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Gastric activity involved in digestion is divided into three phases of digestion known as the cephalic phase, the gastric phase, and the intestinal phase. These phases overlap and all three can occur simultaneously. [1] A fourth phase of acid secretion is known as the basal state which occurs in the times between meals (interdigestive phase).
Exhalation (or expiration) is the flow of the breath out of an organism. In animals, it is the movement of air from the lungs out of the airways , to the external environment during breathing . This happens due to elastic properties of the lungs, as well as the internal intercostal muscles which lower the rib cage and decrease thoracic volume.
The first stage, the cephalic phase of digestion, begins with secretions from gastric glands in response to the sight and smell of food. This stage includes the mechanical breakdown of food by chewing , and the chemical breakdown by digestive enzymes , that takes place in the mouth .
The reverse happens during exhalation. This process (of inhalation and exhalation) is exactly the same at sea level, as on top of Mt. Everest , or in a diving chamber or decompression chamber . Fig. 14 A graph showing the relationship between total atmospheric pressure and altitude above sea level
Digestion is a form of catabolism that is often divided into two processes based on how food is broken down: mechanical and chemical digestion. The term mechanical digestion refers to the physical breakdown of large pieces of food into smaller pieces which can subsequently be accessed by digestive enzymes.
Also, it helps the carbon dioxide transport from the lung tissue to the alveoli in the pulmonary capillary, where the carbon dioxide will be excreted during exhalation. [10] Carbonic anhydrase is a very ancient enzyme found in both domains of prokaryotes that exists in six different classes among most of the living organisms. [11]
Next, thrust in an inward and upward motion on the diaphragm. This will force air out of the lungs and remove the blockage. Repeat these abdominal thrusts up to five times, the doctor advised.
The alveolar air pressure is therefore always close to atmospheric air pressure (about 100 kPa at sea level) at rest, with the pressure gradients that cause air to move in and out of the lungs during breathing rarely exceeding 2–3 kPa. [8] [9] Other muscles that can be involved in inhalation include: [10] External intercostal muscles; Scalene ...