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Chapter 47 – The Circulatory and Respiratory Systems THE CIRCULATORY SYSTEM Most of the cells in the human body are not in direct contact with the external environment. The circulatory system acts as a transport service for these cells. Two fluids move through the circulatory system: blood and lymph. The blood, heart, and blood vessels form the cardiovascular system. The lymph, lymph nodes, and lymph vessels form the lymphatic system. The cardiovascular system and lymphatic system collectively make up the circulatory system. The Heart - Is the central organ of the cardiovascular system - It beats more than 2.5 billion times in one lifespan. - It is surrounded by a tough membrane called the pericardium o Used to reduce friction - it is divided vertically in half by the septum. o The right side of the heart pumps blood to the lungs; the left side pumps blood to the rest of the body. - there are upper and lower parts to the heart. The upper parts are the atria, the lower parts are the ventricles. o The atrioventricular valves (AV) separate the atria from the ventricles. The mitral valve (bicuspid) separates the left side. The tricuspid valve separates the right side. These both prevent blood from flowing back into the atria when blood is being pumped. - The semilunar (SL) valves prevent backflow of blood back into the ventricles. o The SL valve on the right side is called the pulmonary valve. o The SL valve on the left side is called the aortic valve. The Flow of Blood The right atrium the right ventricle the pulmonary arteries lungs the left atrium the left ventricle the aorta the body the vena cava. Control of the Heartbeat - done by the sinoatrial (SA) node (aka the pacemaker). o The electrical impulses of the SA node reach the AV node, which in turn causes the ventricles to contract, slightly after the atria. - the heartbeat has 2 phases: systole and diastole. o Phase one, systole, occurs when the ventricles contract , which closes the AV valves and opens the SL valves. o Phase two, diastole, occurs when the ventricles relax, closing the SL valves and opening the AV valves. If one valve fails to close properly, you develop what is known as a heart murmur. Blood Vessels - the circulatory system is a closed system because blood is contained within the heart or blood vessels all of the time. - The largest blood vessels are the arteries. o They have 3 layers: an inner endothelial layer, a middle smooth muscle layer, and an outer connective tissue layer. These give arteries their strength. The stretching of your arteries is known as your pulse. The force with which the blood moves through blood vessels is known as your blood pressure. Systolic pressure is caused by blood overcoming the pressure exerted by the cuff, which means that some blood has flowed through the artery. Diastolic pressure is caused by blood continuously flowing through the artery. o High blood pressure is known as hypertension. - Arteries turn into smaller blood vessels called arterioles. - Arterioles branch into capillaries. o Capillaries are the site of gas and nutrient exchange. - capillaries merge into thicker blood vessels called venules. - Venules form veins. o The inferior vena cava returns deoxygenated blood to the heart from the bottom of the body. o The superior vena cava returns deoxygenated blood to the heart from the upper part of the body. Patterns of Circulation - there are 2 types of blood circulation: pulmonary and systemic. o Pulmonary circulation is when blood travels between the heart and the lungs. Note: the pulmonary vein carries oxygenated blood into the left atrium of the heart. o Systemic circulation is when blood travels between the heart and the rest of the body (not the lungs). Coronary circulation is blood flow through the heart only and is a subdivision of systemic circulation. Artherosclerosis is a condition in which a blood vessel is blocked, thus impeding blood flow through the heart, and usually leads to a heart attack. Renal circulation is a type of systemic circulation that is characterized by blood flow to the kidneys. Hepatic portal circulation is a type of systemic circulation in which nutrients are absorbed in the small intestine and are transported to the liver for storage Lymphatic Circulation Lymph -a clear yellowish, slightly alkaline, coagulable fluid, containing white blood cells in a liquid resembling blood plasma, that is derived from the tissues of the body and conveyed to the bloodstream by the lymphatic vessels. - lymph vessels form a one-way system which transports excess lymphatic fluid back into the bloodstream and moves when skeletal muscles contract. - As lymph moves through the body, it passes through lymph nodes, which filter out impurities in the lymph before they reach the heart. o Lymphocytes are WBCs which are stored in the lymph nodes and will fight off bacteria and viruses. Composition of Blood - A healthy adult has about 4-5L of blood in their body. - Plasma is the liquid medium. It contains dissolved minerals and protein that nourish cells. It also carries waste products to the kidney for removal. o Proteins – albumin, blood clotting factors, antibodies. - RBCs (aka erythrocytes). Contains hemoglobin, which carries oxygen to the body (and sometimes CO2). o Mature RBCs don’t have a nucleus. o They are replaced every 120-130 days. - WBCs (aka leukocytes). Help defend the body against diseases. They are capable of changing shape in order to reach the site of infection. o Phagocytes o Antibodies - Platelets. Form blood clots using fibrin, which is a sticky substance that forms a net to capture RBCs so that a clot (scab) will form. Blood Types - A, B, O, AB and the Rh factor. o Erythroblastosis fetalis. The Lungs - are the site of gas exchange. - The left lung has 2 lobes, the right lung has 3. The Flow of Air Mouth/nose pharynx (protected by the epiglottis) trachea (the upper part is the larynx) two bronchi bronchioles alveoli Mechanisms for Breathing - Inspiration: the process of taking in air. o Flattens the diaphragm which allows the lungs to expand. - Expiration: the process of letting out air. o Diaphragm expands which causes the lungs to deflate. - the rate of breathing is controlled by the brain and the brain stem, which monitors the amount of CO2 present in the body and is all done subconsciously. o This subconscious control can be overridden for short periods of time, like for swimming underwater.