Small intestine duodenum jejunum ileum o Main site for nutrient digestion and

Small intestine duodenum jejunum ileum o main site

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Small intestine (duodenum, jejunum, ileum) o Main site for nutrient digestion and absorption o Surface area = 30m 2 (efficient at absorbing nutrients) o Intestinal motility controlled by longitudinal and circular muscles o Chyme acidity neutralized by pancreatic juice (enzymes and bicarbonate) o Food digested by pancreatic juice and bile acids - Large intestine (also called the colon) o Site of fermentation (Majority where gut bacteria reside) Product of short chain fatty acids (SFCA) can be used as source of energy by bacteria or us, which are also known as volatile fatty acids (VFA) 102-1012 bacteria / g content (region specific) 500-1000 species identified per person in the gut 1000:1 anaerobic to aerobic bacteria Bacteria are very important for fermentation of non-digestible CHO o CHO fermentation produces many compounds, ex. Lactate and SCFA o Site for water absorption Nutrient Transport Mechanisms 12 Crypts are where stem cells are replenished, Villi are where nutrients are absorbed Working against [ ] gradient (requires ATP) Working along [ ] gradient (no energy required)
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Which transport mechanism used will depend of the nutrients: 1) Solubility 2) Concentration gradient 3) Molecular size 2. Simple System w/ functional caecum Ex. Horse, rabbit, hamster Key Features: - ‘Pseudo-ruminant’ - Functional caecum - All other regions of the gut function similar to the Monogastric system - Suited for a diet with large amounts of fodder - Purpose of a functional caecum? o Enormous hindgut (20-30L capacity) filled with bacteria Takes place after stomach and after small intestine o SCFA provide 70% of total energy needs for host o Site for the production of vitamins - Signs of an energy or nutrient deficiency? o Coprophagy (eating dung or faces) allows vitamins in stool to be re-absorbed in small intestine Where Nutrients are Absorbed 3. Multiple System: Ruminant Ex., cattle, sheep, goats Key Features: - Large stomach divided into 4 1. Rumen 2. Reticulum 3. Omasum 4. Abomasum - System highly suited for animals that eat a high quantity of fodder - All other regions of the gut function similar to the Monogastric system 13
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Ruminant Digestion - Reticulum o Honeycomb appearance in order to capture nutrients and trap foreign material (wire, nails, etc.) Helps filter out food, particles that pass through reticulum get broken down Bigger items are regurgitated and end up back in the mouth where cow can reduce size of particle o Rich in bacteria (fermentation vat) - Rumen o The largest section of the stomach o Rich in bacteria (fermentation vat) o Rumen papillae increases surface area for absorption (like microvilli in the human intestine) o Food is mixed & partially broken down, and stored temporarily o 60-80% of total energy produced here as SCFA - Omasum o Reabsorption of water and some electrolytes o Filters large particles - Abomasum o Digestive enzymes secreted from gastric glands (HCL, mucin, pepsinogen, lipase, etc.) o The “true stomach”; similar to that of Monogastric animals -
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