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The Human Microbiome: How Our Health is Impacted by Microorganisms
Published in Michael Hehenberger, Zhi Xia, Huanming Yang, Our Animal Connection, 2020
Michael Hehenberger, Zhi Xia, Huanming Yang
The oral cavity serves as the main channel for feeding. The glands in the oral cavity secrete saliva. The food is lubricated by saliva through the esophagus. The saliva amylase in saliva decomposes some of the carbohydrates. The pharynx serves as a common passage for the respiratory tract and digestive tract and mainly completes the swallowing action. The esophagus is one of the muscular conduits, typically having a total length of 25 to 30 cm. The anatomy of the stomach is quite complicated and the total volume of the stomach is considerable, 1000–3000 ml. The mucous membrane contains a large number of glands that secrete gastric juice and become acidic. The small intestine is located in the abdominal cavity and its total length is 4 to 6 m. Its last part is equipped with a very strong digestive function. The total intestinal surface area is very large, up to 200∼300 m2, enough to accommodate a large variety of microorganisms. Note that the intestine is not only an important place for digestion and absorption of the human body, but also the largest immune organ. Being a good habitat for microorganisms, it can maintain normal immune defense function. The number of microorganisms in the intestine is larger than the number of human cells and their weight is estimated at up to 1.2 kg, about as heavy as the human liver. The human metabolic function does not cover all digestive needs and is therefore critically dependent on the microbiome.
Basic Chemical Hazards to Human Health and Safety — I
Published in Jack Daugherty, Assessment of Chemical Exposures, 2020
Eight sinuses, four on each side of the nose, help equalize air pressure in the nasal cavity, and, because they are linked with the nasal passage, are easily irritated. The pharynx and larynx are also easily irritated by either inhaled or ingested irritants. On either side of the pharynx, behind the mouth, tonsil tissue can be susceptible to irritants. The pharynx serves as a passageway for air, but also for food and other ingested materials. At the lower end of the pharynx is the glottis, a narrow slit covering the opening into the larynx. Covering the glottis is the epiglottis a small flap that prevents swallowed materials from entering the larynx. This is where the pharynx separates into the larynx and esophagus. Next, on the respiratory side, are the trachea and bronchi, then the bronchioles and alveoli are attacked by irritants in the worst exposures.
Toxic Responses of the Lung
Published in Stephen K. Hall, Joana Chakraborty, Randall J. Ruch, Chemical Exposure and Toxic Responses, 2020
From the nasal cavity, air moves into the pharynx. The pharynx is a tubular passageway attached to the base of the skull and extending downward behind the nasal cavity, the mouth, and the larynx to continue as the esophagus. Its walls are composed of skeletal muscle, and the lining consists of mucous membrane.
Modelling of swallowing organs and its validation using Swallow Vision®, a numerical swallowing simulator
Published in Computer Methods in Biomechanics and Biomedical Engineering: Imaging & Visualization, 2019
Yukihiro Michiwaki, Tetsu Kamiya, Takahiro Kikuchi, Yoshio Toyama, Keigo Hanyuu, Megumi Takai, Seiichi Koshizuka
Swallowing occurs inside the body involving the mouth, pharynx, larynx and oesophagus. Although the pharynx connects with both the larynx and oesophagus, the pharynx essentially functions as the respiratory tract, simultaneously playing a role as the digestive tract only during the process of swallowing. Therefore, during swallowing, these organs specifically accomplish two functions, namely, transporting a food bolus from the mouth through the pharynx to the oesophagus, and at the same time, preventing the bolus from entering the larynx. In other words, the organs change their shapes and positions according to the flow of the bolus in the upper airway. Therefore, elucidating the biomechanics of swallowing essentially needs to visualise how the organs change their shapes and positions in synchronisation with the bolus flow. However, none of the recent medical imaging technologies have yet been able to visualise the movements of the organs during swallowing.