Large intestine by Pandian M

FUNCTIONAL ANATOMY
SECRETIONS OF LARGE INTESTINE
FUNCTIONS OF LARGE INTESTINE
DIETARY FIBER
APPLIED PHYSIOLOGY

1. Large Intestine Pandian M Dept . of P hysiology D.Y. Patil Medical College, Kop

2. FUNCTIONAL ANATOMY OF LARGE INTESTINE Large intestine or colon extends from ileocecal valve up to anus

3. PARTS OF LARGE INTESTINE Large intestine is made up of the following parts: 1 . Cecum with appendix 2 . Ascending colon 3 . Transverse colon 4 . Descending colon 5 . Sigmoid colon or pelvic colon 6 . Rectum 7 . Anal canal.

4. The large intestine is a tube 6.5 cm (2.5 inches) in diameter about 1.5 m (5 feet) long . Its first portion, the cecum , forms a blind-ended pouch from which extends the appendix , a small, finger like projection that may participate in immune function but is not essential The colon consists of three relatively straight segments—the ascending, transverse , and descending portions.

5. STRUCTURE OF WALL OF LARGE INTESTINE 1.Serous layer: 2 . Muscular layer 3. Submucus layer 4. Mucus layer

6. SECRETIONS OF LARGE INTESTINE

7. FUNCTIONS OF LARGE INTESTINE ABSORPTIVE FUNCTION FORMATION OF FECES EXCRETORY FUNCTION SECRETORY FUNCTION 5. SYNTHETIC FUNCTION

8. APPLIED PHYSIOLOGY DIARRHEA:- Diarrhea is the frequent and profuse discharge of intestinal contents in loose and fluid form. It occurs due to the increased movement of intestine . It may be acute or chronic.

9. T he general causes of diarrhea are: Dietary abuse : 2. Food intolerance : 3.Infections by: 4. Reaction to medicines such as : i . Antibiotics, ii . Antihypertensive drugs, iii . Antacids containing magnesium, iv . Laxatives 5. Intestinal diseases : irritable bowel syndrome and abnormal motility of the intestine

10. CONSTIPATION:- Failure of voiding of feces, which produces discomfort is known as constipation . Dysfunction of myenteric plexus in large intestine – megacolon APPENDICITIS ULCERATIVE COLITIS -- IBD

11. DEFECATION

12. 3. MOTILITY OF SMALL INTESTINE There are 3 types of movements:- Rhythmic segmental contractions or pendular movements and Peristalsis Tonic Contraction

13. 1.Rhythmic segmental contractions or pendular movements and Mixing movements of small intestine are responsible for proper mixing of chyme with digestive juices such as pancreatic juice , bile and intestinal juice . The mixing movements of small intestine are segmentation contractions Pendular movements .

14. Pendular Movement

15. occur regularly or irregularly , but in a rhythmic fashion . The ring like contractions occur at regularly spaced intervals along the gut involving localized ‘segment’ of 1-2 cm by ↑se in Ca 2+ influx . They’re two types :- Eccentric contraction located in a localized segment less than 2 cm in length & concentric contraction Longer than 2 cm and are of relatively uniform circumference

16. also called rhythmic segmentation contractions Here the food divided & mixed with digestive juice again & again and finally formed Chyme

17. time

18. Control of rhythmic segmentation contractions ❶ Contraction is initiated by Pacemaker cells Located in 2 nd part of duodenum , near entry of bile duct A basic electric rhythm of ‘slow wave’ coordinated by myenteric reflexes

19. ❷ the frequency of contraction is directly related to the slow waves Which is initiated by Pacemaker cells I t’s not influenced by neuronal or circulatory hormones

20. ❸ the strength of contr n is proportional to frequency of spike generated by ‘ slow waves ’ This frequency is controlled by amplitude of ‘ slow wave ’ amplitude of ‘slow wave’ ↑ sed by GIT hormones released during digestion e.g. gastrin , CCK-PZ & motilin Whereas, secretin and glucagon ↓se slow wave amplitude

21. Note – vagus N ↑& sympathetic N ↓ ❹5HT released during contr n make the smooth muscle sensitive to distension Distension of short segment causes – proximal seg . contr n & distal seg . relaxation

22. 2.Peristalsis Stretched or distended by food ( chyme ) Which push the chyme in aboral direction through intestine . The movement also called as vermicular or peristaltic movements. It moves analwards at rate of 0.5 to 2cm/min But its weak & dies out after travelling only 3 to 5 cm, rarely up to 10cm So net movement of chyme in analward direction is (1cm/min) slow

23. Starling’s law of intestine or law of gut or Polarity of the intestine:- The peristaltic waves always travel from the oral end towards the aboral end of the intestine. This phenomenon has been labelled as the Law of the intestine

24. Factor influence peristalsis It is increased after meal. This is caused by gastro- enteric reflex (N.C) Gastrin , CCK, insulin, and serotonin enhance GI motility (H.C) Secretin and Glucagon inhibit or reduce the intestinal motility

25. Functions subserved by the peristaltic waves are : Help to propel the intestinal contents aborally . Also help in digestion and absorption of the food particles because different types of nutrients are digested and absorbed in different segments of the small intestine

26. Peristaltic rush Initiated by chemical or physical irritation the small intestine shows a powerful peristaltic contraction . Initiated by extrinsic nervous reflex & partly by myenteric relex . It is caused by excessive irritation of intestinal mucosa or extreme distention of the intestine.

27. This type of powerful contraction begins in duodenum and passes through entire length of small intestine reaches the ileocecal valve within few minutes. This is called peristaltic rush or rush waves . Peristaltic rush sweeps the contents of intestine into the colon .

28. Functions of ileocaecal Ileocaecal valve prevent back flow of feacal content from colon into small intestine The valve usually resists pressure of 50 to 60cm of H 2 O Gastrin produces relaxt n & Secretin causes contr n These agent show opposite effects on cardiac sphincter

29. Tonic contraction These’re relatively prolonged contract n that isolate one segment of intestine from another Along with segmental contr n , permits longer contact of chyme with enterocytes and promotes absorpt n

30. Applied 1. Adynamic ileus or Paralytic ileus :- It’s painless condition produced by (a)Handling - - of intestine during abdominal operations or trauma to intestine This causes direct inhibition of smooth muscle (b) Irritation- - of peritoneum causes reflex inhibition of smooth muscle due to ↑ non adrenergic fibers in splanchnic nerves & (b) ↓ intestinal motility to cause adynamic ileus .

31. 2. Mechanical obstruction This condition associated with production of sever pain ?? This pressure in the segment causing : ( i ) compression of blood vessels – local ischemia (ii) stimulate visceral afferent nerve fibers to cause sweating, Ht, & severe vomiting . if not relieved it may prove fatal due to resultant metabolic alkalosis & dehydration.

32. Gastro – Ileal reflex When food leaves the stomach, the caecum reflex Passage of chyme through the ileocaecal valve ↑ - so called. This is vagally mediated reflex Sympathetic stimul n ↑ contr n of the valve

33. MOVEMENTS OF LARGE INTESTINE the large intestine shows sluggish movements. Still, these movements are important for mixing , propulsive and absorptive functions . Types of Movements of Large Intestine two types : 1 . Mixing movements: Segmentation contractions 2. Propulsive movements: Mass peristalsis .

34. 1. MIXING MOVEMENTS – SEGMENTATION CONTRACTIONS Large circular constrictions, which appear in the colon, are called… These contractions occur at regular distance in colon. Length of the portion of colon involved in each contraction is nearly about 2.5 cm.

35. 2. PROPULSIVE MOVEMENTS – MASS PERISTALSIS Mass peristalsis or mass movement propels the feces from colon towards anus . Usually , this movement occurs only a few times every day . Duration of mass movement is about 10 minutes in the morning before or after breakfast. This is because of the neurogenic factors like gastrocolic reflex (see below) and parasympathetic stimulation .

36. Referred :- Text book of Medical Physiology Guyton, 13 th edition, Text book of Medical Physiology Indu khurana , Text book of Medical Physiology Vander’s Text book of Medical Physiology Sembulingam & LPR

37. THANK YOU . . .