| Respiratory System |
Article Index for Respiratory |
Website Links For Respiratory System |
Information AboutRespiratory System |
| CATEGORIES ABOUT RESPIRATORY SYSTEM | |
| exercise physiology | |
| respiratory systemexercise physiology | |
| respiratory system | |
| organ systems | |
| respiration | |
|
Among Quadruped s, the respiratory system generally includes tubes, such as the Bronchi , used to carry Air to the Lungs , where gas exchange takes place. A Diaphragm pulls air in and pushes it out. Respiratory systems of various types are found in a wide variety of organisms. Even trees have respiratory systems. In Human s and other Mammal s, the respiratory system consists of the airways, the lungs, and the respiratory muscles that mediate the movement of air into and out of the body. Within the Alveolar system of the lungs, molecules of Oxygen and Carbon Dioxide are passively exchanged, by Diffusion , between the gaseous environment and the blood. Thus, the respiratory system facilitates oxygenation of the blood with a concomitant removal of carbon dioxide and other gaseous metabolic wastes from the circulation. The system also helps to maintain the acid-base balance of the body through the efficient removal of carbon dioxide from the blood. ANATOMY In humans and other animals, the respiratory system can be conveniently subdivided into an Upper Respiratory Tract (or ''conducting zone'') and Lower Respiratory Tract (''respiratory zone''), trachea and lungs. Air moves through the body in the following order:
Upper respiratory tract/conducting zone The conducting zone begins with the (behind the oral cavity). The oropharynx leads to the Laryngopharynx , and empties into the Larynx (voicebox), which contains the Vocal Cords , passing through the Glottis , connecting to the Trachea (wind pipe). Lower respiratory tract/respiratory zone The trachea leads down to the s. The bronchioles lead to the respiratory zone of the lungs which consists of Respiratory Bronchiole s, Alveolar Duct s and the Alveoli , the multi-lobulated sacs in which most of the gas exchange occurs. VENTILATION Ventilation of the lungs is carried out by the muscles of respiration. Control Inhalation Inhalation is initiated by the Diaphragm and supported by the External Intercostal Muscles . Normal resting respirations are 10 to 18 breaths per minute. Its time period is 2 seconds. During vigorous inhalation (at rates exceeding 35 breaths per minute), or in approaching respiratory failure, Accessory Muscles Of Respiration are recruited for support. These consist of Sternocleidomastoid , Platysma , and the Strap Muscles Of The Neck . Inhalation is driven primarily by the Diaphragm . When the diaphragm contracts, the ribcage expands and the contents of the abdomen are moved downward. This results in a larger thoracic volume, which in turn causes a decrease in intrathoracic pressure. As the pressure in the chest falls, air moves into the conducting zone. Here, the air is filtered, warmed, and humidified as it flows to the lungs. During forced inhalation, as when taking a deep breath, the External Intercostal Muscles and accessory muscles further expand the thoracic cavity. Exhalation Exhalation is generally a passive process, however active or ''forced'' exhalation is achieved by the Abdominal and the Internal Intercostal Muscles . The lungs have a natural elasticity; as they recoil from the stretch of inhalation, air flows back out until the pressures in the chest and the atmosphere reach equilibrium.A simple can be built from a Bell Jar During forced exhalation, as when blowing out a candle, expiratory muscles including the Abdominal Muscles and Internal Intercostal Muscles , generate abdominal and thoracic pressure, which forces air out of the lungs. CIRCULATION The right side of the heart pumps blood from the Right Ventricle through the Pulmonary Semilunar Valve into the Pulmonary Trunk . The trunk branches into right and left Pulmonary Arteries to the Pulmonary Blood Vessel s. The vessels generally accompany the Airway s and also undergo numerous branchings. Once the gas exchange process is complete in the pulmonary capillaries, blood is returned to the left side of the heart through four Pulmonary Veins , two from each side. The Pulmonary Circulation has a very low resistance, due to the short distance within the lungs, compared to the Systemic Circulation , and for this reason, all the pressures within the pulmonary blood vessels are normally low as compared to the pressure of the systemic circulation loop. Virtually all the body's blood travels through the lungs every minute. The lungs add and remove many chemical messengers from the blood as it flows through pulmonary capillary bed . The fine capillaries also trap blood clots that have formed in systemic veins. GAS EXCHANGE The major function of the respiratory system is , a life threatening condition, and 2) Respiratory Alkalosis . Upon inhalation, gas exchange occurs at the Alveoli , the tiny sacs which are the basic functional component of the lungs. The alveolar walls are extremely thin (approx. 0.2 micrometres), and are permeable to gases. The alveoli are lined with pulmonary capillaries, the walls of which are also thin enough to permit gas exchange. All gases diffuse from the alveolar air to the blood in the pulmonary capillaries, as carbon dioxide diffuses in the opposite direction, from capillary blood to alveolar air. At this point, the pulmonary blood is oxygen-rich, and the lungs are holding carbon dioxide. Exhalation follows, thereby ridding the body of the carbon dioxide and completing the cycle of respiration. In an average resting adult, the lungs take up about 250ml of oxygen every minute while excreting about 200ml of carbon dioxide. During an average breath, an adult will exchange from 500 ml to 700 ml of air. This average breath capacity is called Tidal Volume . DEVELOPMENT The respiratory system lies dormant in the human fetus during pregnancy. At birth, the respiratory system is drained of fluid and cleaned to assure proper functioning of the system. If an infant is born before forty weeks gestational age, the newborn may experience respiratory failure due to the under-developed lungs. This is due to the incomplete development of the Alveoli type II cells in the lungs. The infant lungs do not function due to the collapse of the alveoli caused by surface tension of water remaining in the lungs. Surfactant is lacking from the lungs, leading to the condition. This condition may be avoided if the mother is given a series of steroid shots in the final week prior to delivery. The steroids accelerate the development of the type II cells. Department of Environmental Biology, University of Adelaide, Adelaide, South Australia ROLE IN COMMUNICATION The movement of gas through the larynx, pharynx and mouth allows Human s to speak, or '' Phonate ''. Because of this, gas movement is extremely vital for communication purposes. CONDITIONS OF THE RESPIRATORY SYSTEM Disorders of the respiratory system can be classified into four general areas:
The respiratory tract is constantly exposed to Microbe s due to the extensive surface area, which is why the respiratory system includes many mechanisms to defend itself and prevent Pathogen s from entering the body. Disorders of the respiratory system are usually treated internally by a Pulmonologist . GAS EXCHANGE IN PLANTS Plants use Carbon Dioxide gas in the process of Photosynthesis , and then exhale Oxygen gas, a waste product of photosynthesis. However, plants also sometimes respire as humans do, using Oxygen and producing Carbon Dioxide . Plant respiration is limited by the process of . Most plants have relatively few living cells outside of their surface because Air (which is required for metabolic content) can penetrate only skin deep. However, most plants are not involved in highly Aerobic activities, and thus have no need of these living cells. SEE ALSO
REFERENCES
NOTES EXTERNAL LINKS
|
|
|