Practice Test 1

OVERVIEW

The cardiocirculatory system consists of blood, vessels to transport the blood, and a four-chambered muscular pump called the heart. The cardiocirculatory system is responsible for transporting food and oxygen to all the cells and organs of the body.

Blood vessels in the lungs absorb oxygen that is inhaled from the air, and blood vessels in the small intestine absorb food materials from the digestive tract. Blood also provides a means whereby cellular wastes, i.e., carbon dioxide and urea, are transported to the lungs and kidneys, where they are eliminated from the body.

Blood Vessels

There are three types of blood vessels: arteries, veins, and capillaries.

Arteries

Arteries are large vessels that carry oxygenated blood away from the heart. In order to withstand the high pressure of the heart's pumping action, arteries are made of connective tissue, elastic fibers, and inner walls of epithelial cells. As the heart forces blood into the arteries, their elastic qualities enable them to expand and contract. Some of the arteries in the body are very large compared to their smaller branches, called arterioles. The walls of arterioles are much thinner than the walls of the larger arteries. The thin walls of arterioles allow them to carry blood to the smallest of vessels, which are known as capillaries.

Capillaries

The walls of capillaries are very thin (just one epithelial cell thick). Because they are so small (microscopic), they are capable of allowing oxygen and nutrients to pass out of the bloodstream and into the tissue fluid (interstitial fluid) that surrounds all body cells. Once nutrients and oxygen are inside the cells, the nutrients are burned (catabolized) and needed energy is released within the cells. At the same time that oxygen and nutrients are passing into the interstitial fluid, the waste products of catabolism, namely, carbon dioxide and water, pass out of the cells and into the thin-walled capillaries. These waste products flow back to the heart via small veins known as venules, which branch to form larger vessels known as veins.

Veins

Veins do not have to withstand the pressures that arteries do. Therefore, vein walls are thinner than arterial walls, and veins are less elastic and have less connective tissue than arteries. Compared to arteries, blood pressure in the veins is low. To keep blood flowing toward the heart, veins have small valves on their inner walls that prevent blood from flowing backward. In addition to these valves, muscular action also helps to "milk" blood flow along in the veins.

The Heart

The four chambers of the heart actually form two pumps. The right side of the heart pumps blood from the heart into the lungs, where it gives off carbon dioxide and picks up oxygen; the left side of the heart pumps the oxygenated blood from the lungs into the body.

Pulmonary Circulation

Pulmonary circulation consists of the flow of blood through the vessels from the heart to the lungs and then back to the heart again.

When blood goes into the heart, the top two chambers (the right and left atria) relax and deoxygenated blood flows from the veins into the right atrium. This is known as venous return. At the same time, oxygenated blood coming from the lungs flows into the left atrium. At this point the blood-filled atria contract and the blood pushes open the heart valves (the bicuspid and tricuspid valves). This allows oxygenated blood from the left atrium to pass into the left ventricle, and deoxygenated blood from the right atrium to pass into the right ventricle.

When blood leaves the heart, the right and left ventricles contract and deoxygenated blood in the right ventricle flows into the lung (via the pulmonary artery), where it will give off its carbon dioxide and pick up oxygen, and oxygenated blood in the left ventricle flows out of the heart (via the coronary arteries and aorta), where it begins its travels into the body.

Diseases/disorders of the Cardiocirculatory System Include

Acquired Inflammatory Heart Disease

Endocarditis Other names for endocarditis are infective or bacterial endocarditis. The infection affects the endocardium, heart valves, or cardiac processes and is characterized by bacteria or fungi creating vegetative growths on the heart valves and on the endocardial lining of the heart chambers. These growths may also be located on the endothelium of a blood vessel, where they may embolize to organs such as the spleen, kidneys, central nervous system, and lungs. An organism commonly associated with endocarditis is Streptococcus viridans.

Myocarditis Myocarditis is associated with diffuse inflammation of the cardiac muscle (the myocardium). This condition is caused by viral infections, bacterial infections, immune reactions, radiation therapy, chemical poisons, parasitic infestations, and helminthic infestations.

Pericarditis Pericarditis is the inflammation of the pericardium (the membranous fibroserous sac that encloses the heart and the bases of the great vessels). Common causes include infections with bacteria, viruses, or fungi; also neoplasms, radiation to the chest, and postcardiac injury.

Rheumatic Fever/Heart Disease Rheumatic fever is a consequence of infection with a group of beta-hemolytic streptococcal bacteria. Rheumatic heart disease refers to the sequelae, or aftereffects, of rheumatic fever, and may include: Myocarditis, pericarditis, endocarditis, and eventually, valvular disease.

Cardiac Complications

Cardiac Arrhythmias/Dysrhythmias Cardiac arrhythmias/dysrhythmias are faulty electrical conductions that change the rate and rhythm of the heart. Types of arrhythmias include: Sinus arrhythmia, sinus tachycardia, sinus bradycardia, sinoatrial arrest/block, premature atrial contraction, ventricular tachycardia, and ventricular fibrillation.

Cardiac Tamponade Cardiac tamponade is a sequela of pericarditis or injuries to the heart or great blood vessels that cause an accumulation of blood in the pericardial sac. The classic signs of cardiac tamponade are increased venous pressure with neck vein distention, reduced arterial blood pressure, muffled heart sounds, and pulsus paradoxus (an abnormal...