10-8-10-10Circulation

10-8-10-10Circulation - Physiology of Aging THE CIRCULATORY...

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Physiology of Aging THE CIRCULATORY SYSTEM
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Page 2 Circulatory System consists of the HEART, the BLOOD, and three types of flexible tubes called the BLOOD VESSELS (FIGURE 4.1). ARTERIES channel blood from the heart to all parts of the body to CAPILLARIES which are the narrowest blood vessels. Nutrients and Oxygen diffuse into tissues and Waste Products and Carbon Dioxide diffuse out. Blood is carried through the VEINS to return to the heart. The passage of blood through vessels in a part of the body is called perfusion. Some waste materials do not pass into the blood but are collected by vessels called LYMPH VESSELS (FIGURE 4.2). LYMPH is carried through the lymph nodes where harmful chemicals and microbes are removed. The lymph is added to the blood in the veins before the blood enters the heart . MAIN FUNCTIONS FOR HOMEOSTASIS Transportation 1) Ensures concentrations of substances surrounding cells are kept at proper levels. Materials consumed by cells are replenished, and materials produced by cells are removed before their concentrations become too high. 2) Takes useful materials from their point of entry into the body (or production) to the organs that need them: oxygen, nutrients, hormones 3) As a person's rate of activity changes, the consumption of nutrients and the production of wastes and hormones also increases. Circulatory system helps the body adapt to these changes by increasing rate of blood flow through each part of the body. Defense 1) Lymph nodes trap and destroy dangerous chemicals and microbes. 2) Blood and lymph contain several types of White Blood Cells (WBC) which eliminate dangerous materials contained in blood and lymph. Some WBC on the inner walls of blood vessels, remove undesirable materials from blood. Other WBC leave capillaries and work among the cells. 3) Defense increases when needed. The number, mobility, and effectiveness of WBC increases if harmful microbes or foreign materials are detected within the body. Temperature Control 1) Temperature regulation and the role of dermal blood vessels in this process were discussed in Chapter 3. 2) Circulatory system also contributes to thermal regulation by distributing heat from heat-producing sites to colder areas; e.g. from muscles to spinal cord, bones, and skin. Acid/Base Balance 1) Most body functions are strongly affected by the balance between acidic and basic (or alkaline) materials. 2) The relative amounts of acids and bases are usually indicated by a numerical value called pH. The normal range for the body is about pH 7.35 to pH 7.45. 3) Metabolic processes result in the formation of acids. Foods and beverages also add acids or bases to the body. Excess acid or base must be neutralized or eliminated to maintain a proper
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Page 3 pH. Certain minerals and proteins in blood and red blood cells—buffers—act as reservoirs for acids. These buffers absorb and store excess acids. When the pH is too basic some of the stored acid is released to balance pH. THE HEART
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10-8-10-10Circulation - Physiology of Aging THE CIRCULATORY...

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