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Physiology of Digestion and Absorption PowerPoint Presentation

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Description : Check out this medical presentation on Digestive System, which is titled "Physiology of Digestion and Absorption", to know about the digestive tract or gastrointestinal tract- where digestion and absorption take place.

Tags : Digestive System, Digestion, Absorption, digestive tract, gastrointestinal tract

Published on : Jul 10, 2021 | Views : 5833 | Downloads : 28

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Slide 1-

Physiology of Digestion and Absorption By Dr. Abdel-aziz M. Hussein Lecturer of Medical Physiology
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Overview of the Digestive System The Digestive System Consists of ; Long hollow muscular tube or canal or tract called gastrointestinal tract or (GIT): it is about 5 meters long Accessory glands: include: Salivary glands Liver and gall bladder Pancreas
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Overview of the Digestive Tract GIT consists of; Oral cavity or mouth Pharynx Esophagus Stomach Small intestine Large intestine Rectum Anus
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Components of Digestive System and Their Functions
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Main Functions of Digestive System 4 major activities of GI tract Motility Propel ingested food from mouth toward rectum Secretion of juices e.g. saliva Aid in digestion and absorption Digestion Food broken down into absorbable molecules Absorption Nutrients, electrolytes, and water are absorbed or transported from lumen of GIT to blood stream
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Motor Functions (Motility) of GIT
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Motility of the GIT 1. Motility in the mouth 2 types; a) Chewing is important because -The food is lubricated by being mixed with saliva -The food is exposed to salivary amylase enzyme, which begins digestion of starch -It breaks the food into small pieces to be easily swallowed b) Swallowing is the transport of food from mouth to stomach It consists of 3 phases or steps;
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Steps of swallowing Buccal Phase:
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Steps of swallowing Pharyngeal Phase:
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Steps of swallowing Oesophageal Phase:
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2. Motility of Esophagus The esophagus prevents air from entering the GI tract through the function of the upper esophageal sphincter. The esophagus prevents GI contents from re-entering the esophagus from the stomach through the function of the lower esophageal sphincter. The contraction that sweeps down the esophagus (primary and secondary esophageal peristalsis) Motility of GIT
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3. Motility of Stomach The stomach is divided into proximal and distal areas. Proximal area is thin walled, holds large volumes of food (to store food) because of receptive relaxation, and contracts weakly and infrequently. Distal area is thick walled with strong and frequent contractions that mix and propel food into the duodenum. Also, distal area is responsible for gastric emptying into duodenum Motility of GIT
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3. Motility of stomach Gastric peristalsis Arrow showing partial liquid chyme pushed into duodenum via pylorus and more chyme pushed forth and back in stomach cavity being small pieces Motility of GIT
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Motility of GIT
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4. Motility of Small intestine Motility of the small intestine serves four functions: - Mixing contents with enzymes and other secretions. - Further reduction in particle size. - Maximizing exposure of the contents to membranes of intestinal cells for absorption and digestion. - Propulsion of contents into the large intestine. Two basic motility patterns exist: segmentation and peristalsis. Motility of GIT
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Motility of GIT and cutting Segmentation movements
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Peristalsis Orad caudad Motility of GIT
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5. Motility of Large intestine or colon 2 basic motility patterns: a) Segmentation in the large intestine causes the contents to be continuously mixed b) Mass movement propels the contents of one segment of the large intestine into the next downstream segment. Defecation involves involuntary reflexes and voluntary reflexes Motility of GIT
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Secretory Functions (Secretions) of GIT
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GI secretions function to lubricate (water and mucus), protect (mucus), sterilize (HCl), neutralize (HCO3-), and digest (enzymes). Secretions arise from specialized cells lining the GI tract, the pancreas, liver and gallbladder. The total volume of GIT secretions is about 6-8 L/day Secretions of GIT
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Secretions of GIT in Mouth Salivary Glands Three pairs of glands Parotid Sublingual Submandibular Functions of saliva Lubricates, cleanses oral cavity Dissolves chemicals Suppresses bacterial growth Digest starch by amylase
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GIT secretions in Stomach
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Function of hydrochloric acid Activating pepsinogen Provide optimum for pH for action of pepsins Food protein denaturation and easy decomposition； Kill bacteria in food into the stomach Promoting pancreatic, small intestinal and bile secretion Helping Fe2+、Ca2+ absorption.
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Pepsinogen Pepsin protein peptone pH 2-3.5 HCl Function of pepsinogen Function of pepsins
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Mucus secretion Soluble and insoluble mucus are secreted by cells of the stomach. Soluble mucus mixes with the contents of the stomach and helps to lubricate chyme. Insoluble mucus forms a protective barrier against the high acidity of the stomach content. Intrinsic Factor Help absorption of vitamin B12 Function of mucous and intrinsic factor
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Pancreas has 2 functions: a) Endocrine functions: secretes insulin and glucagon from islets of Langerhans b) Exocrine function: secretion of pancreatic juice It has 2 components: aqueous and enzymatic components. Aqueous component (contains HCO3) is important for neutralizing stomach acid in the duodenum so pancreatic enzymes can function properly Enzymatic component is essential for the proper digestion and absorption of carbohydrates, fats, and proteins Pancreatic enzymes include trypsin, chemotrypsin, lipase, and amylase Pancreatic Secretion
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starch maltose + glucose pancreatic amylase pH 6.7-7.0 fat（Triglyceride） oil + monoglyceride + fatty acids pancrelipase + colipase pH 7.8-8.5 trypsinogen trypsin Kinase, HCl, tissue fluid chymotrypsinogen chymotrypsin protein polypeptide carboxypeptidase amino acid Functions of pancreatic juice enzymes
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The Liver and Gall Bladder Functions of the Liver Metabolic regulation Store absorbed nutrients, vitamins Release nutrients as needed Hematological regulation Plasma protein production Remove old RBCs Production of bile Required for fat digestion and absorption
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Secretion from duodenal gland and intestinal gland Secretory volume is 1～3L/day It contains inorganic ion, mucoprotein, IgA, various enzyme, e.g. enterokinase ,etc Function: Protective effect by mucous Digestion by enzymes such as peptidase, sucrase, lipase Dilution Secretion of small intestine
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colonic alkaline secretion to neutralize acids produced by intestinal bacteria secretion of mucous for protection, lubrication of fecal matter Vitamin B and K absorption made from bacterial flora in colon Secretion of large intestine
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Digestion and Absorption
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Digestion is a process essential for the conversion of food into a small and simple form.  mechanical digestion by mastication and swallowing  chemical digestion by enzymes Absorption is the process of transporting small molecules from the lumen of the gut into blood stream or lymphatic vessel. Digestion and Absorption
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Digestion and Absorption
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Small intestine is primary site for digestion and absorption of food. Digestion occurs in the GI lumen by secreted enzymes and on surface of enterocytes by membrane-bound enzymes. Absorption occurs by simple diffusion, facilitated diffusion, active transport, endocytosis, and paracellular transport. Surface area of small intestine is greatly increased by extensive folding and the projection of fingerlike villi covered with microvilli. Digestion and Absorption
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Intestinal Villi
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Intestinal Villi
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(salivary and pancreatic) Digestion of CHO
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Enterocytes absorb glucose and galactose through an Na-dependent secondary active transport process, while fructose is absorbed by facilitated transport. Absorption of CHO
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Digestion of proteins
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Absorption of proteins The whole proteins by endocytosis Amino acids and di and tripetides by Na-dependent 2ry active transport
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Digestion of fats
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Lipid digestion and absorption
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