Information AboutLungs |
| CATEGORIES ABOUT LUNG | |
| organs | |
| respiratory system | |
| thorax | |
| cardiovascular system | |
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'', 20th ed. 1918.]] The lung is the essential Respiration Organ in air-breathing vertebrates, the most primitive being the Lungfish . Its principal function is to transport Oxygen from the Atmosphere into the Bloodstream , and to excrete Carbon Dioxide from the bloodstream into the atmosphere. This exchange of gases is accomplished in the mosaic of specialized Cells that form millions of tiny, exceptionally thin-walled air sacs called Alveoli . The lungs also have non respiratory functions. Medical terms related to the lung often begin with ''pulmo-'', from the Latin ''pulmonarius'' ("of the lungs"), or with '''''pneumo-''''' (from Greek πνεύμω "lung")12 RESPIRATORY FUNCTION that conveyed Gas es to and from the deepest tissues in the body, and a large, internalized Respiratory System that centralized the task of obtaining oxygen from the atmosphere and bringing it into the body, whence it could rapidly be distributed to all the circulatory system. In air-breathing vertebrates, respiration occurs in a series of steps. Air is brought into the animal via the airways — in reptiles, birds and mammals this often consists of the Nose ; the Pharynx ; the Larynx ; the Trachea (also called the windpipe); the Bronchi and Bronchiole s; and the terminal branches of the Respiratory Tree . The lungs of mammals are a rich lattice of alveoli, which provide an enormous surface area for gas exchange. A network of fine Capillaries allows transport of Blood over the surface of alveoli. Oxygen from the air inside the alveoli diffuses into the bloodstream, and carbon dioxide diffuses from the blood to the alveoli, both across thin alveolar Membranes . The drawing and expulsion of air is driven by Muscular action; in early Tetrapod s, air was driven into the lungs by the Pharyngeal muscles, whereas in Reptile s, Bird s and Mammal s a more complicated Musculoskeletal System is used. In the mammal, a large muscle, the Diaphragm (in addition to the internal intercostal muscles), drive ventilation by periodically altering the intra-thoracic Volume and Pressure ; by increasing volume and thus decreasing pressure, air flows into the airways down a pressure gradient, and by reducing volume and increasing pressure, the reverse occurs. During normal Breath ing, expiration is passive and no muscles are contracted (the diaphragm relaxes). Another name for this inspiration and expulsion of air is Ventilation . Vital capacity is the maximum volume of air that a person can exhale after maximum inhalation. A person's vital capacity can be measured by a spirometer (spirometry). In combination with other physiological measurements, the vital capacity can help make a diagnosis of underlying lung disease. NON RESPIRATORY FUNCTIONS In addition to respiratory functions such as Gas Exchange and regulation of Hydrogen Ion Concentration , the lungs also:
MAMMALIAN LUNGS The lungs of mammals have a spongy texture and are honeycombed with Epithelium having a much larger surface area in total than the outer surface area of the lung itself. The Lungs Of Humans are typical of this type of lung. Breathing is largely driven by the muscular Diaphragm at the bottom of the thorax. Contraction of the diaphragm pulls the bottom of the cavity in which the lung is enclosed downward. Air enters through the oral and nasal cavities; it flows through the larynx and into the trachea, which branches out into bronchi. Relaxation of the diaphragm has the opposite effect, passively recoiling during normal breathing. During exercise, the diaphragm Contracts , forcing the air out more quickly and forcefully. The Rib Cage itself is also able to expand and contract to some degree, through the action of other respiratory and accessory respiratory muscles. As a result, air is sucked into or expelled out of the lungs, always moving down its pressure gradient. This type of lung is known as a bellows lung as it resembles a blacksmith's Bellows . ANATOMY In humans, it is the two main bronchi (produced by the bifurcation of the trachea) that enter the roots of the lungs. The bronchi continue to divide within the lung, and after multiple divisions, give rise to bronchioles. The bronchial tree continues branching until it reaches the level of terminal bronchioles, which lead to alveolar sacks. Alveolar sacs are made up of clusters of Alveoli , like individual grapes within a bunch. The individual alveoli are tightly wrapped in blood vessels, and it is here that gas exchange actually occurs. Deoxygenated blood from the Heart is pumped through the Pulmonary Artery to the lungs, where oxygen Diffuses into blood and is exchanged for carbon dioxide in the Hemoglobin of the Erythrocytes . The oxygen-rich blood returns to the heart via the pulmonary veins to be pumped back into systemic circulation. |
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