Circulatory System CH 17 Lesson 1

Functions Maintains internal environment in which all cells of your body are nourished. As your heart beats (pumps blood) blood vessels carry oxygen & nutrients to body cells. Carbon dioxide is carried along with waste matter from your cells and delivered to your lungs & kidneys for removal from body.

Structure of circulatory system Heart Blood Network of branching vessels (arteries, veins, and capillaries). These carry blood throughout the body.

heart Never rests. Beats continuously to send blood to lungs and rest of body. Much of heart consists of a special type of muscle called myocardium. When given sufficient oxygen & nutrients, the myocardium contracts rhythmically & automatically.

Chambers of the heart Septum – divides the interior of the heart into right & left halves. Each half has two chambers Upper chambers – atrium Lower (larger) chambers – ventricle One way valves are at the exit of each heart chamber guaranteeing that blood can only flow one direction.

Chambers of the heart

Right atrium serves as a natural pacemaker, controlling the rate at which the heart beats. This area sends an electrical impulse through the heart causing it to contract. This contraction forces blood forward into the ventricles. Within milliseconds, the same electric charge causes ventricles to contact, increasing the pressure of blood in the heart. This increased pressure causes the valves to close, preventing backflow.

Circulation in the heart Blood that has been depleted of oxygen but contains carbon dioxide and waste matter is carried to the heart by two large blood vessels called the vena cava. This blood enters the right atrium, is transferred to the right ventricle, and is then pumped to the lungs. In the lungs, the blood picks up oxygen from inhaled air and releases carbon dioxide. The newly oxygenated blood returns to the heart. Newly oxygenated blood enters the left atrium, is transferred to the left ventricle, and is then pumped to all the tissues of the body.

Blood Fluid that transports all of the substances your body needs to sustain life. Oxygen, hormones, and nutrients. It also carries away waste that cells produce. 55% of the total volume of blood is made up of plasma (fluid in which other parts of the blood are suspended). Plasma is most water, contains many important nutrients, salts, proteins, and blood cells. Blood cells include white & red blood cells.

Red Blood cells Carry oxygen from the lungs to the body tissues, where oxygen is exchanged for carbon dioxide. Each red blood cell contains hemoglobin (oxygen carrying part of blood). Rich in iron Binds with oxygen in lungs and releases oxygen in tissues Is the pigment that gives blood its red color

White blood cells Principle role is to protect body against infection and to fight infection when it occurs. Larger than red blood cells, but few of them. Production increases when there is infection in the body.

Platelets Platelets are the smallest type of blood cell. They prevent the body’s loss of blood. Initiate a chain reaction that causes blood to clot.

Blood vessels Blood is distributed throughout the body through a network of vessels. More than 60,000 miles of blood vessels in your body! They are divided into 3 groups: ARTERIES CAPILLARIES VEINS

Arteries Vessels that carry blood away from the heart. Pulmonary arteries carry blood from right ventricle (RV) to lungs. Systemic arteries carry blood from left ventricle (LV) through aorta. Arteries are flexible tubes with a smooth inner lining and thick walls so it can withstand the high blood pressure it is subjected to every time the heart beats. Arteries branch off into smaller vessels called arterioles (arterioles then break off into capillaries).

capillaries The smallest blood vessels. Carry blood between arterioles and small vessels called venules. Form a network throughout the body’s organ and tissues. Some are 50 times thinner than a single strand of hair. Can open & close in response to body’s needs. Play a role in regulating body temperature.

veins Capillaries lead into tine vessels called venules. The venules join to form veins. Veins are vessels that return deoxygenated blood toward the heart from the body’s organs and tissues. 2 main exceptions: pulmonary veins (carry O blood from lungs to left side of heart) & portal vein. Blood pressure in veins is lower than it is in arteries.

Your blood is not blue A common myth is that your deoxygenated blood is blue but when it hits oxygen (wound) it turns red. Your blood is AWLAYS red. Oxygenated or deoxygenated. Light wavelengths (specifically red/blue) and their absorption into skin give it the bluish look.

Lymphatic system Supports the circulatory system. All body tissues are bathed in a watery fluid that comes from blood. Much of this fluid returns to the blood through walls of capillaries. The remainder is carried to the heart though the lymphatic system. Serves 2 functions: Drains tissue fluid back into bloodstream Fights against infection. Lymphatic fluid is circulated by movement for the body’s muscles.

lymph A clear yellow fluid that fills the spaces around body cells. Made up of proteins, fats, and lymphocytes (white blood cells that protect against pathogens). 2 main types of lymphocytes: B CELLS T CELLS - killer cells - helper cells