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circulatory system.docx

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Laura Parker

Circulatory System - the circulatory system is the transport system for the body - it moves blood to all cells of the body - the blood carries nutrients, oxygen, and wastes among other things Heart - the job of the heart is to pump blood to all parts of the body - the blood travels through blood vessels - it is really a double pump: - the right side pumps blood to the lungs - the left side pumps blood to the rest of the body - each side is divided into two chambers: - smaller, upper chambers called the left and right atrium - larger, lower chambers called the left and right ventricle - the atria receive blood coming to the heart and pump it to the ventricles - the ventricles are much stronger as they must pump blood to all parts of the body - when the atria fill with blood they contract, pushing blood into the ventricles - when the ventricles fill with blood they contract, pushing blood to other parts of the body Heart Valves - valves are strong flaps of tissue that act as a one-way door - when a chamber contracts, the valves close to prevent blood from flowing backward - e.g., blood can pass easily from the left atrium into the left ventricle but it cannot flow back - the valves between atria and ventricles are called AV valves - the valves between ventricles and blood vessels are called semilunar valves - when the ventricles contract, the AV valves close to prevent blood flowing back into the atria Heartbeat - the pumping rhythm of the heart is called the heartbeat - the sound of the heartbeat is made by the valves closing - the first sound of the beat is caused by the AV valves closing - the second sound is caused by the semilunar valves closing Blood Vessels The circulatory system has three kinds of blood vessels: 1. Arteries - carry blood away from the heart - they have thick, muscular walls - when the heart beats, it forces blood into the arteries - the elastic arteries stretch when they fill with blood - you can feel this as your pulse - blood pressure is the force of blood pushing against the walls of the arteries 2. Veins - carry blood back to the heart - they have thinner walls than the arteries and are less muscular - the blood in veins is at lower pressure so they do not need to be as strong - this low pressure makes it difficult for blood to get back to the heart - as skeletal muscles push against veins, blood is squeezed out an helped back to the heart - veins have valves that prevent blood from flowing backward 3. Capillaries - these are the smallest blood vessels that connect the branches of arteries and veins - they have very thin walls so materials can move into and out of them easily - everything carried by the blood is exchanged with body cells through the walls of capillaries - nutrients and oxygen move from the blood to body cells - carbon dioxide and other wastes move from body cells into the blood Diseases of the Circulatory System - Heart disease is the leading cause of death in North America - there are several common disorders of the circulatory system: Heart murmur - caused by a damaged valve which does not close properly - blood flows back through the valve and causes a swishing sound High Blood Pressure - blood pressure is recorded as two different numbers and expressed as a fraction - the top number is the pressure when the ventricles are contracting - when the heart pumps - the bottom number is the pressure when the ventricles are relaxed - a blood pressure of 120/80 is normal - high blood pressure is dangerous because it puts extra strain on the heart - high blood pressure can be caused by different things: - genetics (family history) - a high salt diet - narrowing arteries from a high fat diet. Cholesterol can deposit on the walls of an artery, making it narrower. It is more difficult for blood to move through the narrow artery so the heart must work harder. Heart Attack - the heart is made of living muscle cells and they need blood to survive - if an arter
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