PHGY 210 Lecture : PHGY210- Lecture 24- Dr. Wechsler.docx
14 May 2012
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Document Summary
Physiology of the gastrointestinal tract (git) and its accessory structures. Git role in homeostasis- provide nutients see slides. Tubular structure of the earthworm git maintained in humans. Enormous elongation of the tract (from mouth to anus) Git is many times the length of the human body (around 4. 5 meters) Surface area of the lining of the lumen of the git also increases. Internal surface area is 600x the area of the outer lining (200-250 m squared). Manifests into different regions of the tube specialized to perform specific aspects of digestion. see slides. Tough layer, continuous with the mesenteries lining the abdominal cavity. Next layer towards the lumen is the muscularis externa, which is 2 layers of muscle. Outermost layer has fibres arranged parallel to the lengths of the digestive tube- when they contract, the tract will shorten. Underneath are the circular fibres of muscle, spiral arrangement wound around the circumference- when they contract, the lumen diamter decreases in size.
