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Anatomy Exam 4Digestive System Major functions of the Gi tract: secretion (hormones, digestive enzymes) and motility (muscle activity). Functions of the Digestive System1. ingestion: conscious placement of food material into the mouth2. mechanical processing: grinding and chewing with teeth (mastication) and squashing and compacting with tongue3. digestion: chemical breakdown of food via various digestive enzymes 4. secretion (moving things into a lumen or space – stuff is still in body) : release of water, acids, mucus, enzymes, buffers and salts by the digestive tract epithelium and accessory organs5. absorption (mainly in small and large intestine): movement of organic substrates, electrolytes, vitamins and water across the digestive tract epithelium6. excretion (removing things from the body): removal of waste products from body fluids (defecation)7. protection: of underlying tissues from acids, enzymes and bacteriaThe Digestive Organs and the Peritoneum- digestive organs are within the peritoneal cavity; cavity is bound by serous membranes (parietal and visceral peritoneum); peritonitis - mesenteries are peritoneal folds; vasculature, nerves, stabilization - retroperitoneal organs develop outside of the peritoneal cavityGi tract is line with a thick muscle made of 4 layers (visceral to parietal) – Mucusa: epithelial lining very regenerative (simple columnar with goblet cells (unicellular exocrine gland that releases mucus): lamina propria loose connective tissue that contain a lot of glands for absorption: muscularis mucosae regulate conformation of organization submuscusa (dense connective tissue): submucusal plexus (Meissner’s plexus) nerve network responsible for secretory and motility purpose, found between submucosa and muscularis externa
muscularis externa has an inner layer of muscle (allow you to change the diameter) and outer longitudinal layer (allow you to make it flatter to make it wider) doing both at the same time allow for movement myenteric plexus (auerbach’s plexus) motility of muscularis externa (GI tract)/ found between the inner circular and outer longitudinal layer of muscleserosa loose connective tissue with a visceral perotenium (loose connective with NO visceral perotenium is not a serosa)most of your esophagus is adventia, so is your duodenum and rectum anal junction loose connective tissue with no visceral peroteniumMost abundant tissue in the GI tract – simple columnar epitheliumNo goblet cells in the stomach. ** Degluttition – the act of swallowing -pharynx is skeletal muscle -upper 1/3 esophagus is skeletal but bottom 2/3 is all smooth muscle esophagus is controlled by enteric NS via reflexes but is modulated by autonomic NS-Enteric system is controlling food after it leaves the upper 1/3 of the esophagus.