digestion lecture.docx

Types of movement peristalsis segmentation gut

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Types of movement: Peristalsis Segmentation: gut secretion mixed with food, mainly self-controlled Monogastric stomach motility: deliver processed ingesta at a controlled rate - Material consistency Stomach: Proximal – storage of food Distal – peristalsis begins at the middle and migrate to pylorus, which constricts to allow only <2mm diameter food particles to enter SI, otherwise would be crushed and injected back into distal stomach Enterogastric reflex: regulates gastric emptying rate Chemicals and receptors help monitor conditions in the duodenum, and signals are sent back to the stomach to slow down, controls how much enzymes and acids secreted, and how much particles the duodenum needs to process Rumen - Motility for gas removal from fermentation, mix content and take food to be ready for next part of digestion in next part of stomach SI
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Digestive phase Interdigestive phase: little food in gut eg. When youre hungry and tummy rumbles; strong peristaltic waves, remove undigested material and prevent bacterial migration from colon Colon - Absorb water and nutrients - Fermentation – produce a lot of gas, especially herbivores - Faeces storage DIGESTION – SECRETION AND ABSORPTION IN THE GIT (14/05/18) Gastric secretions - Starts from the stomach not only mechanical breakdown
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o Gastric pits in mucosal surface, have mucus lining the stomach to prevent the stomach from digesting itself – creating ulcers o Endocrine cells control acid secretion o Chief cells secrete pepsinogen pepsin to break down proteins o Parietal cells secrete HCl o Gastrin (hormone) helps control HCl secretion and motility Pancreas - Produce hormones to maintain glucose balance - Pancreatic acinar cells produce ~10 types of digestive enzymes in an inactive form to prevent them damaging the pancreas itself, sent to duodenum, which is then activated - If inflamed, sometimes the enzymes become activated within the pancreas - Bicarbonate is produced in response to the secretion of HCl from stomach to duodenum, to act as a buffer/ counteract, to increase pH Liver - Filters blood - Made of lobules - Receives blood full of nutrients from intestines via portal vein and hepatic artery carries oxygenated blood - Hepatocytes monitor blood content: take up and packaging nutrients/ storing nutrients/ removing toxin - Waste is drained to the bile duct, to the gall bladder which stores the bile to be excreted into the digestive tract - Bile: bright green bilirubin substance – old red blood cells, if build up, makes us go yellow, build-up of toxin e.g. Urea/ alcohol - Bile salt makes lipid solubilise i.e. emulsify lipid – similar to detergent - Food in duodenum especially fat stimulates bile secretion - Some animals don’t have a gall bladder, bile is produced constantly - Bile salts experience enterohepatic recirculation due to the reabsorption of it in the digestive tract - However, medication which has been filtered by the liver is reabsorbed and could sometimes give side effects, but sometimes a good thing 2 phases of digestion Luminal phase
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- Food breakdown
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