Dr. Santos Anatomy and Physiology Medgar Evers College Cardiovascular System; Major Veins of the body and Histology of vessels Dr. Santos Anatomy and Physiology Medgar Evers College

Veins carry deoxygenated blood back to the heart Veins carry deoxygenated blood back to the heart. One exception is the pulmonary veins which bring back oxygenated blood from the lungs! Two largest veins in the body are the Inferior vena cava and the superior vena cava.

Head and Neck Drained primarily by the internal and external Jugular veins. External- drains the face and scalp Internal- drains the brain *keep in mind that blood from the brain first drains into the dural sinuses (space between the 2 layers of the dura mater).

The inferior dural sinus called the transverse sinus drains into the internal jugular.

Organs of the abdomen These organs are drained by veins that are named largely in parallel with the arteries that serve the organs; Renal vein- drain kidneys Gastric vein- drains the stomach Splenic vein- drains spleen Superior mesenteric vein- drains the small intestine and most of the large intestine Inferior mesenteric vein- drains the large intestine

Hepatic portal system Blood from splenic, inferior mesenteric, superior mesenteric, and gastric veins drain into a common vein called the hepatic portal vein. The blood is filtered and any toxins are removed. So blood must pass to the liver before entering systemic circulation. Once the blood is filtered, it enters the hepatic vein and then drains into the inferior vena cava.

Deep structures of upper limbs Blood from the deep structures of the upper limb is drained by the Radial vein and Ulnar vein. These 2 merge to form Brachial vein ---------axillary vein -------near the clavicle, it becomes the subclavian vein --- drains into brachiocephalic vein ----- drains into the superior vena cava.

Superficial structures of upper limbs Drained by cephalic vein (lateral side) and basilic vein (medial side). These 2 veins are united in the antecubital fossa by the median antecubital vein (frequent site of blood drawing) The basilic vein joins the brachial vein ----- axillary vein -----joins the cephalic vein --- the subclavian vein.

Deep structures of lower limbs Drained by the anterior and posterior tibial veins. These 2 veins unite in the popliteal fossa and become the popliteal vein. The popliteal vein, in the distal thigh, becomes the femoral vein---- external iliac vein. The external iliac vein merges with the internal iliac vein to form the common iliac vein.

The 2 common iliac veins merge to form the Inferior vena cava. * the largest superficial vein of the lower limb is the greater saphenous vein, which drains the medial leg and thighs and empties into the femoral vein.

Histology of blood vessel wall Three tissue layers make up the walls of arteries and veins. Tunica interna- consists of endothelium cells. It rests on top of a thin layer of connective tissue. Tunica media- consists of smooth muscle and elastic fibers. The smooth muscle, innervated by SNS, regulates the diameter of the vessel and plays a role in blood pressure and tissue perfusion. The elastic fibers allow the vessels to expand.

Tunica externa (adventitia)- consists of dense irregular collagenous connective tissue with collagen fibers. The fibers prevent rupture when pressure is high.