 section 36 of Grey's Anatomy part 2. 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 Morgan Scorpion. Anatomy of the Human Body part 2 by Henry Grey. Muscles of the Thorax part 1. 6. See the muscles of the thorax. The muscles belonging to this group are the intercostales externii, intercostales internii, subcostales, transversus thoracus, levitores costaum, seratus posterior superior, seratus posterior inferior, diaphragm. Intercostal fascii. In each intercostal space, thin but firm layers of fascia cover the outer surface of the intercostalis externas and the inner surface of the intercostalis internas, and a third, more delicate layer, is interposed between the two planes of muscular fibres. They are best marked in those situations where the muscular fibres are deficient, as between the intercostales externii and sternum in front, and between the intercostales internii and vertebral column behind. The intercostales, intercostal muscles, are two thin planes of muscular and tendinous fibres occupying each of the intercostal spaces. They are named external and internal from their surface relations, the external being superficial to the internal. The intercostales externii, external intercostals, are eleven in number on either side. They extend from the tubercles of the ribs behind to the cartilages of the ribs in front, where they end in thin membranes, the anterior intercostal membranes, which are continued forward to the sternum. Each arises from the lower border of a rib, and is inserted into the upper border of the rib below. In the two lower spaces they extend to the ends of the cartilages, and in the upper two or three spaces they do not quite reach the ends of the ribs. They are thicker than the intercostalis internii, and their fibres are directed obliquely downward and lateral wood on the back of the thorax, and downward, forward, and medial wood on the front. Variations Continuation with the obliquous externaus or seratus anterior. A supracostalis muscle from the anterior end of the first rib down to the second, third or fourth ribs occasionally occurs. The intercostalis internii, internal intercostals, are also eleven in number on either side. They commence anteriorly at the sternum in the interspaces between the cartilages of the true ribs and the anterior extremities of the cartilages of the false ribs, and extend backward as far as the angles of the ribs, once they are continued to the vertebral column by thin aponeuroses, the posterior intercostal membranes. Each arises from the ridge on the inner surface of a rib, as well as from the corresponding costal cartilage, and is inserted into the upper border of the rib below. Their fibres are also directed obliquely, but pass in a direction opposite to those of the intercostalis externii. The subcostalis, infracostalis, consist of muscular and aponeurotic fasciculi, which are usually well developed only in the lower part of the thorax. Each arises from the inner surface of one rib near its angle, and is inserted into the inner surface of the second or third rib below. Their fibres run in the same direction as those of the intercostalis internii. The transversus thoracus, triangularis sterni, is a thin plate of muscular and tendinous fibres situated upon the inner surface of the front wall of the chest. It arises on either side from the lower third of the posterior surface of the body of the sternum, from the posterior surface of the ziphoid process, and from the sternal ends of the costal cartilages of the lower three or four true ribs. Its fibres diverge upward and lateral wood, to be inserted by slips into the lower borders and inner surfaces of the costal cartilages of the second, third, fourth, fifth and sixth ribs. The lowest fibres of this muscle are horizontal in their direction, and are continuous with those of the transversus abdominis. The intermediate fibres are oblique, while the highest are almost vertical. This muscle varies in its attachments, not only in different subjects, but on opposite sides of the same subject. The levatoris costarum. Twelve in number on either side are small tendinous and fleshy bundles, which arise from the ends of the transverse processes of the seventh cervical and upper 11 thoracic vertebrae. They pass obliquely downward and lateral wood, like the fibres of the intercostalis externii, and each is inserted into the outer surface of the rib, immediately below the vertebra from which it takes origin, between the tubercle and the angle, levatoris costarum reves. Each of the four lower muscles divides into two fasciculae, one of which is inserted as above described, the other passes down to the second rib below its origin, levatoris costarum longi. The serratus posterior superior, serratus pasticus superior, is the thin quadrilateral muscle situated at the upper and back part of the thorax. It arises by a thin and broad upper neurosis from the lower part of the ligamentum nucae, from the spinous processes of the seventh cervical and upper two or three thoracic vertebrae, and from the supra-spinal ligament. Inclining downward and lateral wood it becomes muscular, and is inserted by four fleshy digitations into the upper borders of the second, third, fourth and fifth ribs, a little beyond their angles. Variations Increase or decrease in size and number of slips or entire absence. The serratus posterior inferior, serratus pasticus inferior, is situated at the junction of the thoracic and lumbar regions. It is of an irregularly quadrilateral form, broader than the preceding, and separated from it by a wide interval. It arises by a thin upper neurosis from the spinous processes of the lower two thoracic and upper two or three lumbar vertebrae, and from the supra-spinal ligament. Passing obliquely upward and lateral wood, it becomes fleshy and divides into four flat digitations, which are inserted into the inferior borders of the lower four ribs, a little beyond their angles. The thin upper neurosis of origin is intimately blended with the lumbar dorsal fascia and upper neurosis of the latissimus dorsi. Variations Increase or decrease in size and number of slips or entire absence. Nerves The muscles of this group are supplied by the intercostal nerves. The diaphragm is a dome-shaped muscular fibroceptum which separates the thoracic from the abdominal cavity. It convects up a surface forming the floor of the former, and it concave undersurface the roof of the latter. Its peripheral part consists of muscular fibres which take origin from the circumference of the thoracic outlet and converge to be inserted into a central tendon. The muscular fibres may be grouped according to their origins into three parts, sternal, costal, and lumbar. The sternal part arises by two fleshy slips from the back of the zipoid process, the costal part from the inner surfaces of the cartilages and adjacent portions of the lower six ribs on either side, interdigitating with the transversus abdominis, and the lumbar part from the upper neurotic arches, named the lumbar costal arches. Then from the lumbar vertebrae by two pillars or quora, there are two lumbar costal arches, a medial and a lateral on either side. The medial lumbar costal arch, arcus lumbocostalis medialis, hilari, internal arcuate ligament, is a tendinous arch in the fascia covering the upper part of the psoas major. Medially it is continuous with the lateral tendinous margin of the corresponding cruse, and is attached to the side of the body of the first or second lumbar vertebra. Laterally it is fixed to the front of the transverse process of the first and sometimes also to that of the second lumbar vertebra. The lateral lumbocostal arch, arcus lumbocostalis lateralis, hilari, external arcuate ligament, arches across the upper part of the quadratus lumborum, and is attached medially to the front of the transverse process of the first lumbar vertebra and laterally to the tip and lower margin of the twelfth rib. The quora. At their origins the quora are tendinous in structure, and blend with the anterior longitudinal ligament of the vertebral column. The right cruse, larger and longer than the left, arises from the anterior surfaces of the bodies and intervertebral fibrocardiages of the upper three lumbar vertebrae, while the left cruse arises from the corresponding parts of the upper two only. The medial tendinous margins of the quora pass forward and medial would, and meet in the middle line to form an arch across the front of the aorta. This arch is often poorly defined. From this series of origins the fibres of the diaphragm converge to be inserted into the central tendon. The fibres arising from the ziphoid process are very short and occasionally aponeurotic. Those from the medial and lateral lumbocostal arches, and more especially those from the ribs and their cartilages, are longer, and describe marked curves as they ascend and converge to their insertion. The fibres of the quora diverge as they ascend, the most lateral being directed upward and lateral would to the central tendon. The medial fibres of the right cruse ascend on the left side of the esophageal hiatus, and occasionally a fasciculus of the left cruse crosses the aorta and runs obliquely through the fibres of the right cruse toward the vener cable foramen. The central tendon. The central tendon of the diaphragm is a thin but strong aponeurosis situated near the centre of the vault formed by the muscle, but somewhat closer to the front than to the back of the thorax, so that the posterior muscular fibres are the longer. It is situated immediately below the pericardium, with which it is partially blended. It is shaped somewhat like a trefoil leaf, consisting of three divisions or leaflets separated from one another by slight indentations. The right leaflet is the largest, the middle directed towards the ziphoid process, the next in size, and the left, the smallest. In structure the tendon is composed of several planes of fibres which intersect one another at various angles and unite into straight or curved bundles, an arrangement which gives it additional strength. End of section number 36 Section 37 of Grey's Anatomy Part 2 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 Morgan Scorpion Anatomy of the Human Body Part 2 by Henry Grey Muscles of the thorax Part 2 Openings in the diaphragm The diaphragm is pierced by a series of apertures to permit of the passage of structures between the thorax and the abdomen. Three large openings, the aortic, the esophageal, and the vena carval, and a series of smaller ones are described. The aortic hiatus is the lowest and most posterior of the large apertures. It lies at the level of the 12th thoracic vertebra. Strictly speaking it is not an aperture in the diaphragm but an osteo-aponeurotic opening between it and the vertebral column, and therefore behind the diaphragm. Occasionally some tendinous fibres, prolonged across the bodies of the vertebra from the medial part of the lower ends of the clover, pass behind the aorta, and thus convert the hiatus into a fibrous ring. The hiatus is situated slightly to the left of the middle line, and is bounded in front by the quarra, and behind by the body of the first number vertebra. Through it pass the aorta, the azygosvane, and the thoracic duct. Occasionally the azygosvane is transmitted through the right cruise. The esophageal hiatus is situated in the muscular part of the diaphragm at the level of the 10th thoracic vertebra, and is elliptical in shape. It is placed above, in front, and a little to the left of the aortic hiatus, and transmits the esophagus, the vagus nerves, and some small esophageal arteries. The vena carval foramen is the highest of the three, and is situated about the level of the fibrocartilage between the 8th and 9th thoracic vertebrae. It is quadrilateral in form, and is placed at the junction of the right and middle leaflets of the central tendon, so that its margins are tenderness. It transmits the inferior vena carval, the wall of which is adherent to the margins of the opening, and some lesser branches of the right phrenic nerve. Of the lesser apertures, two in the right cruise transmit the greater and lesser right splanchnic nerves. Three in the left cruise give passage to the greater and lesser left splanchnic nerves and the hemias azygosvane. The ganglated trunks of the sympathetic usually enter the abdominal cavity behind the diaphragm under the medial lumbocostal arches. On either side, two small intervals exist at which the muscular fibres of the diaphragm are deficient, and are replaced by areola tissue. One between the sternal and costal parts transmits the superior epigastric branch of the internal mammary artery, and some lymphatics from the abdominal wall and convex surface of the liver. The other, between the fibres, springing from the medial and lateral lumbocostal arches, is less constant. When this interval exists, the upper and back part of the kidney is separated from the pleura by areola tissue only. Variations. The sternal portion of the muscle is sometimes wanting, and more rarely defects occur in the lateral part of the central tendon or adjoining muscle fibres. Nerves. The diaphragm is supplied by the phrenic and lower intercostal nerves. Actions. The diaphragm is the principal muscle of inspiration, and presents the form of a dome concave towards the abdomen. The central part of the dome is tenderness, and the pericardium is attached to its upper surface. The circumference is muscular. During inspiration, the lowest ribs are fixed, and from these and the crura, the muscular fibres contract and draw downward and forward the central tendon with the attached pericardium. In this movement, the curvature of the diaphragm is scarcely altered. The dome moving downward nearly parallel to its original position, and pushing before it the abdominal viscera. The descent of the abdominal viscera is permitted by the elasticity of the abdominal wall, but the limit of this is soon reached. The central tendon applied to the abdominal viscera then becomes a fixed point for the action of the diaphragm, the effect of which is to elevate the lower ribs and through them to push forward the body of the sternum and the upper ribs. The right cupola of the diaphragm, lying on the liver, has a greater resistance to overcome than the left, which lies over the stomach. But to compensate for this, the right crus and the fibres of the right side generally are stronger than those of the left. In all expulsive acts, the diaphragm is called into action to give additional power to each expulsive effort. Thus, before sneezing, coughing, laughing, crying or vomiting, and previous to the expulsion of urine or feces, all of the fetus from the uterus, a deep inspiration takes place. The height of the diaphragm is constantly varying during respiration. It also varies with the degree of distention of the stomach and intestines and with the size of the liver. After a forced expiration, the right cupola is on a level in front with the fourth costal cartilage, at the side with the fifth, sixth and seventh ribs, and behind with the eighth rib. The left cupola is a little lower than the right. Hall's Dali, Journal of Anatomy and Physiology, 1908, Volume XLIII, states that the absolute range of movement between deep inspiration and deep expiration averages in the male and female 30 mm on the right side and 28 mm on the left. In quiet respiration, the average movement is 12.5 mm on the right side and 12 mm on the left. Sceography shows that the height of the diaphragm in the thorax varies considerably with the position of the body. It stands highest when the body is horizontal and the patient on his back, and in this position it performs the largest respiratory excursions with normal breathing. When the body is erect, the dome of the diaphragm falls, and its respiratory movements become smaller. The dome falls still lower when the sitting posture is assumed, and in this position its respiratory excursions are smallest. These facts may, perhaps, explain why it is that patients suffering from severe dyspnea are most comfortable and least short of breath when they sit up. When the body is horizontal and the patient on his side, the two halves of the diaphragm do not behave alike. The uppermost half sinks to a level lower even than when the patient sits, and moves little with respiration. The lower half rises higher in the thorax than it does when the patient is supine, and its respiratory excursions are much increased. In unilateral disease of the pleura or lung's analogous interference with the position or movement of the diaphragm can generally be observed skeographically. It appears that the position of the diaphragm in the thorax depends upon three main factors, vis. One, the elastic retraction of the lung tissue tending to pull it upward. Two, the pressure exerted on its undersurface by the viscera. This naturally tends to be a negative pressure or downward suction when the patient sits or stands and positive or an upward pressure when he lies. Three, the intra-abdominal tension due to the abdominal muscles. These are in a state of contraction in the standing position and not in the sitting, hence the diaphragm when the patient stands is pushed up higher than when he sits. The intercostalis interne and externe have probably no action in moving the ribs. They contract simultaneously and form strong elastic supports which prevent the intercostal space being pushed out or drawn in during respiration. The anterior portions of the intercostalis interne probably have an additional function in keeping the sternocostal and intercondle joint surfaces in opposition. The posterior parts of the intercostalis externe performing a similar function for the costal-vertible articulations. The laboratory's costarum being inserted near the fulcrum of the ribs can have little action on the ribs. They act as rotators and lateral flexors of the vertical column. The transversus thoracus draws down the costal cartilages and is therefore a muscle of expiration. The serrati are respiratory muscles. The serratis posterior superior elevates the ribs and is therefore an inspiratory muscle. The serratis posterior inferior draws the lower ribs downward and backward and thus elongates the thorax. It also fixes the lower ribs, thus assisting the inspiratory action of the diaphragm and resisting the tendency it has to draw the lower ribs upward and forward. It must therefore be regarded as a muscle of inspiration. Mechanism of Respiration The respiratory movements must be examined during A. quiet respiration and B. deep respiration. Quiet respiration The first and second pairs of ribs are fixed by the resistance of the cervical structures, the last pair, and through it the eleventh, by the quadratus lumborum. The other ribs are elevated so that the first two intercostal spaces are diminished while the others are increased in width. It has already been shown that elevation of the third, fourth, fifth and sixth ribs leads to an increase in the anterior posterior and transverse diameters of the thorax. The vertical diameter is increased by the descent of the diaphragmatic dome so that the lungs are expanded in all directions except backward and upward. Elevation of the eighth, ninth and tenth ribs is accompanied by a lateral and backward movement, leading to an increase in the transverse diameter of the upper part of the abdomen. The elasticity of the anterior abdominal wall allows a slight increase in the antroposterior diameter of this part, and in this way the decrease in the vertical diameter of the abdomen is compensated and space provided for its displaced viscera. Expiration is affected by the elastic recoil of its walls and by the action of the abdominal muscles, which push back the viscera displaced downward by the diaphragm. Deep Respiration All the movements of quiet respiration are here carried out, but to a greater extent. In deep inspiration the shoulders and the vertebral borders of the scapulae are fixed and the limb muscles, trapezius, serratus anterior, pectoralis and latissimus dorsi are called into play. The scalini are in strong action, and the sternocleidomastoidae also assist when the head is fixed by drawing up the sternum and by fixing the clavicles. The first rib is therefore no longer stationary, but with the sternum is raised. With it, all the other ribs accept the last to raise to a higher level. In conjunction with the increased descent of the diaphragm, this provides for a considerable augmentation of all the thoracic diameters. The anterior abdominal muscles come into action so that the umbilicus is drawn upward and backward, but this allows the diaphragm to exert a more powerful influence on the lower ribs. Transverse diameter of the upper part of the abdomen is greatly increased and the subcostal angle opened out. The deeper muscles of the back, e.g. the serrati posteriori superiori and the sacrospinalis and the continuations, are also brought into action. The thoracic curve of the vertebral column is partially straightened, and the whole column, above the lower lumbar vertebrae, drawn backward. This increases the anterior posterior diameters of the thorax and upper part of the abdomen and widens the intercostal spaces. Deep expiration is affected by the recoil of the walls and by the contraction of the anterior lateral muscles of the abdominal wall, and the serrati posteriori's, inferiori's and transversus thoracus. Hall's dally, Abzit, gives the following figures as representing the average changes which occurred during deepest possible respiration. The manubrium sternum moves 13 mm in an upward and 14 mm in a forward direction. The width of the subcostal angle at a level of 30 mm below the articulation between the body of the sternum and the ziphoid process is increased by 26 mm. The umbilicus is retracted and drawn upward for a distance of 13 mm. End of section 37 Section 38 of Grey's Anatomy Part 2 This is a LibriVox recording. All LibriVox recordings are in the public domain. To find out more information or to volunteer, please visit LibriVox.org Recording by Rebecca Case Anatomy of the Human Body Part 2 by Henry Gray Muscles and fascia of the abdomen Part 1 The muscles of the abdomen may be divided into two groups. One, the anterolateral muscles. Two, the posterior muscles. One, the anterolateral muscles of the abdomen. The muscles of this group are Obligus externus, Obligus internus, transversus, rectus, pyramidalis. The superficial fascia The superficial fascia of the abdomen consists over the greater part of the abdominal wall of a single layer containing a variable amount of fat. But near the groin it is easily divisible into two layers, between which are found the superficial vessels and nerves and the superficial inguinal lymph glands. The superficial layer, fascia of camber, is thick, areolar in texture and contains in its meshes a varying quantity of adipose tissue. Below, it passes over the inguinal ligament and is continuous with the superficial fascia of the thigh. In the male, camber's fascia is continued over the penis and outer surface of the spermatic cord to the scrotum, where it helps to form the dartos. As it passes to the scrotum, it changes its characteristics becoming thin, destitute of adipose tissue, and of a pale reddish color. And in the scrotum, it acquires some involuntary muscular fibers. From the scrotum, it may be traced backward into continuity with the superficial fascia of the perineum. In the female, camber's fascia is continued from the abdomen into the labia majora. The deep layer, fascia of scarpa, is thinner and more membranous in character than the superficial and contains a considerable quantity of yellow elastic fibers. It is loosely connected by areolar tissue to the aponeurosis of the obliquus externus abdominis. But in the middle line, it is more intimately adherent to the linea alba and to the pubic symphysis and is prolonged onto the dorsum of the penis, forming the fundiform ligament. Above, it is continuous with the superficial fascia over the rest of the trunk. Below and laterally, it blends with the fascialata of the thigh, a little below the inguinal ligament. Immediately and below, it is continued over the penis and spermatic cord to the scrotum, where it helps to form the dartos. From the scrotum, it may be traced backward into continuity with the deep layer of the superficial fascia of the perineum, fascia of collies. In the female, it is continued into the labia majora and thence to the fascia of collies. The obliquus externus abdominis, external or descending oblique muscle, situated on the lateral and anterior parts of the abdomen, is the largest and the most superficial of the three flat muscles in this region. It is broad, thin, and irregularly quadrilateral. Its muscular portion occupying the side, its aponeurosis, the anterior wall of the abdomen. It arises by eight fleshy digitations from the external surfaces and inferior borders of the lower eight ribs. These digitations are arranged in an oblique line which run downward and backward, the upper ones being attached close to the cartilages of the corresponding ribs, the lowest to the apex of the cartilage of the last rib, the intermediate ones to the ribs at some distance from their cartilages. The five superior serrations increase in size from above downward and are received between corresponding processes of the serratus anterior. The three lower ones diminish in size from above downward and receive between them corresponding processes from the latissimus dorsi. From these attachments, the fleshy fibers proceed in various directions. Those from the lowest ribs pass nearly vertically downward and are inserted into the anterior half of the outer lip of the iliac crest. The middle and upper fibers, directed downward and forward, end in an aponeurosis, opposite a line drawn from the prominence of the ninth costal cartilage to the anterior superior iliac spine. The aponeurosis of the obliquus externus abdominis is a thin but strong membranous structure. The fibers of which are directed downward and medial upward. It is joined with that of the opposite muscle along the middle line and covers the whole of the front of the abdomen. Above, it is covered by and gives origin to the lower fibers of the pectoralis major. Below, its fibers are closely aggregated together and extend obliquely across from the anterior superior iliac spine to the pubic tubercle and the pectinial line. In the middle line, it interlaces with the aponeurosis of the opposite muscle, forming the linea alba, which extends from the xyphoid process to the symphysis pubis. That portion of the aponeurosis, which extends between the anterior superior iliac spine and the pubic tubercle, is a thick band, folded inward and continuous below with the fascialata. It is called the inguinal ligament. The portion which is reflected from the inguinal ligament at the pubic tubercle is attached to the pectinial line and is called the lacunar ligament. From the point of attachment of the ladder to the pectinial line, a few fibers pass upward and medialward behind the medial crux of the subcutaneous inguinal ring to the linia alba. They diverge as they ascend and form a thin triangular fibrous band which is called the reflected inguinal ligament. In the aponeurosis of the oblicus externus, immediately above the crest of the pubis, is a triangular opening, the cutaneous inguinal ring, formed by a separation of the fibers of the aponeurosis in this situation. The following structures require further description vis the subcutaneous inguinal ring, the intracural fibers and fascia, and the inguinal lacunar and reflected inguinal ligaments. The subcutaneous inguinal ring, annulus inguilinus subcutaneous, external abdominal ring. The subcutaneous inguinal ring is an interval in the aponeurosis of the oblicus externus, just above and lateral to the crest of the pubis. The aperture is oblique in direction, somewhat triangular in form, and corresponds with the course of the fibers of the aponeurosis. It usually measures from base to apex about 2.5 centimeters and transversely about 1.25 centimeters. It is bounded below by the crest of the pubis, on either side by the margins of the opening in the aponeurosis, which are called the crora of the ring, and above by a series of curved intracural fibers. The inferior cruse, external pillar, is the stronger and is formed by that portion of the inguinal ligament which is inserted into the pubic tubercle. It is curved so as to form a kind of groove, upon which, in the male, the spermatic cord rests. The superior cruse, or internal pillar, is a broad, thin, flat band attached to the front of the symphysis pubis and interlacing with its fellow on the opposite side. The subcutaneous inguinal ring gives passage to the spermatic cord and ilio-inguinal nerve in the male and to the round ligament of the uterus and the ilio-inguinal nerve in the female. It is much larger in men than in women on account of the large size of the spermatic cord. The intracural fibers fri-ray, intracuralis, intracolumnar fibers. The intracural fibers are a series of curved, tendinous fibers which arch across the lower part of the aponeurosis of the obliques externus, describing curves with the convexities downward. They have received their name from stretching across between the two crura of the subcutaneous inguinal ring and they are much thicker and stronger at the inferior cruse where they are connected to the inguinal ligament and superiorly where they are inserted into the linia alba. The intracural fibers increase the strength of the lower part of the aponeurosis and prevent the divergence of the crura from one another. They are more strongly developed in the male than in the female. As they pass across the subcutaneous inguinal ring, they are connected together by delicate fibrous tissue, forming a fascia called the intracural fascia. This intracural fascia is continued down as a tubular prolongation around a spermatic cord and testes and encloses them in a sheath. Hence it is also called the external spermatic fascia. The subcutaneous inguinal ring is seen as a distinct aperture only after the intracural fascia has been removed. The inguinal ligament ligamentum inguini poparti or popart's ligament. The inguinal ligament is the lower border of the aponeurosis of the obliques externus and extends from the anterior superior iliac spine to the pubic tubercle. From this latter point it is reflected backward and lateral word to be attached to the pectinial line for about 1.25 centimeters forming the lacuna ligament. Its general direction is convex downward toward the thigh where it is continuous with the fascia lata. Its lateral half is rounded in oblique indirection. Its medial half gradually widens at its attachment to the pubis and is more horizontal in direction beneath this chromatic cord. The lacuna ligament ligamentum lacunar gimbernaughti gimbernaughts ligament. The lacuna ligament is that part of the aponeurosis of the obliques externus which is reflected backward and lateral word and is attached to the pectinial line. It is about 1.25 centimeters long larger in the male than in the female almost horizontal indirection and of a triangular form with the base directed lateral word. Its base is concave, thin and sharp and forms the medial boundary of the femoral ring. Its apex corresponds to the pubic tubercle. Its posterior margin is attached to the pectinial line and is continuous with the pectinial fascia. Its anterior margin is attached to the inguinal ligament. Its surfaces are directed upward and downward. The reflected inguinal ligament ligamentum inguinali reflexum coalesce triangular fascia The reflected inguinal ligament is a layer of tendinous fibers of a triangular shape formed by an expansion from the lacuna ligament and the inferior cross of the subcutaneous inguinal ring. It passes medial word and expands into a somewhat fan shaped band lying behind the superior cross of the subcutaneous inguinal ring and in front of the inguinal aponeurotic falx and interlaces with the ligament on the other side of the linea alba. Ligament of Cooper This is a strong fibers band which was first described by Sir Astley Cooper. It extends lateral word from the base of the lacuna ligament line to which it is attached. It is strengthened by the pectinial fascia and by a lateral expansion from the lower attachment of the linea alba. Adminiculum linea alba Variations The obliquous externus may show decrease or doubling of its attachments to the ribs. Addition slips from lumbar aponeurosis doubling between lower ribs and ileum or inguinal ligament Rarely tendinous inscriptions occur. The obliquous internus abdominis internal or ascending oblique muscle thinner and smaller than the obliquous externus beneath which it lies is of an irregularly quadrilateral form and situated at the lateral and anterior parts of the abdomen. It arises by fleshy fibers from the lateral half of the grooved upper surface of the inguinal ligament. From the anterior two thirds of the middle lip of the iliac crest and from the posterior lamina of the lumbodorsal fascia. From this origin the fibers diverge. Those from the inguinal ligament few in number and paler in color than the rest arch downward and medial word across the spermatic cord in the male and the uterus in the female and becoming tendinous are inserted conjointly with those of the transversus into the crest of the pubis and medial part of the pectinial line behind the lacuna ligament forming what is known as the inguinal aponeurotic falx. Those from the anterior third of the iliac origin are horizontal in their direction and becoming tendinous along the lower fourth of the linea semilunaris pass in front of the rectus abdominis to be inserted into the linea alba. Those arising from the middle third of the iliac origin run obliquely upward and medial word and end in an aponeurosis. This divides at the lateral border of the rectus into two laminae which are continued forward one in front of and the other behind this muscle to the linea alba. The inferior lamina has an attachment to the cartilages of the seventh, eighth and ninth ribs. The most posterior fibers pass almost vertically upward to be inserted into the inferior borders of the cartilages of the lower three ribs being continuous with the intercostalus interni. Variations. Occasionally tendinous inscriptions occur from the tips of the tenth or eleventh cartilages An additional slip to the ninth cartilage is sometimes found. Separation between iliac and inguinal parts may occur. End of section 38 Section 39 of Grey's Anatomy Part 2 This is a LibriVox recording. All LibriVox recordings are in the public domain. To find out more information or to volunteer, please visit LibriVox.org Recording by Rebecca Case Anatomy of the Human Body Part 2 by Henry Gray Muscles and Fascia of the Abdomen Part 2 The chromaster is a thin muscular layer composed of a number of fasciculi which arrives from the middle of the inguinal ligament where its fibers are continuous with those of the obliquus echinternus and also occasionally with the transversus. It passes along the lateral sides of the chromatic cord descends with it through the subcutaneous inguinal ring upon the front and sides of the cord and forms a series of loops which differ in thickness and length in different subjects. At the upper part of the cord the loops are short but they become in succession longer and longer, the longest reaching down as low as the testis where a few are inserted into the tunica vaginalis. They are inserted by areolar tissue and form a thin covering over the cord and testis the chromasteric fascia. The fibers ascend along the medial side of the cord and are inserted by a small pointed tendon into the tubercle and crest of the pubis and into the front of the sheath of the rectus abdominis. The transversus abdominis transversalis muscle so called from the direction of the flat muscles of the abdomen being placed immediately beneath the oblicus internus. It arises by fleshy fibers from the lateral third of the inguinal ligament from the anterior three fourths of the inner lip of the iliac crest from the inner surfaces of the cartilages of the lower six ribs interdigitating with the diaphragm and from the lumbo dorsal fascia. The muscle ends in front of the aponeurosis, the lower fibers of which curve downward and medial and are inserted together with those of the oblicus internus into the crest of the pubis and pectinial line forming the inguinal aponeuratic fulcs. Throughout the rest of its extent the aponeurosis passes horizontally to the middle line as inserted into the linea alba. Its upper three fourths lie behind the rectus and blend with the aponeurosis of the oblicus internus. Its lower fourth is in front of the rectus. Variations. It may be more or less fused with the oblicus internus or absent. Spheromatic cord may pierce its lower border. Slender muscle slips from the ilio pectinial line to transfer salis fascia, the aponeurosis of the transversus abdominis or the outer end of the linea semicircularis and other slender slips are occasionally found. The inguinal aponeurotic fulcs, fulcs aponeurotica inguinalis can join tendon of internal oblique and transversalis muscle. Of the oblicus internus and transversus is mainly formed by the lower part of the tendon of the transversus and is inserted into the crest of the pubis and pectinial line immediately behind the subcutaneous inguinal ring, serving to protect what would otherwise be a weak point in the abdominal wall. Lateral to the falcs is a ligamentous band connected with the lower margin of the transversus and extending down in front of the inferior epigastric artery to the superior ramus of the pubis. It is termed the interfovular ligament of Hasselbeck and sometimes contains a few muscular fibers. The rectus abdominis is a long, flat muscle which extends along the whole length of the front of the abdomen and is separated from its fellow on the opposite side by the linea alba. It is much broader, but thinner, above and below and arises by two tendons. The lateral or larger is attached to the crest of the pubis, the medial interlaces with its fellow of the opposite side and is connected with the ligaments in the front of the synthesis pubis. The muscle is inserted by three portions of unequal size into the cartilages of the fifth, sixth, and seventh ribs. The upper portion attached principally to the cartilage of the fifth rib usually has some fibers of insertion into the anterior extremity of the rib itself. Some fibers are occasionally connected with the costosyphoid ligaments and the side of the syphoid process. The rectus is crossed by fibrous bands, three in number, which are named the tendinous inscriptions. One is usually situated opposite the umbilicus, one at the extremity of the syphoid process and the third about midway between the syphoid process and the umbilicus. These inscriptions pass transversely or obliquely across the muscle in a zigzag course. They rarely extend completely through its substance and may pass only halfway across it. They are intimately adherent in front to the sheath of the muscle. Sometimes one or two additional inscriptions generally incomplete are present below the umbilicus. The rectus is enclosed in a sheath formed by the aponeurosis of the oblique and transversus, which are arranged in the following manner. At the lateral margin of the rectus, the aponeurosis of the oblique and transversus internus divides into two laminate, one of which passes in front of the rectus, blending with the aponeurosis of the obliquus externus, the other behind it, blending with the aponeurosis of the transversus, and these, joining again at the medial border of the rectus, are inserted into the linia alba. This arrangement of the aponeurosis exists from the costal margin to midway between the umbilicus and the synthesis pubis, where the posterior wall of the sheath ends in a thin curved margin, the linia semicircularis, the concavity of which is directed downward. Below this level, the aponeurosis of all three muscles passes in front of the rectus. The rectus, in the situation where a sheath is deficient below, is separated from the peritoneum by the transversalis fascia. Since the tendons of the obliquus internus and transversus only reach as high as the costal margin, it follows that above this level, the sheath of the rectus is deficient behind, the muscle resting directly on the cartilages of the ribs, and being covered merely by the tendon of the obliquus externus. The pyramidalis is a small triangular muscle placed at the lower part of the abdomen in front of the rectus and contained in the sheath of that muscle. It arises by tendinous fibers from the front of the pubis and the anterior pubic ligament. The fleshy portion of the muscle passes upward, diminishing in size as it ascends, and ends by a pointed extremity which is inserted into the linea alba, midway between the umbilicus and pubis. This muscle may be wanting on one or both sides. The lower end of the rectus then becomes proportionately increased in size. Occasionally, it is double on one side, and the muscles of the two sides are sometimes of unequal size. It may extend higher than the level stated. Beside the rectus and pyramidalis, the sheath of the rectus contains the superior and inferior epigastric arteries and the lower intercostal nerves. Variations The rectus may insert as high as the fourth or third rib or may fail to reach the fifth. Fibers may spring from the lower part of the linea alba. Nerves The abdominal muscles are supplied by the lower intercostal nerves. The obliquous internus and transversus also receive filaments from the anterior branch of the iliohypogastric and sometimes from the ilioinguinal. The cremaster is supplied by the external spermatic branch of the genitofemeral and the pyramidalis usually by the twelfth thoracic. The linea alba The linea alba is a tendinous rafae in the middle line of the abdomen stretching between the cyphoid process and the symphysis pubis. It is placed between the medial borders of the recti and is formed by the blending of the aponeurosis of the obliquiae and transversi. It is narrow below corresponding to the linear interval existing between the recti but broader above where these muscles diverge from one another. At its lower end the linea alba has a double attachment. Its superficial fibers passing in front of the medial heads of the recti to the symphysis pubis while its deeper fibers form a triangular lamina attached behind the recti to the posterior lip of the crest of the pubis and named the adminiculum lineae albae. It presents apertures for the passage of vessels and nerves. The embilicus which in the fetus exists as an aperture which transmits the embilical vessels is closed in the adult. The lineae semulineris The lineae semulineris are two curved tendinous lines placed one on either side of the lineae alba. Each corresponds with the lateral border of the rectis extends from the cartilage of the ninth rib to the pubic tubercle and is formed by the aponeurosis of the obliquus internus at its line of division to enclose the rectis reinforced in front by that of the obliquus externus and behind by that of the transversus. Actions When the pilvis and thorax are fixed the abdominal muscles compress the abdominal viscera by constricting the cavity of the abdomen in which action they are materially assisted by the descent of the diaphragm. By these means assistance is given in expelling the feces from the rectum, the urine from the bladder the fetus from the uterus and the contents of the stomach and vomiting. If the pilvis and the vertebral column be fixed these muscles compress the lower part of the thorax materially assisting expiration. If the pilvis alone be fixed the thorax is bent directly forward when the muscles of both sides act. When the muscles of only one side contract the trunk is bent toward that side and rotated toward the opposite side. If the thorax be fixed the muscles acting together draw the pilvis upward as in climbing or acting singly they draw the pilvis upward and bend the vertebral column to one side or the other. The recti acting from below depress the thorax and consequently flex the vertebral column. When acting from above they flex the pilvis upon the vertebral column. The pyramidalis are tensors of the linea alba. The transversalis fascia The transversalis fascia is a thin aponeuratic membrane which lies between the inner surface of the transversus and the extraperitoneal fat. It forms part of the general layer of fascia lining the abdominal parities and is directly continuous with the iliac and pelvic fascia. In the inguinal region the transversalis fascia is thick and dense in structure and is joined by fibers from the aponeurosis of the transversus but it becomes thin as it ascends to the diaphragm and blends with the fascia covering the under surface of this muscle. Behind it is lost in the fat which covers the posterior surfaces of the kidney. Below it has the following attachments posteriorly to the whole length of the iliac crest between the attachments of the transversus and iliacus. Between the anterior superior iliac spine and the femoral vessels it is connected to the posterior margin of the inguinal ligament and is there continuous with the iliac fascia. Medial to the femoral vessels it is thin and attached to the pubis and pectinial line behind the inguinal aponeuratic faults with which it is united. It descends in front of the femoral vessels to form the anterior wall of the femoral sheath. Beneath the inguinal ligament it is strengthened by a band of fibrous tissue which is only loosely connected to the ligament and is specialized as a deep choral arch. The spermatic cord in the male and the round ligament of the uterus in the female pass through the transversus fascia at a spot called the abdominal inguinal ring. This opening is not visible externally since the transversus fascia is longed on these structures as the infendibular form fascia. The abdominal inguinal ring annulus inguinalis abdominis internal or deep abdominal ring. The abdominal inguinal ring is situated in the transversus fascia midway between the anterior superior iliac spine and the symphysis pubis and about 1.25 cm above the inguinal ligament. It is of an oval form the long axis of the oval being vertical. It varies in size in different subjects and is much larger in the male than in the female. It is bounded above and laterally by the arched lower margins of the transversus below and medially by the inferior epigastric vessels. It transmits the spermatic cord in the male and the round ligament of the uterus in the female. From its circumference a thin funnel shaped membrane the infendibular form fascia is continued around this cord and the testis and closing them in a distinct covering. The inguinal canal annulus inguinalis spermatic canal The inguinal canal contains the spermatic cord and the ilioinguinal nerve in the male and the round ligament of the uterus and the ilioinguinal nerve in the female. It is an oblique canal about 4 cm long planting downward and medial and placed parallel with and a little above the inguinal ligament. It extends from the abdominal inguinal ring to the subcutaneous inguinal ring. It is bounded in front by the integument and superficial fascia by the aponeurosis of the obelicus externus throughout its whole length and by the obelicus internus in its lateral third. Behind by the reflected inguinal ligament the transversalis fascia the extraperitoneal connective tissue and the peritoneum above by the arched fibres of the obelicus internus and the transversis abdominis below by the union of the transversalis fascia with the inguinal ligament and at its medial end by the lacunar ligament. Extraperitoneal connective tissue Between the inner surface of the general layer of the fascia which lines the interior of the abdominal and petalic cavities and the peritoneum there is a considerable amount of connective tissue termed the extraperitoneal or subperitoneal connective tissue. The parietal portion lines the cavity in varying quantities in different situations. It is especially abundant on the posterior wall of the abdomen and particularly around the kidneys where it contains much fat. On the anterior wall of the abdomen except in the pubic region and on the lateral wall above the iliac crest it is scanty and here the transversalis fascia is more closely connected with the peritoneum. There is a considerable amount of extraperitoneal connective tissue in the pelvis. The visceral portion follows the course of the branches of the abdominal aorta between the layers of the mesenterics and other folds of the peritoneum which connect the various viscera to the abdominal wall. The two portions are directly continuous with each other. The deep creural arch curving over the external iliac vessels at the spot where they become femoral on the abdominal side of the inguinal ligaments and loosely connected with it is a thickened band of fibers called the deep creural arch is apparently a thickening of the transversalis fascia joined laterally to the center of the lower margin of the inguinal ligament and arching across the front of the femoral sheath to be inserted by a broad attachment into the pubic tubercle and pectinial line behind the inguinal aponeurotic faults. In some subjects this structure is not very prominently marked and not infrequently it is altogether wanting. 2. The posterior muscles of the abdomen psoas major, psoas minor iliacus quadratus lumborum psoas major, psoas minor and the iliacus with the fascia covering them will be described with the muscles of the lower extremity c page 466 the fascia covering the quadratus lumborum this is a thin layer attached immediately to the bases of the transverse processes of the lumbar vertebrae below to the ilio lumbar ligament above to the apex and lower border of the last rib the upper margin of this fascia which extends from the transverse process of the first lumbar vertebra to the apex and lower border of the last rib constitutes the lateral lumbocostal arch page 405 laterally it blends with the lumbodorsal fascia the anterior layer of which intervenes between the quadratus lumborum and the sacrospinalis the quadratus lumborum page 398 is irregularly quadrilateral in shape and broader above than below it arises by apnoeratic fibers from the ilio lumbar ligament and the adjacent portion of the iliac crest for about 5 centimeters and is inserted into the lower border of the last rib for about half its length and by four small tendons into the apices of the transverse processes of the upper four lumbar vertebrae occasionally a second portion of this muscle is found in front of the preceding it arises from the upper borders of the transverse processes of the lower three or four lumbar vertebrae and is inserted into the lower margin of the last rib in front of the quadratus lumborum are the colon the kidney, the psoas major and minor and the diaphragm between the fascia and the muscle are the twelfth thoracic iliolinguinal and iliohypogastric nerves variations the number of attachments to the vertebrae and the extent of its attachment to the last rib vary nerve supplying the twelfth thoracic and first and second lumbar nerves supply this muscle actions the quadratus lumborum draws down the last rib and acts as a muscle inspiration by helping to fix the origin of the diaphragm if the thorax and vertebral column are fixed it may act upon the pelvis raising it toward its own side when only one muscle is put in action and when both muscles act together either from below or above they flex the trump end of section 39 section 40 of Grey's Anatomy part 2 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 Laurie Ann Walden anatomy of the human body part 2 by Henry Grey the muscles and fascia of the pelvis obturator internus piriformis levator ani coxidius the muscles within the pelvis may be divided into two groups one the obturator internus and the piriformis which are muscles of the lower extremity and will be described with these two the levator ani and the coxidius which together form the pelvic diaphragm and are associated with the pelvic viscera the classification of the two groups under a common heading is convenient in connection with the fascia investing the muscles these fascia are closely related to one another and to the deep fascia of the perineum and in addition have special connections with the fibrous coverings of the pelvic viscera it is customary therefore to describe them together under the term pelvic fascia pelvic fascia the fascia of the pelvis may be resolved into A. the fascial sheaves of the obturator internus, piriformis and pelvic diaphragm B. the fascia associated with the pelvic viscera the fascia of the obturator internus covers the pelvic surface of and is attached around the margin of the origin of the muscle above it is loosely connected to the back part of the arcuate line and here it is continuous with the iliac fascia in front of this as it follows the line of origin of the obturator internus it gradually separates from the iliac fascia and the continuity between the two is retained only through the periosteum it arches beneath the obturator vessels and nerve completing the obturator canal and at the front of the pelvis is attached to the back of the superior ramus of the pubis below the obturator fascia is attached to the falciform process of the sacro tuberous ligament and to the pubic arch where it becomes continuous with the superior fascia of the urogenital diaphragm behind it is prolonged into the gluteal region the internal pudendal vessels and pudendal nerve cross the pelvic surface of the obturator internus and are enclosed in a special canal alcox canal formed by the obturator fascia the fascia of the piriformis is very thin and is attached to the front of the sacrum and the sides of the greater sciatic foramen it is prolonged on the muscle into the gluteal region at it's sacral attachment around the margins of the anterior sacral foramina it comes into intimate association with and enshees the nerves emerging from these foramina hence the sacral nerves are frequently described as lying behind the fascia the internal iliac vessels and their branches on the other hand lie in the sub peritoneal tissue in front of the fascia it is attached to the gluteal region emerge in special sheaths of this tissue above and below the piriformis muscle the diaphragmatic part of the pelvic fascia covers both surfaces of the levatoris anae the inferior layer is known as the anal fascia it is attached above to the obturator fascia along the line of origin of the levator anae while below it is continuous with the superior fascia of the urogenital diaphragm and with the fascia on the sphincter anae internus the layer covering the upper surface of the pelvic diaphragm follows above the line of origin of the levator anae and is therefore somewhat variable in front it is attached to the back of the synthesis pubis about two centimeters above its lower border it can then be traced laterally across the back of the superior ramus of the pubis for a distance of about 1.25 centimeters when it reaches the obturator fascia it is attached to this fascia along a line which pursues a somewhat irregular course to the spine of the ischium the irregularity of this line is due to the fact that the origin of the levator anae which in lower forms is from the pelvic brim is in man lower down tendinous fibers of origin of the muscle are therefore often found extending up toward and in some cases reaching the pelvic brim and on these the fascia is carried it will be evident that the fascia covering that part of the obturator internus which lies above the origin of the levator anae is a composite fascia and includes the following a. the obturator fascia of the levator anae c. degenerated fibers of origin of the levator anae the lower margin of the fascia covering the upper surface of the pelvic diaphragm is attached along the line of insertion of the levator anae at the level of a line extending from the lower part of the synthesis pubis to the spine of the ischium is a thickened whitish band in this upper layer of the pelvic fascia it is termed the tendinous arch or white line of the pelvic fascia and marks the line of attachment of the special fascia pars endopalvina fascia pelvis which is associated with the pelvic viscera the endopalvic part of the pelvic fascia is continued over the various pelvic viscera to form for them fibrous coverings which will be described later in splankology it is attached to the diaphragmatic part of the pelvic fascia along the tendinous arch and has been subdivided in accordance with the viscera to which it is related thus its anterior part known as the vesicle layer forms the anterior and lateral ligaments of the bladder its middle part crosses the floor of the pelvis between the rectum and vesiculi seminalis in the female this is perforated by the vagina its posterior portion passes to the side of the rectum it forms a loose sheath for the rectum but is firmly attached around the anal canal this portion is known as the rectal layer the levator ani is a broad thin muscle situated on the side of the pelvis it is attached to the inner surface of the side of the lesser pelvis and unites with its fellow of the opposite side to form the greater part of the floor of the pelvic cavity it supports the viscera in this cavity and surrounds the various structures which pass through it it arises in front from the posterior surface of the superior ramus of the pubis lateral to the symphysis behind from the inner surface of the spine of the ischium and between these two points from the obturator fascia posteriorly this fascial origin corresponds more or less closely with the tenderness arch of the pelvic fascia but in front the muscle arises from the fascia at a varying distance above the arch in some cases reaching nearly as high as the canal for the obturator vessels and nerve the fibers pass downward and backward to the middle line of the floor of the pelvis the most posterior are inserted in the last two segments of the coccyx those placed more anteriorly unite with the muscle of the opposite side in the median fibrous raffae anal coccygeal raffae which extends between the coccyx and the margin of the anus the middle fibers are inserted into the side of the rectum blending with the fibers of the sphincter muscles lastly the anterior fibers descend upon the side of the prostate unite beneath it with the muscle of the opposite side joining with the fibers of the sphincter ani externus and transversus perineae at the central tenderness point of the perineum the anterior portion is occasionally separated from the rest of the muscle by connective tissue from this circumstance as well as from its peculiar relation with the prostate which it supports as in a sling it has been described as a distinct muscle in the name of levator prostitae in the female the anterior fibers of the levator ani descend upon the side of the vagina the levator ani may be divided into ileococcygeal and pubococcygeal parts the ileococcygeus arises from the ischial spine and from the posterior part of the tendinous arch of the pelvic fascia and is attached to the coccyx it is usually thin and may fail entirely or be largely replaced by fibrous tissue an accessory slip at its posterior part is sometimes named the ileo sacralis the pubococcygeus arises from the back of the pubus and from the anterior part of the obturator fascia and is directed backward almost horizontally along the side of the anal canal toward the coccyx and sacrum to which it finds attachment between the termination of the vertebral column and the anus the two pubococcygei muscles come together and form a thick fibromuscular layer lying on the raffae formed by the ileococcygei Peter Thompson the greater part of this muscle is inserted into the coccyx and into the last one or two pieces of the sacrum and the vertebral column is, however, not admitted by all observers the fibres which form a sling for the rectum are named the pubo rectalis or sphincter rectae they arise from the lower part of the synthesis pubis and from the superior fascia of the urogenital diaphragm they meet with the corresponding fibres of the opposite side around the lower part of the rectum and form for it a strong sling nerve supply the levator ani is supplied by a branch from the fourth sacral nerve and by a branch which is sometimes derived from the perineal sometimes from the inferior hemorrhoidal division of the pudendal nerve the coccyge is situated behind the preceding it is a triangular plane of muscular and tendinous fibres arising by its apex the spine of the ischium and sacrospinus ligament and inserted by its base into the margin of the coccyx and into the side of the lowest piece of the sacrum it assists the levator ani and piriformis in closing in the back part of the outlet of the pelvis nerve supply the coccyge is supplied by a branch from the fourth and fifth sacral nerves actions the levatoris ani constrict the lower end of the rectum and vagina they elevate and invert the lower end of the rectum after it has been protruded and averted during the expulsion of the feces they are also muscles of forced exploration the coccygei pull forward and support the coccyx after it has been pressed backward during defecation or parturition the levatoris ani and coccygei together form a muscular diaphragm which supports the pelvic viscera end of section 40 section 41 of grey's anatomy part 2 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 Laurie Ann Walden anatomy of the human body part 2 by Henry Gray the muscles and fascia of the perineum the perineum corresponds to the outlet of the pelvis its deep boundaries are in front the pubic arch and the arcuate ligament of the pubis behind the tip of the coccyx and on either side the inferior ramey of the pubis and ischium and the sacro tuberous ligament the space is somewhat lozenge shaped and is limited on the surface of the body by the scrotum in front by the buttocks behind and laterally by the medial side of the thigh a line drawn transversely across in front of the ischial tuberosities divides the space into two portions the posterior contains the termination of the anal canal and is known as the anal region the anterior which contains the external urogenital organs is termed the urogenital region the muscles of the perineum may therefore be divided into two groups one those of the anal region two those of the urogenital region A in the male B in the female one the muscles of the anal region corrugator cutis ani sphincter ani externus sphincter ani internus the superficial fascia the superficial fascia is very thick areolar in texture and contains much fat in its meshes on either side a pad of fatty tissue extends deeply between the levator ani and obturator internus into a space known as the ischio rectal fascia the deep fascia the deep fascia forms the lining of the ischio rectal fascia it comprises the anal fascia and the portion of the obturator fascia below the origin of levator ani ischio rectal fascia fascia ischio rectalis the fascia is somewhat prismatic in shape with its base directed to the surface of the perineum and its apex at the line of meeting of the obturator and anal fascia it is bounded medially by the sphincter ani externus and the anal fascia laterally by the tuberosity of the ischium and the obturator fascia anteriorly by the fascia of collies covering the transversus perineae superficialis and by the inferior fascia of the urogenital diaphragm posteriorly by the gluteus maximus and the sacrotuberous ligament crossing the space transversely are the inferior hemorrhoidal vessels and nerves at the back part are the perineal and perforating cutaneous branches of the pudendal plexus while from the fore part the posterior scrotal or labial vessels and nerves emerge the internal pudendal vessels and pudendal nerve lie in alkox canal on the lateral wall the fascia is filled with fatty tissue across which numerous fibrous bands extend from side to side the corrugator cutis ani around the anus is a thin stratum of involuntary muscular fiber which radiates from the orifice immediately the fibers fade off into the submucous tissue while laterally they blend with the true skin by its contraction it raises the skin into ridges around the margin of the anus the sphincter ani externus external sphincter ani is a flat plane of muscular fibers elliptical in shape and intimately adherent to the entanglement surrounding the margin of the anus it measures about 8 to 10 cm in length from its anterior to its posterior extremity and is about 2.5 cm broad opposite the anus it consists of two strata superficial and deep the superficial constituting the main portion of the muscle arises from a narrow tendinous band the anocoxigil raffae which stretches from the tip of the coccyx to the posterior margin of the anus it forms two flattened planes of muscular tissue which encircle the anus and meet in front to be inserted into the central tendinous point of the perineum joining with the transversus perineae superficialis the levator ani and the bulbo cavernosis the deeper portion forms a complete sphincter to the anal canal its fibers surround the canal closely applied to the sphincter ani internus in front blend with the other muscles at the central point of the perineum in a considerable proportion of cases the fibers decussate in front of the anus and are continuous with the transversi perineae superficialis posteriorly they are not attached to the coccyx but are continuous with those of the opposite side behind the anal canal the upper edge of the muscle is ill defined since fibers are given off from it to join the levator ani nerve supply a branch from the fourth sacral and twigs from the inferior hemorrhoidal branch of the pudendal supply the muscle actions the action of this muscle is peculiar one it is like other muscles always in a state of tonic contraction and having no antagonistic muscle it keeps the anal canal and orifice closed two it can be put into a condition of greater contraction under the influence of the will so as more firmly to occlude the anal aperture in expiratory efforts unconnected with defecation three taking its fixed point at the coccyx it helps to fix the central point of the perineum so that the bulbo cavernosis may act from this fixed point the sphincter ani internus internal sphincter ani is a muscular ring which surrounds about 2.5 cm of the anal canal its inferior border is in contact with but quite separate from the sphincter ani externus it is about 5 mm thick and is formed by an aggregation of the involuntary circular fibers of the intestine its lower border is about 6 mm from the orifice of the anus actions its action is entirely involuntary it helps the sphincter ani externus to occlude the anal aperture and aids in the expulsion of the feces two the muscles of the urogenital region in the male transversus perinei superficialis bulbo cavernosis ischiocavernosis transversus perinei profundus sphincter urethra membranaceae superficial fascia the superficial fascia of this region consists of two layers superficial and deep the superficial layer is thick loose areolar in texture and contains in its meshes much adipose tissue the amount of which varies in different subjects in front it is continuous with the dartos tunic of the scrotum behind with the subcutaneous areolar tissue surrounding the anus and on either side with the same fascia on the inner sides of the thigh in the middle line it is adherent to the skin on the raffae and to the deep layer of the superficial fascia the deep layer of superficial fascia fascia of collies is thin aponeurotic in structure and of considerable strength serving to bind down the muscles of the root of the penis it is continuous in front with the dartos tunic the deep fascia of the penis the fascia of the spermatic cord and scarpus fascia upon the anterior wall of the abdomen on either side it is firmly attached to the margins of the ramae of the pubis and ischium lateral to the crust's penis and as far back as the tuberosity of the ischium posteriorly it curves around the transversae perineae superficialis to join the lower margin of the inferior fascia in the middle line it is connected with the superficial fascia and with the median septum of the bulbo cavernosis this fascia not only covers the muscles in this region but at its back part sends upward a vertical septum from its deep surface which separates the posterior portion of the subjacent space into two the central tendinous point of the perineum this is a fibrous point in the middle line of the perineum between the urethra and anus and about 1.25 cm in front of the ladder at this point six muscles converge and are attached that is the sphincter anae externus the bulbo cavernosis the two transversae perineae superficialis and the anterior fibres of the levitorious anae the transversae perineae superficialis transversae perineae superficial transverse perineal muscle is a narrow muscular slip which passes more or less transversely across the perineal space in front of the anus it arises by tendinous fibres from the inner and four part of the tuberosity of the ischium and running medial word is inserted into the central tendinous point of the perineum joining in this situation with the muscle of the opposite side with the sphincter anae externus behind and with the bulbo cavernosis in front in some cases the fibres of the deeper layer of the sphincter anae externus decussate in front of the anus and are continued into this muscle occasionally it gives off fibres which join with the bulbo cavernosis of the same side variations are numerous it may be absent or double or insert into the bulbo cavernosis or external sphincter actions the simultaneous contraction of the two muscles serves to fix the central tendinous point of the perineum the bulbo cavernosis ejaculator urinae accelerator urinae is placed in the middle line of the perineum in front of the anus it consists of two symmetrical parts united along the median line by a tendinous raffae it arises from the central tendinous point of the perineum and from the median raffae in front it's fibres diverge like the barbs of a quill pin the most posterior form a thin layer which is lost on the inferior fascia of the urogenital diaphragm the middle fibres encircle the bulb and adjacent parts of the corpus cavernosum urethri and join with the fibres of the opposite side on the upper part of the corpus cavernosum urethri and a strong aponeurosis the anterior fibres spread out over the side over the corpus cavernosum penis to be inserted partly into that body anterior to the ischiocavernosis occasionally extending to the pubis and partly ending in a tendinous expansion which covers the dorsal vessels of the penis the latter fibres are best seen by dividing the muscle longitudinally and reflecting it from the surface of the corpus cavernosum urethri actions this muscle serves to empty the canal of the urethra after the bladder has expelled its contents during the greater part of the act of mixturision its fibres are relaxed and it only comes into action at the end of the process the middle fibres are supposed by crowds to assist in the erection of the corpus cavernosum urethri by compressing the erectile tissue of the bulb the anterior fibres according to Terrell also contribute to the erection of the penis by compressing the deep dorsal vein of the penis as they are inserted into and continuous with the fascia of the penis the ischiocavernosis erector penis covers the crust penis it is an elongated muscle broader in the middle than at either end and situated on the lateral boundary of the perineum it arises by tendinous and fleshy fibres from the inner surface of the tuberosity of the ischium behind the crust penis and from the ramie of the pubis and ischium on either side of the crust from these points fleshy fibres succeed and end in an aponeurosis which is inserted into the sides and under surface of the crust penis action the ischiocavernosis compresses the crust penis and retards the return of the blood through the veins and thus serves to maintain the organ erect between the muscles just examined a triangular space exists bounded medially by the bulbocavernosis laterally by the ischiocavernosis and behind by the transversus perinei superficialis the floor is formed by the inferior fascia of the urogenital diaphragm running from behind forward in the space are the posterior scrotal vessels and nerves and the perineal branch of the posterior femoral cutaneous nerve the transverse perineal artery courses along its posterior boundary on the transversus perinei superficialis the deep fascia the deep fascia of the urogenital region forms an investment for the transversus perinei profundus and the sphincter urethri membranaceae but within it lie also the deep vessels and nerves of this part the hole forming a transverse septum which is known as the urogenital diaphragm from its shape it is usually termed the triangular ligament and is stretched almost horizontally across the pubic arch so as to close in the front part the outlet of the pelvis it consists of two dense membranaceae which are united along their posterior borders but are separated in front by intervening structures the superficial of these two layers the inferior fascia of the urogenital diaphragm is triangular in shape and about four centimeters in depth its apex is directed forward and is separated from the arcuate pubic ligament by an oval opening for the transmission of the deep dorsal vein of the penis its lateral margins are attached on either side to the inferior of the pubis and ischium above the crust penis its base is directed toward the rectum and connected to the central tendinous point of the perineum it is continuous with the deep layer of the superficial fascia behind the transversus perineae superficialis and with the inferior layer of the diaphragmatic part of the pelvic fascia it is perforated about 2.5 centimeters below the dorsal artery's pubis by the urethra the aperture for which is circular and about 6 millimeters in diameter by the arteries to the bulb and the ducts of the bulbo urethral glands close to the urethral orifice by the deep arteries of the penis one on either side close to the pubic arch and about half way along the attached margin of the fascia by the dorsal arteries and nerves of the penis near the apex of the fascia its base is also perforated by the perineal vessels and nerves while between its apex and the arcuate pubic ligament the deep dorsal vein of the penis passes upward into the pelvis if the inferior fascia of the urogenital diaphragm be detached on either side the following structures will be seen between it and the superior fascia the deep dorsal vein of the penis the membranous portion of the urethra the transversus perineae the transversus perineae profundus and sphincter urethrae membranaceae muscles the bulbo urethral glands and their ducts the pudendal vessels and dorsal nerves of the penis the arteries and nerves of the urethral bulb and aplexus of veins the superior fascia of the urogenital diaphragm is continuous with the obturator fascia and stretches across the pubic arch if the obturator fascia is traced medially after leaving the obturator internus muscle it will be found attached by some of its deeper or anterior fibers to the inner margin of the pubic arch while its superficial or posterior fibers pass over this attachment to become continuous with the superior fascia of the urogenital diaphragm behind this layer of the fascia is continuous with the inferior fascia and with the fascia of collies in front it is continuous with the fascial sheath of the prostate and is fused with the inferior fascia to form the transverse ligament of the pelvis the transversus perineae profundus arises from the inferior ramae of the ischium and runs to the median line where it interlaces in a tendinous rafae with its fellow of the opposite side it lies in the same plane as the sphincter urethrae membranaceae formerly the two muscles were described together as the constrictor urethrae the sphincter urethrae membranaceae surrounds the whole length of the membranous portion of the urethra and is enclosed in the fascia of the urogenital diaphragm its external fibers arise from the junction of the inferior ramae of the pubis and ischium to the extent of 1.25 to 2 centimeters and from the neighboring fascia they arch across the front of the urethra and bulbour urethral glands pass around the urethra and behind it unite with the muscle of the opposite side by means of a tendinous rafae its innermost fibers form a continuous circular investment for the membranous urethrae nerve supply the perineal branch of the pudendal nerve supplies this group of muscles actions the muscles of both sides act together as a sphincter compressing the membranous portion of the urethra during the transmission of fluids they, like the bulbocabinosis are relaxed and only come into action at the end of the process to eject the last drops of the fluid 2b the muscles of the urogenital region in the female transversus perineae superficialis bulbocabinosis isiocabinosis transversus perineae profundus sphincter urethrae membranaceae the transversus perineae superficialis transversus perineae superficial transverse perineal muscle in the female is a narrow muscular slip which arises by a small tendon from the inner and four part of the tuberosity of the isium and is inserted into the central tendinous point of the perineum joining in this situation with the muscle of the opposite side the sphincter ani externus behind and the bulbocabinosis in front action the simultaneous contraction of the two muscles serves to fix the central tendinous point of the perineum the bulbocabinosis sphincter vaginae surrounds the orifice of the vagina it covers the lateral parts of the vestibular bulbs and is attached posteriorly to the central tendinous point of the perineum where it blends with the sphincter ani externus its fibers pass forward on either side of the vagina to be inserted into the corpora cavernosa clitoridus a fasciculus crossing over the body of the organ so as to compress the deep dorsal vein actions the bulbocabinosis diminishes the orifice of the vagina the anterior fibers contribute to the erection of the clitoris as they are inserted into and are continuous with the fascia of the clitoris compressing the deep dorsal vein during the contraction of the muscle the ischiocavernosis erector clitoridus is smaller than the corresponding muscle in the male it covers the unattached surface of the crust clitoridus it is an elongated muscle broader at the middle than at either end and situated on the side of the lateral boundary of the perineum it arises by tendinous and fleshy fibers from the inner surface of the tuberosity of the ischium behind the crust clitoridus from the surface of the crust and from the adjacent portion of the ramus of the ischium from these points fleshy fibers succeed and end in an aponeurosis which is inserted into the sides and under surface of the crust clitoridus actions the ischiocavernosis compresses the crust clitoridus and retards the return of blood through the veins and thus serves to maintain the organ erect the fascia of the urogenital diaphragm in the female is not so strong as in the male it is attached to the pubic arch its apex being connected with the arcuate pubic ligament it is divided in the middle line by the aperture of the vagina with the external coat of which it becomes blended and in front of this is perforated by the urethra its posterior border is continuous as in the male with the deep layer of the superficial fascia around the transversus perineae superficialis like the corresponding fascia in the male it consists of two layers between which are to be found the following structures the deep dorsal vein of the clitoris a portion of the urethra and the constrictor urethra muscle the larger vestibular glands in their ducts the internal pudendal vessels and the dorsal nerves of the clitoris the arteries and nerves of the bulbi vestibuli and aplexus of veins the transversus perineae profundus arises from the inferior rami of the ischium and runs across to the side of the vagina the sphincter urethra membranesiae constrictor urethrae like the corresponding muscle on the male consists of external and internal fibers the external fibers arise on either side from the margin of the inferior ramus of the pubis they are directed across the pubic arch in front of the urethra and pass around it to blend with the muscular fibers of the opposite side between the urethra and vagina the innermost fibers encircle the lower end of the urethra nerve supply the muscles of this group are supplied by the perineal branch of the pudendal end of section 41 section 42 of Gray's Anatomy Part 2 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 Selena Arter Anatomy of the Human Body Part 2 by Henry Gray 7 the fascia and muscles of the upper extremity A the muscles connecting the upper extremity to the vertebral column the muscles of this group are trapezius latissimus dorsi rhombordius major rhombordius minor levator scapulae superficial fascia the superficial fascia of the back forms a layer of considerable thickness and strength and contains a quantity of granular fat it is continuous with the general superficial fascia deep fascia the deep fascia is a dense fibrous layer attached above to the superior nuchal line of the occipital bone in the middle line it is attached to the ligamentum nuchae and supra-spinal ligament and to the spinous processes of all the vertebrae below the seventh cervical laterally in the neck it is continuous with the deep cervical fascia over the shoulder it is attached to the spine of the scapula and to the acromion and is continued downward over the deltoidius to the arm on the thorax it is continuous with the deep fascia of the axilla and chest and on the abdomen with that covering the abdominal muscles below it is attached to the crest of the ileum the trapezius is a flat triangular muscle covering the upper and back part of the neck and shoulders it arises from the external occipital protuberance and the medial third of the superior nuchal line of the occipital bone from the ligamentum nuchae the spinous process of the seventh cervical and the spinous processes of all the thoracic vertebrae and from the corresponding portion from this origin the superior fibers proceed downward and lateralward the inferior upward and lateralward and the middle horizontally the superior fibers are inserted into the posterior border of the lateral third of the clavicle the middle fibers into the medial margin of the acromion and into the superior lip of the posterior border of the spine of the scapula the inferior fibers converge near the scapula and end in an aponeurosis which glides over the smooth triangular surface on the medial end of the spine to be inserted into a tubercle at the apex of the smooth triangular surface at its occipital origin the trapezius is connected to the bone by a thin fibrous lamina firmly adherent to the skin at the middle it is connected to the spinous processes by a broad semi-eliptical aponeurosis which reaches from the sixth cervical to the third thoracic vertebrae and forms with that of the opposite muscle a tenonous ellipse the rest of the muscle arises by numerous short tenonous fibers the two trapezius muscles together resemble a trapezium or diamond shaped quadrangle two angles corresponding to the shoulders a third to the occipital protuberance and the fourth to the spinous process of the 12th thoracic vertebra variations the attachments to the dorsal vertebrae are often reduced and the lower ones are often wanting the occipital attachment is often wanting separation between cervical and dorsal portions is frequent extensive deficiencies and complete absence occur the clavicular insertion of this muscle varies in extent it sometimes reaches as far as the middle of the clavicle and occasionally may blend with the posterior edge of the sternocleidomastoidius or overlap it the latissimus dorsi is a triangular flat muscle which covers the lumbar region and the lower half of the thoracic region and is generally contracted into a narrow fasciculus at its insertion into the humerus it arises by tenonous fibers from the spinous processes of the lower sixth thoracic vertebrae and from the posterior layer of the lumbodorsal fascia by which it is attached to the spines of the lumbar and sacral vertebrae to the supraspinal ligament and to the posterior part of the crest of the ilium it also arises by muscular fibers from the external lip of the crest from lateral to the margin of the sacrospinalis and from the three or four lower ribs by fleshy digitations which are interposed between similar processes of the obliquus abdominis externus from this extensive origin the fibers pass in different directions the upper ones horizontally the middle obliquely upward and the lower vertically upward so as to converge and form a thick fasciculus which crosses the inferior angle of the scapula and usually receives a few fibers from it the muscle curves around the lower border of the teres major and is twisted upon itself so that the superior fibers become at first posterior and then inferior and the vertical fibers at first anterior and then superior it ends in a quadrilateral tendon about 7 centimeters long which passes in front of the tendon of the teres major and is inserted into the bottom of the enter tubercular groove of the humerus its insertion extends higher on the humerus than that of the tendon of the pectoralis major the lower border of its tendon is united with that of the teres major the surfaces of the two are integrated near their insertions by a bursa another bursa is sometimes interposed between the muscle and the inferior angle of the scapula the tendon of the muscle gives off an expansion to the deep fascia of the arm variations the number of dorsal vertebrae to which it is attached vary from 4 to 7 or 8 the number of costal attachments varies muscle fibers may or may not reach the crest of the ilium a muscular slip the axillary arch varying from 7 to 10 centimeters in length and from 5 to 15 millimeters in breadth occasionally springs from the upper edge of the latissimus dorsi about the middle of the posterior fold of the axilla and crosses the axilla in front of the axillary vessels and nerves the under surface of the tendon of the pectoralis major the coricobrachialis or the fascia over the biceps brachii this axillary arch crosses the axillary artery just above the spot usually selected for the application of a ligature and may mislead the surgeon during the operation it is present in about 7 percent of subjects and may be easily recognized by the transverse direction of its fibers a fibrous slip usually passes from the lower border of the tendon of the latissimus dorsi near its insertion to the long head of the triceps brachii this is occasionally muscular and is the representative of the dorso epitrochliaris brachii of apes the lateral margin of the latissimus dorsi is separated below from the obliquous externus abdominis by a small triangular interval the lumbar triangle of pettit the base of which is formed by the iliac crest and its floor by the obliquous internus abdominis another triangle is situated behind the scapula it is bounded above by the trapezius below by the latissimus dorsi and laterally by the vertebral border of the scapula the floor is partly formed by the rhomboidius major if the scapula be drawn forward by folding the arms across the chest and the trunk bent forward parts of the sixth and seventh ribs and the interspace between them become subcutaneous and available for osculation the space is therefore known as the triangle of osculation nerves the trapezius is supplied by the accessory nerve and by branches from the third and fourth cervical nerves the latissimus dorsi by the sixth seventh and eighth cervical nerves through the thoracodorsal long subscapular nerve the rhomboidius major arises by tendinous fibers from the spinous processes of the second third fourth and fifth thoracic vertebrae and the supra-spinal ligament and is inserted into a narrow tendinous arch attached above to the lower part of the triangular surface at the root of the spine of the scapula below to the inferior angle the arch being connected to the vertebral border by a thin membrane when the arch extends as it occasionally does only a short distance the muscular fibers are inserted into the scapula the rhomboidius minor arises from the lower part of the ligamentum nuke and from the spinous processes of the seventh cervical and first thoracic vertebrae it is inserted into the base of the triangular smooth surface at the root of the spine of the scapula and is usually separated from the rhomboidius major by a slight interval but the adjacent margins of the two muscles are occasionally united variations the vertebral and scapular attachments of the two muscles vary in extent a small slip from the scapula to the occipital bone close to the minor occasionally occurs the rhomboidius occipitalis muscle the levator scapulae levator anguli scapulae is situated at the back and side of the neck it arises by tendinous slips from the transverse processes of the atlas and axis from the posterior tubercles of the transverse processes of the third and fourth cervical vertebrae it is inserted into the vertebral border of the scapula between the medial angle and the triangular smooth surface at the root of the spine variations the number of vertebral attachments varies a slip may extend to the occipital or mastoid to the trapezius scalene or serratus anterior or to the first or second rib the muscle may be subdivided into several distinct parts from origin to insertion levator clavicle from the transverse processes of one or two upper cervical vertebrae to the outer end of the clavicle which corresponds to a muscle of lower animals more or less union with the serratus anterior nerves the rhomboid eye are supplied by the dorsal scapular nerve from the fifth cervical the levator scapulae by the third and fourth cervical nerves and frequently by a branch from the dorsal scapular actions the movements affected by the preceding muscles are numerous as may be conceived from their extensive attachments when the whole trapezius is in action it retracts the scapula and braces back the shoulder if the head be fixed the upper part of the muscle will elevate the point of the shoulder as in supporting weights when the lower fibers contract they assist in depressing the scapula the middle and lower fibers of the muscle rotate the scapula causing elevation of the acromion if the shoulders be fixed the trapezius acting together will draw the head directly backward or if only one act the head is drawn to the corresponding side when the latissimus dorsi acts upon the humerus it depresses and draws it backward and at the same time rotates it inward it is the muscle which is principally employed in giving a downward blow as in felling a tree or in saber practice if the arm be fixed the muscle may act in various ways upon the trunk thus it may raise the lower ribs and assist in forcible inspiration or if both arms be fixed the two muscles may assist the abdominal muscles and pectoralis in suspending and drawing the trunk forward as in climbing if the head be fixed the levator scapulae raises the medial angle of the scapula if the shoulder be fixed the muscle inclines the neck to the corresponding side and rotates it in the same direction the rhomboid eye carry the inferior angle backward and upward thus producing a slight rotation of the scapula upon the side of the chest the rhomboidus major acting especially on the inferior angle of the scapula through the tendinous arch by which it is inserted the rhomboid eye acting together with the middle and inferior fibers of the trapezius will retract the scapula end of section 42 recording by Selena Arter