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به نام خدا English for the Students of Disaster Management & Related Subjects By: Dr. Gholamreza Poorheidari انتشارات :هوسسه آهوزش عالي علوي-كاربردي هالل ايراى تابستاى 87 فصل دوم Unit 2 )Human Body (2 تهيه كننده :اعظن ضياء بروجني شواره دانشجويي884700131049 : دانشجوي هديريت اهداد سوانح هعرفي به استاد 1390 1 Part I Section A: The Circulatory System The circulatory system is made up of the blood, the heart, and the blood vessels. Blood is the great delivery system for cells throughout the body. It carries nutrients and other products from the digestive tract in its plasma, and oxygen from the lungs in its hemoglobin. It also transports wastes produced by the cells to the lungs, kidneys, and other excretory organs for removal from the body. Heart The human circulatory system is a completely closed circuit of tube like vessels through which blood flows. The heart, by contracting and relaxing, pumps blood through the vessels. It is a powerful, hollow, muscular organ about as big as a man's clenched fist, shaped like a pear, and located in the left center of the chest, behind the sternum (breast bone). The heart is divided by a wall in the middle. Right and left compartments are divided into two chambers, atrium above, and ventricle below. Check valves are located between each atrium and its corresponding ventricle and at the exit of the major arteries leading out of each ventricle. 2 The opening and shutting of these valves at just the right time in the heartbeat keeps the blood from backing up. At each beat, or contraction, the heart pumps blood rich in carbon dioxide and low in oxygen from the right ventricle to the lungs and returns oxygen-rich blood to the left atrium of the heart. The left ventricle pushes blood rich in oxygen freshly obtained to the rest of the body and returns oxygen-poor blood to the right atrium. At each relaxation of the heart, blood flows into the left atrium from the lungs and into the right atrium from the rest of the body. Answer the following questions orally: 1.What is the circulatory system? 2.How does the blood act in the body? 3.What is the role of the heart in the body? 4.Do you know about the heart compartments? 5.What do the heart valves do? 6.What does happen at each beat? Section B: Blood Vessels & Blood Pressure The arteries are elastic, muscular tubes that carry blood away from the heart. They begin at the heart as two large tubes: the pulmonary artery, which carries blood to the lungs for the carbon dioxide-oxygen exchange, and the aorta, which carries blood to all the other parts of the body. The aorta divides and subdivides until it ends in networks of 3 extremely fine vessels smaller than hairs. Through the thin walls of the capillaries, oxygen and food pass out of the bloodstream into the stationary cells of the body, while the body cells discharge their waste products into the bloodstream. In the capillaries of the lungs, carbon dioxide is released and oxygen is absorbed. Capillaries, having reached their limit of subdivision, begin to join together again into veins. The veins become larger and larger and finally form major trunks that empty blood returning from the body into the right atrium and blood from the lungs into the left atrium. It is impossible to prick normal skin anywhere without puncturing capillaries. Because the flow of blood through the capillaries is relatively slow and under little pressure, blood merely oozes from a punctured capillary and usually has time to clot, promptly plugging the leak. 4 Each time the heart contracts, the surge of blood can be felt as a pulse at any point where an artery lies close to the surface of the body, near the skin surface and over a bone. When an artery is cut, blood spurts out. There is no pulse in a vein because the pulse is lost by the time the blood has passed through the capillaries. Hence, blood from a cut vein flows out in a steady stream. It has much less pressure behind it than blood from a cut artery. Major locations for feeling pulses include the following: Carotid: the major artery of the neck, which supplies the head with blood. Pulsations can be palpated (felt) on either side of the neck (do not try to feel both at the same time). Use the carotid to check an unconscious person's pulse. Femoral: the major artery of the thigh supplying the lower extremities with blood. Pulsations can be palpated in the groin area (the crease between the abdomen and thigh). Radial: the major artery of the lower arm. Pulsations can be palpated at the palm side of the wrist on the thumb side. Use the radial to check a conscious person's pulse. Brachial: an artery of the upper arm. Pulsations can be palpated on the inside of the arm between the elbow and the armpit. Use the brachial to determine a pulse in an infant. 5 Posterior tibial: located behind the inside ankle knob. Pulsations can be palpated on the posterior surface of the medial malleolus. Dorsal is paddies: Pulsations can be palpated on the top surface of the foot (20% of the population has no pulsations). Blood pressure Blood pressure is a measure of the pressure exerted by the blood on the walls of the flexible arteries. Blood pressure may be high or low according to the resistance offered by the walls to the passage of blood. This difference in resistance may be due to several causes. For example, if blood does not fill the system, as following hemorrhage, the pressure will be low (hypotension). High blood pressure (hypertension) may be present when the arterial walls have become hard and cannot expand readily. Part II: Exercises Exercise- 1: Read the following statements and decide whether they are True or False 1.The heart is about the size of clenched fist and shaped like a pear. A pulse happens where a vein passes near the skin's surface and over a bone. 3.Hemorrhage is the term for profuse bleeding. 4.The heart receives its nutrients and oxygen via the coronary veins. 5.The right ventricle pumps blood to the body. 6 6.The lungs absorb the oxygen. 7.The arteries are the muscular tubes that carry blood to the heart. 8.The pulmonary artery carries blood to the lungs for the carbon dioxide oxygen exchange. 9.Hypertension will present if the arterial walls become hard and cannot expand readily. Part III: Homework A. Reading Comprehension: Blood Blood has liquid and solid portions. The liquid portion is called plasma. The solid portion, which is transported by the plasma, includes disk-like red blood cells; slightly larger, irregularly shaped white blood cells; and an immense number of smaller bodies called platelets. Plasma, the liquid part of the blood, is about 90% water, in which minerals, sugar, and other materials are dissolved. Plasma carries food materials picked up from the digestive tract and transports them to the body cells. It also carries waste materials produced by cells to the kidneys, digestive tract, sweat glands, and lungs for elimination (excretion) in urine, feces, sweat, and expired breath. The red blood cells, which give blood its color, carry oxygen to the organs. The white blood cells are part of the body's defense against bacteria. These cells can go wherever they are needed in the body to fight infection, for example, a wound in the skin or other tissue that is diseased or injured. Pus, a sign of wound infection, gets its 7 yellowish-white color from the innumerable white blood cells that are fighting the invading bacteria. Platelets are essential for the formation of blood clots. If blood plasma did not clot at the site of a wound, the slightest cut or abrasion would produce death from bleeding. Clots plug the openings through which blood escapes from punctured blood vessels. Bleeding from a large blood vessel may be too rapid to permit the formation of a clot. Hemorrhage is the term for profuse bleeding. Perfusion refers to the circulation of blood through an organ or a structure. Hypo perfusion is the inadequate circulation of blood through an organ or a structure. The average-size adult male has about six quarts (12 pints) of blood. Inadequate circulation is known as shock (hypo perfusion). Shock is a state of profound depression of the vital processes of the body, characterized by the following signs and symptoms: pale, cyanotic (bluish), cool, clammy skin; rapid pulse; rapid breathing; restlessness, anxiety, or mental dullness; nausea and vomiting; reduction in total blood volume; low or decreasing blood pressure; and subnormal temperature. 8