1. Movements of large intestine
Ingestion of food
GIT
Movements of large intestine
Dr.Rashid Mahmood

2. Propulsion and Mixing of Food in the Alimentary Tract
Ingestion of food
Motor functions of Stomach
Movements of Small Intestine
Movements of Colon

3. Large Intestine
Teniae coli are bands of longitudinal muscle along the length of the colon

6. Radiograph of large intestine after barium enema

7. Movements of Colon Mixing Movements (Haustrations)
Proximal half
Propulsive Movements (Mass Movements)
Distal half
Functions of colon:
Absorption
Storage of fecal matter

8. Mixing Movements (Haustrations)
Large circular constrictions
Circular muscle + longitudinal muscle
Unstimulated areas bulge→Haustrations
< 2 minutes

9. Propulsive Movements (Mass Movements)
For many minutes
1-3 times/day
Especially for about 15 minutes during the 1st hour after breakfast

10. Sequence of events in Mass Movements
Distension/irritation in colon →Constrictive ring (usually in Transverse colon
→20 or more cm of colon distally loose haustrations & contract as a unit
→fecal material pushed down
→10-30 minutes →Relaxation/desire to defecate (if pushed into rectum)
→recur perhaps half a day later

11. Sequence of events in Mass Movements
Stimulus:
Distension/irritation in colon
Constrictive ring
(usually in Transverse colon)
Distal colon looses Haustrations
20 or more cm
Distal colon contracts as a unit
fecal material pushed down
Duration: minutes
Relaxation/desire to defecate
(if pushed into rectum)
Recur perhaps half a day later

12. Propulsive Movements (Mass Movements)
Facilitation of initiation of mass movements
Gastrocolic Reflex
Duodenocolic Reflex
Controlled by Extrinsic nerves
Irritation
Ulcerative colitis

13. Defecation
Defecation is the expulsion of feces from the anus and rectum. Also known as bowel movement

14. Definitions Feces (Stool):
Excrement (Excretion) discharged from the bowl
Defecation:
Expulsion of feces
Sphincter:
A ring like muscle which closes a natural orifice or passage

15. Defecation process: Internal sphincter Sm .M (Involuntary).
External sphincter Sk .M (Voluntary).
Steps:
Distention of the rectum
Which stimulate the stretch receptors
Initiating the defecation reflex
If the ex. sphincter is relaxed defecation will take place.
If not the defecation will be inhibited (Subside).

17. Defecation reflex

18. Defecation Rectum is empty most of the time
Weak functional sphincter at juncture between sigmoid colon & rectum
Sharp angulation
Feces into rectum → Defecation reflex
Desire for Defecation
Reflex contraction of rectum
Reflex relaxation of anal sphincters

19. Defecation Reflexes
Intrinsic Reflex
Parasympathetic Defection reflex

20. Intrinsic Reflex Distension → Afferent signals
→Myenteric Plexus →Peristaltic waves →Inhibition of Internal Sphincter
(Defecation if External Sphincter is inhibited voluntarily)
Weak reflex

21. Parasympathetic Defection Reflex Contd….

22. Parasympathetic Defection reflex
Distension →
Afferent signals
→sacral segments of Spinal cord →Pelvic nerves → Peristaltic waves →Inhibition of Internal Sphincter (Defecation if External Sphincter is inhibited voluntarily)
Powerful reflex

23. Parasympathetic Defecation reflex Contd……..
Other effects
Deep breath
Closure of Glottis
Contraction of abdominal wall
Pelvic floor to relax downwards and pull outwards
Purposeful activation
Less effective

24. Components of Parasympathetic defecation reflex
1. Stimulus:
Distension
2. Receptors:
Nerve endings in wall of the rectum

26. Components of Parasympathetic defecation reflex
3. Afferent nerves:
Parasympathetic nerves
4. CNS:
sacral segments of Spinal cord

27. Components of Parasympathetic defecation reflex
5. Efferent nerves:
Parasympathetic (Pelvic) nerves
6. Effectors:
Internal anal sphincter
Descending colon, sigmoid colon, rectum, anus

28. Components of Parasympathetic defecation reflex
7. Response:
Inhibition of Internal Sphincter (Defecation if External Sphincter is inhibited voluntarily)
Contraction of Descending colon, sigmoid colon, rectum, anus
Other effects
Deep breath
Closure of Glottis
Contraction of abdominal wall
Pelvic floor to relax downwards and pull outwards

29. Roll of external sphincter
Newborn babies
Transected / Diseased spinal cord
Lack of conscious control
Emptying at inconvenient time

30. Paralysis of defecation in Spinal Cord injuries
Spinal cord mediated defecation reflex:
Through Conus Medullaris of spinal cord
Injuries above Conus Medullaris
Loss of voluntary control but defecation reflex maintained
Enema
Injuries at or below Conus Medullaris
Loss of defecation reflex

31. Other Autonomic Reflexes
Peritoneo intestinal reflex
Reno intestinal reflex
Vesico intestinal reflex

32. Sample Questions Write short notes on: Gastrin Cholecystokinin
Secretin
Pharyngeal stage of swallowing
Esophageal stage of swallowing
First stage of deglutition
Emptying of stomach
Functions of Antrum of stomach
Pyloric pump
Mixing movements in small intestine
Duodenal factors affecting Emptying of stomach
Control of peristalsis in small intestine