Anatomy & Physiology

Anatomy & Physiology Study Guide The systemic circuit transports oxygenated blood from the left ventricle to tissues and organs other than the pulmonary exchange surfaces, and returns deoxygenated blood to the right atrium: • The ascending aorta gives rise to the coronary circulation. The aortic arch communicates with the descending aorta. • Three elastic arteries originate along the aortic arch: the left common carotid artery, the left subclavian artery, and the brachiocephalic trunk. • The remaining major arteries of the body begin at the descending aorta. • Arteries in the neck and limbs are deep beneath the skin; in contrast, there are two sets of peripheral veins, one superficial and one deep. This dual venous drainage is important for controlling body temperature. • The superior vena cava receives blood from the head, neck, chest, shoulders, and arms. The inferior vena cava collects most of the venous blood from organs inferior to the diaphragm. • The hepatic portal system directs blood from the other digestive organs to the liver before the blood returns to the heart. Modifications of fetal and maternal cardiovascular systems promote the exchange of materials, and independence is achieved at birth: • Blood flow to the placenta is provided by two umbilical arteries and is drained by a single umbilical vein. • The interatrial partition remains functionally incomplete until birth. The foramen ovale allows blood to flow freely from the right to the left atrium, and the ductus arteriosus short-circuits the pulmonary trunk. • The foramen ovale closes, leaving the fossa ovalis. The ductus arteriosus constricts, leaving the ligamentum arteriosum. • Congenital cardiovascular problems reflect abnormalities of the heart or interconnections between the heart and great vessels. Aging affects the blood, heart, and blood vessels: • Age-related changes in the blood include a decreased hematocrit, constriction or blockage of peripheral veins by a thrombus (stationary blood clot), and pooling of blood in the veins of the legs because valves are not working effectively. • Age-related changes in the heart include a reduction in the maximum cardiac output, changes in the activities of nodal and conducting cells, a reduction in the elasticity of the fibrous skeleton, progressive atherosclerosis that can restrict coronary circulation, and the replacement of damaged cardiac muscle cells by scar tissue. • Age-related changes in blood vessels, commonly associated with arteriosclerosis, include a weakening in the walls of arteries, potentially leading to the formation of an aneurysm; deposition of calcium salts on weakened vascular walls, increasing the risk of a stroke or myocardial infarction; and the formation of a thrombus at atherosclerotic plaques.

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