L9: Colonic Motility and Defecation Flashcards
Flow between Ileum and Caeum is controlled by the _______________ at the end of the Ileum (Responds to both ileal and colonic distention)
- Tone increased by __________________
- Tone decreased by _________________
Flow between Ileum and Caeum is controlled by the High-Pressure Zone at the end of the Ileum (Responds to both ileal and colonic distention)
- Tone increased by SYMPATHETIC Innervation
- Tone decreased by GASTRIN
_____________________: Intussusception of terminal ileum into caecum that prevents flow of material (esp. bacteria) from colon into small intestine
- _____________Distention=> Relaxation of Valve
- ____________ Distention => Contraction of Valve
Ileocecal valve: Intussusception of terminal ileum into caecum that prevents flow of material (esp. bacteria) from colon into small intestine
- Ileal Distention => Relaxation of Valve
- Colonic Distention => Contraction of Valve
Roles/ transit times of various parts of the Large Intestine?
Total Transit Time?
Ascending Colon: Half of Chyme entering caecum cleared in 90 minutes
Transverse Colon: Removal of Water/Electrolytes. Material retained for ~24 hours
Descending Colon: Storage of material (after 24 hrs. in colon)
Recto-Sigmoid Region: Reservoir for feces
Total Transit Time: 36-48 Hours
Muscular structure of colon is different to other regions:
- Circular same as rest of GIT
- Longitudinal aggregated into three bands (__________) shorter than the length of colon => leads to ________________
Muscular structure of colon is different to other regions:
- Circular same as rest of GIT
- Longitudinal aggregated into three bands (Tenia Coli) shorter than the length of colon => leads to Haustra (Pouches)
Propulsive Motility in the Colon?
Haustral Shuttling : short distances – both directions. Squirting of contents – kneading the fecal mass. Most Frequent
Segmental Propulsion (Peristalsis): haustrum to haustrum - both directions
Mass Contraction (Multi-haustral propulsion): Drive bulk of movement of material through the colon over large distance. Infrequent – 1-3 per day
Triggers of Mass Contraction?
- Gastroileal Reflex (stimulated by the opening of the ileocecal valve and the movement of the digested contents from the ileum of the small intestine into the colon)
- Gastrocolic Reflex (in response to stretch in the stomach following ingestion and byproducts of digestion entering the small intestine)
- Irritation (e.g. ulcerative colitis)
- Intense parasympathetic stimulation
- Over-distension of a segment of colon
Control of Large Intestinal Motility (4 Aspects)?
- Basal electrical rhythm: Interstitial Cells of Cajal
- Increased by: Strecthm ACh, Histamine
- Decreased by: Noradrenaline/Adrenaline
- Intrinsic nerves: Myenteric plexus
- Extrinsic nerves
- Parasympathetic: Promotes Colonic Motility
- Sympathetic: Inhibits Colonic Motility
- Endocrine/paracrine control
________________________:
- Congenital ABSENCE of ganglia in large intestine
- Delayed passage of first faeces (_______________) (>48 hours)
- Tonic contraction of affected segment => Megacolon, Abdominal distension, Constipation
Hirschsprung’s Disease:
- Congenital ABSENCE of ganglia in large intestine
- Delayed passage of first faeces (Meconium) (>48 hours)
- Tonic contraction of affected segment => Megacolon, Abdominal distension, Constipation
____________________________: DAMAGE to myenteric (Auerbach’s) plexus of colon and esophagus from Infection with Trypanosoma cruzi, from Rhodnius prolixus bites=> Megacolon, Megaesophagus, Severe weight loss
Chaga’s Disease: DAMAGE to myenteric (Auerbach’s) plexus of colon and esophagus from Infection with Trypanosoma cruzi, from Rhodnius prolixus bites=> Megacolon, Megaesophagus, Severe weight loss
Muscles that contribute to Fecal Continence?
Epidemiology/Causes of Fecal Incontinence?
2% of population (Female: Male 8:1)
Obstetric injury – a principal cause of faecal incontinence
Damage to pudental nerve
