 Section 7 of Grey's Anatomy Part 3. 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 3 by Henry Gray. The Heart, Part 2. Left Vintricle, Vintriculus Sinister. The left Vintricle is longer and more conical in shape than the right, and on transverse section its concavity presents an oval or nearly circular outline. It forms a small part of the sternocostal surface and a considerable part of the diaphragmatic surface of the heart. It also forms the apex of the heart. Its walls are about three times as thick as those of the right Vintricle. Its interior presents the following parts for examination. The left atrioventricular opening, mitral orifice, is placed below and to the left of the aortic orifice. It is a little smaller than the corresponding aperture of the opposite side, admitting only two fingers. It is surrounded by a dense fibrous ring covered by the lining membrane of the heart and is guarded by the bicuspid or mitral valve. The aortic opening is a circular aperture in front and to the right of the atrioventricular, from which it is separated by the anterior cusp of the bicuspid valve. Its orifice is guarded by the aortic simulunar valves. The portion of the Vintricle immediately below the aortic orifice is termed the aortic vestibule and possesses fibrous instead of muscular walls. The bicuspid or mitral valve, valvula bicuspidalis or metralis, is attached to the circumference of the left atrioventricular orifice in the same way that the tricuspid valve is on the opposite side. It consists of two triangular cusps formed by duplicatures of the lining membrane strengthened by fibrous tissue and containing a few muscular fibers. The cusps are of unequal size and are larger, thicker, and stronger than those of the tricuspid valve. The larger cusp is placed in front and to the right between the atrioventricular and aortic orifices and is known as the anterior or aortic cusp. The smaller or posterior cusp is placed behind and to the left of the opening. Two smaller cusps are usually found at the angles of junction of the larger. The cusps of the bicuspid valve are furnished with cordy tendony which are attached in a manner similar to those on the right side. They are, however, thicker, stronger, and less numerous. The aortic semi-lunar valves are three in number and surround the orifice of the aorta. Two are anterior, right and left and one posterior. They are similar in structure and in their mode of attachment to the pulmonary semi-lunar valves but are larger, thicker, and stronger. The lunuli are more distinct and the noduli or corpora erentee thicker and more prominent. Opposite the valves, the aorta presents slight dilatations, the aortic sinuses, sinuses of val salva which are larger than those at the origin of the pulmonary artery. The trabeculae carnae are of three kinds like those upon the right side but they are more numerous and present a dense interlacement especially at the apex and upon the posterior wall of the ventricle. The musculae papillaries are two in number, one being connected to the anterior the other to the posterior wall. They are of large size and end in rounded extremities from which the cordy tendony arise. The cordy tendony from each papillary muscle are connected to both cusps of the bicuspid valve. Ventricular septum. Septum ventricularum interventricular septum. The ventricular septum is directed obliquely backward and to the right and is curved with a convexity toward the right ventricle. Its margins correspond with the anterior and posterior longitudinal sulci. The greater portion of it is thick and muscular and constitutes the muscular ventricular septum but its upper and posterior part which separates the aortic vestibule from the lower part of the right atrium and upper part of the right ventricle is thin and fibrous and is termed the membranous ventricular septum. An abnormal communication may exist between the ventricles at this part owing to defective development of the membranous septum. Structure. The heart consists of muscular fibers and of fibrous rings which serve for their attachment. It is covered by the visceral layer of the cirrus pericardium, epicardium, and lined by the endocardium. Between these two membranes is the muscular wall or myocardium. The endocardium is a thin, smooth membrane which lines and gives the glistening appearance to the inner surface of the heart. It assists in forming the valves by its reduplications and is continuous with the lining membrane of the large blood vessels. It consists of connective tissue and elastic fibers attached to the muscular structure by loose elastic tissue which contains blood vessels and nerves. Its free surface is covered by endothelial cells. The fibrous rings surround the atrioventricular and arterial orifices and are stronger upon the left than on the right side of the heart. The atrioventricular rings serve for the attachment of the muscular fibers of the atria and ventricles and for the attachment of the blood vessels and valves. The left atrioventricular ring is closely connected by its right margin with the aortic arterial ring. Between these and the right atrioventricular ring is a triangular mass of fibrous tissue, the trigonum fibrosum which represents the oscortus seen in the heart of some of the larger animals as the ox and elephant. Lastly, there is the tendinous band already referred to on the posterior surface of the conus arteriosus. The fibrous rings surrounding the arterial orifices serve for the attachment of the great vessels and semilunar valves. Each ring receives by its ventricular margin the attachment of some of the muscular fibers of the ventricles. Its opposite margin presents three deep semicircular notches to which the middle coat of the artery is firmly fixed. The artery to its fibrous ring is strengthened by the external coat and cirrus membrane externally and by the endocardium internally. From the margins of the semicircular notches the fibrous structure of the ring is continued into the segments of the valves. The middle coat of the artery in this situation is thin and the vessel is dilated to form the sinuses of the aorta and pulmonary artery. Cardiac muscular tissue The fibers of the heart differ very remarkably from those of other striped muscles. They are smaller by one third and their transverse striae are by no means so well marked. They show faint longitudinal striation. The fibers are made up of distinct quadrangular cells joined end to end so as to form a sensation. Each cell contains a clear oval nucleus located near its center. The extremities of the cells have a tendency to branch or divide the subdivisions uniting with offsets from other cells and thus producing an anastomosis of the fibers. The connective tissue between the bundles of fibers is much less than an ordinary striped muscle and no sarcolemma has been proved to exist. Perkinje fibers Between the endocardium and the ordinary cardiac muscle are found embedded in a small amount of connective tissue peculiar fibers known as Perkinje fibers. They are found in certain mammals and in birds and can be best seen in the sheep's heart where they form a considerable portion of the moderator band and also appear as gelatinous looking strands on the inner walls of the atria and ventricles. They also occur in the human heart associated with the terminal distributions of the bundle of his. The fibers are very much larger in size than the cardiac cells and differ from them in several ways. In longitudinal section they are quadrilateral in shape being about twice as long as they are broad. The central portion of each fiber contains one or more nuclei and is made up of granular protoplasm with no indication of striations. The peripheral portion is clear and has distinct transverse striations. The fibers are intimately connected with each other possess no definite sarco-lima and do not branch. The muscular structure of the heart consists of bands of fibers which present an exceedingly intricate interlacement. They comprise A. The fibers of the atria B. The fibers of the ventricles and C. The atria-ventricular The atria-ventricular bundle of his. The fibers of the atria are arranged in two layers a superficial common to both cavities and a deep proper to each. The superficial fibers are most distinct on the front of the atria across the bases of which they run in a transverse direction forming a thin and incomplete layer. Some of these fibers run into the atrial septum. The deep fibers consist of looped and annular fibers. The looped fibers pass upward over each atrium being attached by their two extremities to the corresponding atrio-ventricular ring in front and behind. The annular fibers surround the auriculi and form annular bands around the terminations of the veins and around the fossa ovalis. The fibers of the ventricles are arranged in a complex manner and various accounts have been given of their course and connections. The following description is based on the work of McCallum. They consist of superficial and deep layers, all of which with the exception of two are inserted into the papillary muscles of the ventricles. The superficial layers consist of the following. A. Fibers which spring from the tendon of the conus arteriosus and sweep downward and toward the left across the anterior longitudinal socus and around the apex of the heart, where they pass upward and inward to terminate in the papillary muscles of the left ventricle. Those arising from the upper half of the tendon of the conus arteriosus pass to the anterior papillary muscle. Those from the lower half to the posterior papillary muscle and the papillary muscles of the septum. B. Fibers which arise from the right atrio-ventricular ring and run diagonally across the diaphragmatic surface of the right ventricle and around its right border onto its costo-sternal surface where they dip beneath the fibers just described and crossing the anterior longitudinal socus wind around the apex of the heart and end in the posterior papillary muscle of the left ventricle. C. Fibers which spring from the left atrio-ventricular ring and crossing the posterior longitudinal socus pass successively into the right ventricle and end in its papillary muscles. The deep layers are three in number. They arise in the papillary muscles of one ventricle and curving in an S-shaped manner turn in at the longitudinal socus and end in the papillary muscles of the other ventricle. The layer which is most superficial in the right ventricle lies next the lumen of the left and vice versa. Those of the first layer almost encircle the right ventricle and crossing in the septum to the left unite with the superficial fibers from the right atrio-ventricular ring to form the posterior papillary muscle. Those of the second layer have a less extensive course in the wall of the right ventricle and a correspondingly greater course in the left where they join with the superficial fibers from the anterior half to form the papillary muscles of the septum. Those of the third layer pass almost entirely around the left ventricle and unite with the superficial fibers from the lower half of the tendon of the conus arteriosus to form the anterior papillary muscle. Besides the layers just described there are two bands which do not end in papillary muscles. One springs from the right atrio-ventricular ring and crosses in the atrio-ventricular septum. It then encircles the deep layers of the left ventricle and ends in the left atrio-ventricular ring. The second band is apparently confined to the left ventricle. It is attached to the left atrio-ventricular ring and encircles the portion of the ventricle adjacent to the aortic orifice. The atrio-ventricular bundle of his is the only direct muscular connection known to exist between the atria and the ventricles. Its cells differ from ordinary cardiac muscle cells in being more spindle-shaped. They are, moreover, more loosely arranged and have a richer vascular supply than the rest of the heart muscle. It arises in connection with two small collections of spindle-shaped cells, the sinoatrial and atrio-ventricular nodes. The sinoatrial node is situated on the anterior border of the opening of the superior vena cava. From it, strands of fusiform fibers run under the endocardium of the wall of the atrium to the atrio-ventricular node. The atrio-ventricular node lies near the orifice of the coronary sinus in the annular and septal fibers of the right atrium. From it, the atrio-ventricular bundle passes forward in the lower part of the membranous septum and divides into right and left vesiculi. These run down in the right and left ventricles, one on either side of the ventricular septum, covered by endocardium. In the lower parts of the ventricles, they break up into numerous strands which end in the papillary muscles and in the ventricular muscle generally. The greater portion of the atrio-ventricular bundle consists of narrow, somewhat fusiform fibers, but its terminal strands are composed of Purkinje fibers. Dr. A. Morrison has shown that in the sheep and pig, the atrio-ventricular bundle is a great avenue for the transmission of nerves from the auricular to the ventricular heart, large and numerous nerve trunks entering the bundle and coursing with it. From these, branches pass off and form plexuses around groups of Purkinje cells. And from these plexuses, fine fibrils go to innervate individual cells. Clinical and experimental evidence go to prove that this bundle conveys the impulse to systolic contraction from the atrial septum to the ventricles. Vessels and nerves The arteries supplying the heart are the right and left coronary from the aorta. The veins end in the right atrium. The lymphatics end in the thoracic and right lymphatic ducts. The nerves are derived from the cardiac plexus, which are formed partly from the vagae and partly from the sympathetic trunks. They are freely distributed both on the surface and in the substance of the heart, the separate neurofilaments being furnished with small ganglia. The cardiac cycle and the actions of the valves. By the contractions of the heart, the blood is pumped through the arteries to all parts of the body. These contractions occur regularly and at the rate of about 70 per minute. Each wave of contraction or period of activity is followed by a period of rest, the two periods constituting what is known as a cardiac cycle. Each cardiac cycle consists of three phases which succeed each other as follows. One a short simultaneous contraction of both atria, termed the atrial systole, followed after a slight pause by two, a simultaneous but more prolonged contraction of both ventricles named the ventricular systole. And three, a period of rest during which the whole heart is relaxed. The atrial contraction commences around the venous openings and sweeping over the atria forces their contents through the atrial ventricular openings into the ventricles, regurgitation into the veins being prevented by the contraction of their muscular coats. When the ventricles contract the icuspid valves are closed and prevent the passage of the blood back into the atria. The musculae papillaries at the same time are shortened and pulling on the cordy tendony prevent the inversion of the valves into the atria. As soon as the pressure in the ventricles exceeds that in the pulmonary artery and aorta the valves guarding the arthuses of these vessels are opened and the blood is driven from the right ventricle into the pulmonary artery and from the left into the aorta. The moment the systole of the ventricles ceases the pressure of the blood in the pulmonary artery and aorta closes the pulmonary and aortic semilunar valves to prevent regurgitation of blood into the ventricles. The valves remaining shut until reopened by the next ventricular systole. During the period of rest the tension of the tricuspid and bicuspid valves is relaxed and the blood is flowing from the veins into the atria being aspirated by negative intrathoracic pressure and slightly also from the atria into the ventricles. The average duration of a cardiac cycle is about 8 tenths of a second made up as follows. Atrial systole 1 tenth Atrial diastole 7 tenths Ventricular systole 3 tenths Ventricular diastole 5 tenths Total systole 4 tenths Complete diastole 4 tenths Complete diastole 4 tenths The rhythmical action of the heart is muscular in origin. That is to say the heart muscle itself possesses the inherent property of contraction apart from any nervous stimulation. The more embryonic the muscle the better is it able to initiate and propagate the contraction wave. This explains why the normal systole of the heart starts at the entrance of the veins for there the muscle is most embryonic in nature. At the atrioventricular junction there is a slight pause in the wave of muscular contraction. To obviate this so far as possible a peculiar band of marked embryonic type passes across the junction and so carries on the contraction wave to the ventricles. This band composed of special fibres is the atrioventricular bundle of his. The nerves although not concerned in originating the muscles of the heart muscle play an important role in regulating their force and frequency in order to subserve the physiological needs of the organism. End of section 7 Section 8 of Grey's Anatomy Part 3 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 Leanne Howlett. Anatomy of the Human Body Part 3 by Henry Gray. Peculiarities in the vascular system in the fetus. The chief peculiarities of the fetal heart are the direct communication between the atria through the foramen oval and the large size of the valve of the inferior vena cava. Among other peculiarities the following may be noted. 1. In early fetal life the heart lies immediately below the mandibular arch and is relatively large in size. As development proceeds it is gradually drawn within the thorax but at first it lies in the middle line. Toward the end of pregnancy it gradually becomes oblique in direction. 2. For a time the atrial portion exceeds the ventricular in size and the walls of the ventricles are of equal thickness. Toward the end of fetal life the ventricular portion becomes the larger and the wall of the left ventricle exceeds that of the right in thickness. 3. Its size is large as compared with that of the rest of the body. The proportion at the second month being 1 to 50 and at birth 1 to 120 while in the adult the average the foramen oval situated at the lower part of the atrial septum forms a free communication between the atria until the end of fetal life. A septum, septum secundum grows down from the upper wall of the atrium to the right of the primary septum in which the foramen oval is situated. Shortly after birth it fuses with the primary septum and the foramen oval is obliterated. The valve of the inferior vena cava serves to direct the blood from that vessel through the foramen oval into the left atrium. The peculiarities in the arterial system of the fetus are the communication between the pulmonary artery and the aorta by means of the ductus arteriosus and the continuation of the hypogastric arteries as the umbilical arteries to the placenta. The ductus arteriosus is a short tube about 1.25 centimeters in length at birth and of the diameter of a goose quill. In the early condition it forms the continuation of the pulmonary artery and opens into the aorta just beyond the origin of the left subclavian artery and so conducts the greater amount of the blood from the right ventricle into the aorta. When the branches of the pulmonary artery have become larger relatively to the ductus arteriosus the bladder is chiefly connected to the left pulmonary artery. The hypogastric arteries run along the sides of the bladder and thence upward on the back of the anterior abdominal wall to the umbilicus. Here they pass out of the abdomen and are continued as the umbilical arteries in the umbilical cord to the placenta. They convey the fetal blood to the placenta. The peculiarities in the venous are the communications established between the placenta and the liver and portal vein through the umbilical vein and between the umbilical vein and the inferior vena cava through the ductus venosis. Fetal circulation The fetal blood is returned from the placenta to the fetus by the umbilical vein. This vein enters the abdomen at the umbilicus and passes upward along the free margin of the liver to the under surface of that organ where it gives off two or three branches one of large size to the left lobe and others to the lobus quadratus and lobus caudatus. At the portahepatus transverse fissure of the liver it divides into two branches. Of these the larger is joined by the portal vein and enters the right lobe. The smaller is continued upward under the name of the ductus venosis and joins the inferior vena cava. The blood therefore which traverses the umbilical vein passes to the inferior vena cava in three different ways. A considerable quantity circulates through the liver with the portal venous blood before entering the inferior vena cava by the hepatic veins. Some enters the liver directly and is carried to the inferior cava by the hepatic veins. The remainder passes directly into the inferior vena cava through the ductus venosis. In the inferior vena cava the blood carried by the ductus venosis and hepatic veins become mixed with that returning from the lower extremities and abdominal wall. It enters the right atrium and guided by the valve of the inferior vena cava passes through the foramen oval into the left atrium with a small quantity of blood returned from the lungs by the pulmonary veins. From the left atrium it passes into the left ventricle and from the left ventricle into the aorta by means of which it is distributed almost entirely to the head and upper extremities a small quantity being probably carried into the descending aorta. From the head and upper extremities the blood is returned by the superior vena cava to the right atrium and it mixes with a small portion of the blood from the inferior vena cava. From the right atrium it descends into the right ventricle and thence passes into the pulmonary artery. The lungs of the fetus being inactive only a small quantity of the blood of the pulmonary artery is distributed to them by the right and left pulmonary arteries and returned by the pulmonary veins to the left atrium. The greater part passes through this arteriosus into the aorta where it mixes with a small quantity of the blood transmitted by the left ventricle into the aorta. Through this vessel it descends and is in part distributed to the lower extremities and the viscera of the abdomen and pelvis but the greater amount is conveyed by the umbilical arteries to the placenta. From the preceding account of the circulation of the blood in the fetus the following facts will be evident. 1. The placenta serves the purposes of nutrition and excretion receiving the impure blood from the fetus and returning it purified and charged with additional nutritive material. 2. Nearly the whole of the blood of the umbilical vein traverses the liver before entering the inferior vena cava hence the large size of the liver especially at an early period of fetal life. 3. The right atrium is the point of meeting of a double current the blood in the inferior vena cava being guided by the valve of this vessel into the left atrium while that in the superior vena cava descends into the right ventricle. 4. At an early period of fetal life it is highly probable that the two streams are quite distinct for the inferior vena cava opens almost directly into the left atrium and the valve of the inferior vena cava exclude the current from the right ventricle. At a later period as a separation between the two atria becomes more distinct it seems probable that some mixture of the two streams must take place. 4. The pure blood carried from the placenta to the fetus by the umbilical vein mixed with the blood from the portal vein in inferior vena cava passes almost directly to the arch of the aorta and is distributed by the branches of that vessel to the head and upper extremities. 5. The blood contained in the descending aorta chiefly derived from that which is already circulated through the head and limbs together with a small quantity from the left ventricle is distributed to the abdomen in lower extremities. 6. Changes in the vascular system at birth at birth when respiration is established an increased amount of blood from the pulmonary artery passes through the lungs and the placental circulation is cut off. The foramen oval is closed by about the tenth day after birth. The valvular fold above mentioned adheres to the margin of the foramen for the greater part of its circumference. But a slit like opening is left between the two atria above and this sometimes persists. The ductus arteriosus begins to contract immediately when respiration is established and is completely closed from the fourth to the tenth day. It ultimately degenerates into an impervious cord the ligamentum arteriosum which connects the left pulmonary artery to the arch of the aorta. Of the hypogastric arteries the parts extending from the sides of the bladder to the umbilicus become obliterated between the second and fifth days after birth in other words the lateral umbilical ligaments toward the abdominal cavity carrying on them folds of peritoneum. The umbilical vein and ductus venosis are completely obliterated between the second and fifth days after birth. The former becomes the ligamentum tiris the latter the ligamentum venosum of the liver. End of section 8 Recording by Leanne Howlett Part 3 This is a LibriVox recording. All LibriVox recordings are in the public domain. For more information or to volunteer please visit LibriVox.org Anatomy of the Human Body Part 3 by Henry Gray The Arteries Introduction The distribution of the systemic arteries is like a highly ramified tree the common trunk of which formed by the aorta is ventricle while the smallest ramifications extend to the peripheral parts of the body and the contained organs. Arteries are found in all parts of the body except in the hairs, nails, epidermis, cartilages, and cornea. The larger trunks usually occupy the most protected situations running in the limbs along the flexor surface where they are less exposed to injury. There is considerable variation in the mode of division of the arteries. Arteries are found at the same point as may be observed in the celiac artery in the thyrocervical trunk. The vessel may give off several branches in succession and still continue as the main trunk as is seen in the arteries of the limbs or the division may be dichotomous as for instance when the aorta divides into the two common iliacs. A branch of an artery is smaller than the trunk from which it arises but if an artery divides into two branches the combined sectional area of the arteries in nearly every instance somewhat greater than that of the trunk and the combined sectional area of all the arterial branches greatly exceeds that of the aorta so that the arteries collectively may be regarded as a cone the apex of which corresponds to the aorta and the base to the capillary system. The arteries in their distribution communicate with one another forming what are called anastomoses and these communications are very free between the large as well as between the smaller branches. The anastomosis between trunks of equal size is found where great activity of the circulation is requisite as in the brain. Here the two vertebral arteries unite to form the basilar and the two anterior cerebral arteries are connected by a short communicating trunk. It is also found in the abdomen where the intestinal arteries have very ample anastomoses between their larger branches. In the limbs the anastomoses are most numerous and of largest size around the joints the branches of an artery above uniting with branches from the vessels below. These anastomoses are of considerable interest to the surgeon as it is by their enlargement that a collateral circulation is established after the application of a ligature to an artery. The smaller branches of arteries anastomose more frequently than the larger and between the smallest twigs these anastomoses become so numerous as to constitute a close network that pervades nearly every tissue of the body. Throughout the body generally the larger arterial branches pursue a fairly straight course but in certain situations they are torturous thus the external maxillary artery in its course over the face and the arteries of the lips are extremely torturous to accommodate themselves to the movements of the parts. The uterine arteries are also torturous to accommodate themselves to the increase in size which the uterus undergoes during pregnancy. The pulmonary artery conveys the venous blood from the right ventricle of the heart to the lungs. It is a short, wide vessel about 5 cm in length and 3 cm in diameter arising from the conus arteriosus of the right ventricle. It extends obliquely upward and backward passing at first in front and then to the left of the ascending aorta as far as the under surface of the aortic arch where it divides about the level of the fibrocartilage between the fifth and sixth thoracic vertebrae into right and left branches of nearly equal size. Relations. The hull of this vessel is contained within the pericardium. It is enclosed with the ascending aorta in a single tube of the visceral layer of the cirrus pericardium which is continued upward upon them from the base of the heart. The fibrous layer of the pericardium is gradually lost upon the external coats of the two branches of the artery. In front, the pulmonary artery is separated from the anterior end of the second left intercostal space by the pleura and the left lung in addition to the pericardium. It rests at first upon the ascending aorta and higher up lies in front of the left atrium on a plain posterior to the ascending aorta. On either side of its origin is the auricula of the corresponding atrium and a coronary artery. The left coronary artery passing in the first part of its course behind the vessel. The superficial part of the cardiac plexus lies above its bifurcation between it and the arch of the aorta. The right branch of the pulmonary artery ramus dexter apulinalis longer and larger than the left runs horizontally to the right behind the ascending aorta in superior vena cava and in front of the right bronchus to the root of the right lung where it divides into two branches. The lower and larger of these goes to the middle and lower lobes of the lung. The upper and smaller is connected to the upper lobe. The left branch of the pulmonary artery ramus sinister apulinalis shorter and somewhat smaller than the right passes horizontally in front of the descending aorta and left bronchus to the root of the left lung where it divides into two branches one for each lobe of the lung. Above it is connected to the concavity of the aortic arch by the ligamentum arteriosum on the left of which is the left recurrent nerve and on the right is the superficial part of the cardiac plexus. Below it is joined to the upper left pulmonary vein by the ligament of the left vena cava. The terminal branches of the pulmonary arteries will be described with the anatomy of the lungs. End of section 9 Section 10 of Grey's Anatomy Part 3 This is a LibriVox recording. All LibriVox recordings are public domain. For more information or to volunteer please visit LibriVox.org Recording by Suzanne Olson Anatomy of the Human Body Part 3 by Henry Gray The aorta The aorta is the main trunk of a series of vessels which convey the oxygenated blood to the tissues of the body for their nutrition. It commences at the upper part of the left ventricle where it is about 3 cm in diameter and after ascending for a short distance arches backward to the left side over the root of the left lung. It then descends within the thorax on the left side of the vertebral column, passes into the abdominal cavity through the aortic hiatus in the diaphragm and ends considerably diminished in size. About 1.75 cm in diameter opposite the lower border of the fourth lumbar vertebra by dividing into the right and left common iliac arteries. Hence it is described in several portions these the ascending aorta the arch of the aorta and the descending aorta which last is again divided into the thoracic and abdominal aorta. The ascending aorta aorta ascendants The ascending aorta is about 5 cm in length It commences at the upper part of the base of the left ventricle on a level with a lower border of the third costal cartilage behind the left half of the sternum. It passes obliquely upward forward into the right in the direction of the heart's axis as high as the upper border of the second right costal cartilage describing a slight curve in its course and being situated about 6 cm behind the posterior surface of the sternum. At its origin it presents opposite the segments of the aortic valve three small dilatations called the aortic sinuses. At the union of the ascending aorta with the aortic arch the caliber of the vessel is increased owing to a bulging of its right wall. This dilatation is termed the bulb of the aorta and on transverse section presents a somewhat oval figure. The ascending aorta is contained within the pericardium and is enclosed in a tube of the cirrus pericardium common to it and the pulmonary artery. Relations The ascending aorta is covered at its commencement by the trunk of the pulmonary artery in the right auricula and higher up is separated from the sternum by the pericardium the anterior margin of the right lung and some loose areolar tissue and the remains of the thymus. Posteriorly it rests upon the left atrium and right pulmonary artery. On the right side it is in relation with the superior vena cava and right atrium the former lying partly behind it on the left side with the pulmonary artery. Branches The only branches of the ascending aorta are the two coronary arteries which supply the heart. They arise near the commencement of the aorta immediately above the attached margins of the semilunar valves. The coronary arteries The right coronary artery a coronaria cordus dextra arises from the right anterior aortic sinus. It passes at first between the conus arteriosus and the right auricula and then runs in the right portion of the coronary sulcus coursing at first from left to right and then on the diaphragmatic surface of the heart from right to left as far as the posterior longitudinal sulcus down which it continued to the apex of the heart as a posterior descending branch. It gives off a large marginal branch which follows the acute margin of the heart and supplies branches to both surfaces of the right ventricle. It also gives twigs to the right atrium and to the part of the left ventricle which adjoins the posterior longitudinal sulcus. The left coronary artery a coronaria cordus sinistra larger than the right arises from the left anterior aortic sinus and divides into an anterior descending and a circumflex branch. The anterior descending branch passes at first behind the pulmonary artery and then comes forward between that vessel and the left auricula to reach the anterior longitudinal sulcus along which it descends to the incisura apicus cordus. It gives branches to both ventricles. The circumflex branch follows the left part of the coronary sulcus running first to the left and then to the right reaching nearly as far as the posterior longitudinal sulcus. It gives branches to the left atrium and ventricle. There is a free anastomosis between the minute branches of the two coronary arteries in the substance of the heart. Peculiarities These vessels occasionally arise by a common trunk or their number may be increased to three the additional branch being of small size. More rarely there are two additional branches. The arch of the aorta arcus aorta transfers aorta. The arch of the aorta begins at the level of the upper border of the second sternocosal articulation of the right side and runs at first upward backward and to the left in front of the trachea. It is then directed backward on the left side of the trachea and finally passes downward on the left side of the body of the fourth thoracic vertebra which becomes continuous with the descending aorta. It thus forms two curvatures one with its convexity upward the other with its convexity forward and to the left. Its upper border is usually about 2.5 centimeters below the superior border to the manubrium sterni. Relations The arch of the aorta is covered anteriorly by the plurae and anterior margins of the lungs and by the remains of the thymus. As the vessel runs backward its left side is in contact with the left lung and plurae. Passing downward on the left side of this part of the arch are four nerves. In order from backwards these are the left phrenic the lower of the superior cardiac branches of the left vagus the superior cardiac branch of the left sympathetic and the trunk of the left vagus. As the last nerve crosses the arch it gives off its recurrent branch which hooks around below the vessel and then passes upward on its right side. The highest left intercostal vein runs obliquely upward and forward on the left side of the arch between the phrenic and vagus nerves. On the right are the deep part of the cardiac plexus the left recurrent nerve the esophagus and the plastic duct. The trachea lies behind and to the right of the vessel. Above are the inominate left common carotid and left subclavian arteries which arise from the convexity of the arch and are crossed close to their origins by the left inominate vein. Below are the bifurcation of the pulmonary artery the left bronchus the ligamentum anteriorosum the vessel part of the cardiac plexus and the left recurrent nerve. As already stated the ligamentum arteriosum connects the commencement of the left pulmonary artery to the aortic arch. Between the origin of the less subclavian artery and the attachment of the ductus arteriosus the lumen of the fetal aorta is considerably narrowed forming what is termed the aortic isthmus. When the ductus arteriosus the vessel presents a fusiform dilation which hiss has named the aortic spindle the point of junction of the two parts being marked in the concavity of the arch by an indentation or angle. These conditions persist to some extent in the adult where hiss found that the average diameter of the spindle exceeded that of the isthmus by three millimeters. Distinct from this diffuse and moderate stenosis the isthmus is the condition known as coarctation of the aorta or marked stenosis often amounting to complete obliteration of its lumen seen in adults and occurring at or near oftenest a little below the insertion of the ligamentum arteriosum into the aorta. According to Bonet this coarctation is never found in the fetus or at birth and is due to an abnormal extension of the peculiar tissue of the ductus into the aortic wall which gives rise to a simultaneous stenosis of both vessels as it contracts after birth. The ductus is usually obliterated in these cases. An extensive collateral circulation is set up by the costoservicals internal mammaries and the descending branches of the transfer cervical above the stenosis and below it by the first four aortic intercostals and the superior and inferior epigastrics. Peculiarities The height to which the aorta rises in the thorax is usually about 2.5 cm below the upper border of the sternum but it may ascend nearly to the top of the bone. Occasionally it's found 4 cm more rarely from 5 to 8 cm below this point. Occasionally it is found 4 cm more rarely from 5 to 8 cm below this point. Sometimes the aorta arches over the root of the right lung right aortic arch instead of over that of the left and passes down on the right side of the vertebral column, a condition which is found in birds. In such cases all the thoracic and abdominal viscera are transposed. Less frequently the aorta after arching over the root of the right lung is directed to its usual position on the left side of the vertebral column. This peculiarity is not accompanied by transposition of the viscera. The aorta occasionally divides as in some quadrupeds into an ascending and a descending trunk the former of which is directed vertically upward and subdivides into three branches to supply the head and upper extremities. Sometimes the aorta subdivides near its origin into two branches which soon reunite. In one of these cases the esophagus and trachea were found to pass through the interval between the two branches. This is the normal condition of the vessel and the reptilia. Branches the branches given off from the arch of the aorta are three in number the inominent the left common carotid and the left subclavian. Peculiarities position of the branches the branches instead of arising from the highest part of the arch may spring from the commencement of the arch or upper part of the ascending aorta or the distance between them at their origins may be increased or diminished the most frequent change in this respect being the approximation of the left carotid toward the inominent artery the number of the primary branches may be reduced to one or more commonly two the left carotid arising from the inominent artery or more rarely the carotid and subclavian arteries of the left side arising from a left inominent artery but the number may be increased to four from the right carotid and subclavian arteries arising directly from the aorta the inominent being absent in most of these latter cases the right subclavian has been found to arise from the left end of the arch in other cases it is the second or third branch given off instead of the first another common form in which there are four primary branches is that in which the left vertebral artery arises from the arch of the aorta between the left carotid and subclavian arteries lastly the number of trunks from the arch may be increased to five or six in these instances the external and internal carotids arise separately from the arch the common carotid being absent on one or both sides in some cases six branches have been found and this condition is associated with the origin of both vertebral arteries from the arch number usual arrangement different when the aorta arches over to the right side the three branches have an arrangement the reverse of what is usual the inominent artery is the left one and the right carotid and subclavian arise separately in other cases where the aorta takes its usual course the two carotids may be joined in a common trunk and the subclavians arise separately from the arch the right subclavian generally arising from the left end of the arch in some instances other arteries spring from the arch of the aorta of these the most common are the bronchial one or both and the thyroidia ima but the internal mammary and the inferior thyroid have been seen to arise from this vessel the inominent artery a anonoma brachiosophallic artery the inominent artery is the largest branch of the arch of the aorta and is from 10 centimeters in length it arises on a level with the upper border of the second right costal cartilage from the commencement of the arch of the aorta on a plane anterior to the origin of the left carotid it ascends obliquely upward backward and to the right to the level of the upper border of the right sternocleovicular articulation where it divides into the right common carotid right subclavian arteries relations anteriorly it is separated from the manubrium sterni by the sternohioidis and sternothyroidis the remains of the thymus the left inominent and right inferior thyroid veins which cross its root and sometimes the superior cardiac branches of the right vagus posterior to it is the trachea which it crosses obliquely on the right side are the right inominent vein the superior vena cava the right phrenic nerve and the pleura and on the left side the remains of the thymus the origin of the left common carotid artery the inferior thyroid veins and the trachea branches the inominent artery usually gives off no branches but occasionally a small branch the thyroidia ima arises from it sometimes it gives off a thymic or bronchial branch the thyroidia ima a thyroidia ima ascends in front of the trachea to the lower part of the thyroid gland which it supplies it varies greatly in size and appears to compensate for deficiency or absence of one of the other thyroid vessels it occasionally arises from the carotid, the subclavian or the internal mammary point of division the inominent artery sometimes divides the level of the sternoclavicular joint less frequently below it position when the aortic arch is on the right side the inominent is directed to the left side of the neck collateral circulation alan burns demonstrated on the dead subject the establishment of the collateral circulation after ligature of the inominent artery by tying and dividing that artery he then found that even coarse injection impelled into the aorta passed freely by the anastomosing branches into the arteries of the right arm filling them and all the vessels of the head completely the branches by which the circulation would be carried on are very numerous the communications across the middle line between the branches of the carotid arteries of the opposite sides would be available for the supply of blood to the right side of the head neck while the anastomosis between the costo cervical of the subclavian and the first aortic intercostal C-infra on the collateral circulation after obliteration of the thoracic aorta would bring the blood by a free and direct course to the right subclavian the numerous connections also between the intercostal arteries and the branches of the axillary and internal mammary arteries would doubtless assist in the supply of blood to the right arm while the inferior epigastric from the external iliac would by means of its anastomosis with the internal mammary compensate for any deficiency in the vascularity of the wall of the chest end of section 10 part 3 recorded by Suzanne Olson section 11 of Grey's Anatomy part 3 this is a LibriVox recording all LibriVox recordings are in the public domain for more information or to volunteer please visit LibriVox.org Anatomy of the Human Body part 3 by Henry Gray the common carotid artery the principal arteries of supply to the head and neck are the two common carotids they ascend in the neck and each divides into two branches this one the external carotid supplying the exterior of the head the face and the greater part of the neck two the internal carotid supplying to a great extent the parts within the cranial and orbital cavities the common carotid artery a carotis communis the common carotid arteries differ in length and in their mode of origin the right begins at the bifurcation of the inominent artery behind the sternoclavicular joint and is confined to the neck the left springs from the highest part of the arch of the aorta to the left of and on a plane posterior to the inominent artery it consists of a thoracic and a cervical portion the thoracic portion of the left common carotid artery ascends from the arch of the aorta through the superior mediastinum to the level of the left sternoclavicular joint where it is continuous with the cervical portion relations in front it is separated from the manubrium sterni by the sternohyroideus the anterior portions of the left pleura and lung the left inominent vein and the remains of the thymus behind it lies on the trachea esophagus left recurrent nerve and thoracic duct to its right side below is the inominent artery and above the trachea the inferior thyroid veins and the remains of the thymus to its left side are the left vagus and phrenic nerves left pleura and lung the left subclavian artery is posterior and slightly lateral to it the cervical portions of the common carotid resemble each other so closely that one description will apply to both each vessel passes obliquely upward from behind the sternoclavicular articulation to the level of the upper border of the thyroid cartilage where it divides into the external and internal carotid arteries at the lower part of the neck the two common carotid arteries are separated from each other by a very narrow interval which contains the trachea but at the upper part the thyroid gland the larynx and pharynx project forward between the two vessels the common carotid artery is contained in a sheath which is derived from the deep cervical fascia and encloses also the internal regular vein and vagus nerve the vein lying lateral to the artery and the nerve between the artery and vein on a plane posterior to both on opening the sheath each of these three structures is seen to have a separate fibrous investment relations at the lower part of the neck the artery is very deeply seated being covered by the integument superficial fascia platysma and deep cervical fascia the sternocleidomastoidius sternohioidius sternothyroidius and amohioidius in the upper part of its course it is more superficial being covered merely by the integument the superficial fascia platysma, deep cervical fascia and medial margin of the sternocleidomastoidius when the latter muscle is drawn backward the artery is seen to be contained in a triangular space the carotid triangle bounded behind by the sternocleidomastoidius above by the stylohyoidius and posterior belly of the digastricus and below by the superior belly of the amohioidius this part of the artery is crossed obliquely from its medial to its lateral side by the sternocleidomastoid branch of the superior thyroid artery it is also crossed by the superior and middle thyroid veins which end in the internal jugular descending in front of its sheath is the descending branch of the hypoglossal nerve this filament being joined by one or two branches from the cervical nerves which cross the vessel obliquely sometimes the descending branch of the hypoglossal nerve is contained within the sheath the superior thyroid vein crosses the artery near its termination and the middle thyroid vein a little below the level of the cricoid cartilage the anterior jugular vein crosses the artery just above the clavicle but is separated from it by the sternohioidius and sternothyroidius behind the artery is separated from the transverse processes of the cervical vertebrae by the longest coli and longest capitis the sympathetic trunk being interposed between it and the muscles the inferior thyroid artery crosses behind the lower part of the vessel medially it is in relation with the esophagus trachea and thyroid gland which overlaps it the inferior thyroid artery and recurrent nerve being interposed higher up with the larynx and pharynx lateral to the artery are the internal jugular vein and vagus nerve at the lower part of the neck the right recurrent nerve crosses obliquely behind the artery the right internal jugular vein diverges from the artery left approaches and often overlaps the lower part of the artery behind the angle of bifurcation of the common carotid artery is a reddish brown oval body known as the glomus caroticum carotid body it is similar in structure to the glomus castagem castageal body which is situated on the middle sacral artery peculiarities as to origin the right common carotid may arise above the level of the upper border of the sternoclavicular articulation this variation occurs in about 12% of cases in other cases the artery may arise as a separate branch from the arch of the aorta or in conjunction with the left carotid the left common carotid varies in its origin more than the right in the majority of abnormal cases it arises with the predominant artery if that artery is absent the two carotids arise usually by a single trunk it is rarely joined with the left subclavian except in cases of transposition of the aortic arch peculiarities as to point of division in the majority of abnormal cases this occurs higher than usual the artery dividing opposite or even above the hyoid bone rarely it occurs below opposite the middle of the larynx or the lower border of the criacoid cartilage one case is related by morgagni where the artery was only 4 cm in length and divided at the root of the neck very rarely the common carotid ascends in the neck without any subdivision either the external or the internal carotid being wanting and in a few cases the common carotid is often found to be absent the external and internal carotids arising directly from the arch of the aorta this peculiarity existed on both sides in some instances on one side in others occasional branches the common carotid usually gives off no branch previous to its bifurcation but it occasionally gives origin to the superior thyroid or its laryngeal branch the ascending pharyngeal the inferior thyroid or more rarely the vertebral artery collateral circulation after ligature of the common carotid the collateral circulation can be perfectly established by the free communication which exists between the carotid arteries of opposite sides both without and within the cranium and by enlargement of the branches of the subclavian artery on the side corresponding to that on which the vessel has been tied the chief communications outside the skull take place between the superior and inferior thyroid arteries and the profunda services and ramus descendants of the occipital the vertebral takes the place of the internal carotid within the cranium end of section 11 recording by Selena Arter section 12 of Gray's Anatomy Part 3 this is a LibriVox recording all LibriVox recordings are in the public domain for more information or to volunteer please visit LibriVox.org anatomy of the human body Part 3 by Henry Gray section 12 part 1 the external carotid artery a. carotis externa the external carotid artery begins opposite the upper border of the thyroid cartilage and taking a slightly curved course passes upward and forward and then inclines backward to the space behind the neck of the mandible where it divides into the superficial temporal and internal maxillary arteries it rapidly diminishes in size in its course up the neck owing to the number and large size of the branches given off from it in the child it is somewhat smaller than the internal carotid but in the adult the two vessels are of nearly equal size at its origin this artery is more superficial and placed nearer the middle line than the internal carotid and is contained within the carotid triangle relations the external carotid artery is covered by the skin of the facial fascia platysma deep fascia and anterior margin of the sternocleidomastodius it is crossed by the hypoglossal nerve by the lingual reynine, common facial and superior thyroid veins and by the digastricus and stylohyoidius higher up it passes deeply into the substance of the parotid gland where it lies deep to the facial nerve and the junction of the lateral and internal maxillary veins medial to it are the hyoid bone the wall of the pharynx the superior laryngeal nerve and a portion of the parotid gland lateral to it in the lower part of its course is the internal carotid artery posterior to it near its origin is the superior laryngeal nerve and higher up it is separated from the internal carotid styloglossus and stylopharyngeus the glasopharyngeal nerve the pharyngeal branch of the vagus and part of the parotid gland branches the branches of the external carotid artery may be divided into four sets one anterior superior thyroid lingual external maxillary two posterior auricular ascending pharyngeal terminal superficial temporal internal maxillary one the superior thyroid artery arises from the external carotid artery just below the level of the greater corneal of the hyoid bone and ends in the thyroid gland relations from its origin under the anterior border of the sternocleidomastodias it runs upward and forward for a short distance in the carotid triangle where it is covered by the skin platysma and fascia it then arches downward beneath the omohyoidias sternohyoidias and sternothyroidias to its medial side are the constrictor pharyngeus inferior and the external branch of the superior laryngeal nerve branches it distributes twigs to the adjacent muscles and numerous branches to the thyroid gland anastomosing with its fellow of the opposite side and with the inferior thyroid arteries the branches to the gland are generally two in number one, the larger supplies principally the anterior surface on the isthmus of the gland in anastomoses with the corresponding artery of the opposite side a second branch descends on the posterior surface of the gland and anastomoses with the inferior thyroid artery besides the arteries distributed to the muscles and to the thyroid gland the branches of the superior thyroid are hyoid, sternocleidomastoid superior laryngeal cricothyroid the hyoid branch ramus hyoidias infrahoyoid branch is small and runs along the lower border of the hyoid bone beneath the thyroid hyoidias and anastomoses with the vessel of the opposite side the sternocleidomastoid branch ramus sternocleidomastoidias sternomastoid branch runs downward and lateral across the sheath of the common carotid artery and supplies the sternocleidomastoidias and neighboring muscles and integment it frequently arises as a separate branch from the external carotid the superior laryngeal artery a laryngea superior larger than either of the preceding accompanies the internal laryngeal branch of the superior laryngeal nerve beneath the thyroid hyoidias it pierces the hyothyroid membrane and supplies the muscles mucous membrane and glands of the larynx anastomosing with the branch from the opposite side the cricothyroid branch ramus cricothyroidias is small and runs transversely across the cricothyroid membrane communicating with the artery of the opposite side the lingual artery a lingualis arises from the external carotid between the superior thyroid and external maxillary it first runs obliquely upward and medial word to the greater of the hyoid bone it then curves downward and forward forming a loop which is crossed by the hypoglossal nerve and passing beneath the digastricus and the stylohyoidias it runs horizontally forward beneath the hyoglossus and finally ascending almost perpendicularly to the tongue turns forward on its lower surface as far as the tip under the name of the profunda lingui relations its first or oblique portion is superficial and is contained within the carotid triangle it rests upon the constrictor for ringus medius and is covered by the platysma and the fascia of the neck its second or curved portion also lies upon the constrictor for ringus medius being covered at first by the tendon of the digastricus and by the stylohyoidias and afterward by the hyoglossus its third or horizontal portion lies between the hyoglossus and genioglossus the fourth or terminal part under the name of the profunda lingui reynine artery runs along the under surface of the tongue to its tip here it is superficial being covered only by the mucous membrane above it is the longitude analysis inferior and on the medial side the genioglossus the hypoglossal nerve crosses the first part of the lingual artery but is separated from the second part by the hyoglossus branches the branches of the lingual artery are hyoid dorsalis lingui sublingual profunda lingui the hyoid branch ramus hyoidius suprahyoid branch runs along the upper border of the hyoid bone supplying the muscles attached to it and anastomocene with its fellow of the opposite side the artery eye dorsalis lingui ramidorsalis lingui consist usually of two or three small branches which arise beneath the hyoglossus they ascend to the back of the dorsum of the tongue and supply the mucous membrane in this situation the glossopalatine arch the tonsil soft palate and epiglottis anastomocene with the vessels of the opposite side the sublingual artery a sublinguelis arises at the anterior margin of the hyoglossus and runs forward between the genioglossus and mylohyoidius to the sublingual gland it supplies the gland and gives branches to the mylohyoidius and neighboring muscles and to the mucous membrane of the mouth and gums one branch runs behind the alveolar process of the mandible in the substance of the gum to anastomose with a similar artery from the other side another pierces the mylohyoidius and anastomoses with the submental branch of the external maxillary artery the arterya profunda lingui renine artery is the terminal portion of the lingual artery it pursues a tortuous course and runs along the under surface of the tongue below the longitudinalis inferior and above the mucous membrane it lies on the lateral side of the genioglossus accompanied by the lingual nerve at the tip of the tongue it is said to anastomose with the artery of the opposite side but this is denied by hurdle in the mouth these vessels are placed one on either side of the phrenulum lingui the external maxillary artery a maxillaris externa facial artery arises in the carotid triangle a little above the lingual artery and sheltered by the ramus of the mandible passes obliquely up beneath the dagastricus and stylohyoidius over which it arches to the posterior grove on the posterior surface of the submaxillary gland it then curves upward over the body of the mandible at the antero inferior angle of the masseter passes forward and upward across the cheek to the angle of the mouth then ascends along the side of the nose and ends at the medial commissure of the eye under the name of the angular artery this vessel both in the neck and on the face is remarkably tortuous in the former situation to accommodate itself to the movements of the pharynx and deglutition and in the latter to the movements of the mandible lips and cheeks relations in the neck its origin is superficial being covered by the integument platysma and fascia it then passes beneath the dagastricus and stylohyoidius muscles and part of the maxillary gland and frequently beneath the hypoglossal nerve it lies upon the constrictory's pharyngous medius and superior the latter of which separates it at the summit of its arch from the lower and back part of the tonsil on the face where it passes over the body of the mandible it is comparatively superficial lying immediately beneath the platysma in its course over the face it is covered by the integument the fat of the cheek and near the angle of the mouth by the platysma, rhizorius and zygomaticus it rests on the buccanator and cananus and passes either over or under the infororbital head of the quadratus labii superioris the anterior facial vein lies lateral to the artery and takes a more direct course across the face where it is separated from the artery by a considerable interval in the neck it lies superficial to the artery the branches of the facial nerve cross the artery from behind forward the branches of the artery may be divided into two sets those given off in the neck, cervical and those on the face facial ascending palatine tonsil glandular, submental muscular facial branches inferior labial superior labial lateral nasal angular, muscular the ascending palatine artery a palatina ascendance arises close to the origin of the external maxillary artery and passes up between the styloglossus and styloferangeus to the side of the pharynx along which it is continued between the constrictor pharynx superior and the pterogortius internus to near the base of the skull it divides near the levator vilei palatine eye into two branches one follows the course of this muscle and winding over the upper border of the constrictor pharynx superior supplies the soft palate and the palatine glands anastomocene with its fellow of the opposite side and with the descending palatine branch of the internal maxillary artery the other pierces the constrictor pharynx superior and supplies the palatine tonsil and auditory tube anastomocene with the tonsil and ascending pharyngeal arteries the tonsil branch ramus tonsilaris ascends between the pterogortius internus and styloglossus and then along the side of the pharynx perforating the constrictor pharynx superior to ramify in the substance of the palatine tonsil and root of the tongue the glandular branches ramiglandularis submaxillary branches consist of three or four large vessels which supply the submaxillary gland some being prolonged to the neighboring muscles lymph glands and integument the submental artery A submentalis the largest of the cervical branches is given off from the facial artery just as that vessel quits the submaxillary gland it runs forward upon the mylohyoidius just below the body of the mandible and beneath the digastricus it supplies the surrounding muscles and anastomoses with the sublingual artery and with the mylohyoid branch of the inferior alveolar at the symphysis menti it runs upward over the border of the mandible and divides into a superficial and a deep branch the superficial branch passes between the integument and quadratus labii inferioris and anastomoses with the inferior labial artery the deep branch runs between the muscle and the bone supplies the lip and anastomoses with the inferior labial and mental arteries A labialis inferior inferior coronary artery arises near the angle of the mouth it passes upward and forward beneath the triangularis and penetrating the orbicularis auris runs in a tortuous course along the edge of the lower lip between this muscle and the mucous membrane it supplies the labial glands the mucous membrane and the muscles on the upper lip and anastomoses with the artery of the opposite side and with the mental branch of the inferior alveolar artery the superior labial artery A labialis superior superior coronary artery is larger and more tortuous than the inferior it follows a similar course along the edge of the upper lip lying between the mucous membrane and the orbicularis auris with the artery of the opposite side it supplies the upper lip and gives off in its course two or three vessels which ascend to the nose a septal branch ramifies on the nasal septum as far as the point of the nose and an aler branch supplies the ala of the nose the lateral nasal branch is derived from the external maxillary as that vessel ascends along the side of the nose it supplies the ala and of the nose anastomosing with its fellow with the septal and aler branches with the dorsal nasal branch of the ophthalmic and with the infer orbital branch of the internal maxillary the angular artery A angularis is the terminal part of the external maxillary it ascends to the medial angle of the orbit embedded in the fibers of the angular head of the quadratus labii superioris and accompanied by the angular vein on the cheek it distributes branches which anastomose with the infer orbital after supplying the lacrimal sac and orbicularis oculi it ends by anastomosing with the dorsal nasal branch of the ophthalmic artery the muscular branches in the neck are distributed to the pterogortius internus and stylo hyoidius and on the face to the anastomoses of the external maxillary artery are very numerous not only with the vessel of the opposite side but in the neck with the sublingual branch of the lingual with the ascending pharyngeal and by its ascending palatine and tonsular branches with the palatine branch of the internal maxillary on the face with the mental branch of the inferior alveolar as it emerges from the mental foramen with the adverse facial branch of the superficial temporal with the infer orbital branch of the internal maxillary and with the dorsal nasal branch of the ophthalmic peculiarities the external maxillary artery not infrequently arises in common with the lingual it varies in its size and in the extent to which it supplies the face it occasionally ends at the submental and not infrequently extends only as the angle of the mouth or nose the deficiency is then compensated for by enlargement of one of the neighboring arteries for the occipital artery a occipitalis arises from the posterior part of the external carotid opposite the external maxillary near the lower margin of the posterior belly of the digastricus and ends in the posterior part of the scalp course and at its origin it is covered by the posterior belly of the digastricus and the stylohyoidus and the hypoglossal nerve winds around it from behind forward higher up it crosses the internal carotid artery the internal jugular vein and the vagus and accessory nerves it next ascends to the interval between the transverse process of the atlas and the mastoid process of the temporal bone and passes horizontally backward grooving the surface of the latter bone being covered by the sternocleidomastoidus plenius capidus longissimus capidus and digastricus and resting upon the rectus capidus lateralis the obliquus superior and semi-spinalis capidus it then changes its course and runs vertically upward here's is the fascia connecting the cranial attachment of the trapezius with the sternocleidomastoidus and ascends in a tortuous course in the superficial fascia of the scalp where it divides into numerous branches which reaches high as the vertex of the skull and the nastamos with the posterior auricular and superficial temporal arteries its terminal portion is accompanied by the greater occipital nerve branches the branches of the occipital artery are muscular sternocleidomastoid auricular meningeal descending the muscular branches rami muscularies supply the digastricus stylohyoidus splenius and longissimus capidus the sternocleidomastoid artery a sternocleidomastoidia sternomastoid artery generally arises from the occipital close to its commencement but sometimes springs directly from the external carotid it passes downward and backward over the hypoglossal nerve and enters the substance of the muscle in company with the accessory nerve the auricular branch ramus auricularis supplies the back of the concha and frequently gives off a branch which enters the skull through the mastoid foramen and supplies the dura matter the diploi and the mastoid cells this latter branch sometimes arises from the occipital artery and is then known as the mastoid branch the meningeal branch ramus meningeus dural branch ascends from the internal jugular vein and enters the skull through the jugular foramen and condyloid canal to supply the dura matter in the posterior fossa the descending branch ramus descendens arteria princips services the largest branch of the occipital descends on the back of the neck and divides into a superficial and deep portion the superficial portion runs beneath the splineus giving off branches which pierce that muscle to supply the trapezius and anastomose with the ascending branch of the transverse cervical the deep portion runs down between the semispinalis capitis and coli and anastomoses with the vertebral and with the a profundus cervicalis a branch of the costoservical trunk the anastomoses between these vessels assists in establishing the collateral circulation after ligature of the common carotid or subclavian artery the terminal branches of the occipital artery are distributed to the back of the head they are very tortuous and lie between the entegument and the occipitalis anastomosing with the artery of the opposite side and with the posterior auricular and temporal arteries and supplying the occipitalis the entegument and pericranium one of the terminal branches may give off a meningial twig which passes through the parietal foramen end of section 12 recording by Selena Arter section 13 part 3 this is a lepervox recording all lepervox recordings are in the public domain for more information or to volunteer please visit lepervox.org anatomy of the human body part 3 by Henry Gray the external carotid artery part 2 the posterior auricular artery a auricularis posterior is small and arises from the external carotid above the digastricus and stylohyoidius opposite the apex of the styloid process it ascends under cover of the parotid gland on the styloid process of the temporal bone to the groove between the cartilage of the ear and the mastoid process immediately above which it divides into its auricular and occipital branches beside several small branches to the digastricus, stylohyoidius and sternocleidomastoidius and to the parotid gland this vessel gives off three branches stylo-mastoid auricular occipital the stylo-mastoid artery a stylo-mastoidia enters the styloid mastoid foramen and supplies the tympanic cavity the tympanic antrum and mastoid cells and the semi-circular canals in the young subject a branch from this vessel forms with the anterior tympanic artery from the internal maxillary a vascular circle which surrounds the tympanic membrane and from which delicate vessels ramify on that membrane it anastomoses with the superficial pitrosal branch of the middle meningeal artery by a twig which enters the hiatus canalis fascialis the auricular branch ramus auricularis ascends behind the ear beneath the auricularis posterior and is distributed to the back of the auricula upon which it ramifies minutely some branches curving around the margin of the cartilage others perforating it to supply the anterior surface it anastomoses with the parietal and anterior auricular branches of the superficial temporal the occipital branch ramus occipitalis passes backward over the sternocleidomastoidius to the scalp above and behind the ear it supplies the occipitalis and the scalp in this situation and anastomoses with the occipital artery 6. The ascending pharyngeal artery a pharyngea ascendens the smallest branch of the external carotid is a long slender vessel deeply seated in the neck beneath the other branches of the external carotid and under the stylo pharyngeus it arises from the back part of the external carotid near the commencement of that vessel and ascends vertically between the internal carotid and the side of the pharynx to the under surface of the base of the skull lying on the longest capitus branches its branches are palatine prevertebral inferior tympanic posterior meningeal the pharyngeal branches rami pharyngea are three or four in number two of these descend to supply the constrictory's pharyngeus medius and inferior and the stylo pharyngeus ramifying in their substance and in the mucous membrane lining them the palatine branch varies in size they break the place of the ascending palatine branch of the facial artery when that vessel is small it passes inward upon the constrictor pharyngeus superior sends ramifications to the soft palate and tonsil and supplies a branch to the auditory tube the prevertebral branches are numerous small vessels which supply the long eye, capitus and coli the sympathetic trunk nerves and the lymph glands they anastomose with the ascending cervical artery the inferior tympanic artery A. tympanica inferior is a small branch which passes through a minute foramen in the petrus portion of the temporal bone in company with the tympanic branch of the glossopharyngeal nerve to supply the medial wall of the tympanic cavity and anastomose with the other tympanic arteries the meningeal branches are several small vessels which supply the dura mater one, the posterior meningeal enters the cranium through the jugular foramen a second passes through the foramen lacerum and occasionally a third through the canal for the hypoglossal nerve the superficial temporal artery A. temporalis superficialis the smaller of the two terminal branches of the external carotid appears from its direction to be the continuation of that vessel it begins in the substance of the carotid gland behind the neck of the mandible and crosses over the posterior root of the zygomatic process of the temporal bone about five centimeters above this process it divides into two branches a frontal and a parietal as it crosses the zygomatic process it is covered by the auricularis anterior muscle and by a dense fascia it is crossed by the temporal and zygomatic branches of the facial nerve and one or two veins and is accompanied by the auriculotemporal nerve which lies immediately behind it branches besides some twigs to the parotid gland to the temporal mandibular joint and to the masseter muscle these branches are transverse facial middle temporal anterior auricular frontal parietal the transverse facial artery A transversa fascia is given off from the superficial temporal before that vessel quits the parotid gland running forward through the substance of the gland it passes transversely across the side of the face between the parotid duct the masseter of the zygomatic arch and divides into numerous branches which supply the parotid gland and duct the masseter and the integument and anastomose with the external maxillary, masseteric, buccinator and infororbital arteries this vessel rests on the masseter and is accompanied by one or two branches of the facial nerve the middle temporal artery A temporalis media rises immediately above the zygomatic arch and perforating the temporal fascia gives branches to the temporalis anastomosing with the deep temporal branches of the internal maxillary it occasionally gives off a zygomatic orbital branch which runs along the upper border of the zygomatic arch between the two layers of the temporal fascia to the lateral angle of the orbit which may arise directly from the superficial temporal artery supplies the orbicularis oculi and anastomoses with the lacrimal and palpibril branches of the ophthalmic artery the anterior auricular branches rami, auricularis, anterioris are distributed to the anterior portion of the auricula the lobule and part of the external meatus anastomosing with the posterior auricular the frontal branch ramus, frontalis anterior temporal runs tortuously upward and forward to the forehead supplying the muscles integument and pericranium in this region and anastomosing with the super orbital and frontal arteries the parietal branch ramus, parietalis posterior temporal further than the frontal curves upward and backward on the side of the head lying superficial to the temporal fascia and anastomosing with its fellow of the opposite side and with the posterior auricular and occipital arteries the internal maxillary artery a. maxillaris interna the larger of the two terminal branches of the external carotid arises behind the neck of the mandible embedded in the substance of the parotid gland it passes forward between the ramus of the mandible and the sphenomandibular ligament and then runs either superficial or deep to the pterygoidus externus to the pterygopalatine fascia it supplies the deep structures of the face and may be divided into mandibular, pterygoid and pterygopalatine portions the first or mandibular portion passes horizontally forward between the ramus of the mandible and the sphenomandibular ligament where it lies parallel to and a little below the auriculotemporal nerve it crosses the inferior alveolar nerve and runs along the lower border of the pterygoidus externus the second or pterygoid portion runs obliquely forward and upward under cover of the ramus of the mandible and insertion of the temporalis on the superficial very frequently on the deep surface of the pterygoidus externus it then passes between the two heads of origin of this muscle and enters the fascia the third or pterygopalatine portion lies in the pterygopalatine fascia in relation with the sphenopalatine ganglion the branches of this vessel may be divided into three groups corresponding with its three divisions branches of the first or mandibular portions anterior tympanic, deep auricular middle meningeal accessory meningeal inferior alveolar the anterior tympanic artery a tympanica interior tympanic artery passes upward behind the temporal mandibular articulation enters the tympanic cavity through the petro-tympanic fissure and ramifies upon the tympanic membrane forming a vascular circle around the membrane with the stylo mastoid branch of the posterior auricular and anastomocene with the artery of the pterygoid canal and with the carotico-tympanic branch from the internal carotid the deep auricular artery a auricularis profunda often arises in common with the preceding it ascends in the substance of the parotid gland behind the temporal mandibular articulation pierces the cartilaginous or bony wall of the external acoustic meadis and supplies its cuticular lining and the outer surface of the tympanic membrane it gives a branch to the temporal mandibular joint with the spheno-mendigial artery a meningea media medidural artery is the largest of the arteries which supply the dura matter it ascends between the sphenomendibular ligament and the pterygoidus externus and between the two roots of the auriculotemporal nerve to the foramen spinosum of the sphenoid bone through which it enters the cranium it then runs forward in a groove wing of the sphenoid bone, and divides into two branches, anterior and posterior. The anterior branch, the larger, crosses the great wing of the sphenoid, reaches the groove or canal in the sphenoidal angle of the parietal bone, and then divides into branches which spread out between the dura mater and internal surface of the cranium, some passing upward as far as the vertex, and others backward to the occipital region. The posterior branch curves backward on the squama of the temporal bone, and reaching the parietal some distance in front of its mastoid angle divides into branches which supply the posterior part of the dura mater and cranium. The branches of the middle meningeal artery are distributed partly to the dura mater, but chiefly to the bones. They anastomose with the arteries of the opposite side, and with the anterior and posterior meningeal. The middle meningeal on entering the cranium gives off the following branches. 1. Numerous small vessels supply the semi-lunar ganglion and the dura mater in this situation. 2. A superficial patrosal branch enters the hiatus of the facial canal, supplies the facial nerve, and anastomoses with the stylo-mastoid branch of the posterior auricular artery. 3. A superior tympanic artery runs in the canal for the tensor tympani, and supplies this muscle and the lining membrane of the canal. 4. Orbital branches pass through the superior orbital fissure, or through the separate canals in the great wing of the sphenoid, to anastomose with the lacrimal or other branches of the ophthalmic artery. 5. Temporal branches pass through the foramina in the great wing of the sphenoid and anastomose in the temporal fossa with the deep temporal arteries. The accessory meningeal branch, ramus, meningis accessorius, small meningeal, or parvadoral branch, is sometimes derived from the preceding. It enters the skull through the foramina valley and supplies the semi-lunar ganglion and duramatter. The inferior alveolar artery, A alveolaris inferior inferior dental artery descends with the inferior alveolar nerve to the mandibular foramina on the medial surface of the ramus of the mandible. It runs along the mandibular canal in the substance of the bone, accompanied by the nerve, and opposite the first premolar tooth divides into two branches, incisor and mental. The incisor branch is continued forward beneath the incisor teeth as far as the middle line, where it anastomoses with the artery of the opposite side. The mental branch escapes with the nerve at the mantle foramen, supplies the chin, and the anastomoses with the submental and inferior labial arteries. Under its origin, the inferior alveolar artery gives off a lingual branch, which descends with the lingual nerve and supplies the mucous membrane of the mouth. As the inferior alveolar artery enters the foramen, it gives off a mylohyoid branch, which runs in the mylohyoid groove and ramifies on the undersurface of the mylohyoidius. The inferior alveolar artery and its incisor branch during their course through the substance of the bone give off a few twigs, which are lost in the cancerless tissue and a series of branches which correspond in number to the roots of the teeth. These enter the minute apertures at the extremities of the roots and supply the pulp of the teeth. As of the second or pterogoid portion, deep temporal, pterogoid, mesoteric, buccinator, the deep temporal branches, two in number, anterior and posterior, ascend between the temporalis and the pericranium. They supply the muscle and anastomose with the middle temporal artery. The anterior communicates with the lacrimal artery by means of small branches which perforate the zygomatic bone and great wing of the sphenoid. The pterogoid branches, rami pterogoidae, irregular in their number and origin, supply the pterogoidae. The mesoteric artery, A. mesoterica, is small and passes lateral word through the mandibular notch to the deep surface of the masseter. It supplies the muscle and anastomoses with the mesoteric branches of the external maxillary and with the transverse facial artery. The buccinator artery, A. buccinatoria, buccal artery, is small and runs obliquely forward between the pterogoidus internus and the insertion of the temporalis to the outer surface of the buccinator, to which it is distributed. The anastomosing with branches of the external maxillary and with the infraorbital. Branches of the third, or pterogopalatine, portion. Posterior superior alveolar, infraorbital, descending palatine, artery of the pterogoid canal, pharyngeal sphenopalatine, the posterior superior alveolar artery, A. alveolaris superior posterior alveolar or posterior dental artery, is given off from the internal maxillary, frequently in conjunction with the infraorbital just as the trunk of the vessel is passing into the pterogopalatine fossa. Descending upon the tuberosity of the maxilla, it divides into numerous branches, some of which enter the alveolar canals, to supply the molar and premolar teeth and the lining of the maxillary sinus, while others are continued forward on the alveolar process to supply the gums. The infraorbital artery, A. infraorbitalis, appears from its direction to be the continuation of the trunk of the internal maxillary, but often arises in conjunction with the posterior superior alveolar. It runs along the infraorbital groove and canal with the infraorbital nerve and emerges on the face through the infraorbital foramen, beneath the infraorbital head of the quadratus labi superioris. While in the canal it gives off A, orbital branches which assist in supplying the rectus inferior and obliquus inferior and the lacrimal sac, and B, anterior superior alveolar branches, which descend through the anterior alveolar canals to supply the upper incisor and canine teeth and the mucous membrane of the maxillary sinus. On the face, some branches pass upward to the medial angle of the orbit and the lacrimal sac, anastomocene with the angular branch of the external maxillary artery, others run toward the nose, anastomocene with the dorsal nasal branch of the aphthalmic, and others descend between the quadratus labi superioris and the cananus, and anastomose with the external maxillary, transverse facial, and buccinator arteries. The four remaining branches arise from that portion of the internal maxillary, which is contained in the pterigopalatine fossa. The descending phthalatine artery, A phthalatina descendants, descends through the pterigopalatine canal with the anterior phthalatine branch of the sphenopalatine ganglion, and emerging from the greater phthalatine foramen runs forward in a groove on the medial side of the alveolar border of the hard palate to the incisive canal. The terminal branch of the artery passes upward through this canal to anastomose with the sphenopalatine artery. Branches are distributed to the gums, the phthalatine glands, and the mucus membrane of the roof of the mouth. While in the pterigopalatine canal it gives off twigs which descend in the lesser phthalatine canals to supply the soft palate and phthalatine tonsil, anastomocene with the ascending phthalatine artery. The artery of the pterigoid canal, A canalis pterigordia vidian artery, passes backward along the pterigoid canal with the corresponding nerve. It is distributed to the upper part of the pharynx and to the auditory tube. Sending into the tympanic cavity is small branch which anastomoses with the other tympanic arteries. The pharyngeal branch is very small. It runs backward through the pharyngeal canal with the pharyngeal nerve and is distributed to the upper part of the pharynx and to the auditory tube. The sphenopalatine artery, A sphenopalatina nasopalatine artery passes through the sphenopalatine foramen into the cavity of the nose at the back part of the superior meatus. Here it gives off its posterior lateral nasal branches which spread forward over the conchee and meatases, anastomose with the ethmoidal arteries and the nasal branches of the descending phthalatine and assist in supplying the frontal, maxillary, ethmoidal, and sphenoidal sinuses. Crossing the undersurface of the sphenoid, the sphenopalatine artery ends on the nasal septum as the posterior septal branches. These anastomose with the ethmoidal arteries and the septal branch of the superior labial. One branch descends in a groove on the vomer to the incisive canal and anastomoses with the descending phthalatine artery. End of section 13, recording by Selena Arder.