface of its mucous membrane are the openings of 60 or 70 mucous glands which are lodged in the submucous areolar tissue this sac is enclosed in a fibrous capsule continuous below with the ventricular ligament its medial surface is covered by a few delicate muscular fasciculi which arise from the apex of the retinoid cartilage and become lost in the area epiglottic fold of mucous membrane laterally it is separated from the thyroid cartilage by the thyroepiglotticus these muscles compress the sac and express the secretion it contains upon the vocal folds to lubricate their surfaces the remaglottis is the elongated fissure or chink between the vocal folds in front and the bases and vocal processes of the retinoid cartilages behind it is therefore subdivided into a larger anterior intramembranous part glottis vocalis which measures about three fifths of the length of the entire aperture and a posterior inter cartilaginous part glottis respiratorya posteriorly it is limited by the mucous membrane passing between the retinoid cartilages the remaglottis is the narrowest part of the cavity of the larynx and its level corresponds with the bases of the retinoid cartilages its length in the male is about 23 millimeters in the female from 17 to 18 millimeters the width and shape of the remaglottis vary with the movements of the vocal folds of the retinoid cartilages during respiration and phonation in the condition of rest that is when these structures are uninfluenced by muscular action as in quiet respiration the intramembranous part is triangular with its apex in front and its base behind the latter being represented by a line about 8 millimeters long connecting the anterior ends of the vocal processes while the medial surfaces are parallel to each other and hence the inter cartilaginous part is rectangular during extreme adduction of the vocal folds as in the emission of a high note the intramembranous part is reduced to a linear slit by the opposition of the vocal folds while the inter cartilaginous part is triangular its apex corresponding to the anterior ends of the vocal processes of the retinoids which are approximated by the medial rotation of the cartilages conversely in extreme abduction of the vocal folds as in forced inspiration the retinoids and their vocal processes are rotated lateral word and the inter cartilaginous part is triangular in shape but with its apex directed backward in this condition the entire glottis is somewhat lozenge shaped the sides of the intramembranous part diverging from before backward those of the inter cartilaginous part diverging from behind forward the widest part of the aperture corresponding with the attachments of the vocal folds to the vocal processes muscles the muscles of the larynx are extrinsic passing between the larynx and parts around these have been described in the section on myology and intrinsic confined entirely to the larynx the intrinsic muscles are the cricothyroidias cricothyroidias posterior cricothyroidias lateralis arytenoidias thyro arytenoidias the cricothyroidias triangular in form arises from the front and lateral part of the cricoid cartilage its fibers diverge and are arranged in two groups the lower fibers constitute a pars oblica and slant backward and lateral word to the lower border of the inferior corneum the interior fibers forming a pars recta run upward, backward and lateral word to the posterior part of the lower border of the lamina of the thyroid cartilage the medial borders of the two muscles are separated by a triangular interval occupied by the middle cricothyroid ligament the crico arytenoidias posterior posterior crico arytenoid arises from the broad depression on the corresponding half of the posterior surface of the lamina of the cricoid cartilage its fibers run upward and lateral word and converge to be inserted into the back of the muscular process of the arytenoid cartilage the uppermost fibers are nearly horizontal the middle oblique and the lowest almost vertical the crico arytenoidias lateralis lateral crico arytenoid is smaller than the proceeding and of an oblong form it arises from the upper border of the arch of the cricoid cartilage and passing obliquely upward and backward is inserted into the front of the muscular process of the arytenoid cartilage the arytenoidias is a single muscle filling up the posterior concave surfaces of the arytenoid cartilages it arises from the posterior surface and lateral border of one arytenoid cartilage and is inserted into the corresponding parts of the opposite cartilage it consists of oblique and transverse parts the arytenoidias obliquus the more superficial forms two fasciculi which pass from the base of one cartilage to the apex of the opposite one and therefore cross each other like the limbs of the letter X a few fibers are continued around the lateral margin of the cartilage and are prolonged into the aryepiglottic fold they are sometimes described as a separate muscle the aryepiglotticus the arytenoidias transverses crosses transversely between the two cartilages the thyroarytenoidias thyroarytenoid is a broad thin muscle which lies parallel with and lateral to the vocal fold and supports the wall of the ventricle and its appendix it rises in front from the lower half of the angle of the thyroid cartilage and from the middle cricothyroid ligament its fibers pass backward and lateral word to be inserted into the base and anterior surface of the arytenoid cartilage the lower and deeper fibers of the muscle can be differentiated as a triangular band which is inserted into the vocal process of the arytenoid cartilage and into the adjacent portion of its anterior surface it is termed the vocalis parallel with the vocal ligament to which it is adherent a considerable number of the fibers of the thyroarytenoidias are prolonged into the aryepiglottic fold where some of them become lost while others are continued to the margin of the epiglottis they have received a distinctive name thyroepiglotticus and are sometimes described as a separate muscle a few fibers extend along the wall of the ventricle of the arytenoid cartilage to the side of the epiglottis and constitute the ventricularis muscle actions in considering the actions of the muscles of the larynx they may be conveniently divided into two groups that is, one, those which open and close the glottis two, those which regulate the degree of tension of the vocal folds the chrycoarytenoidiposterioris separate the vocal folds and consequently open the glottis by rotating the arytenoid cartilages outward around a vertical axis passing through the chrycoarytenoid joints so that their vocal processes and the vocal folds attached to them become widely separated the chrycoarytenoidilateralis close the glottis by rotating the arytenoid cartilages inward so as to approximate their vocal processes the arytenoidias approximates the arytenoid cartilages and thus closes the opening of the glottis, especially at its back part the chrycothyroidi produce tension and elongation of the vocal folds by drawing up the arch of the chrycoid cartilage and tilting back the upper border of its lamina the distance between the vocal processes and the angle of the thyroid is thus increased and the folds are consequently elongated the thyroarytenoidi consisting of two parts having different attachments and different directions are rather complicated as regards their action their main use is to draw the arytenoid cartilages forward toward the thyroid and thus shorten and relax the vocal folds but owing to the connection of the deeper portion with the vocal fold this part effecting separately is supposed to modify its elasticity and tension while the lateral portion rotates the arytenoid cartilage inward by bringing the two vocal folds together the manner in which the entrance of the larynx is closed during deglutination is referred to on page 1140 mucus membrane the mucus membrane of the larynx is continuous above with that lining the mouth and pharynx and is prolonged through the trachea and bronchi into the lungs it lines the posterior surface and the upper part of the anterior surface of the epiglottis to which it is closely adherent and forms the aryepiglottic folds which bound the entrance of the larynx it lines the whole of the cavity of the larynx forms by its reduplication the chief part of the ventricular fold and from the ventricle is continued into the ventricular appendix it is then reflected over the vocal ligament where it is thin and very intimately adherent covers the inner surface of the conus of the elasticus and cricoid cartilage and is ultimately continuous with the lining membrane of the trachea the interior surface and the upper half of the posterior surface of the epiglottis the upper part of the aryepiglottic folds and the vocal folds are covered by stratified squamous epithelium all the rest of the laryngeal mucus membrane is covered by columnar ciliated cells but patches of stratified squamous epithelium are found in the laryngeal membrane above the glottis glands the mucus membrane of the larynx is furnished with numerous mucus secreting glands the orifices of which are found in nearly every part they are very plentiful upon the epiglottis being lodged in little pits in its substance they are also found in large numbers along the margin of the aryepiglottic fold in front of the erytenoid cartilages where they are termed the erytenoid glands are also found in large numbers in the ventricular appendages none are found on the free edges of the vocal folds vessels and nerves the chief arteries of the larynx are the laryngeal branches derived from the superior and inferior thyroid the veins accompany the arteries those accompanying the superior laryngeal artery join the superior thyroid vein which opens into the internal jugular vein while those accompanying the inferior laryngeal artery join the inferior thyroid vein which opens into the inominate vein the lymphatic vessels consist of two sets superior and inferior the former accompany the superior laryngeal artery and pierce the hyothyroid membrane to end in the gland situated near the bifurcation of the common carotid artery of the latter some pass through the middle kychothyroid ligament and open into a gland in front of that ligament or in front of the upper part of the trachea while others pass to the deep cervical glands and to the glands accompanying the inferior thyroid artery the nerves are derived from the internal and external branches of the superior laryngeal nerve from the recurrent nerve and from the sympathetic the internal laryngeal branch is almost entirely sensory but some motor filaments are said to be carried by it to the arytenoidias it enters the larynx by piercing the posterior part of the hyothyroid membrane above the superior laryngeal vessels and divides into a branch which is distributed to both surfaces of the epiglottis a second to the area epiglottic fold and a third the largest which supplies the mucous membrane over the back of the larynx and communicates with the recurrent nerve the external laryngeal branch supplies the kychothyroidias the recurrent nerve passes upward beneath the lower border of the constrictor pharyngeus inferior immediately behind the kychothyroid joint it supplies all the muscles of the larynx except the kychothyroidias and perhaps a part of the arytenoidias the sensory branches of the laryngeal nerves form subipithelial plexuses from which fibers pass to end between the cells covering the mucous membrane over the posterior surface of the epiglottis in the area epiglottic folds unless regularly in some other parts taste buds similar to those in the tongue are found and of section 3 section 4 of Graze Anatomy Part 5 this is a LibriVox recording all LibriVox recordings are in the public domain for more information or to volunteer please visit LibriVox.org Anatomy of the Human Body Part 5 by Henry Gray 1 B the trachea and bronchi the trachea or windpipe is a catalaginous and membranous tube extending from the lower part of the larynx on a level with the 6th cervical vertebra to the upper border of the 5th thoracic vertebra where it divides into the 2 bronchi one for each lung the trachea is nearly but not quite cylindrical being flattened posteriorly it measures about 11 cm in length its diameter from side to side is from 2 to 2.5 cm being always greater in the male than in the female in the child the trachea is smaller more deeply placed and more movable than in the adult Relations the anterior surface of the trachea is convex and covered in the neck from above downward isthmus of the thyroid gland the inferior thyroid veins the arterial thyroid where that vessel exists the sternothorioidus and sternohiaeodius muscles the cervical fascia and more superficially by the anestomosing branches between the anterior jugular veins in the thorax it is covered more backward by the mannubium sterno the remains of the thymus the left inanimate vein the aortic arch the inominate and left common carotid arteries and the deep cardiac plexus posteriorly it is in contact with the esophagus laterally in the neck it is in relation with the common carotid arteries the right and left lobes the inferior thyroid arteries and the recurrent nerves in the thorax it lies in the superior mediastinum and is in relation on the right side with the pleura and the right vagus and near the root of the neck with the inanimate artery and its left sides the left recurrent nerve the aortic arch and the left common carotid and subclavian arteries the right bronchus the wider, shorter and more vertical in direction than the left is about 2.5 cm long and enters the right lung nearly opposite the fifth thoracic vertebra the esophagus vein arches over it from behind and the right pulmonary artery lies at first below and then in front of it about 2 cm from its commencement it gives off a branch to the upper lobe of the right lung this is termed the epatherial branch of the bronchus because it arises above the right pulmonary artery the bronchus now passes below the artery and is known as the hyperarterial branch it divides into two branches for the middle and lower lobes the left bronchus bronchus sinister is smaller in calibre but longer than the right being nearly 5 cm long it enters the root of the left lung opposite the sixth thoracic vertebra it passes beneath the aortic arch crosses in front of the esophagus the thoracic duct and the descending aorta and has the left pulmonary artery lying at first above and then in front of it the left bronchus has no epatherial branch and therefore has been supposed by some that there is no upper lobe to the left lung that the so-called upper lobe corresponds to the middle lobe of the right lung the further sub-divisions of the bronchus will be considered with the anatomy of the lung if a transverse section be made across the trachea a short distance above its point of bifurcation and a bird's eye view taken of its interior the septum place at the bottom of the trachea and separating the two bronchus will be seen to occupy the left of the medium lung and the right bronchus appears to be a more direct continuation of the trachea than the left so that any solid body dropping into the trachea would naturally be directed toward the right bronchus this tendency is aided by the larger diameter of the right tube as compared to its fellow this act serves to explain why a foreign body in the trachea more frequently falls into the right bronchus footnote Regal asserts that the entry of a foreign body into the left bronchus is by no means so infrequent as is generally supposed end of footnote the trachea and extra pulmonary broncho are composed of imperfect rings of hyaline cartilage fibrous tissues muscle fibres mucous membranes and glands the cartilages of the trachea vary from 16 to 20 in number each forms an imperfect ring which occupies the anterior two thirds or so of the circumference of the trachea being deficient behind where the tube is completed by fibrous tissue and unstriped muscular fibres the cartilages are placed horizontally above each other separated by narrow intervals they measure about 4 mm in depth and 1 mm in thickness the outer surfaces are flattened in a vertical direction the cartilages being thicker in the middle than at the margins two or more of the cartilages often unite partially or completely and they are sometimes bifurcated at their extremities they are highly elastic but may become calcified in advanced life in the right bronchus the cartilages vary in number from 6 to 8 in the left from 9 to 12 they are shorter and narrower than those at the trachea that have the same shape and arrangement the peculiar tracheal cartilages are the first and last the first cartilage is broader than the rest and often divided at one end it is connected by the cricotracheal ligament with the lower border of the cricotracheal with which, or with the succeeding cartilage it is sometimes blended the last cartilage is thick and bored in the middle in consequence of its lower border being prolonged into a triangular hook-shark process which curves downwards and backwards between the two broncho it ends on each side in an imperfect ring which encloses the commencement of the bronchus the cartilage above the last is somewhat broader than the others at its centre the fibrous membrane the cartilages are enclosed in an elastic fibrous membrane which consists of two layers one the thicker passing over the outer surface of the ring the other over the inner surface at the upper and lower margins of the cartilages the two layers blend together to form a single membrane which connects the rings one with another they are thus invested by the membrane in the space behind between the ends of the rings the membrane forms a single layer the muscular tissue consists of two layers of non-striated muscle longitudinal and transverse the longitudinal fibres are external and consist of a few scattered bundles the transverse fibres tracheleus muscle are internal and form a thin layer which extends transversely between the ends of the cartilages mucus membrane the mucus membrane is continuous above with that of the larynx and below with that of the bronchi it consists of areola and nipfoid tissue and presents a well marked basement membrane supporting a stratified epithelium the surface layer of which is columnar and ciliated while the deeper layers are composed of oval or rounded cells beneath the basement membrane there is a distinct layer of longitudinal elastic fibres with a small amount of intervening areola tissue the submucous layer is composed of a loose mesh work of connective tissue containing large blood vessels, nerves and mucus glands the ducts of the latter pierce the overlaying layers and open on the surface vessels and nerves the trachea is supplied with blood by the inferior thyroid arteries the veins end in the thyroid venous plexus the nerves are derived from the vagus and the recurrent nerves and from the sympathetic they are distributed to the trachealis muscles and between the epithelial cells end of section 4 section 5 of Grey's Anatomy part 5 this is a LibriVox recording all LibriVox recordings are in the public domain for more information or to volunteer please visit LibriVox.org recording by Peter Bloomfield Anatomy of the Human Body part 5 by Henry Grey the plurae each lung is invested by an exceedingly delicate ceris membrane, the plura which is arranged in the form of a closed invaginated sac a portion of the ceris membrane covers the surface of the lung and dips into the fissures between its lobes it is called the pulmonary plura the rest of the membrane lines on the inner surface of the chest wall covers the diaphragm and is reflected over the structures occupying the middle of the thorax this portion is termed the parietal plura the two layers are continuous with one another around and below the root of the lung in health they are in actual contact with one another but the potential space between them is known as the pleural cavity when the lung collapses or when air or fluid collects between the two layers the cavity becomes apparent the right and left pleural sacs are entirely separate from one another between them are all the thoracic viscera except the lungs and they only touch each other for short distance in front opposite the second and third pieces of the sternum the interval between the two sacs is termed the mediastinum different portions of the parietal plura have received special names which indicate their position thus that portion which lines the inner surfaces of the ribs and intercostales is the costal plura that clothing the convex surface of the diaphragm is the diaphragmatic plura that which rises into the neck over the summit of the lung is the cupula of the plura, cervical plura and that which is applied to the other thoracic viscera is the mediastinal plura reflections of the plura commencing at the sternum the plura passes lateralward lines the inner surfaces of the costal cartilages ribs and intercostales and at the back part of the thorax sympathetic trunk and its branches and is reflected upon the sides of the bodies of the vertebrae where it is separated by a narrow interval, the posterior mediastinum from the opposite plura from the vertebral column the plura passes to the side of the pericardium which it covers to a slight extent it then covers the back part of the root of the lung from the lower border of which a triangle sheet descends vertically toward the diaphragm this sheet is the posterior layer of a wide fold known as the pulmonary ligament from the back of the lung root the plura may be traced over the costal surface of the lung the apex and base and also over the sides of the fissures between the lobes onto its mediastinal surface and the front part of its root it is continued from the lower margin of the root as the anterior layer of the pulmonary ligament and from this it is reflected onto the pericardium pericardial plura and from it to the back of the sternum above the level of the root of the lung however the mediastinal plura passes uninterruptedly from the vertebral column to the sternum of the structures in the superior mediastinum below it covers the upper surface of the diaphragm and extends in front as low as the costal cartilage of the seventh rib at the side of the chest to the lower border of the 10th rib on the left side and at the upper border of the same rib on the right side and behind it reaches as low as the 12th rib and sometimes even to the transverse process of the first lumbar vertebra above its cupular project through the superior opening of the thorax into the neck extending from 2.5 to 5 cm above the sternal end of the first rib this portion of the sac is strengthened by a dome-like expansion of fascia sipsons fascia attached in front to the inner border of the first rib and behind to the anterior border of the transverse process of the 7th cervical vertebra this is covered and strengthened by a few spreading muscular fibres derived from the scelinae in the front of the chest where the parietal pleura is reflected backward to the pericardium the two pleural sacs are in contact for a short distance at the upper part of the chest behind the minubrium they are separated by an angular interval the line of reflection being represented by a line drawn from the sternoclavicular articulation to the midpoint of the junction of the minubrium by the body of the sternum from this point the two pleurae descend in close contact to the level of the fourth the costal cartilages and the line of reflection on the right side is continued downward in nearly a straight line to the ziphoid process and then turns lateralward while on the left side the line of reflection diverges lateralward and is continued downward close to the left board of the sternum as far as the 6th costal cartilage the inferior limit of the pleura is on a considerably lower level than the corresponding limit of the lung but does not extend to the attachment of the diaphragm so that below the line of reflection of the pleura from the chest wall the center is in direct contact with the rib cartilages and the intercostal is internal moreover, in ordinary inspiration the thin inferior margin of the lung does not extend as low as the line of the pleural reflection with the result that the costal and diaphragmatic pleurae here are in contact the intervening narrow slit being termed the phrenicocostal sinus a similar condition exists behind the sternum and rib cartilages where the anterior thin margin of the lung falls short of the line of pleural reflection and where the slit-like cavity between the two layers of pleura forms what is called the costomediastinal sinus the line along which the right pleura is reflected from the chest wall to the diaphragm starts in front immediately below the 7th sternocostal joint and runs downward and backward behind the 7th costal cartilage so as to cross the 10th rib in the mid axillary line from which it is prolonged to the spinous process of the 12th thoracic vertebra the reflection of the left pleura is at first the ascending part of the 6th costal cartilage and in the rest of its course is slightly lower than that of the right side the free surface of the pleura is smooth polished and moistened by a serous fluid its attached surface is intimately adherent to the lung and to the pulmonary vessels as they emerge from the pericardium it is also adherent to the upper surface of the diaphragm throughout the rest of its extent it is easily separable from the adjacent parts the right pleural sac is shorter, wider and reaches higher in the neck than the left pulmonary ligament ligamentum pulmonale ligamentum latum pulmonis from the above description it will be seen that the root of the lung is covered in front, above and behind by pleura and that at its lower border the investing layers come into contact here they form a sort of misinteric fold the pulmonary ligament which extends between the lower part of the lung and the pericardium just above the diaphragm the ligament ends in a free falciform border it serves to retain the lower part of the lung in position structure of the pleura like other serous membranes the pleura is covered by a single layer of flattened nucleated cells united at their edges by cement substance these cells are modified connected tissue corpuscles and rest on a basement membrane beneath the basement membrane networks of yellow elastic and white fibres embedded in ground substance which also contains connective tissue cells blood vessels, lymphatics and nerves are distributed in the substance of the pleura vessels and nerves the arteries of the pleura are derived from the intercostal internal mammary muscular phrenic, thymic, pericardiac and bronchial vessels the veins correspond to the arteries the nerves are derived from the phrenic and sympathetic coulaker states that nerves accompany the ramifications of the bronchial arteries in the pulmonary pleura the medial stynum interplural space the medial stynum lies between the right and left pleury in and near the median sagittal plane of the chest it extends from the sternum in front to the vertebral column behind and contains all the thoracic viscera accepting the lungs it may be divided for purposes of description into two parts an upper portion above the upper level of the pericardium which is named the superior medial stynum and a lower portion below the upper level of the pericardium this lower portion is again subdivided into three parts vis-à-vis that in front of the pericardium the anterior mediastynum that containing the pericardium and it's contents the middle mediastynum and that behind the pericardium the posterior mediastynum the superior mediastynum portion of the interplural space which lies between the manubrium sterni in front and the upper thoracic vertebrae behind. It is bounded below by a slightly oblique plane passing backward from the junction of the manubrium and body of the sternum to the lower part of the body of the fourth thoracic vertebra and laterally by the plurae. It contains the origins of the sternohioidei and the sternothioidei, and the lower ends of the longi coli, the aortic arch, the inominate artery in the thoracic portions of the left common carotid and the left subclavian arteries, the inominate veins and the upper half of the superior vena cava, the left highest intercostal vein, the vagus cardiac, phrenic and left recurrent nerves, the trachea, esophagus and thoracic duct, the remains of the thymus and some lymph glands. The anterior mediastinum exists only on the left side where the left plurae diverges from the midsternal line. It is bounded in front by the sternum, laterally by the plurae and behind by the pericardium. It is narrow above but widens out a little below. Its anterior wall is formed by the left transversus thoracis and the fifth, sixth and seventh left costal cartilages. It contains a quantity of loose areola tissue, some lymphatic vessels which ascend from the convex surface of the liver, two or three anterior mediastinal lymph glands and the small mediastinal branches of the internal mammary artery. The middle mediastinum is the broadest part of the interplural space. It contains the heart enclosed in the pericardium, the ascending aorta, the lower half of the superior vena cava with the azigos veins opening into it, the bifurcation of the trachea and the two bronchi, the pulmonary artery dividing into its two branches, the right and left pulmonary veins, the phrenic nerves and some bronchial lymph glands. The posterior mediastinum is an irregular triangular space running parallel with the vertebral column. It is bounded in front by the pericardium above and by the posterior surface of the diaphragm below, behind by the vertebral column from the lower border of the fourth to the twelfth thoracic vertebra and on either side by the mediastinal pleura. It contains the thoracic part of the descending aorta, the azigos and the two hemi-azigos veins, the vagus and splansionic nerves, the esophagus, the thoracic duct and some lymph glands. End of section 5, recording by Peter Bloomfield of Paisley, Scotland. The lungs are the essential organs of respiration. They are two in number, placed one on either side within the thorax and separated from each other by the heart and other contents of the mediastinum. The substance of the lung is of a light porous spongy texture. It floats in water and crepitates when handled owing to the presence of air in the alveoli. It is also highly elastic, hence the retracted state of these organs when they are removed from the closed cavity of the thorax. The surface is smooth, shining and marked out into numerous polyhedral areas, indicating the lobules of the organ. Each of these areas is crossed by numerous tighter lines. At birth, the lungs are pinkish-white in color. In adult life, the color is a dark slady gray modeled in patches, and as age advances, this modeling assumes a black color. The coloring matter consists of granules of a carbonaceous substance deposited in the areolar tissue near the surface of the organ. It increases in quantity as age advances and is more abundant in males than in females. As a rule, the posterior border of the lung is darker than the anterior. The right lung usually weighs about 625 grams, the left 567 grams, but much variation is met with according to the amount of blood or cirrus fluid they may contain. The lungs are heavier in the male than in the female. They're proportioned to the body being in the former as 1 to 37, in the latter as 1 to 43. Each lung is conical in shape and presents for examination an apex, a base, three borders, and two surfaces. The apex, apex pulmonis, is rounded and extends into the root of the neck, reaching from 2.5 to 4 centimeters above the level of the sternal end of the first rib. A sulcus produced by the subclavian artery as it curves in front of the pleura runs upward and lateralward immediately below the apex. The base, basis pulmonis, is broad, concave, and rests upon the convex surface of the diaphragm, which separates the right lung from the right lobe of the liver and the left lung from the left lobe of the liver, the stomach, and the spleen. Since the diaphragm extends higher on the right than on the left side, the concavity on the base of the right lung is deeper than that on the left. Laterally and behind, the base is bounded by a thin, sharp margin which projects for some distance into the pharynicocostal sinus of the pleura between the lower ribs and the costal attachment of the diaphragm. The base of the lung descends during inspiration and ascends during expiration. The costal surface, fascis costalis, external or thoracic surface, is smooth, convex of considerable extent and corresponds to the form of the cavity of the chest, being deeper behind than in front. It is in contact with the costal pleura and presents in specimens which have been hardened in situ, slight grooves corresponding with the overlying ribs. The mediastinal surface, fascis mediastinalis inner surface, is in contact with the mediastinal pleura. It presents a deep concavity, the cardiac impression, which accommodates the pericardium. This is larger and deeper on the left than on the right lung, on account of the heart projecting farther to the left than to the right side of the median plane. Above and behind this concavity is a triangular depression named the hylum, where the structures which form the root of the lung enter and leave the viscous. These structures are invested by pleura, which, below the hylus and behind the pericardial impression, forms the pulmonary ligament. On the right lung, immediately above the hylus, is an arched furrow which accommodates the asiagus vein, while running upward and then arching lateralwards some little distance below the apex is a wide groove for the superior vena cava and right inominate vein. Behind this and near the apex is a furrow for the inominate artery. Behind the hylus and the attachment of the pulmonary ligament is a vertical groove for the esophagus. This groove becomes less distinct below owing to the inclination of the lower part of the esophagus to the left of the middle line. In front and to the right of the lower part of the esophageal groove is a deep concavity for the extra pericardiac portion of the thoracic part of the inferior vena cava. On the left lung, immediately above the hylus, is a well marked curved furrow produced by the aortic arch and running upward from this towards the apex is a groove accommodating the left subclavian artery. A slight impression in front of the ladder and close to the margin of the lung lodges the left inominate vein. Behind the hylus and pulmonary ligament is a vertical furrow produced by the descending aorta and in front of this, near the base of the lung, the lower part of the esophagus causes a shallow impression. Borders. The inferior border, Margo inferior, is thin and sharp where it separates the base from the costal surface and extends into the frinico-costal sinus. Medially where it divides the base from the mediastinal surface, it is blunt and rounded. The posterior border, Margo posterior, is broad and rounded and is received into the deep concavity on either side of the vertical column. It is much longer than the anterior border and projects below into the frinico-costal sinus. The anterior border, Margo anterior, is thin and sharp and overlaps the front of the pericardium. The anterior border of the right lung is almost vertical and projects into the costal mediastinal sinus. That of the left presents below an angular notch, the cardiac notch, in which the pericardium is exposed. Opposite this notch, the anterior margin of the left lung is situated some little distance lateral to the line of reflection of the corresponding part of the pleura. Fissures and lobes of the lungs. The left lung is divided into two lobes, an upper and a lower, by an inter lobular fissure, which extends from the costal to the mediastinal surface of the lung, both above and below the hilus. As seen on the surface, this fissure begins on the mediastinal surface of the lung at the upper and posterior part of the hilus and runs backward and upward to the posterior border, which it crosses at a point about six centimeters below the apex. It then extends downward and forward over the costal surface and reaches the lower border a little behind its anterior extremity and its further course can be followed upward and backward across the mediastinal surface as far as the lower part of the hilus. The superior lobe lies above and in front of this fissure and includes the apex, the anterior border and a considerable part of the costal surface and the greater part of the mediastinal surface of the lung. The inferior lobe, the larger of the two, is situated below and behind the fissure and comprises almost the whole of the base, a large portion of the costal surface and the greater part of the posterior border. The right lung is divided into three lobes, superior, middle and inferior, by two inter lobular fissures. One of these separates the inferior from the middle and superior lobes and corresponds closely with the fissure in the left lung. Its direction is, however, more vertical and it cuts the lower border about 7.5 centimeters behind its interior extremity. The other fissure separates the superior from the middle lobe. It begins in the previous fissure near the posterior border of the lung and, running horizontally forward, cuts the anterior border on a level with the sternal end of the fourth costal cartilage. On the mediastinal surface, it may be traced backward to the hilus. The middle lobe, the smallest lobe of the right lung, is wedge shaped and includes the lower part of the interior border and the interior part of the base of the lung. The right lung, although shorter by 2.5 centimeters than the left, in consequence of the diaphragm rising higher on the right side to accommodate the liver, is broader, owing to the inclination of the heart to the left side. Its total capacity is greater and it weighs more than the left lung. The root of the lung. Radix pulmonis. A little above the middle of the mediastinal surface of each lung and nearer its posterior than its anterior border is its root by which the lung is connected to the heart and the trachea. The root is formed by the bronchus, the pulmonary artery, the pulmonary veins, the bronchial arteries and veins, the pulmonary plexuses of nerves, lymphatic vessels, bronchial lymph glands, and areolar tissue, all of which are enclosed by a reflection of the pleura. The root of the right lung lies behind the superior vena cava and part of the right atrium and below the azygous vein. That of the left lung passes beneath the aortic arch and in front of the descending aorta. The phrenic nerve, the pericardiac ophrenic artery in vein, and the anterior pulmonary plexus lie in front of each and the vagus and posterior pulmonary plexus behind each. Below each is the pulmonary ligament. The chief structures composing the root of each lung are arranged in a similar manner from before backward on both sides, vis the upper of the two pulmonary veins in front, the pulmonary artery in the middle, and the bronchus together with the bronchial vessels behind. From above downward on the two sides their arrangement differs thus. On the right side their position is eparterial bronchus, pulmonary artery, hyper arterial bronchus, pulmonary veins, but on the left side their position is pulmonary artery, bronchus, pulmonary veins. The lower of the two pulmonary veins is situated below the bronchus at the apex or lowest part of the hilus. Divisions of the bronchi. Just as the lungs differ from each other in the number of their lobes so the bronchi differ in their mode of subdivision. The right bronchus gives off about 2.5 centimeters from the bifurcation of the trachea a branch for the superior lobe. This branch arises above the level of the pulmonary artery and is therefore named the eparterial bronchus. All the other divisions of the main stem come off below the pulmonary artery and consequently are termed hyper arterial bronchi. The first of these is distributed to the middle lobe and the main tube then passes downward and backward to the inferior lobe giving off in its course a series of large ventral and small dorsal branches. The ventral and dorsal branches arise alternately and are usually eight in number four of each kind. The branch to the middle lobe is regarded as the first of the ventral series. The left bronchus passes below the level of the pulmonary artery before it divides and hence all its branches are hyper arterial. It may therefore be looked upon as equivalent to that portion of the right bronchus which lies on the distal side of its eparterial branch. The first branch of the left bronchus arises about five centimeters from the bifurcation of the trachea and is distributed to the superior lobe. The main stem then enters the inferior lobe where it divides into ventral and dorsal branches similar to those in the right lung. The branch to the superior lobe of the left lung is regarded as the first of the ventral series. Structure. The lungs are composed of an external cirrus coat, a sub cirrus ariolar tissue, and the pulmonary substance or perinchaima. The cirrus coat is the pulmonary pleura. It is thin, transparent, and invests the entire organ as far as the root. The sub cirrus ariolar tissue contains a large proportion of elastic fibers. It invests the entire surface of the lung and extends inward between the lobules. The perinchaima is composed of secondary lobules which, although closely connected together by an inter lobular ariolar tissue, are quite distinct from one another and may be teased asunder without much difficulty in the fetus. The secondary lobules vary in size. Those on the surface are large, of pyramidal form, the base turned toward the surface. Those in the interior smaller and of various forms. Each secondary lobule is composed of several primary lobules, the anatomical units of the lung. The primary lobule consists of an alveolar duct, the air spaces connected with it, and their blood vessels, lymphatics, and nerves. The intra pulmonary bronchi divide and subdivide throughout the entire organ, the smallest subdivisions constituting the lobular bronchioles. The larger divisions consist of, one, an outer coat of fibrous tissue in which are found at intervals irregular plates of hyaline cartilage, most developed at the points of division. Two, internal to the fibrous coat, a layer of circularly disposed smooth muscle fibers, the bronchial muscle, and three, most internally, the mucous membrane, lined by columnar ciliated epithelium resting on a basement membrane. The corium of the mucous membrane contains numerous elastic fibers running longitudinally and a certain amount of lymphoid tissue. It also contains the ducts of mucous glands, the asinine of which lie in the fibrous coat. The lobular bronchioles differ from the larger tubes in containing no cartilage and in the fact that the ciliated epithelial cells are cubical in shape. The lobular bronchioles are about 0.2 millimeters in diameter. Each bronchiol divides into two or more respiratory bronchioles with scattered alveoli and each of these again divides into several alveolar ducts with a greater number of alveoli connected with them. Each alveolar duct is connected with a variable number of irregularly spherical spaces which also possess alveoli, the atria. When each atrium, a variable number, two to five, of alveolar sacs are connected which bear on all parts of their circumference alveoli or air sacs. The alveoli are lined by a delicate layer of simple squamous epithelium, the cells of which are united at their edges by cement substance. Between the squames are here and there smaller polygonal nucleated cells outside the epithelial lining is a little delicate connected tissue containing numerous elastic fibers and a close network of blood capillaries and forming a common wall to adjacent alveoli. The fetal lung resembles a gland in that the alveoli have a small lumen and are lined by cubical epithelium. After the first respiration the alveoli become distended and the epithelium takes on the characters described above. Vessels and nerves. The pulmonary artery conveys the venous blood to the lungs. It divides into branches which accompany the bronchial tubes and end in a dense capillary network in the walls of the alveoli. In the lung the branches of the pulmonary artery are usually above and in front of a bronchial tube, the vein below. The pulmonary capillaries form plexuses which lie immediately beneath the lining epithelium in the walls and septa of the alveoli and of the infundibula. In the septa between the alveoli the capillary network forms a single layer. The capillaries form a very minute network the meshes of which are smaller than the vessels themselves. Their walls are also exceedingly thin. The arteries of neighboring mobules are independent of each other but the veins freely anastomose. The pulmonary veins commence in the pulmonary capillaries, the radicals coalescing into larger branches which run through the substance of the lung independently of the pulmonary arteries and bronchi. After freely communicating with other branches they form large vessels which ultimately come into relation with the arteries and bronchial tubes and accompany them to the hilus of the organ. Finally they open into the left atrium of the heart conveying oxygenated blood to be distributed to all parts of the body by the aorta. The bronchial arteries supply blood for the nutrition of the lung. They are derived from the thoracic aorta or from the upper aortic intercostal arteries and accompanying the bronchial tubes are distributed to the bronchial glands and upon the walls of the larger bronchial tubes and pulmonary vessels. Those supplying the bronchial tubes form a capillary plexus in the muscular coat from which branches are given off to form a second plexus in the mucus coat. This plexus communicates with small venous trunks that empty into the pulmonary veins. Others are distributed in the inter lobular areolar tissue and end partly in the deep partly in the superficial bronchial veins. Lastly some ramify upon the surface of the lung beneath the pleura where they form a capillary network. The bronchial vein is formed at the root of the lung receiving superficial and deep veins corresponding to branches of the bronchial artery. It does not however receive all the blood supplied by the artery as some of it passes into the pulmonary veins. It ends on the right side in the azygous vein and on the left side in the highest intercostal or in the accessory hemi-azygous vein. The lymphatics are described on page 718. Nerves. The lungs are supplied from the anterior and posterior pulmonary plexuses formed chiefly by branches from the sympathetic and vagus. The filaments from these plexuses accompany the bronchial tubes supplying efferent fibers to the bronchial muscle and afferent fibers to the bronchial mucus membrane and probably to the alveoli of the lung. Small ganglia are found upon these nerves. End of section 6. Section 7 of Gray's Anatomy part 5. This is a LibriVox recording. All LibriVox recordings are in the public domain. For more information or to volunteer please visit LibriVox.org. Recording by Corey Samuel. Anatomy of the Human Body part 5 by Henry Gray. The Digestive Apparatus. Apparatus digestorius, organs of digestion. The apparatus for digestion of the food consists of the digestive tube and of certain accessory organs. The Digestive Tube, alimentary canal, is a muscular membranous tube about nine meters long extending from the mouth to the anus and is lined throughout its entire extent by mucus membrane. It has received different names in the various parts of its course, at its commencement is the mouth where provision is made for the mechanical division of the food, mastication, and for its admixture with a fluid secreted by the salivary glands in salivation. Beyond this are the organs of deglutition, the pharynx and the esophagus, which convey the food into the stomach, in which it is stored for a time, and in which also the first stages of the digestive process take place. The stomach is followed by the small intestine, which is divided for purposes of description into three parts, the duodenum, the jejunum, and ileum. In the small intestine the process of digestion is completed and the resulting products are absorbed into the blood and lacteal vessels. Finally the small intestine ends in the large intestine, which is made up of cecum, colon, rectum, and anal canal, the last terminating on the surface of the body at the anus. The accessory organs are the teeth for purposes of mastication, the three pairs of salivary glands, the parotid, submaccillary, and sublingual, the secretion from which mixes with the food in the mouth and converts it into a bolus and acts chemically on one of its constituents. The liver and pancreas, two large glands in the abdomen, the secretions of which, in addition to that of numerous minute glands in the wall of the elementary canal, assist in the process of digestion, the development of the digestive tube. The primitive digestive tube consists of two parts, that is, one, the foregut, within the cephalic flexure and dorsal to the heart, and two, the hindgut, within the caudal flexure. Between these is the wide opening of the yolk sac, which is gradually narrowed and reduced to a small foramen leading into the vitiline duct. At first, the foregut and hindgut end blindly. The anterior end of the foregut is separated from the stomadium by the bucopharyngeal membrane. The hindgut ends in the cloaca, which is closed by the cloacal membrane. The mouth. The mouth is developed partly from the stomadium and partly from the floor of the anterior portion of the foregut. By the growth of the head end of the embryo and the formation of the cephalic flexure, the pericardial area and the bucopharyngeal membrane come to lie on the ventral surface of the embryo. With the further expansion of the brain and the forward bulging of the pericardium, the bucopharyngeal membrane is depressed between these two prominences. This depression constitutes the stomadium. It is lined by ectoderm and is separated from the anterior end of the foregut by the bucopharyngeal membrane. This membrane is devoid of mesoderm, being formed by the apposition of the stomadial ectoderm with the foregut ectoderm. At the end of the third week it disappears and thus the communication is established between the mouth and the future pharynx. No trace of the membrane is found in the adult, and the communication just mentioned must not be confused with the permanent isthmus forcium. The lips, teeth and gums are formed from the walls of the stomadium, but the tongue is developed in the floor of the pharynx. The visceral arches extend in a ventral direction between the stomadium and the pericardium, and with the completion of the mandibular arch and the formation of the maxillary processes, the mouth assumes the appearance of a pentagonal orifice. The orifice is bounded in front by the frontal nasal process, behind by the mandibular arch and laterally by the maxillary processes. With the inward growth and fusion of the palatine processes the stomadium is divided into an upper nasal and a lower buccal part. Along the free margins of the processes bounding the mouth cavity a shallow groove appears. This is termed the primary labial groove, and from the bottom of it a down growth of ectoderm takes place into the underlying mesoderm. The central cells of the ectodermal downgrowth degenerate and a secondary labial groove is formed. By the deepening of this the lips and cheeks are separated from the alveolar processes of the maxillary and mandible. The salivary glands. The salivary glands arise as buds from the epithelial lining of the mouth. The parotid appears during the fourth week in the angle between the maxillary process and the mandibular arch. The submaxillary appears in the sixth week and the sublingual during the ninth week in the hollow between the tongue and the mandibular arch. The tongue. The tongue is developed in the floor of the pharynx and consists of an anterior or buccal and a posterior or pharyngeal part which are separated in the adult by the V-shaped sulcus terminalis. During the third week there appears immediately behind the ventral ends of the two halves of the mandibular arch a rounded swelling named the tuberculum impar which was described by Heese as undergoing enlargement to form the buccal part of the tongue. More recent researches however show that this part of the tongue is mainly if not entirely developed from a pair of lateral swellings which rise from the inner surface of the mandibular arch and meet in the middle line. The tuberculum impar is said to form the central part of the tongue immediately in front of the foramen cecum but Hammer insists that it is purely a transitory structure and forms no part of the adult tongue. From the ventral ends of the fourth arch there arises a second and larger elevation in the centre of which is a median groove or furrow. This elevation was named by Heese the furcular and is at first separated from the tuberculum impar by a depression but later by a ridge the copula formed by the forward growth and fusion of the ventral ends of the second and third arches. The posterior or pharyngeal part of the tongue is developed from the copula which extends forward in the form of a V so as to embrace between its two limbs the buccal part of the tongue. At the apex of the V a pit like invagination occurs to form the thyroid gland and this depression is represented in the adult by the foramen cecum of the tongue. In the adult the union of the anterior and posterior parts of the tongue is marked by the V-shaped sulcus terminalis the apex of which is at the foramen cecum while the two limbs run lateral wood and forward parallel to but a little behind the valet papilli the palatine tonsils. The palatine tonsils are developed from the dorsal angles of the second branchial pouches. The entoderm which lines these pouches grows in the form of a number of solid buds into the surrounding mesoderm. These buds become hollowed out by the degeneration and casting off of their central cells and by this means the tonsilocrypts are formed. Lymphoid cells accumulate around the crypts and become grouped to form the lymphoid follicles the latter however are not well defined until after birth the further development of the digestive tube the upper part of the foregut becomes dilated to form the pharynx in relation to which the branchial arches are developed the succeeding part remains tubular and with the descent of the stomach is elongated to form the esophagus. About the fourth week a fusiform dilation the future stomach makes its appearance and beyond this the gut opens freely into the yolk sac the opening is at first wide but is gradually narrowed into a tubular stalk the yolk stalk or vitiline duct between the stomach and the mouth of the yolk sac the liver diverticulum appears from the stomach to the rectum the elementary canal is attached to the notochord by a band of mesoderm from which the common mesentery of the gut is subsequently developed the stomach has an additional attachment that is to the ventral abdominal wall as far as the umbilicus by the septum transversum the cephalic portion of the septum takes part in the formation of the diaphragm while the caudal portion into which the liver grows forms the ventral mesogastrium the stomach undergoes a further dilation and its two curvatures can be recognized the greater directed towards the vertebral column and the lesser towards the anterior wall of the abdomen while its two surfaces look to the left and right respectively behind the stomach the gut undergoes great elongation and forms a v-shaped loop which projects downwards and forward from the bend or angle of the loop the vitiline duct passes to the umbilicus for a time a considerable part of the loop extends beyond the abdominal cavity into the umbilical cord but by the end of the third month it is withdrawn within the cavity with the lengthening of the tube the mesoderm which attaches it to the future vertebral column and carries the blood vessels for the supply of the gut is thinned and drawn out to form the posterior common mesentery the portion of this mesentery attached to the greater curvature of the stomach is named the dorsal mesogastrium and the part which suspends the colon is termed the mesocolon about the sixth week a diverticulum of the gut appears just behind the opening of the vitiline duct and indicates the future cecum and vermiform process the part of the loop on the distal side of the cecal diverticulum increases in diameter and forms the future ascending and transverse portions of the large intestine until the fifth month the cecal diverticulum has a uniform caliber but from this time onward its distal part remains rudimentary and forms the vermiform process while its proximal part expands to form the cecum changes also take place in the shape and position of the stomach its dorsal part or greater curvature to which the dorsal mesogastrium is attached grows much more rapidly than its ventral part or lesser curvature to which the ventral mesogastrium is fixed further the greater curvature is carried downward and to the left so that the right surface of the stomach is now directed backward and the left surface forward a change in position which explains why the left vagus nerve is found on the front and the right vagus on the back of the stomach the dorsal mesogastrium being attached to the greater curvature must necessarily follow its movements and hence it becomes greatly elongated and drawn lateralward and ventralward from the vertical column and as in the case of the stomach the right surfaces of both the dorsal and ventral mesogastria are now directed backward and the left forward in this way a pouch the bursa omentalis is formed behind the stomach and this increases in size as the digestive tube undergoes further development the entrance to the pouch constitutes the future furriman epiploicum or furriman of Winslow the duodenum is developed from that part of the tube which immediately succeeds the stomach it undergoes little elongation being more or less fixed in position by the liver and pancreas which arises diverticular from it the duodenum is at first suspended by a mesentery and projects forward in the form of a loop the loop and its mesentery are subsequently displaced by the transverse colon so that the right surface of the duodenal mesentery is directed backward and adhering to the peritoneum is lost the remainder of the digestive tube becomes greatly elongated and as a consequence the tube is coiled on itself and this elongation demands a corresponding increase in the width of the intestinal attachment of the mesentery which becomes folded at this stage the small and large intestines are attached to the vertebral column by a common mesentery the coils of the small intestine falling to the right of the middle line while the large intestine lies on the left side footnote sometimes this condition persists throughout life and it is then found that the duodenum does not cross from the right to the left side of the vertebral column but lies entirely on the right side of the median plane where it is continued into the titunum the arteries to the small intestine also arise from the right instead of the left side of the superior mesentery end of footnote the gut is now rotated upon itself so that the large intestine is carried over in front of the small intestine and the cecum is placed immediately below the liver about the sixth month the cecum descends into the right iliac fossa and the large intestine forms an arch consisting of the ascending transverse and descending portions of the colon the transverse portion crossing in front of the duodenum and lying just below the greater curvature of the stomach within this arch the coils of the small intestine are disposed sometimes the downward progress of the cecum is arrested so that in the adult it may be found lying immediately below the liver instead of in the right iliac region further changes take place in the bursa omentalis and in a common mesentery and give rise to the peritoneal relations seen in the adult the bursa omentalis which at first reaches only as far as the greater curvature of the stomach grows downward to form the greater omentum and this downward extension lies in front of the transverse colon and the coils of the small intestine above before the pleuroperitoneal opening is closed the bursa omentalis sends up a diverticulum on either side of the esophagus the left diverticulum soon disappears but the right is constricted off and persists in most adults as a small sac lying within the thorax on the right side of the lower end of the esophagus the anterior layer of the transverse mesocolon is at first distinct from the posterior layer of the greater omentum but ultimately the two blend and hence the greater omentum appears as if attached to the transverse colon the mesenteries of the ascending and descending parts of the colon disappear in the majority of cases while that of the small intestine assumes the oblique attachment characteristic of its adult condition the lesser omentum is formed as indicated above by a thinning of the mesoderm or ventral mesogastrium which attaches the stomach and eudinum to the anterior abdominal wall by the subsequent growth of the liver this leaf of mesoderm is divided into two parts that is the lesser omentum between the stomach and liver and the falciform and coronary ligaments between the liver and the abdominal wall and diaphragm the rectum and anal canal the hind gut is at first prolonged backward into the body stalk as the tube of the elantois but with the growth and flexure of the tail end of the embryo the body stalk with its contained elantoic tube is carried forward to the ventral aspect of the body and consequently a bend is formed at the junction of the hind gut and elantois this bend becomes dilated into a pouch which constitutes the entodermal cloaca into its dorsal part the hind gut opens and from its ventral part the elantois passes forward at a later stage the wolfian and malaria ducts open into its ventral portion the cloaca is for a time shut off from the anterior by a membrane the cloacal membrane formed by the apposition of the ectoderm and entoderm and reaching at first as far forward as the future umbilicus behind the umbilicus however the mesoderm subsequently extends to form the lower part of the abdominal wall and symphysis pubis by the growth of the surrounding tissues the cloacal membrane comes to lie at the bottom of a depression which is lined by ectoderm and named the ectodermal cloaca the entodermal cloaca is divided into a dorsal and a ventral part by means of a partition the urorectal septum which grows downward from the ridge separating the elantoic from the cloacal opening of the intestine and ultimately fuses with the cloacal membrane and divides it into an anal and a urogenital part the dorsal part of the cloaca forms the rectum and the anterior part of the urogenital sinus and bladder for a time a communication named the cloacal duct exists between the two parts of the cloaca below the urorectal septum this duct occasionally persists as a passage between the rectum and urethra the anal canal is formed by an invagination of the ectoderm behind the urorectal septum this invagination is termed the proctodium and it meets with the entoderm of the hindgut and forms with it the anal membrane by the absorption of this membrane the anal canal becomes continuous with the rectum a small part of the hindgut projects backward beyond the anal membrane it is named the post anal gut and usually becomes obliterated and disappears end of section seven section eight of grace anatomy part five this is a lipovox recording or lipovox recordings in the public domain for more information or to volunteer please visit lipovox.org recording by ellie anatomy of the human body part five by henry gray the mouse part one 2a the mouse carbon oris oral opocal cavity the cavity of the mouse is placed at the commandment of the digestive tube it is a nearly oval-shaped cavity which consists of two parts an outer smaller portion the vestibule and an inner larger part the mouse cavity proper the vestibule vestibulum oris is a slit-like space bounded externally by the lips and cheeks internally by the gums and teeth it communicates with the surface of the body by the rima or orifice of the mouse a bathroom below this limited by the reflection of the mucous membrane from the lips and cheeks to the gum covering the upper and lower alveolar arch respectively it receives the secretion from the perit cellivary cleanse and communicates when the jaws are closed with the mouse cavity proper by an aperture on either side behind the wisdom teeth and by narrow clefts between opposing teeth the mouse cavity proper carbon oris proprium is bounded laterally in front by the alveolar arches with the contained teeth behind it communicates with the pharynx by a constricted aperture termed the ismosphorcium it is roofed in by the hardened soft pellets while the greener part of the floor is formed by the tongue the remainder by the reflection of the mucous membrane from the sides and under surface of the tongue to the gum lining of the inner aspect of the mandible it receives the secretion from the submaxillary and sublingual cellivary cleanse structure the mucous membrane lining the mouse is continuous with the enticament with the free matching of the lips and with the mucous lining of the pharynx behind it is of a rose pink tinge during life and very secret overlies the hard parts bounding the cavity it is covered by stratified screamer's epicillium the lips labia oris the two fleshy folds which surround the rim or orifice of the mouse are formed externally of enticament and internally of mucous membrane between which are found the obicularis oris muscle the labial vessels some nerves a roll of tissue and fat numerous small labial clans the inner surface of each lip is connected in the middle line to the corresponding gumball fold of mucous membrane the phrenolum the upper being the larger the labial clans clandulae labialis are situated between the mucous membrane and the obicularis oris around the orifice of the mouse they are circular in form and about the size of small piece the ducts open by minute orifices upon the mucous membrane in structure they resemble the salivary clans the cheeks bucce form the sides of the face and are continuous in front with the lips they are composed externally of enticament internally of mucous membrane in between the two of a muscular stratum besides a large quantity of fat a roll of tissue vessels nerves and buccal clans structure the mucous membrane lining the cheek is reflected the bathroom below upon the gums and is continuous behind with the lining membrane of the soft palate opposite the second molar tooth of the manipula is a poppillar and the summit of which is the aperture of the parotid duct the principal muscle of the cheek is the buccinator but other muscles enter into this formation the sycomaticus resorios and platysma the buccal clans are placed between the mucous membrane and buccinator muscle they are similar in structure to the labial clans but smaller about five of the larger size than the rest are placed between the mucate and the buccinator muscles around the distal extremity of the parotid ducts the ducts open the mouth opposite the last molar tooth they are called molar clans the gums gingivere are composed of a dense fibros tissue closely connected to the periosteum of the alveolar processes and surrounding the necks of the teeth they are covered by smooth and vascular mucous membrane which is remarkable for its limited sensibility around the necks of the teeth this membrane presents numerous fine poppillar and is reflected into the alveoli where it is continuous with the periostal membrane lining these cavities the pellet palatum forms the roof of the mouse it consists of two portions the hard pellet in front the soft pellet behind the hard pellet palatum dorum is bounded in front and it decides with the alveolar arches and gums behind it is continuous with the soft pellet it is covered by dense structure formed by the periosteum and mucous membrane of the mouse which are intimately adherent along the middle line is a linear raffle which ends interially in the small popillar corresponding with the incisive canal on either side and in front of the raffle the mucous membrane is thick pale in color and corrugated behind it is thin smooth and of a deeper color it is covered with stratified squamous epicillium and furnished with numerous palatinal clans which lie between the mucous membrane and the surface of the bone the soft pellet palatum molle is a movable fold suspended from the posterior board of the hard pellet and forming an incomplete septum between the mouse and the pharynx it consists of a full of mucous membrane including muscular fibers and upon erosive vessels nerves adenoid tissue and mucous clans in occupying its usual position an example relax dependent its anterior surface is concave continuous with the roof of the mouse and marked by the median raffle its posterior surface is convex and continuous with the mucous membrane covering the floor of the nasal cavities its upper border is attached to the posterior margin of the hard pellet and its sides are plated with the pharynx its lower border is free its lower portion which hangs like a curtain between the mouse and pharynx is termed the palatum vellum hanging from the middle of its lower border is a small conical pendulous process the pellet and uvula an arching lateral warden downward from the base of the uvula on either side are two curved folds of mucous membrane containing muscular fibers called the arches or pillars of the pharxes the teeth dentis man is provided with two sets of teeth which make the appearance at different periods of life those of the first set the peering childhood and are called to the city as a milk teeth those of the second set which appeared in early period may continue until old age and are called permanent the city as teeth are 20 in number four incisors to canines and formulas in each jar the permanent teeth are 32 in number four incisors to canines for primolars and six molars in each jar the dental formula may be represented as follows the city as teeth up a job to molars for canine twin sizes twin sizes for cannon on OM over JasmineScript two molars on canine twin sizes twin sizes one canine two molars total 20 permanent ease upper jaw 3 molars, 2 primolas, 1 k9, 2 incisors, 2 incisors, 1 k9, 2 primolas, 3 molars. Lower jaw, 3 molars, 2 primolas, 1 k9, 2 incisors, 2 incisors, 1 k9, 2 primolas, 3 molars. Total 32. General characteristics Each tooth consists of 3 portions. The teeth are firmly implanted in depressions within the alveoli. This depressions align with periosteum, which invests the tooth as far as the neck. At the margins of the alveoli, the periosteum is continuous with the fibrous structure of the gums. In consequence with the curve, the dental arch terms as anterior and posterior as applied to the teeth are misleading and confusing. Special terms are therefore used to indicate the different surfaces of the tooth. The surface directed toward the lips and the cheek is known as the labial buccal surface. The directed toward the tongue is described as the lingual surface. Those surfaces, which touch neighboring teeth, are termed surfaces of contact. In the case of incisors and k9 teeth, the surfaces of contact are medial and lateral. In primolyte, the surfaces of contact are medial and lateral. In primolyte and molar teeth, they are anterior and posterior. The superior dental arch is larger than the inferior, so that in the normal condition the teeth in the maxillae slightly overlap those of the mandible bones in front and at the sides. Since the upper central incisors are wider than the lower, the other teeth in the upper arch are stronger distally, and the two sets do not quite correspond to each other when the mouth is closed. Thus, the upper canine tooth rests partially on the lower canine, partly on the first primolyte, and the casts of the upper molar teeth lie behind the corresponding casts of the lower molar teeth. The two series, however, ended nearly the same point behind. This is mainly because the molars in the upper arch are the smaller.