Small Intestine_disorders-causes_symptoms.pptx

Small intestine

1. Small Intestine

2. F UNCTIONAL ANATOMY Small intestine is the part of gastrointestinal (GI) tract, extending between the pyloric sphincter of stomach and ileocecal valve, which enters into large intestine. It is otherwise known as small intestine due to its small diameter, compared to that of the large intestine. But it is longer than large intestine. Its length is appeoximately 6 meter. 4) Important function of small intestine is primarily absorption. Maximum absorption of digested food products happens in small intestine.

3. Small intestine contains three portions: 1. Proximal part termed as duodenum 2. Middle part termed as jejunum 3. Distal part termed as ileum. Wall of the small intestine consists of all the four layers as in stomach .

4. INTESTINAL VILLI AND GLANDS OF SMALL INTESTINE Mucous membrane of small intestine is surrounded by minute projections termed as villi. 2) The height of villi is approximately 1 mm and the diameter is less than 1 mm. 3) Villi are lined by columnar cells, which are termed as Enterocytes. 4) Each enterocyte leads to the formation of hair-like projections known as microvilli. Villi and microvilli enhance the surface area of mucous membrane with the help of many folds. 5) Within each villus, there is a central channel termed as lacteal, which enters into lymphatic vessels. It con sists of blood vessels als

5. INTESTINAL GLANDS OR CRYPTS OF LIEBERKÜHN Crypts of Lieberkühn or intestinal glands are simple tubular glands of intestine. Intestinal glands do not penetrate the muscularis mucosa of the intestinal wall, but open into the lumen of intestine between the villi. Intestinal glands are lined by columnar cells. Lining of each gland is continuous with epithelial lining of the villi e pithelial cells lining the intestinal glands undergo division by mitosis at a faster rate. Newly formed cells push the older cells upward over the lining of villi. These cells which move to villi are called enterocytes. Enterocytes secrete the enzymes. Old enterocytes are continuously shed into lumen along with enzymes.

6. Types of cells interposed between columnar cells of intestinal glands: 1. Argentaffin cells or enterochromaffin cells, which secrete intrinsic factor of Castle 2. Goblet cells, which secrete mucus 3. Paneth cells, which secrete the cytokines called defensins.

7. BRUNNER GLANDS In addition to intestinal glands, the first part of duodenum c on sists of some mucus glands, which are known as Brunner glands. 2) These glands penetrate muscularis mucosa and extend particulary up to the submucus coat of the intestinal wall. Brunner glands open into the lumen of intestine in a direct manner . Brunner gland secretes mucus as well as traces of enzymes.

8. PROPERTIES AND COMPOSITION OF SUCCUS ENTERICUS Secretion from small intestine is termed as succus entericus. PROPERTIES OF SUCCUS ENTERICUS Volume : 1800 mL/day Reaction : Alkaline pH : 8.3 COMPOSITION OF SUCCUS ENTERICUS Succus entericus con sists of water (99.5%) and solids (0.5%). Solids include organic and inorganic substances . Bicarbonate concentration is high to certain extent in succus entericus.

9. FUNCTIONS OF SUCCUS ENTERICUS 1. DIGESTIVE FUNCTION a) Enzymes of succus entericus act on the partially digested food and c hange them into final digestive products. b) Enzymes are produced and released into succus entericus with the help of enterocytes of the villi. Proteolytic Enzymes Proteolytic enzymes observed in succus entericus are the peptidases, . These peptidases c hange peptides into amino acids.  

10. Amylolytic Enzymes Amylolytic enzymes are observed in succus entericus Lactase, sucrase and maltase c hange the disaccharides (lactose, sucrose and maltose) into two molecules of monosaccharides . Dextrinase c hanges dextrin, maltose and maltriose into glucose. Trehalase or trehalose glucohydrolase Is responsible for hydrolysis of trehalose (carbohydrate seen in mushrooms and yeast) and changes it into glucose. Lipolytic Enzyme Intestinal lipase acts on triglycerides and c hanges them into fatty acids.

11. 2. PROTECTIVE FUNCTION i. Mucus observed in the succus entericus protects the intestinal wall particularly from the acid chyme, which e nters the intestine from stomach; thereby it Inhibits the intestinal ulcer. ii. Defensins secreted by paneth cells of intestinal glands are the antimicrobial peptides. These peptides are known as natural peptide antibiotics due to their role regarding killing of the phagocytosed bacteria.

12. 3. ACTIVATOR FUNCTION Enterokinase present in intestinal juice stimulates trypsinogen into trypsin. Trypsin, in turn stimulates other enzymes . 4. HEMOPOIETIC FUNCTION Intrinsic factor of Castle present in the intestine plays an important role regarding erythropoiesi s . It is essential for the absorption of vitamin B12.

13. 5. HYDROLYTIC PROCESS Intestinal juice plays an important role regarding the enzymatic reactions of digestion.   Digestive enzymes of succus entericus Peptidases Peptides into Amino acids Sucrase Sucrose into Fructose and glucose Maltase Maltose and maltriose into Glucose Lactase Lactose into Galactose and glucose Dextrinase Dextrin, maltose and maltriose into Glucose Trehalase Trehalose into Glucose

14. FUNCTIONS OF SMALL INTESTINE 1. MECHANICAL FUNCTION Mixing movements of small intestine lead to the n the thorough mixing of chyme along with the digestive juices namely succus entericus, pancreatic juice and bile. 2. SECRETORY FUNCTION Small intestine secretes succus entericus, enterokinase as well as the GI hormones. 3. HORMONAL FUNCTION a) Small intestine secretes many GI hormones namely secretin, cholecystokinin, etc. b) These hormones control the movement of GI tract a s well as secretory activities of small intestine and pancreas .

15. 4. DIGESTIVE FUNCTION Specificy functions of succus entericus. 5. ACTIVATOR FUNCTION Specificy functions of succus entericus. 6. HEMOPOIETIC FUNCTION Specificy functions of succus entericus. 7. HYDROLYTIC FUNCTION Specificy functions of succus entericus.

16. 8.AB SORPTIVE FUNCTIONS a) Presence of villi and microvilli in small intestinal mucosa enhances the surface area of mucosa. b) This facilitates the absorptive function of intestine. c) Digested products of foodstuffs, proteins, carbohydrates, fats and other nutritive substances namely vitamins, minerals and water are absorbed in small i ntestine to the maximum extent. d) From the lumen of intestine, these substances pass through lacteal of villi, cross the mucosa and open into the blood in a direct manner or through lymphatics.

17. Absorption of Water and Minerals i. In small intestine, sodium is absorbed in an active manner . It is essential for absorption of glucose, amino acids and other substances with the help of sodium cotransport. ii. Water moves in or out of the intestinal lumen until the osmotic pressure of intestinal contents becomes equal to that of plasma. iii. In ileum, chloride ion is absorbed in an active manner in exchange for bicarbonate. The significance of this exchange is not yet known. iv. Calcium is absorbed in an active manner primarily in upper part of small intestine.

18. Absorption of Vitamins Most of the vitamins are absorbed particularly in upper part of small intestine and vitamin B12 is absorbed in ileum. Absorption of water-soluble vitamins is faster compare to that of fatsoluble vitamins.

19. REGULATION OF SECRETION OF SUCCUS ENTERICUS Secretion of succus entericus is controlled by both nervous and hormonal mechanisms. NERVOUS REGULATION Stimulation of parasympathetic nerves leadst o vasodilatation and enhances the secretion of succus entericus. Activation of sympathetic nerves results in vasoconstriction and reduces the secretion of succus entericus. But, the role of these nerves in the regulation of intestinal secretion in physiological conditions is uncertain. Whatevet it may be , the local nervous reflexes play an important role in enhancing the secretion of intestinal juice. If chyme gains an entry into the small intestine, the mucosa is activated by tactile stimuli or irritation. It causes the development of local nervous reflexes, which stimulate the glands of intestine.

20. HORMONAL REGULATION When chyme enters the small intestine, intestinal mucosa secretes enterocrinin, secretin and cholecystokinin, which enhance the secretion of succus entericus by activating the intestinal glands.

21. METHODS OF COLLECTION OF SUCCUS ENTERICUS IN HUMAN In human beings, the intestinal juice is collected with the help of multilumen tube. The multilumen tube is inserted through nose or mouth, until the tip of this tube arrives the intestine. 3) A line is marked on the tube. Entrance of tip of the tube into small intestine is indicated if this line comes near the mouth. This tube consists of three lumens. 4) To the outer two lumens, small balloons are attached. When these balloons are inflated, an enlargement of intestine takes place . 5) Now, the intestinal juice is collected through the middle lumen, with the aspiration aspiration.

22. IN ANIMALS Thiry Loop A portion of intestine is separated from the gut by incising at both ends. The cut ends of the main gut are connected and the continuity is again established . One end of isolated segment is closed and the other end is brought out through abdominal wall. It is termed as Thiry loop or Thiry fistula.

23. Thiry-Vella Loop Thiry-Vella loop is the modified Thiry loop. In this, a long segment of intestine is cut and separated particularly from the main gut. 3) Both the ends of this segment are brought out through the abdominal wall. The cut ends of the main gut are joined.

24. APPLIED PHYSIOLOGY 1. MALABSORPTION a) Malabsorption is the failure to absorb nutrients namely proteins, carbohydrates, fats and vitamins. b) Malabsorption also influences growth and development of the body. It also leads to specific diseases .

25. 2. MALABSORPTION SYNDROME a) Malabsorption syndrome is the condition manifested by the failure of digestion a s well as absorption in small intestine. b) Malabsorption syndrome is generally happened by Crohn’s disease, tropical sprue, steatorrhea and celiac disease.

26. 3. CROHN’S DISEASE OR ENTERITIS a) Enteritis is an inflammatory bowel disease (IBD), manifested by inflammation of small intestine. b) Generally , it Influences particulalry the lower part of small intestine, the ileum. c) The inflammation rersults in malabsorption and diarrhea. Causes Crohn’s disease develops due to abnormalities of the immune system. The immune system reacts to a virus or a bacterium, leading to inflammation of the intestine. Features i. Malabsorption of vitamin ii. Weight loss iii. Abdominal pain iv. Diarrhea v. Rectal bleeding, anemia and fever vi. Delayed or stunted growth in children.

27. 4. TROPICAL SPRUE Tropical sprue is a malabsorption syndrome, influencing the residents of or the visitors to tropical areas where the disease is epidemic. Cause The cause of this disease is not known and it may be related to infectious organisms. Features i. Indigestion ii. Diarrhea iii. Anorexia and weight loss iv. Abdominal and muscle cramps.

28. 5. STEATORRHEA Steatorrhea is the condition occurred by deficiency of pancreatic lipase, leading to malabsorption of fat. . 6. CELIAC DISEASE a) Celiac disease is an autoimmune disorder manifested by by the damage of mucosa and atrophy of villi in small intestine, leading to impaired digestion a s well as absorption. b) It is also termed as gluten-sensitive enteropathy, celiac sprue and non-tropical sprue.

29. Cause Celiac disease is happened by gluten. It is a protein present in wheat, oats, rye, barley and other grains. Gluten is like a poison to individuals with celiac disease, because it damages the intestine in a severe manner. Features i. Diarrhea ii. Steatorrhea iii. Abdominal pain iv. Weight loss v. Irritability vi. Depression

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