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small intestine
nutrient absorp OFFI
| Question | Answer | |
|---|---|---|
| amino acids | active transport | blood capillaries |
| simple sugars ( glucose & monosacchrides) | active transport | blood capillaries |
| fatty acids & glycerol (combine in villi to form fats) | simple diffusion | lacteal ( lymph capillaries ) |
| water | simple diffusion | blood capillaries |
| water-soluble vitamins | simple diffusion | blood capillaries |
| Substances that are absorbed by blood capillaries | are carried by the hepatic portal vein to liver for processing or remain in blood to be carried to body cells | |
| Substances absorbed into the lacteals | are transported in lymphatic system which empires into the blood through veins in upper chest | |
| Small intestine | the longest part of the alimentary canal; receives material from stomach • Named due to narrow diameter of tube | |
| Structure | • Approximately 6-7m in length • Made up of 4 layer • Highly vascular (large blood supply) | • 1) outer fibrous layer (serosa) • 2) smooth muscle with longitudinal & circular muscle layer • 3) submucosa has glandular tissue intestinal glands • 4) mucosa is highly folded & formed by a single layer of epithelial cells |
| Three sections: | 1. Duodenum (1st section ~ 20-25cm) a. Most chemical digestion occurs here 2. Jejunum ( middle section ~2.5m) . Allows effective absorption of carbs & proteins | 3. Ileum (final part ~ 3m) . Remaining products, vitamin B12 & bile salts are absorbed |
| The small intestine has 2 main function | 1. Complete digestion of nutrient macromolecules | 2. Absorption of these nutrient molecules across the wall of intestines into the blood & lymph |
| emulsification - physical | • Bile emulsifies fat droplets • Bile is produced by the liver • It is transported from the liver to gall bladder wheere it iis stored & concentrated Bile does not contain eznymes therefore not chemical digestion | • When required, thee gallbladder contracts & releases stored bile into common bile duct • The bile then moves through the common bile duct to thee duodenum • (contains bile salts) bile breaksdown large fat droplets into smaller ones |
| • Segmentation - physical | localised contractions of circular muscle in the intestinal tract ( no net movement) • These contractions isolate small section of the intestine, moving contents back&forth while continuously breaking up & mixing the contents with digestive juices | • Involves the rhythmic contractions of the longitudinal muscles to move chyme through the intestines |
| • Pancreatic juice | produced in pancreas • Ph of 8 (close to water) • Seecreted into the duodenum via common bile duct • Contains digestive enzymes | Large to medium • Pancreatic amylase breaks down polysaccharides into disaccharides • Pancreatic protease (or trypsin) breaks down polypeptide chains into shorter peptide chains • Pancreatic lipase breaks down lipids into fatty acids & glycerol |
| Intestinal juice | secreted by intestinal glands in small intestine • Ph of 8 • Contains Digestive enzymes Pancreas: thin 15cm long organ lies under the stomach & under the liver | Medium to small • Intestinal amylase ( or maltase, sucrase, lactase) breaks down disaccharides into monosaccharides • Intestinal protease ( or peptidase) breaks down peptides into amino acids |
| Absorption | : the uptake of small nutrient molecules across the intestinal wall into the blood or lymph • Carbohydrates → monosaccharides (glucose) • Proteins → amino acids • Lipids → fatty acids & glycerols | To increase the efficiency of absorption the small intestine must have 1. A large surface area 2. A thin surface 3. A large blood supply 4. Continual movement of intestinal wall |
| 3 features that increase SA | • Folded mucosa = highly folded inner layer • Microvilli: microscopic projects on each of th villi’s epithelial cells | • Villi: finger like projections of the mucosa |
| • Villi | • Each villus (siingle villi) is lined by a single layer of epithelial cells containing • Absorptive cells • Secretory cells | •Each villus as a lacteal • Lymph capillaries surrounded by blood capillaries which absorb fats that connot directly enter bloodstream slightly larger diameter than blood capillaries & more permeable - allows large fat molecules |
Created by:
procrast
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