Circulatory System

I. What is the Circulatory System? A. The human circulatory system consists of the heart, a series of blood vessels, and the blood that flows through them. B. The Circulatory system has a very close relationship with our respiratory system that brings in the oxygen that is needed by each cell.

II. Functions of the Circulatory System A. Organisms composed of only a few cells rely on diffusion to obtain nutrients & remove waste B. Cells of larger organisms are not in direct contact with the environment. Instead they have a transportation system that moves substances from one part of the body to the other.

III. Components of the Circulatory System A. The heart, composed almost entirely of muscle (myocardium), is a hollow organ enclosed in a protective sac of tissue called the pericardium.

B. The heart can be divided into the left side & right side by the septum which prevents oxygen-rich blood mixing into oxygen-poor blood. C. The upper chambers, the atria, of the heart receives blood while the lower chambers, the ventricles, pump blood out

A Hole in the Heart

IV. Circulation Through the Body A. The heart functions as 2 separate pumps: – 1. Pulmonary circulation – the right side, pumps oxygen- poor blood from the heart to lungs – 2. Systemic circulation – the left side, pumps the oxygen-rich blood from the heart to the rest of the body B. Blood flows into the heart through the atria then flows into the ventricles and then is sent to either the lungs or rest of body. To prevent back flow there is connective tissue called valves (one direction flow)

V. Blood Vessels A. As blood flows through the circulatory system, it moves through 3 types of blood vessels – arteries, capillaries, & veins – 1. Arteries – large vessels that carry blood from the heart to the other tissues of the body (away from heart) – 2. Capillaries – smallest of the vessels, these are in charge of the exchange of oxygen/nutrients to tissues while getting rid of carbon dioxide/waste – 3. Veins – large vessels that contain valves that return the blood back to the heart.

VI. Blood Pressure A. When the heart contracts in produces a wave of fluid pressure in the arteries, the force on the walls is called blood pressure. – 1. Measured by a sphygmomanameter B. When your heart is relaxed your blood pressure decreases but the system is still under pressure. – 1. Normally regulated by the medulla oblongata (responsible for releasing neurotransmitters to relax/contract muscle along the vessel walls)

VII. Diseases of the Circulatory System A. Cardiovascular diseases common & a leading cause of death/disability in the U.S. – 1.. High Blood pressure – causes heart to work harder, which weaken & damage heart muscle – 2. Atheroscelerosis – fatty deposits called plaque build up in the arteries. a. May lead to a heart attack, which is due to the fact a part of the heart has died with the lack of oxygen. b. Blood clots may form & get free and head to the brain resulting in a stroke

IIX. Changes in Blood Pressure A. Factors that affect blood flow: – 1. How quickly heart pumps – 2. How much water is in blood – 3. Amount of salt in the blood – 4. How often you exercise (makes heart stronger)