Khaleel Alyahya Saturday November 14, 2009

Heart Anatomy  Approximately the size of your fist  Location  Superior surface of diaphragm  Left of the midline  Anterior to the vertebral column, posterior to the sternum

Blood Circulation  The left side of the heart pumps blood out the aorta (which is a large elastic artery) to a system of muscular arteries, arterioles then to capillaries.  Blood from the arterioles enters the capillary bed where exchange of substances occurs.

 The blood enters venules, on to small veins, medium veins, and finally the large veins that empty the venous blood back into the right side of the heart.  Note: At the capillary beds, excess fluid and protein is picked up by lymphatic vessels, filtered through lymph nodes, and returned to the large veins. Blood Circulation

General organization of vessels  Vessel walls are divided into 3 layers, called tunicae.  1) Tunica intima: includes the endothelium (SSE) and the underlying loose C.T.  2) Tunica media: the middle layer which contains smooth muscle and or elastic membranes.  3) Tunica adventitia: the outermost connective tissue layer composed mainly of dense irregular connective tissue. The tunica adventitia is broad and contain numerous vasa vasorum.

General organization of vessels

 The tunica intima of veins is similar to that of arteries, but the internal elastic lamina is thin or absent  The tunica media is much thinner than the accompanying artery.  Tunica adventitia is much thicker than tunica media.

General organization of vesselsVein

Arteries Elastic Arteries  These are the largest arteries in the body, and include the aorta, pulmonary trunk and their major branches.  This elasticity permits elastic arteries to resist the force of pressure of the heart beat.

Elastic Artery

Arteries Muscular (distributing) Arteries  Muscular (Distributing) Arteries have the same basic structure as elastic arteries BUT the elastic tissue is reduced.  The tunica media is composed of concentric layers of smooth muscle.  They show a well-defined Internal elastic lamina (IEL).  They may show External (outer) elastic lamina (EEL).

Muscular Artery

The tunica intima (I), with its internal elastic lamina

Muscular Artery Tunica adventitia (A) is distinct in muscular arteries

Capillaries  Capillaries are the smallest blood vessels, and contain only a single layer of flattened endothelial cells and their basal laminae.  Muscular and adventitial layers are absent.  Pericytes may be present at the periphery of capillaries.  Capillaries are designed to permit exchange of gas, nutrient and waste in the tissue.  Connect the two sides.

Capillaries

Questions?