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Download Lesson 5 (Nutrition in Man Small intestine part 2)
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Nutrition in Man Let’s Recap! • What are the 3 parts of the small intestine? • What are the 3 secretions found in the duodenum? • Are you able to recall what enzymes are involved? • What about bile? How does bile aid in fats digestion? Lesson Objectives Lesson Objectives • What are the things you want to know to about the ileum ? • In your pairs, share what you want to know about the ileum and write it on your whiteboard • 3 minutes Lesson Objectives • Describe the functions of ileum in terms of absorption of carbohydrates, proteins and fats • To state the adaptation of small intestines in absorption of nutrients , closely relating to the structures : villi and microvilli Ileum Wait… What about jejunum? Structure • Highly coiled tube; inner walls contains numerous folds, villi and microvilli Functions • Mainly for absorption • Walls have numerous folds to provide a large surface area for absorption of digested food Functions • Epithelial cells of the villi are one-cell thick to allow for quick diffusion. • Richly supplied with blood capillaries and lymphatic capillaries to carry away absorbed food substances to maintain a concentration gradient. Adaptations Of the small intestine for absorption Terms to remember Ingestion Mechanical digestion Chemical digestion Absorption Assimilation Recall diffusion… • What factors affect the rate of diffusion of molecules across a partially permeable membrane? • Temperature • Surface area • Concentration gradient • Thickness of the membrane Rate of absorption • The rate of absorption of digested food substances depends on: • The length of the small intestine • The thin epithelial wall that lies between the food substances and the blood capillaries • The concentration gradient across the intestinal wall The Digestive System Absorption of Digested Food About 90% of the digested food is absorbed in the small intestine. liver gall bladder hepatic portal vein pancreas bile duct pancreatic duct duodenum Absorption • The process whereby digested food materials are taken into body cells Adaptations of small intestine Increase surface area to volume ratio 1) The small intestine is long and have inner walls with numerous transverse folds 2) The presence of minute finger-like projection called villi 3) The presence of finger like projection called microvilli on each villus Villi and microvilli Small Intestine Lining of small intestine Section of a villus Microvilli Circular folds, villi, microvilli Villi and microvilli • The villi of the small intestine increases the surface area ratio to volume by approximately 100-folds! • Do you know how big that is? Demonstration Adaptations of small intestine Other adaptations 1) Villi have thin walls and membranes to facilitate diffusion • Epithelial wall of the villi is only one cell thick 2) Intestinal wall and villi richly supplied with blood vessels and lymphatic vessels • Carry away absorbed food Villi • Absorbed by villi of small intestine • Simple sugars • Amino acids • Fatty acids and Glycerol How does absorption take place in the intestines? Glucose and amino acids: Diffusion • Transport of substances away from the intestines maintains the concentration gradient for diffusion of new substances across the intestinal walls How does absorption take place in the intestines? Glucose and amino acids: Diffusion • Transport of substances away from the intestines maintains the concentration gradient for diffusion of new substances across the intestinal walls How does absorption take place in the intestines? Fatty acid and glycerol: • Each villus has a lymphatic capillary (lacteal) which transports fats Transport of nutrients… • Lead into small venules joined together forming hepatic portal vein • Carries blood directly to liver Absorption of Digested Food hepatic vein to heart posterior vena cava liver stomach hepatic portal vein intestinal vein gastric vein small intestine Blood is carried directly from the stomach and the intestine to the liver via the hepatic portal vein. Summary Summary • What is absorption? • What are the three adaptations of small intestine to increase surface area ratio to volume? • What are some of the other ways to facilitate the absorption of nutrients? • How are the nutrients being absorbed? Muddiest Point • Any Question?
