BIBC 120 Midterm Review I

BIBC 120 Midterm Review I - BIBC 120 Digestion involves two...

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BIBC 120 Digestion – involves two different processes Digestion: break down of food into absorbable units. I. Physical Digestion: physically breaking the food apart (mastification, cooking, etc) II. Chemical Digestion: enzymatic processes that break the food apart Absorption: the uptake of nutrients GI Tract Main GI Tract: Single tube that starts at oral cavity (stoma) and goes all the way down and ends in the anus Accessory Organs : organs outside the GI tract that have a secretory function to produce something o Liver, pancreas, salivary glands o Not gallbladder, because gallbladder is used for storage Sphincters : rings of muscles that control opening and closing of tube along GI tract o Parts of the GI tract have physiological and functional difference. Sphincters are a mechanism to separate each one form the other o When a sphincter expands, the tube opens. o Sphincters close off specific portions of the GI tract Mucosa Mucus produced by mucous cells located in the mucosal layer Mucus is a slippery secretion that serves for protection. The mucosa is linings of mostly endodermal origin, covered in epithelium, which are involved in absorption and secretion o Life span for these cells is very short Submucosa: layer of connective tissue that supports the mucosa. This connective tissue also joins the mucosa the bulk of underlying smooth muscle (which are fibers running circularly within layer of longitudinal muscle). Also contains gland cells. o Gland cells: could produce acid, mucus, pepcinogens o Submucosa also contains nerve cells that can recognize pain, such as from an ulcer. The reason we can’t feel food going down the GI tract is because the nerve cells are in the in the submucosa, rather than the mucosa.
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Serosa: protects the inside of the GI tracts from things that could from the outside. the longitudinal muscles and circular muscles will relax and contract to change the shape of the GI tract When the circular muscles are contracting, the longitudinal are relaxed and the GI tract is constricted When the circular muscles are relaxed and the longitudinal muscles are contracted, the GI is bulged Peristalsis The pushing of food from the start of the GI tract to the latter part of the GI. It is referred to as the general motion of the GI. o Every part of the GI tract (except the mouth) has peristaltic movement o This movement is not the same in every region Regular Peristaltic Movement : mostly in the esophagus and in the small intestine Rapid Peristalsis : can have as many as 10 motions per minute. This can occur in the small intestine. Haustration : slow peristalsis. The waves of contraction and relaxation are very slow. This is generally seen in the large intestine Mass movement peristalsis : This movement is related to the length of the segment rather than rate of movement. o
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BIBC 120 Midterm Review I - BIBC 120 Digestion involves two...

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