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The lungs' interiors are open to the outside air and being elastic, therefore expand to fill the increased space, pleura fluid between double-layered pleura covering of lungs helps in reducing friction while lungs expand and contract. The inflow of air into the lungs occurs via the respiratory airways (Fig. 2).
Exchange of gases in the lung occurs by ventilation and perfusion. [1] Ventilation refers to the in-and-out movement of air of the lungs and perfusion is the circulation of blood in the pulmonary capillaries. [1] In mammals, physiological respiration involves respiratory cycles of inhaled and exhaled breaths.
The lungs are not capable of inflating themselves, and will expand only when there is an increase in the volume of the thoracic cavity. [6] [7] In humans, as in the other mammals, this is achieved primarily through the contraction of the diaphragm, but also by the contraction of the intercostal muscles which pull the rib cage upwards and outwards as shown in the diagrams on the right. [8]
This negative pressure generates airflow because of the pressure difference between the atmosphere and alveolus. The inflow of air into the lungs occurs via the respiratory airways. In health, these airways begin with the nose. [3] [4] It is possible to begin with the mouth, which is the backup breathing system.
The lungs of most frogs and other amphibians are simple and balloon-like, with gas exchange limited to the outer surface of the lung. This is not very efficient, but amphibians have low metabolic demands and can also quickly dispose of carbon dioxide by diffusion across their skin in water, and supplement their oxygen supply by the same method.
Respiration is the rhythmical process of breathing, in which air is drawn into the alveoli of the lungs via inhalation and subsequently expelled via exhalation. When a human being inhales, air travels down the trachea, through the bronchial tubes, and into the lungs. The entire tract is protected by the rib cage, spine, and sternum. In the ...
TLC is the maximum amount of air in the lungs after maximum inhalation. In men the average TLC is 6000 ml, and in women it is 4200 ml. FRC is the amount of air left in the lungs after normal exhalation. Men leave about 2400 ml on average while women retain around 1800 ml. RV is the amount of air left in the lungs after a forced exhalation. The ...
Evapotranspiration is typically measured in millimeters of water (i.e. volume of water moved per unit area of the Earth's surface) in a set unit of time. [6]: Ch. 1, "Units" Globally, it is estimated that on average between three-fifths and three-quarters of land precipitation is returned to the atmosphere via evapotranspiration.