Circulatory System

3 Pages 870 Words

Blood must be moved through the body continuously throughout an animal’s life. Every human’s heart consists of muscular chambers capable of strong contractions. Chambers called atria collect blood. Atrial contractions send blood into the ventricles, which are chambers whose contractions circulate blood through the body.
Arteries and arterioles are thick-walled vessels that carry blood away from the heart. Arteries carry blood away from the heart. These vessels have thick walls embedded with smooth muscle and elastic tissue. With each surge of blood from the ventricles, the arteries expand slightly. As their elastic walls recoil between heartbeats, the arteries actually help pump the blood and maintain a steady flow through the smaller vessels. Arteries branch into vessels of smaller diameter called arterioles, which play a major role in determining how blood is distributed within the body.
Human hearts can be considered as two separate pumps, each with two chambers. In each pump an atrium receives and briefly stores the blood, passing it to a ventricle that propels it through the body. One pump, consisting of the right atrium and right ventricle, deals with deoxygenated blood. The right atrium receives oxygen-depleted blood from the body through a large vein called the superior vena cava. The right atrium contracts, forcing the blood into the right ventricle, Contraction of the right ventricle sends the oxygen-depleted blood to the lungs via pulmonary arteries, which are vessels that carry blood away from the heart. The other pump, consisting of the left atrium and ventricle deals with oxygenated blood. Oxygen-rich blood from the lungs enters the left atrium through pulmonary veins and is then squeezed into the left ventricle. Strong contractions of the left ventricle, the heart’s most muscular chamber, send the oxygenated blood coursing out through a major artery, the aorta, to the rest of the body.
Veins ...