Anatomy & Physiology I and II

Anatomy & Physiology Study Guide • During exercise, blood flow to skeletal muscles rises at the expense of blood flow to non- essential organs, and cardiac output rises. Cardiovascular performance improves with training. Athletes have larger stroke volumes, slower resting heart rates, and larger cardiac reserves than do non-athletes. • Blood loss decreases blood volume, venous return, and cardiac output. Compensatory mechanisms can include an increase in cardiac output, a mobilization of venous reserves, peripheral vasoconstriction, and the release of hormones that further the retention of fluids and the creation of erythrocytes. • The blood–brain barrier, the coronary circulation, and the circulation to alveolar capillaries in the lungs are instances of special circulations, in which cardiovascular dynamics and regulatory mechanisms are different from those in other tissues. The pulmonary and systemic circuits in the cardiovascular system display three general functional patterns: • The peripheral distributions of arteries and veins are identical on both sides of the body, except near the heart. In the pulmonary circuit, deoxygenated blood enters the lungs in arteries, and oxygenated blood leaves the lungs via veins: • The pulmonary circuit consists of the pulmonary trunk, the left and right pulmonary arteries, and the pulmonary veins, which evacuate into the left atrium. 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. ©2018 Achieve Test Prep Page 276 of 367