Absorption in the Small Intestine INGESTION Food is

Absorption in the Small Intestine

INGESTION Food is taken into body DIGESTION Carbohydrates, proteins and fats are broken down into soluble glucose, amino acids, fatty acids and glycerol. ABSORPTION Glucose, amino acids, fatty acids and glycerol are absorbed into body cells ASSIMILATION Absorbed nutrients are transported and utilized by the body EGESTION Removal of undigested food e. g. dietary fibre 2

ABSORPTION Monosaccharides (glucose, fructose and galactose), amino acids, fatty acids, glycerol and water are absorbed in the small intestine. The absorbed nutrients passes from the lumen of the small intestine into the bloodstream. lumen 3 http: //www. colorado. edu/intphys/Class/IPHY 3430 -200/image/villi. jpg

How to ensure that nutrients are quickly absorbed?

Adaptations of the Small Intestine 1. Large surface area: volume ratio 1. 1 The inner walls of the small intestine have numerous folds http: //www. path. cam. ac. uk/Normal/AR_Alimentary/SI_Small_intestine/N_AR_SI_08 small. jpg 5

Adaptations of the Small Intestine 1. Large surface area: volume ratio • Folded inner walls are lined with numerous minute finger-like projections called villi http: //www. technion. ac. il/~mdcourse/274203/slides/Digestive%20 tract/17 Intestinal%20 villi%20 Jejunum-A. jpg 6

Adaptations of the Small Intestine 1. Continued. . . Large surface area: volume ratio • The epithelial cells of the villi have numerous microvilli. 7

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Adaptations of the Small Intestine 2. The villi wall (epithelial cell layer) is only one cell thick. http: //www. siumed. edu/~dking 2/erg/images/GI 020 b. jpg http: //www. biog 1105 -1106. org/demos/105/unit 6/media/villus. structure. jpg 9

Adaptations of the Small Intestine 3. Presence of numerous capillaries to carry away the absorbed nutrients. lumen Digested food enters villus epithelial cell layer Lacteal/lymphatic capillary blood capillaries 10

Adaptations of the Small Intestine Blood capillaries: transport monosaccharides and amino acids. The continual removal of nutrients maintains a concentration gradient for diffusion. Lymphatic capillaries (lacteals): transport fats liver 11

Adaptations of the Small Intestine 4. Small intestine is long to provide sufficient time for absorption. The small intestine is about 6 m long! http: //blog. lib. umn. edu/trite 001/pstl 1082 anatomy/Small. Intestine. jpg 12

glucose How are the nutrients absorbed? Recall what you have learnt in the topic Movement of Substances! (Diffusion, osmosis, active transport…. ) Fatty Acids glycerol amino acids

How does absorption take place in the villi? Soluble substance Type of movement into the epithelium Note: Monosaccharides (e. g: glucose) Facilitated Diffusion Active Transport High conc. in lumen low conc. in lumen Amino Acids Facilitated Diffusion Active transport High conc. In lumen low conc. In lumen Fatty acids and glycerol Diffusion Glycerol and fatty combine to form small fat droplets that enter the lacteals. Water Osmosis Enter the blood capillaries Mineral Salts Facilitated Diffusion Enter the blood capillaries Water soluble vitamins (B and C) Facilitated Diffusion Enter the blood capillaries Fat –Soluble Vitamins (A, D, E and K) Diffusion Enter the lacteals 14

SUMMARY Adaptations of the small intestine: Movement into villi: 1. Large SA: Vol. folds, villi and microvilli. • Glucose and amino acids absorbed by facilitated diffusion or active transport into blood capillaries of the villi. • Glycerol and fatty acids diffuse into the epithelium combine to form minute fat globules which enter lacteals. • Water and mineral salts are also absorbed by the small 15 intestine. 2. Villi epithelial wall is one cell thick rapid diffusion. 3. Blood capillaries and lacteals maintain concentration gradient. 4. Long allows sufficient time for absorption

Egestion • In the colon, water and mineral salts are absorbed from the undigested food material. • Bacterial Activity • Presence of dietary fibre/roughage helps in peristalsis. • Unabsorbed matter is stored temporarily in the rectum. http: //z. about. com/d/coloncancer/1/0/1/3/Large. Intestine. 300 x 300. jpg • Faeces is discharged through the anus. rectum anus 16