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3c. The Veins of the Upper Extremity and Thorax
FIG. 573 - The veins on the dorsum of the hand. (Bourgery.) The veins of the upper extremity are divided into two sets, superficial and deep; the two sets anastomose frequently with each other. The superficial veins are placed immediately beneath the integument between the two layers of superficial fascia. The deep veins accompany the arteries, and constitute the venæ comitantes of those vessels. Both sets are provided with valves, which are more numerous in the deep than in the superficial veins. The Superficial Veins of the Upper Extremity The superficial veins of the upper extremity are the digital, metacarpal, cephalic, basilic, median. Digital Veins.—The dorsal digital veins pass along the sides of the fingers and are joined to one another by oblique communicating branches. Those from the adjacent sides of the fingers unite to form three dorsal metacarpal veins (Fig. 573), which end in a dorsal venous net-work opposite the middle of the metacarpus. The radial part of the net-work is joined by the dorsal digital vein from the radial side of the index finger and by the dorsal digital veins of the thumb, and is prolonged upward as the cephalic vein. The ulnar part of the net-work receives the dorsal digital vein of the ulnar side of the little finger and is continued upward as the basilic vein. A communicating branch frequently connects the dorsal venous network with the cephalic vein about the middle of the forearm. The volar digital veins on each finger are connected to the dorsal digital veins by oblique intercapitular veins. They drain into a venous plexus which is situated over the thenar and hypothenar eminences and across the front of the wrist. The cephalic vein (Fig. 574) begins in the radial part of the dorsal venous net-work and winds upward around the radial border of the forearm, receiving tributaries from both surfaces. Below the front of the elbow it gives off the vena mediana cubiti (median basilic vein), which receives a communicating branch from the deep veins of the forearm and passes across to join the basilic vein. The cephalic vein then ascends in front of the elbow in the groove between the Brachioradialis and the Biceps brachii. It crosses superficial to the musculocutaneous nerve and ascends in the groove along the lateral border of the Biceps brachii. In the upper third of the arm it passes between the Pectoralis major and Deltoideus, where it is accompanied by the deltoid branch of the thoracoacromial artery. It pierces the coracoclavicular fascia and, crossing the axillary artery, ends in the axillary vein just below the clavicle. Sometimes it communicates with the external jugular vein by a branch which ascends in front of the clavicle. The accessory cephalic vein (v. cephalica accessoria) arises either from a small tributory plexus on the back of the forearm or from the ulnar side of the dorsal venous net-work; it joins the cephalic below the elbow. In some cases the accessory cephalic springs from the cephalic above the wrist and joins it again higher up. A large oblique branch frequently connects the basilic and cephalic veins on the back of the forearm. The basilic vein (v. basilica) (Fig. 574) begins in the ulnar part of the dorsal venous network. It runs up the posterior surface of the ulnar side of the forearm and inclines forward to the anterior surface below the elbow, where it is joined by the vena mediana cubiti. It ascends obliquely in the groove between the Biceps brachii and Pronator teres and crosses the brachial artery, from which it is separated by the lacertus fibrosus; filaments of the medial antibrachial cutaneous nerve pass both in front of and behind this portion of the vein. It then runs upward along the medial border of the Biceps brachii, perforates the deep fascia a little below the middle of the arm, and, ascending on the medial side of the brachial artery to the lower border of the Teres major, is continued onward as the axillary vein. 
FIG. 574 - The superficial veins of the upper extremity. The median antibrachial vein (v. mediana antibrachii) drains the venous plexus on the volar surface of the hand. It ascends on the ulnar side of the front of the forearm and ends in the basilic vein or in the vena mediana cubiti; in a small proportion of cases it divides into two branches, one of which joins the basilic, the other the cephalic, below the elbow. The Deep Veins of the Upper Extremity The deep veins follow the course of the arteries, forming their venæ comitantes. They are generally arranged in pairs, and are situated one on either side of the corresponding artery, and connected at intervals by short transverse branches. Deep Veins of the Hand.—The superficial and deep volar arterial arches are each accompanied by a pair of venæ comitantes which constitute respectively the superficial and deep volar venous arches, and receive the veins corresponding to the branches of the arterial arches; thus the common volar digital veins, formed by the union of the proper volar digital veins, open into the superficial, and the volar metacarpal veins into the deep volar venous arches. The dorsal metacarpal veins receive perforating branches from the volar metacarpal veins and end in the radial veins and in the superficial veins on the dorsum of the wrist. The deep veins of the forearm are the venæ comitantes of the radial and ulnar veins and constitute respectively the upward continuations of the deep and superficial volar venous arches; they unite in front of the elbow to form the brachial veins. The radial veins are smaller than the ulnar and receive the dorsal metacarpal veins. The ulnar veins receive tributaries from the deep volar venous arches and communicate with the superficial veins at the wrist; near the elbow they receive the volar and dorsal interosseous veins and send a large communicating branch (profunda vein) to the vena mediana cubiti. 
FIG. 575 - The deep veins of the upper extremity. (Bourgery.) The brachial veins (vv. brachiales) are placed one on either side of the brachial artery, receiving tributaries corresponding with the branches given off from that vessel; near the lower margin of the Subscapularis, they join the axillary vein; the medial one frequently joins the basilic vein. These deep veins have numerous anastomoses, not only with each other, but also with the superficial veins. The axillary vein (v. axillaris) begins at the lower border of the Teres major, as the continuation of the basilic vein, increases in size as it ascends, and ends at the outer border of the first rib as the subclavian vein. Near the lower border of the Subscapularis it receives the brachial veins and, close to its termination, the cephalic vein; its other tributaries correspond with the branches of the axillary artery. It lies on the medial side of the artery, which it partly overlaps; between the two vessels are the medial cord of the brachial plexus, the median, the ulnar, and the medial anterior thoracic nerves. It is provided with a pair of valves opposite the lower border of the Subscapularis; valves are also found at the ends of the cephalic and subscapular veins. The subclavian vein (v. subclavia), the continuation of the axillary, extends from the outer border of the first rib to the sternal end of the clavicle, where it unites with the internal jugular to form the innominate vein. It is in relation, in front, with the clavicle and Subclavius; behind and above, with the subclavian artery, from which it is separated medially by the Scalenus anterior and the phrenic nerve. Below, it rests in a depression on the first rib and upon the pleura. It is usually provided with a pair of valves, which are situated about 2.5 cm. from its termination. 
FIG. 576 - The veins of the right axilla, viewed from in front. (Spalteholz.) The subclavian vein occasionally rises in the neck to a level with the third part of the subclavian artery, and occasionally passes with this vessel behind the Scalenus anterior. Tributaries.—This vein receives the external jugular vein, sometimes the anterior jugular vein, and occasionally a small branch, which ascends in front of the clavicle, from the cephalic. At its angle of junction with the internal jugular, the left subclavian vein receives the thoracic duct, and the right subclavian vein the right lymphatic duct. The Veins of the Thorax (Fig. 577) The innominate veins (vv. anonymæ; brachiocephalic veins) are two large trunks, placed one on either side of the root of the neck, and formed by the union of the internal jugular and subclavian veins of the corresponding side; they are devoid of valves. The Right Innominate Vein (v. anonyma dextra) is a short vessel, about 2.5 cm. in length, which begins behind the sternal end of the clavicle, and, passing almost vertically downward, joins with the left innominate vein just below the cartilage of the first rib, close to the right border of the sternum, to form the superior vena cava. It lies in front and to the right of the innominate artery; on its right side are the phrenic nerve and the pleura, which are interposed between it and the apex of the lung. This vein, at its commencement, receives the right vertebral vein; and, lower down, the right internal mammary and right inferior thyroid veins, and sometimes the vein from the first intercostal space. 
FIG. 577 - The venæ cavæ and azygos veins, with their tributaries. The Left Innominate Vein (v. anonyma sinistra), about 6 cm. in length, begins behind the sternal end of the clavicle and runs obliquely downward and to the right behind the upper half of the manubrium sterni to the sternal end of the first right costal cartilage, where it unites with the right innominate vein to form the superior vena cava. It is separated from the manubrium sterni by the Sternohyoideus and Sternothyreoideus, the thymus or its remains, and some loose areolar tissue. Behind it are the three large arteries, innominate, left common carotid, and left subclavian, arising from the aortic arch, together with the vagus and phrenic nerves. The left innominate vein may occupy a higher level, crossing the jugular notch and lying directly in front of the trachea. Tributaries.—Its tributaries are the left vertebral, left internal mammary, left inferior thyroid, and the left highest intercostal veins, and occasionally some thymic and pericardiac veins. Peculiarities.—Sometimes the innominate veins open separately into the right atrium; in such cases the right vein takes the ordinary course of the superior vena cava; the left vein—left superior vena cava, as it is then termed—which may communicate by a small branch with the right one, passes in front of the root of the left lung, and, turning to the back of the heart, ends in the right atrium. This occasional condition in the adult is due to the persistence of the early fetal condition, and is the normal state of things in birds and some mammalia. The internal mammary veins (vv. mammariæ internæ) are venæ comitantes to the lower half of the internal mammary artery, and receive tributaries corresponding to the branches of the artery. They then unite to form a single trunk, which runs up on the medial side of the artery and ends in the corresponding innominate vein. The superior phrenic vein, i.e., the vein accompanying the pericardiacophrenic artery, usually opens into the internal mammary vein. The inferior thyroid veins (vv. thyreoideæ inferiores) two, frequently three or four, in number, arise in the venous plexus on the thyroid gland, communicating with the middle and superior thyroid veins. They form a plexus in front of the trachea, behind the Sternothyreoidei. From this plexus, a left vein descends and joins the left innominate trunk, and a right vein passes obliquely downward and to the right across the innominate artery to open into the right innominate vein, just at its junction with the superior vena cava; sometimes the right and left veins open by a common trunk in the latter situation. These veins receive esophageal tracheal, and inferior laryngeal veins, and are provided with valves at their terminations in the innominate veins. The highest intercostal vein (v. intercostalis suprema; superior intercostal veins) (right and left) drain the blood from the upper three or four intercostal spaces. The right vein (v. intercostalis suprema dextra) passes downward and opens into the vena azygos; the left vein (v. intercostalis suprema sinistra) runs across the arch of the aorta and the origins of the left subclavian and left common carotid arteries and opens into the left innominate vein. It usually receives the left bronchial vein, and sometimes the left superior phrenic vein, and communicates below with the accessory hemiazygos vein. The superior vena cava (v. cava superior) drains the blood from the upper half of the body. It measures about 7 cm. in length, and is formed by the junction of the two innominate veins. It begins immediately below the cartilage of the right first rib close to the sternum, and, descending vertically behind the first and second intercostal spaces, ends in the upper part of the right atrium opposite the upper border of the third right costal cartilage: the lower half of the vessel is within the pericardium. In its course it describes a slight curve, the convexity of which is to the right side. Relations.—In front are the anterior margins of the right lung and pleura with the pericardium intervening below; these separate it from the first and second intercostal spaces and from the second and third right costal cartilages; behind it are the root of the right lung and the right vagus nerve. On its right side are the phrenic nerve and right pleura; on its left side, the commencement of the innominate artery and the ascending aorta, the latter overlapping it. Just before it pierces the pericardium, it receives the azygos vein and several small veins from the pericardium and other contents of the mediastinal cavity. The portion contained within the pericardium is covered, in front and laterally, by the serous layer of the membrane. The superior vena cava has no valves. The azygos vein (v. azygos; vena azygos major) begins opposite the first or second lumbar vertebra, by a branch, the ascending lumbar vein (page 678); sometimes by a branch from the right renal vein, or from the inferior vena cava. It enters the thorax through the aortic hiatus in the diaphragm, and passes along the right side of the vertebral column to the fourth thoracic vertebra, where it arches forward over the root of the right lung, and ends in the superior vena cava, just before that vessel pierces the pericardium. In the aortic hiatus, it lies with the thoracic duct on the right side of the aorta; in the thorax it lies upon the intercostal arteries, on the right side of the aorta and thoracic duct, and is partly covered by pleura. Tributaries.—It receives the right subcostal and intercostal veins, the upper three or four of these latter opening by a common stem, the highest superior intercostal vein. It receives the hemiazygos veins, several esophageal, mediastinal, and pericardial veins, and, near its termination, the right bronchial vein. A few imperfect valves are found in the azygos vein; but its tributaries are provided with complete valves. The intercostal veins on the left side, below the upper three intercostal spaces, usually form two trunks, named the hemiazygos and accessory hemiazygos veins. The Hemiazygos Vein (v. hemiazygos; vena azygos minor inferior) begins in the left ascending lumbar or renal vein. It enters the thorax, through the left crus of the diaphragm, and, ascending on the left side of the vertebral column, as high as the ninth thoracic vertebra, passes across the column, behind the aorta, esophagus, and thoracic duct, to end in the azygos vein. It receives the lower four or five intercostal veins and the subcostal vein of the left side, and some esophageal and mediastinal veins. The Accessory Hemiazygos Vein (v. hemiazygos accessoria; vena azygos minor superior) descends on the left side of the vertebral column, and varies inversely in size with the highest left intercostal vein. It receives veins from the three or four intercostal spaces between the highest left intercostal vein and highest tributary of the hemiazygos; the left bronchial vein sometimes opens into it. It either crosses the body of the eighth thoracic vertebra to join the azygos vein or ends in the hemiazygos. When this vein is small, or altogether wanting, the left highest intercostal vein may extend as low as the fifth or sixth intercostal space. In obstruction of the superior vena cava, the azygos and hemiazygos veins are one of the principal means by which the venous circulation is carried on, connecting as they do the superior and inferior venæ cavæ, and communicating with the common iliac veins by the ascending lumbar veins and with many of the tributaries of the inferior vena cava. The Bronchial Veins (vv. bronchiales) return the blood from the larger bronchi, and from the structures at the roots of the lungs; that of the right side opens into the azygos vein, near its termination; that of the left side, into the highest left intercostal or the accessory hemiazygos vein. A considerable quantity of the blood which is carried to the lungs through the bronchial arteries is returned to the left side of the heart through the pulmonary veins. The Veins of the Vertebral Column (Figs. 578, 579) The veins which drain the blood from the vertebral column, the neighboring muscles, and the meninges of the medulla spinalis form intricate plexuses extending along the entire length of the column; these plexuses may be divided into two groups, external and internal, according to their positions inside or outside the vertebral canal. The plexuses of the two groups anastomose freely with each other and end in the intervertebral veins. The external vertebral venous plexuses (plexus venosi vertebrales externi; extraspinal veins) best marked in the cervical region, consist of anterior and posterior plexuses which anastomose freely with each other. The anterior external plexuses lie in front of the bodies of the vertebræ, communicate with the basivertebral and intervertebral veins, and receive tributaries from the vertebral bodies. The posterior external plexuses are placed partly on the posterior surfaces of the vertebral arches and their processes, and partly between the deep dorsal muscles. They are best developed in the cervical region, and there anastomose with the vertebral, occipital, and deep cervical veins. 
FIG. 578 - Transverse section of a thoracic vertebra, showing the vertebral venous plexuses. 
FIG. 579 - Median sagittal section of two thoracic vertebræ, showing the vertebral venous plexuses. The internal vertebral venous plexuses (plexus venosi vertebrales interni; intraspinal veins) lie within the vertebral canal between the dura mater and the vertebræ, and receive tributaries from the bones and from the medulla spinalis. They form a closer net-work than the external plexuses, and, running mainly in a vertical direction, form four longitudinal veins, two in front and two behind; they therefore may be divided into anterior and posterior groups. The anterior internal plexuses consist of large veins which lie on the posterior surfaces of the vertebral bodies and intervertebral fibrocartilages on either side of the posterior longitudinal ligament; under cover of this ligament they are connected by transverse branches into which the basivertebral veins open. The posterior internal plexuses are placed, one on either side of the middle line in front of the vertebral arches and ligamenta flava, and anastomose by veins passing through those ligaments with the posterior external plexuses. The anterior and posterior plexuses communicate freely with one another by a series of venous rings (retia venosa vertebrarum), one opposite each vertebra. Around the foramen magnum they form an intricate net-work which opens into the vertebral veins and is connected above with the occipital sinus, the basilar plexus, the condyloid emissary vein, and the rete canalis hypoglossi. The basivertebral veins (vv. basivertebrales) emerge from the foramina on the posterior surfaces of the vertebral bodies. They are contained in large, tortuous channels in the substance of the bones, similar in every respect to those found in the diploë of the cranial bones. They communicate through small openings on the front and sides of the bodies of the vertebræ with the anterior external vertebral plexuses, and converge behind to the principal canal, which is sometimes double toward its posterior part, and open by valved orifices into the transverse branches which unite the anterior internal vertebral plexuses. They become greatly enlarged in advanced age. The intervertebral veins (vv. intervertebrales) accompany the spinal nerves through the intervertebral foramina; they receive the veins from the medulla spinalis, drain the internal and external vertebral plexuses and end in the vertebral, intercostal, lumbar, and lateral sacral veins, their orifices being provided with valves. The veins of the medulla spinalis (vv. spinales; veins of the spinal cord) are situated in the pia mater and form a minute, tortuous, venous plexus. They emerge chiefly from the median fissures of the medulla spinalis and are largest in the lumbar region. In this plexus there are (1) two median longitudinal veins, one in front of the anterior fissure, and the other behind the posterior sulcus of the cord, and (2) four lateral longitudinal veins which run behind the nerve roots. They end in the intervertebral veins. Near the base of the skull they unite, and form two or three small trunks, which communicate with the vertebral veins, and then end in the inferior cerebellar veins, or in the inferior petrosal sinuses.
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