Thursday 18 June 2009

Circulatory system

We need a transportation system to link up different parts of our body, to supply nutrients and oxygen, and take away wastes and carbon dioxide. It’s known as the circulatory system, made up of the followings: 1) Blood, fluid that transport materials. It’s the suspension of cells in a pale yellow liquid called plasma, containing water, dissolved nutrients, wastes and other substances, and make up 55% of blood. (tables of different blood cells missed here.) 2) Blood vessels, a network of tube for blood to pass through. (Arteries, capillaries and Veins) (Tables on different kinds of blood vessels missed here) 3) Heart, the pump to make the blood to circulate the network. Blood flows like this “(different parts of our body)→right auricle→right ventricle→lung→left auricle→left ventricle”. There’re heart strings to hold the valves between auricles and ventricles, septum is used to separate the left and right parts of heart, and there’re valves in the arteries in the heart (the only arteries that have valves) When auricles relax, blood flows in the auricles, when it contract, blood was squeezed into ventricles, and when ventricles contract, it flows into the large arteries. Blood flows through the heart twice (lung: pulmonary circulation and the rest of the body: systemic circulation) to complete one circulation so it’s called double circulation. Heartbeat rate, pulse rate and blood pressure can be the indicators of our health. Heartbeat rate which we can feel at left chest, equal our pulse rate which we can feel it on areas that arteries pass through near the skin, e.g. wrist, neck and temple. It’s about 70 when we’re at rest. Varies of diseases can be indicated in the change of rate, rhythm and force of the pulse. When blood is pumped out, it rushes into blood vessels and presses on their walls and produces a pressure on the blood vessels, called blood pressure. It’s measured in millimeters of mercury (mm Hg). When the heart contracts, it’s about 120mm Hg, when the heart relax, it’s about 80mm Hg, and it’s expressed as 120/80mm Hg. It can be measured with a stethoscope and a sphygmomanometer. There’re also some electronic measuring devices as well. However, it will change with age, sex, health condition and the mood of the person. Eating for a healthy circulatory system We should not eat a lot of cholesterol, which always appear in fatty foods. Some of them come from membranes and hormones, and also come from our body. There are some uses in our body, but it’ll also deposits in the inner walls of the blood vessels and hardens the walls and cause high blood pressure. When the deposits keep increasing, it’ll even trigger the blood platelets to form clots and totally stuck the blood vessels. If blockage happens in the cor0onary arteries, supply of O2 and nutrients for heart muscles is not enough, coronary heart disease my happen and heart attack will happen. If blockage or rupture happens in the brain arteries, stroke may result, brain cells which can’t be recovered are damaged due to lack of O2, paralysis or death may happen depends on how the brain is damaged. We avoid eating of fatty meats, organ meats and egg yolk. It’s recommend that we shouldn’t take over 300mg per day. Fats are made up of glycerol and fatty acids and can be classifying into two types: 1) Saturated fatty acids raise the cholesterol level in blood. They mainly come from animal origin and some plant product such as coconut and palm oil. 2) Unsaturated (can be further classify into monounsaturated and polyunsaturated) fatty acids reduce the cholesterol level in the blood, usually found in nuts, seed, nuts and oil. No. of red/white blood cells, blood platelets, blood haemoglobin content, blood glucose and blood cholesterol is also indicators of health. We have to keep fit (fitness of body, not the body shape) to have a higher resistance to disease, withstand stress better, react faster, keep a good body figure with healthy weight and fully enjoy our life. There’re several indicators: 1) Body Mass Index (BMI) = Weight (kg)/height (m)2, and18.5-24.9 is normal. Regular exercises help us to keep normal weight. 2) Pulse rate. Healthier person has a healthier heart that can pump more efficiently, and they have a lower resting pulse rate and shorter recovery time after exercise. 3) Vital capacity is the max. vol. of air can be blow out from the lung by the deepest breath, which can be measured by a breath volume kit. Normally 4000mL. 4) S-factors: Strength – the amount of force that your muscles can exert; suppleness --- for us to stretch, bend and twist freely; and stamina keep us going when we exercise hard. Stronger heart and lungs can supply more oxygen to support us.

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