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THE VEINS OF THE SPINAL MEDULLA. The veins of the spinal medulla issue from the substance of the spinal medulla, and terminate in a plexus in the pia mater. In that plexus there are six longitudinal channels-one antero-median, along the anterior fissure, two antero-lateral, immediately behind the anterior nerve-roots, two postero-lateral, immediately posterior to the posterior nerve-roots, and one postero-median, dorsal to the posterior septum. Radicular efferent vessels issue from the plexus, and pass along the nerve roots to communicate with the internal vertebral venous network. The veins of the spinal medulla vary very much in size, but they are largest on the lower and on the posterior portions.

The postero-median and antero-median veins are continued above into the corresponding veins of the medulla oblongata.

The antero-lateral and postero-lateral veins pour their blood partly into the median veins and partly into the radicular veins ; indeed, the greater part of the blood from the spinal medulla is returned by the radicular veins.

THE VEINS OF THE SUPERIOR EXTREMITY.

The veins of each upper limb are divisible into two sets-viz., superficial and deep. Both sets open eventually into a common terminal trunk which is known as the axillary vein. That vein is, therefore, the chief efferent vein of the upper extremity. It is continued as the subclavian vein to the innominate vein, through which its blood, together with that from the corresponding side of the head and neck, reaches the superior vena cava.

THE DEEP VEINS OF THE UPPER EXTREMITY. The deep veins of the upper limb, with the exception of the axillary vein, are arranged in pairs, venæ comites, which accompany the different arteries and are similarly named. So far as these veins are concerned it will be sufficient to state that they are provided with valves, that they are situated one on each side of the artery with which they are associated, and that they are usually united together by numerous transverse anastomoses which cross the line of the artery. The axillary vein, however, requires more detailed consideration.

VENA AXILLARIS.

The axillary vein (Figs. 766 and 806) commences, as the direct continuation of the basilic vein, opposite the lower border of the teres major muscle. It passes · upwards and medially, through the axilla, along the medial side of the axillary

artery, and terminates, at the external border of the first rib, by becoming the subclavian vein. It possesses one or more bicuspid valves of which one is usually situated opposite the lower border of the subscapularis muscle.

Relations. Its anterior relations are similar to those of the axillary artery, but, in addition, the vein is crossed anteriorly, under cover of the clavicular part of the pectoralis major, by the pectoral branches of the thoraco-acromial artery, and by branches of the medial anterior thoracic nerve, and it receives anteriorly, just above the upper border of the pectoralis minor, the termination of the cephalic vein.

Posterior to it are the muscles which form the posterior wall of the axilla, the axillary fat, and the first serration of the serratus anterior. The long thoracic nerve intervenes between it and the serratus anterior, and the subscapular and thoraco-dorsal nerves and the subscapular artery pass between it and the subscapularis.

It is separated from the third part of the axillary artery by the ulnar nerve and medial cutaneous nerves of the forearm ; from the second part of the axillary artery by the medial cord of the brachial plexus ; and in the proximal part of the axilla, behind the costo-coracoid membrane, it is separated from the first part of the artery by the medial anterior thoracic nerve. To its medial side lie the lateral set of axillary glands, and, in the distal part of the axilla, the medial cutaneous nerve of the arm.

Tributaries. In addition to tributaries corresponding with the branches of the axillary artery, it receives the venæ comites of the brachial artery, at the lower border of the subscapularis ; and the cephalic vein, which joins it above the upper border of the pectoralis minor muscle.

THE SUPERFICIAL VEINS OF THE SUPERIOR EXTREMITY. The superficial veins of the upper limb commence in the superficial fascia of the palm and dorsum of the hand and of the digits.

The Veins of the Digits and Hand.—The special volar digital veins are two or more fine longitudinal channels which lie in the superficial fascia of the volar

aspects of the digits. They communicate, proximally, with a fine venous network which lies in the

superficial fascia of Tributaries of cephalic vein

the palm, and, at the proximal ends of the interdigital clefts, by means of intercapitular

veins, which pass Basilic vein.

dorsally between

the heads of the Tributary of

metacarpal bones, cephalic vein

they open into Commencement

the special dorsal of basilic vein

digital veins.

The special Dorsal venous

dorsal digital veins, two in each digit, anastomose freely together on the

dorsal aspects of digital veins

the digits. At the - Dorsal digital veins proximal ends of

the

interdigital clefts they cominunicate, through the intercapitular veins, with the special volar digital veins, and then they unite

together to form an indefinite series of

dorsal metacarpal Fig. 789. -SUPERFICIAL VEINS ON THE DORSUM OF THE HAND AND Digits.

veins which ter

minate, a little! distal to the middle of the dorsum of the hand, in a dorsal venous arch.

The Veins of the Forearm and Arm.—The veins of the forearm emerge from the dorsal venous arch and from the volar venous plexus, and they vary considerably in number and in size. As a rule there are two main longitudinal channels, the cephalic vein on the radial side and the basilic vein on the ulnar side. In some cases there is an additional median vein on the volar aspect of the forearm.

The cephalic vein commences in the radial end of the dorsal venous arch. It receives the metacarpal veins of the thumb, turns round the radial margin of

[graphic]

the distal part of the forearm, and runs proximally, parallel with the volar border of the brachioradialis muscle, to the cubital region. There, frequently much reduced in size, it turns laterally and runs, along the lateral border of the prominence

Subclavius of the biceps, to the interval between the

Costo-coracoid membrane deltoid and pectoralis major, along which it ascends to the delto-pectoral triangle. Cephalic vein At the delto-pectoral triangle it turns medially, between the pectoralis minor and the pectoralis major, to the anterior aspect of the costo-coracoid membrane, which Deltoid. --separates it from the front of the first part of the axillary artery; then, turning back

Pectoralis wards, it pierces the costo-coracoid mem- major brane and ends in the axillary vein. In a few cases instead of piercing the costocoracoid membrane it crosses the front of the clavicle, deep to the platysma, pierces the deep cervical fascia, and joins the lower part of the external jugular vein.

Cephalic vein. As it runs proximally, on the volar aspect of the forearm, a number of tributaries join its lateral border. Some of these

Basilic veincommence in the dorsal venous arch of the hand and others in the superficial fascia of the dorsal aspect of the forearm.

Profunda veinIn the cubital region it is connected with the basilic vein by a large obliquely placed anastomosing channel, the median

Basilic veincubital vein, which runs along the medial border of the distal part of the biceps' prominence, superficial to the lacertus fibrosus which separates it from the distal part of Cephalic vein. the brachial artery. In the delto-pectoral triangle it is joined by tributaries which correspond with the acromial and pectoral Median veinbranches of the thoraco-acromial artery.

The median cubital vein not only connects together the cephalic and basilic veins but it receives also the profunda vein which pierces the deep fascia and connects it with the deep veins of the forearm, and one or more superficial veins, of varying size which pass, proximally, along the volar aspect of the forearm.

In many cases the median cubital vein is relatively very large, and in such cases the more proximal part of the cephalic vein, which lies in the arm, is a comparatively small vessel.

The basilic vein commences in the ulnar end of the dorsal venous arch of the hand. It runs along the dorsal aspect of the

Fig. 790.-SUPERFICIAL VEINS ON THE FLEXOR forearm to the junction of the proximal ASPECT OF THE UPPER EXTREMITY. and middle thirds, where it turns round the ulnar border of the forearm, and runs, anterior to the medial epicondyle of the humerus, to the medial bicipital groove. At the middle of the arm, it pierces the deep fascia. After piercing the fascia, it runs proximally, along the medial border of the brachial artery, to the axilla, and there becomes the axillary vein.

[graphic]

As it runs proximally, in the forearm, it is joined by tributaries from both the volar and dorsal aspects and, in the cubital region, by the median cubital

vein which connects it with the cephalic vein.

The Median Vein of the Forearm.—In a certain number of cases a vein, which commences

in the palmar venous Brachialis

plexus, runs along the muscle

middle of the volar Biceps muscle

Medial tutaneous aspect of the forearm to

nerve of forearm the cubital region. It is Cephalic vein

Basilic vein

called the median vein

of the forearm. At the Median nerve

bend of the elbow it Radial

Brachialis

receives the profunda recurrent artery Lateral

vein and then divides

artery cutaneous nerve

Median basilic into two branches, the

median cephalic and the Median cephalio

Lacertus
fibrosus

median basilic veins Accessory

(Fig. 791). The median radial vein

- Accessory ulnar

cephalic vein runs along Brachio-radialis

Ulnar artery

the lateral bicipital Profunda

sulcus and joins the Radial artery

cephalic vein. The Median veint

median basilic passes of forearm

Pronator teres

along the medial bimuscle

cipital sulcus and joins Cephalic vein

the basilic vein. When the median vein of the forearm is present the median cubital vein is absent.

When venesection FIG. 791.-SUPERFICIAL VEINS AT THE BEND OF THE ELBOW.

is performed in the forearm it is either the median cubital vein or, in its absence, the median basilic vein which is opened.

[graphic]

VENA CAVA INFERIOR AND ITS TRIBUTARIES.

The inferior vena cava (Fig. 792) is a large venous trunk which receives the whole of the blood from the lower extremities, and the greater part of the blood from the walls and contents of the abdomen and pelvis. It commences opposite the right side of the body of the fifth lumbar vertebra, behind and to the right of the right common iliac artery. It ascends through the abdomen, anterior and to the right of the vertebral column and the right crus of the diaphragm, and it pierces the cupola of the diaphragm, between the middle and right sections of the central tendinous leaflet, at the level of the lower part of the eighth thoracic vertebra. It then enters the middle mediastinum, pierces the fibrous pericardium, and terminates in the lower and posterior part of the right atrium. Its intra-thoracic portion is very short, and its intra-pericardial portion, which is still shorter, is covered anteriorly and on its right and left sides by the parietal portion of the serous layer. Attached to the inferior and anterior margin of its atrial orifice is the valve of the inferior vena cava (Eustachian). This is a remnant of an important fold of endocardium by which, in the fætus, the blood from the inferior vena cava is directed, through the foramen ovale, into the left atrium.

Relations. The inferior vena cava is in relation, posteriorly, with the bodies of the

lower lumbar vertebræ and the corresponding part of the anterior longitudinal ligament, the anterior portion of the right psoas major muscle, the right lumbar sympathetic trunk, the roots of the right lumbar arteries, the right crus of the diaphragm, the right renal artery, the right suprarenal artery, the right coeliac ganglion, the right inferior phrenic artery, and the medial and upper portion of the right suprarenal gland.

Anterior to it, from below upwards, are the following structures—the right common iliac artery, the lower end of the mesentery and the superior mesenteric artery, the right

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internal spermatic artery and the third part of the duodenum, the head of the pancreas, the portal vein and the first part of the duodenum, the foramen epiploicum, and the posterior surface of the liver. More superficially are coils of small intestine, the great omentum, and the transverse colon and mesocolon.

To its left side are the aorta and the right crus of the diaphragm.

On its right side, below, is the right ureter, whilst at a higher level the right kidney is separated from the vein by a short interval only.

Tributaries. In addition to the two common iliac veins, by the union of which it is formed, and through which it receives blood from the pelvis and from the lower extremities, the inferior vena cava receives the following tributaries :—The hepatic veins, the

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