Tara Feeney Oct. 24, 1997 1 st Period Cardiovascular System The cardiovascular system, also known as the circulatory system, refers to the course taken by the blood through the arteries, capillaries, and veins and back to the heart. This system enables dissolved materials - oxygen, carbon dioxide, nutrients, and wastes - to be transported throughout the body. Without the cardiovascular system the cells of the body would not be connected to the organs that obtain the needed materials and to those that dispose of wastes.

Arteriole: small artery Artery: blood vessel that carries blood away from the heart Atrium (atria): one of two upper chambers of the heart; receiving chamber of the heart. Capillary: microscopic blood vessels carrying blood from arterioles and venules. Cardiac cycle: each complete heartbeat, including contraction and relaxation of the atria and ventricles. Diastole: relaxation of the heart, interposed between its contractions Pulmonary circulation: blood flow from the lungs to the heart and back to the lungs where exchange of gases occurs. Systemic circulation: blood flow from the heart through the blood vessels to all parts of the body and back to the heart. Systole: contraction of the heart Vein: large blood vessel that returns blood to the heart.

Ventricle: one of two muscular lower chambers of the heart; pumping chamber of heart. Venule: small vein The cardiovascular system consists of a heart and a closed system of vessels called arteries, veins, and capillaries. The heart lies in the mediastinum, behind the body of the sternum between the lungs and above the diaphragm. Posteriorly the heart rests on the bodies of the thoracic vertebrate five through eight. The apex lies on the diaphragm, pointing to the left. The human adult heart is normally slightly large than a clenched fist with average dimensions of about 139 x 6 centimeters and weighing approximately 10.

5 ounces. The arteries, veins, and capillaries are all networked together throughout the body. Blood from the entire body is transported to the right atrium (auricle) through two large veins: the superior vena cava and the inferior vena cava. When the right atrium contracts, it forces the blood through an opening into the right ventricle. This opening is called the tricuspid valve (Blood is prevented from flowing backwards by the closing of each separate valve in the heart). Contraction of the right ventricle drives blood through the pulmonary valve into the pulmonary artery, which leads to the lungs.

It travels from the pulmonary artery to the lung capillaries, this is where the blood becomes oxygenated. The blood is brought back to the heart by four pulmonary veins, which enter the left atrium. When this chamber contracts, blood is forced into the left ventricle and then is forced into the aorta. The bicuspid, or mitral, valve prevents the blood from flowing back into the atrium, and the semilunar valves at the beginning of the aorta stop it from flowing back into the ventricle. Similar valves are present in the pulmonary artery.

The aorta divides into many branches, which in turn divide into smaller ones until the entire body is supplied by a branching series of blood vessels. The smallest arteries divide into a fine network of still more minute vessels, the capillaries, which have extremely thin walls. In the capillaries, the blood releases its oxygen to tissues, furnishes to the body cells the nutrients and other essential substance that it carries, and it takes up waste products from the tissues. The capillaries then come together to form small veins. Those veins unite with each other to form larger veins until the blood is finally collected into the superior and inferior vena cava from which it goes to the heart, completing the circuit. While this process is taking place typical sounds can be heard.

The sounds are generally referred to as lub b- dub b. The first sound, or systolic sound, is caused by the contraction of the ventricles and the closing of the atrioventricular (tricuspid and mitral) valves. The second sound, or diastolic sound, is caused by the closing of the semilunar (pulmonary and aortic) valves. Since the heart is a vital part of our well being it is important to keep it in good condition. However, problems do arise and there are many conditions and disorders of the cardiovascular system. Three examples are hypertension, heart failure, and congestive heart failure.

Hypertension, or high blood pressure, is very common. Over 60 million cases have been diagnosed in the US Ninety percent of these cases are primary-essential, idiopathic, that is there is no known cause. Secondary HON is caused by hormonal problems or kidney disease, or pregnancy, oral contraceptives, or other causes. Heart failure is the inability of the heart to pump enough blood to sustain life. Valve disorders can reduce the pumping efficiency. Cardiomyopathy is a disease of the myocardial tissue which can also reduce pumping effectiveness.

Right-side heart failure accounts for 25% of all cases of heart failure. It often results from left side heart failure or lung disorders that obstruct pulmonary circulation. Congestive heart failure, left-side heart failure, is the inability of the left ventricle to pump effectively. This results from myocardial infarction caused by coronary artery disease. It is called congestive heart failure because it decreases pumping pressure in the systemic circulation, which in turn causes the body to retain fluids. The cardiovascular system is critical in our bodies for the transportation of many nutrients.

Without the cardiovascular system our body would not be supplied with the necessary substance to stay alive. For this reason we must make sure to pay special attention to our hearts.