Intestines(movements and secretions of small and large intestines ) The Guyton and Hall physiology

Intestines(movements and secretions of small and large intestines)
Distended Portion of small intestine with chyme stretching  concentric contractions at intervals  lasting a fraction of a minute These contraction causes “Segmentation” of the small intestine ---forms spaced segments  new points every time  chopping chyme 2-3 times/min  mixing with intestinal secretions  maximum frequencyof segmentation contraction depends on frequency of BER (Basic electrical rhythm) i.e. In duodenum and proximal jejunum is 12/min and in terminal ileum is 8-9/min.
Atropine blocks the segmentation

law of gut
The peristaltic reflex +anal direction of movement of the peristalsis is called “LAW OF GUT”

1. Intestines movements and secretions of small and large intestines Source: The Guyton and Hall physiology Maryam Fida (o-1827)

2. Mixing contractions (Segmentation Contractions) Distended Portion of small intestine with chyme  stretching  concentric contractions at intervals  lasting a fraction of a minute These contraction causes “Segmentation” of the small intestine ---forms spaced segments  new points every time  chopping chyme 2-3 times/min  mixing with intestinal secretions  maximum frequencyof segmentation contraction depends on frequency of BER (Basic electrical rhythm) i.e. In duodenum and proximal jejunum is 12/min and in terminal ileum is 8-9/min. Atropine blocks the segmentation

3. Mixing movement

4. Mixing contraction of the Small Intestine. Rhythmic Segmentations Bring Through Mixing of the Intestinal Content

5. Law of GUT The peristaltic reflex +anal direction of movement of the peristalsis is called “LAW OF GUT”

6. PROPULSIVE MOVEMENTS Peristalsis in the small intestine Peristaltic Rush

7. 1. Peristalsis Chyme is propelled through the small intestine by “ PERISTALTIC WAVES” Start in any part of small intestine at 0.5-2 cm/sec towards anus They are usually weak Die after 3-5 cm not > than 10 cm Very slow Thus, net movement along the small intestine averages only 1 cm / min 3-5 hrs for passage of chyme from pylorus  illeocecal valve Functions : Progression of chyme towards iliocecal valve Spread chyme along intestinal mucosa Gastro enteric reflex: initiation of intestinal peristalsis  foods in stomach Gastroileal reflex : intensification of peristalsis in illium and to presence of 2 nd meal in stomach  forces remaining food through the illiocecal valve into the caecum

8. Peristalsis stretch vagal irritants Contractile rings ++Enteric neurons

9. Nervous signals = Gastroenteric reflex Hormonal : Stimulatory: gastrin , cck ,insulin , motillin & serotonin Inhibitory: secretin , glucagon Factors affecting small intestinal peristalsis:

10. Peristaltic Rush Mostly peristalsis in the small intestine is weak but sometimes , powerful peristaltic contraction occurs is called “PERISTALTIC RUSH “ CAUSE Intense irritation of intestinal mucosa Infectious diarrhea Tanveer Raza MD MS MBBS [email protected]

11. Iliocecal valve Prevents backflow of fecal matter from colon into small intestine Illeocecal sphincter: remained mildly constricted  slows emptying of illeal content into cecum Gastroileal reflex: intensification of illeal peristalsis 2 nd to 2 nd meal 3-4 hrs after the 1 st one ,by which chyme is forcefully pushed through illeocecal valve into the caecum Functions of illiocecal valve Prevention of back flow of fecal content from colon by: Protrusion of illeocecal valve into the caecum  remain forcefully closed in pressure & Can resist 50-60cm of H2O reverse pressure Iliocecal sphincter: Terminal illeal circular muscular constriction Remain mildly closed Slow emptying

12. SECRETIONS OF THE SMALL INTESTINE

13. SECRETION OF THE SMALL INTESTINE Secretion of mucus by Brunner’s Glands in the duodenum Secretion of intestinal Digestive juices by the Crypts of Lieberkuhn Tanveer Raza MD MS MBBS [email protected]

14. Secretion of Mucous by Brunner’s Gland in the Duodenum LOCATION: Brunner’s Glands is located in the wall of the first few centimeters of the duodenum, mainly between the pylorus of the stomach and the papilla of vater , where pancreatic secretion and bile empty in to the duodenum. SECRETION : These glands secrete large amount of alkaline mucous. STIMULI : 1. Tactile or irritating stimuli 2. Vagal stimuli 3. Secretin FUNCTION :1. To protect the duodenum wall from digestion by the acidic gastric juices emptying from the stomach. 2. Neutralizing the HCL entering the duodenum from the stomach INHIBITED BY SYMPATHETIC STIMULI Tanveer Raza MD MS MBBS [email protected]

15. SECRETION BY THE CRYPTS OF LIEBERKUHN LOCATION: Found all over the small intestine CELLS: 1. GOBLET CELL which secrete mucous that lubricates and protect 2. ENTEROCYTES Secrete water and electrolytes such as chloride and bicarbonate and digestive enzymes DIGESTIVE ENZYMES. Peptidases: for splitting small peptides in to aminoacids Four enzymes- sucrose, maltase, isomaltase and lactase for spiltting diasaccharides yin to monosaccharides Intestinal lipase for spiltting neutral fats in to glycerol and fatty acids Tanveer Raza MD MS MBBS [email protected]

16. Large Intestine

17. Basic Function are: Absorption of water & electrolytes from chyme by proximal half Storage of fecal matter by distal half So sluggish movements required MOVEMENTS OF COLON

18. Mixing Movements or “ HAUSTRATIONS” PROPULSIVE MOVEMENTS or “ MaSS MOVEMENTS” Movements of the Colon

19. MIXING MOVEMENTS”HAUSTRATIONS Like mixing movements in small intestine, large circular constrictions occur in large intestine. 2.5 cm circular muscle constriction to occlusion Tinea coli contraction( Three longitudinal strips) These combine contraction of circular and longitudinal strips of muscle cause the unstimulated portion of large intestine to bulge outward in to bag like sacs called “ Haustrations” Haustration reaches to its paek in 30 sec and repeat in 60 sec After another few min new haustration appears Fecal matter dug into & rolled over in large intestine In 8-15 hrs from illeocecal valve  through colon 80-200 milliliter/day semisolid fecal mater is formed

20. PROPULSIVE MOVEMENTS (MASS MOVEMENT Mass movements: Mass movement propels the feces from colon towards the anus. From cecum to sigmoid These movements occurs only 1-3 times each day. Mostly about 15 min during 1 st hour after breakfast Sequence of events: constrictive ring occurs in response to distention & irritation in transverse colon 20 cm distal to it loose haustration & contract as a unit En mass propelling of fecal contents Contraction for 30 sec, relaxation in next 2-3 min Series of such movements persist for 30 min ,then cease and return half day later  Feces reach rectum  desire of defecation

21. STIMUALANT OF MASS MOVEMENT 1.Gastrocolic reflex 2. Duodenocolic reflex These reflexes result from distension of the stomach and duodenum 3. Irritation in the colon 4. Ulcerative Colitis Ulcerative colitis: ulcerated portion of colonic mucosa , leads to intense mass movement [email protected]

22. Secretions of Large Intestine Have only crypts of Lieberkuhn . No villi No digestive enzymes Only secrete Mucus

23. Secretions of Large Intestine Mucus provides protection Parasympathetic stimulation increases rate of goblet cell secretion Bacterial actions produce gases (flatus) from particular kinds of carbohydrates found in legumes and in artificial sugars like sorbitol Bacteria produce vitamin K which is then absorbed Feces consists of water, undigested food (cellulose), microorganisms, sloughed-off epithelial cells