Anatomy and Physiology of Children and Adolescents - M. R. Sapin 2007

Cardiovascular System
Blood Vessels of the Human Body
Veins of the Systemic Circulation

The systemic Veins are divided into three main systems: the SUPERIOR VENA CAVA system, the INFERIOR VENA CAVA system, and the HEPATIC PORTAL VEIN system. The superior vena cava is a short, wide venous vessel formed by the confluence of the right and left brachiocephalic veins at the level of the manubrium of the Sternum. It then descends vertically to empty into the right atrium. On its way to The Heart, the superior vena cava receives the large azygos vein, which drains Blood from the walls of the thoracic and abdominal cavities. Each brachiocephalic vein, in turn, is formed by the union of two venous vessels: the internal jugular and subclavian veins. The Internal jugular vein carries blood from the Brain, as well as from the Organs and Tissues of the HEAD and Neck. Superficial veins collect blood from the Skin and subcutaneous tissue (Fig. 94, see color insert).

The subclavian vein collects blood from the organs and tissues of the neck, shoulder girdle, and upper extremity. The VEINS OF THE upper limb are subdivided into superficial (subcutaneous) veins and deep veins, which run alongside the Arteries. Subcutaneous veins are named according to their anatomical Location, such as the cephalic and basilic veins of the arm. Deep veins generally accompany arteries in pairs. These companion veins, known as venae comitantes, are named after the corresponding arteries based on their location in The Human Body (ulnar, radial, and brachial veins).

The inferior vena cava lies on the posterior abdominal wall to the right of the aorta. This vein is formed at the level of the IV lumbar vertebra by the junction of the right and left common iliac veins. The inferior vena cava then ascends, passes through the Diaphragm, and empties into the inferior aspect of the right atrium. Within the Abdominal cavity, the inferior vena cava receives the lumbar, inferior phrenic, renal, suprarenal, hepatic, and testicular (or ovarian) veins.

Each common iliac vein is formed by the confluence of the internal and external iliac veins. The internal iliac vein collects blood from the pelvic organs and walls. The external iliac vein is a continuation of the femoral vein, receiving blood from the superficial and deep veins of the lower extremity (the great and small saphenous veins of the leg, the popliteal vein, and the anterior and posterior tibial veins).

The abdominal cavity also contains the PORTAL VEIN SYSTEM, which is formed by the union of the splenic, superior mesenteric, and inferior mesenteric veins (Fig. 95). The portal vein collects blood from the walls of The Stomach, Small Intestine, and Large Intestine. This nutrient-rich blood passes through The Liver and then flows via the hepatic veins into the inferior vena cava.

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Fig. 95. The portal vein and its tributaries:

1 — liver; 2 — stomach; 3 — gastric veins; 4 — portal vein; 5 — splenic vein; 6 — Spleen; 7 — inferior mesenteric vein; 8 — descending colon; 9 — sigmoid colon; 10 — rectum; 11 — loops of small intestine; 12 — superior mesenteric vein; 13 — transverse colon; 14 — head of Pancreas

Numerous connections, known as venous anastomoses, exist between the tributaries of the superior and inferior venae cavae and the portal vein within the walls of the thoracic and abdominal cavities, as well as in the walls of certain organs (such as the Esophagus and rectum). These anastomoses allow blood to be redistributed and drained in alternative directions if an obstruction occurs in the main venous channels.

Damage to superficial veins can lead to venous bleeding. In such cases, the superficial vein should be temporarily compressed with a finger, followed by the application of a pressure bandage or tourniquet. Arterial bleeding in a limb can be stopped using the exact same method.