What Is Ventilation In The Body
The body has a self-regulating system for maintaining its temperature at an appropriate level. This system depends on two factors — heat production in the body’s cells and convection (or circulation) to remove excess heat from various parts of the body. Heat can be generated within the body’s cells when they metabolize food, digest it, and so on. As long as the metabolic activity continues, the temperature will rise. However, cell metabolism cannot continue forever without cessation. Therefore, after about three hours, there must come a time when enough energy is being produced to maintain the current temperature while new energy is also being used up to keep the process going. When this happens, the temperature begins to fall slightly until it stabilizes at a certain level that is neither hot nor cold.
Heat can move away from the body if there is a difference in temperature between the inside and outside surfaces of the skin. For example, if you are lying on your back with your head higher than your feet, then the surface area of your head is much greater than that of your feet. Thus, more heat will accumulate near the head than near the feet. If the heat were allowed to remain, it would gradually build up toward the head. But the body has developed special mechanisms called circulatory systems to remove excess heat from various parts of the body. These systems consist of blood vessels and lymphatic vessels which carry blood and lymph fluid out of the capillaries and into larger arteries and veins. Here, they mix with fresh supplies of oxygenated blood and return them to all parts of the body.
Circulation carries waste products such as carbon dioxide out of the tissues and returns them to the lungs where they are exhaled. Waste nitrogen remains in the tissues and passes out of the body by way of urine and feces. Circulation removes these materials from the tissues and flushes them out of the body. It does not merely pass across the surface of the membranes but actually penetrates deep into the tissues.
In addition to removing waste products, circulation keeps the body’s tissues healthy by providing nourishment. Blood transports nutrients like carbohydrates, amino acids, fatty acids, minerals, vitamins, hormones, and gases to every part of the body. Nutrients contain essential elements that tissue cells need to grow and function normally. Without proper circulation, the human body could not survive very long. The heart pumps blood through the blood vessels to deliver oxygen and nutrition throughout the entire organism.
The rate of ventilation determines how fast we perspire. We lose water vapor through our pores in sweat. Sweat rates vary according to environmental conditions. Average daily sweats range from one liter to four liters per day based upon climate and exercise. During rest, sweating averages about 0.3 liters per hour. Exercise increases the rate of perspiration, rising to 1 liter per minute during intense exertion.
We breathe air to supply the body with oxygen for fuel and to eliminate carbon dioxide. Our lungs extract oxygen directly from air while blood delivers it to the organs. Carbon dioxide leaves the body in breath. Two types of breathing occur: inhalation and exhalation. Exhalation occurs when we inhale deeply and slowly, filling the lungs completely. When we hold our breath, the lungs contract, forcing the air down into the chest cavity. At the same time, the diaphragm and other abdominal muscles relax, allowing the stomach contents to drop downward and expand. Then the lungs fill with air. Expansion of the lung capacity takes place only when the lungs become fully filled. After the lungs have been completely filled, further expansion is prevented by elastic ligaments surrounding each lobe.
During inspiration, the upper portion of the chest expands first. Next, the lower lobes follow. Finally, the middle lobes close. They do so rapidly and then open again. All the while, the diaphragm contracts; it pushes against the liver and spleen. By contracting the diaphragm, the respiratory tract becomes shorter and narrower. With narrowing of the trachea, the volume of air passing through the bronchial tubes decreases. Air enters the lungs first in the region nearest the top of the chest. Because some of the air stays behind in the smaller branches of the pulmonary artery, the amount of oxygen in the blood increases. The increased oxygen concentration causes the heart beat to increase temporarily.
When the upper portions of the lungs are full, the next phase begins – exhalation. The air rises gently from the bottom of the lungs and exits through the mouth. The diaphragm relaxes, and the abdomen flattens. The large intestines descend and empty their content into the rectum. The liver, stomach, and kidneys enlarge and begin producing bile. The liver releases stored vitamin A into the small intestine. Digestive juices begin breaking down fats and proteins. The pancreas secretes insulin to control sugar levels. Secretions from the thyroid gland regulate the body’s metabolism.
About 12 percent of the oxygen we breathe is absorbed by hemoglobin in the red blood cells. Most of the remaining percentage goes to the mitochondria in the cytoplasm of muscle cells and to the Krebs cycle in the liver. Some flows to the lungs’ alveoli to support respiration. Only a little reaches the tissues of the brain where it supports the chemical reactions involved in nerve impulses. About 2 percent of the oxygen in air diffuses across the inner membrane of the eye lens and helps form the crystalline structure of the cornea. Another tiny fraction is needed by the retina to lighten the image seen by the optic nerves.
All animals require both respiration and digestion. Respiration provides the source of energy for muscular activities, growth, and maintenance. Digestion produces the bulk of the animal body’s calories. Animals depend mainly upon respiration for their existence. Plants, however, absorb carbon dioxide from the air and release oxygen. This enables them to use sunlight for photosynthesis. Photosynthesis is the primary means of converting solar power into chemical energy.
Animals depend primarily upon respiration for their existence. Plants, however, absorb carbon dioxide from the air and release oxygen. This enables them to use sunlight for photosynthesis. Photosynthesis is the primary means of converting solar power into chemical energy. Animals differ from plants because they are able to transform the carbon dioxide and water into glucose and protein. Glucose serves as the principal material for cellular respiration. Proteins are made of chains of amino acid units linked together by peptide bonds. Amino acids arise naturally in foods, either free or combined with sugars.
Plants produce oxygen instead of using it up. Oxygen is necessary for the combustion of organic matter and for the formation of carbohydrates and fat. In addition, it is required for other chemical processes in plant life. Although plants lack the ability to convert atmospheric molecules, they still obtain oxygen. Light acts as an electron acceptor. Through photosynthesis, green plants take in carbon dioxide and combine it with water and sunlight. This forms carbohydrate. Later, the plant turns the carbohydrate into cellulose. Cellulose is the basic building block of plants. Chlorophyll makes possible the transfer of energy from sun radiation to oxygen in green plants. The chloroplasts located in the leaf cells contain enzymes capable of combining carbon dioxide, water, and visible light.
Carbon dioxide, water, and sunlight react chemically in the presence of the enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase to form the compound ribulose 5-phosphate, which is then converted into glucose-6-phosphate. The CO2 molecule combines with six hydrogen atoms to make glucose-6-phosphate, which is broken down to pyruvic acid and finally changed into acetaldehyde. Acetaldehyde reacts with another CO2 molecule to form acetic acid, which is later oxidized to carbon dioxide. The process of photosynthesis converts sunlight into usable energy.
Animal organisms require oxygen for respiration and for the conversion of glucose into glycogen. Animals also require oxygen to perform oxidation-reduction reactions. Glycogen stores are formed when starch in the diet is digested into glucose. Glucose is transported into the bloodstream and taken to the liver, where it is transformed into triglycerides. Triglycerides are esters of glycerol and fatty acids. Fatty acids are composed of carbon, hydrogen, and oxygen. Three different kinds of fatty acids exist: saturated, unsaturated, and polyunsaturated. Saturated fatty acids contain even numbers of carbon atoms. Unsaturated fatty acids contain odd numbers of carbon atoms. Polyunsaturated fatty acids contain multiple double bonds between pairs of adjacent carbon atoms.
Fatty acids serve many functions in the body. They help transport lipids around the body, aid in hormone secretion, and protect cell membranes. Their most important function is to provide insulation. Fat surrounds the vital organs of the body and cushions the bones. Lipid deposits may cause bone loss.
Lipids are substances whose molecular structures include at least one nonpolar hydrocarbon chain. Nonpolar chains are hydrophobic. Hydrophilic compounds are those that attract water. Water is polar because it contains oxygen and thus is attracted to opposite charges.
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