1 / 12

Human Systems

Human Systems. 8.4 Digestion. Digestion. Initial digestion of carbohydrates: mouth Initial digestion of proteins: stomach Complete digestion of carbs and proteins: small intestine Initial and complete digestion of lipids: small intestine

shiro
Télécharger la présentation

Human Systems

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Human Systems 8.4 Digestion

  2. Digestion • Initial digestion of carbohydrates: mouth • Initial digestion of proteins: stomach • Complete digestion of carbs and proteins: small intestine • Initial and complete digestion of lipids: small intestine • Small intestine- approx. 7 m in length, 2.5 cm in diameter (humans)- in mammals, length related to diet • Absorption of all macronutrients into the bloodstream occurs in the small intestine

  3. Small Intestine • 3 sections: duodenum, jejunum, ileum • Majority of digestion in duodenum (first 25 – 30 cm) • Contents enter from stomach – move by peristalsis • Specific structures for absorption:- villi: finger-like projections to increase surface area- microvilli: fine, thread-like extensions on each villus (further increase surface area)- capillary network: on each villus (transport monosaccharidesand amino acids) - lacteals: intertwines with lymph vessels to transport materials (fats) Villi

  4. Pancreas • Contents enter small intestine coated in HCl & pepsin- initiates conversion of prosecretin into secretin • Carried to pancreas • Signals release of bicarbonate ions (HCO3-) - carried to small intestine • Buffer HCl in gastric fluid- raise pH to ~ 9.0 • Inactivates pepsin • Protects lining of small intestine

  5. Pancreas • Pancreatic secretions also include trypsinogen, erepsins, amylase, lipase • Trypsinogen (inactive): converted to trypsin (active) by enterokinase in small intestine- trypsin breaks down polypeptides into peptides • Erepsins: from pancreas and small intestine- complete protein digestion into individual amino acids • Amylase: continue carbohydrate digestion- broken down into disaccharides • small intestine releases disaccharidases- completes digestion of carbs • Lipase: break down fats into glycerol and fatty acids

  6. Protein digestion in small intestine. Made possible by release of pancreatic juices

  7. Liver and Gall Bladder • Liver produces bile- bile salts to help fat digestion • Bile stored in gall bladder • Fats detected in small intestine:- hormone cholecystokinin (CCK) released- carried to gall bladder- bile salts released • Act to emulsify fat globules (physical digestion)- prepares fat for chemical digestion by lipases CCK and lipids

  8. Liver and Gall Bladder • Bile contains pigments- liver breaks down hemoglobin- brown colour of feces • Liver stores glycogen and vitamins • Able to detoxify substances- harmful ones soluble, dissolve in blood, excrete in urineex) alcohol • See table 2 pg 267 • Problems: gall stones, cirrhosis

  9. Large Intestine • Chemical digestion complete • Colon: largest part of large intestine- stores wastes, allows for water and mineral reabsorption • E. coli bacteria found here- use wastes to produce vitamin B and K • Cellulose: undigested- provides bulk • Build up: receptors signal bowel movement • Not enough cellulose = fewer bowel movements Colonoscopy Round Worm

  10. Control of Digestion • Nervous system- sight/taste/smell signal production gastric juices- swallowing motions • Hormonal systemEx) secretin (release HCO3-), gastrin (release HCl) • Speed of digestion- controlled by receptors- large meal: more receptors activated • Meal very fatty: release of enterogastrone- slows peristalsis

More Related