movements of small and large intestine

1Prof .Dr. Rashid Mahmood

Movements of small & large intestine

A 35 year old female was operated for acute appendicitis. She was advised not to take anything by mouth till further advice by the surgeon. Six hours after surgery she inquired the doctor on duty that whether she can now start taking orally or not. The doctor examined her bowl sounds. He could not listen the bowl sounds and advised her to wait for another few hours.•What is the name of this condition? •Why does the motility of intestine decrease after abdominal surgery?•How the condition can be relieved if the movements of small intestine do not recur in more than 10 hours?


Objectives Goal /Aim

• By the end of this session the student should be able to describe the mechanism, types and functions of the motility of small and large intestine.

Specific objectives By the end of this session the student should be able to

• Enlist the types of movements of small and large intestine• Define the factors that control motility of small and large intestine• Describe how chyme is transported from pylorus to anus• Distinguish between Segmentation and Haustrations• Explain Function and Feedback control of Ileocecal valve and

Ileocecal sphincter


Lesson contents• Movements of Small Intestine • Mixing (Segmentation Contractions)• Progression of segmentation contractions• Peristalsis (Propulsive Movements)• Movements of Muscularis Mucosa• Contraction of villi• Control of Peristalsis of Small Intestine

• Ileocecal valve and Ileocecal sphincter • Function• Feedback control• Emptying at Ileocecal valve

• Movements of Colon• Mixing Movements (Haustrations) • Propulsive Movements (Mass Movements)


Movements of small intestine


Movements of Small Intestine1. Mixing (Segmentation Contractions)2. Propulsive (Peristalsis)

Overlap

3. Movements of Muscularis MucosaFolds

↑ surface area

4. Contraction of villi“milk” the villi

↑ lymph flow


Mixing Contractions (Segmentation Contractions)


Mixing Contractions (Segmentation Contractions)

• Stimulus: Stretching• Receptors: Nerve endings of enteric nervous system• Response: localized concentric contractions

Spaced at intervals Fraction of a minute “Chop” 2-3 times per minute Maximum frequency= 12/minute Frequency depends on frequency of Electrical slow waves

• Integration area: Myenteric nerve plexus + extrinsic control

• Propulsive effect


Progression of segmentation contractions


Propulsive Movements• Peristalsis• Any part • Towards Anus• Velocity: 0.5-2 cm/minute• Net movement: 1 cm/min• 3-5 hours from pylorus to ileocecal valve• Function:

– Progression– Spread of chyme along mucosa

• Peristaltic Rush– Irritation – Diarrhea


Assessment Question 1• List the different types of movements in

small Intestine.


Control of Peristalsis of Small Intestine

1. Nervous Factors2. Hormonal Factors


Control of Peristalsis of Small IntestineNervous Factors

1. Entry of meal in duodenum• Stretch

2. Gastroenteric reflex• Distension of stomach• Myenteric plexus– Blocked at ileocecal valve till another food

→ Gastroileal reflex3. Movements of Muscularis Mucosa and

Contraction of villi are controlled by submucosal plexus


Control of Peristalsis of Small IntestineHormonal Factors

↑ motility• Gastrin• CCK• Insulin• Motilin• Serotonin

↓ motility• Secretin • Glucagon


Assessment Question 2• Fill in the blanks;• Law of gut= ___________ + _________

15Prof .Dr. Rashid Mahmood Next: Ileocecal valve


Ileocecal valve andIleocecal sphincter

• Function– Prevent backflow– Controlled passage– ↑ time for reabsorption in ileum

• 1500-2000 ml of chyme /day into cecum• Feedback control

– Reflexes from ileum– Myenteric plexus + autonomic nerves– Inflamed appendix


Emptying at Ileocecal valveExcitatory

factors

Inhibitory factors


Control of ileocecal valve/sphincter

Excitatory factors

Inhibitory factors


Assessment Question 3• List the factors that increase emptying at

Ileo-cecal valve.


Next: movements of large intestine


Large IntestineAnatomy

Teniae coli are bands of longitudinal muscle along the length of the colon


Radiograph of large intestine after barium

enema


Movements of Colon• Mixing Movements (Haustrations)

– Proximal half• Propulsive Movements (Mass Movements)

– Distal half

• Functions of colon:– Absorption– Storage of fecal matter


Mixing Movements (Haustrations)

• Large circular constrictions• Circular muscle + longitudinal muscle• Unstimulated areas bulge → Haustrations • Fecal matter slowly mixed , rolled over &

propelled• < 2 minutes


Propulsive Movements(Mass Movements)

• For many minutes• 1-3 times/day

–Especially for about 15 minutes during the 1st hour after breakfast

Defecation


Assessment Question 4• Distinguish between Segmentation and

Haustrations


Summary • Movements of Small Intestine are of TWO Types: Mixing (Segmentation)

Contractions and Propulsive (Peristalsis)• Nervous Factors that Control of Peristalsis of Small Intestine include

Gastroenteric reflex, Gastroileal reflex & some other reflexes• These reflexes are controlled by Myenteric plexus, and also by Autonomic

nervous system• Hormones that increase the motility of Small Intestine include Gastrin

and CCK, while Secretin decreases the motility of Small Intestine• Ileocecal valve prevents backflow of chyme from cecum to ileum• Ileocecal sphincter allows controlled emptying at Ileocecal valve• Feedback control of Ileocecal sphincter is by Reflexes from ileum, stomach

and cecum• Movements of Colon are also of TWO types: Mixing Movements

(Haustrations), and Propulsive Movements (Mass Movements)


Learning Resources 1. Guyton and Hall (Text book of physiology), 13th Edition2. Ganong (Text book of physiology), 24th Edition3. Berne & Levy Principles of Physiology (Koeppen BM), 6th Edition4. Human Physiology Stuart Ira Fox, 13th Edition5. Human Physiology : from cells to system Lauralee Sherwood, 9th Edition6. Internet


Next topic • Pancreatic secretion: Regulation & phases• Prior knowledge required for next lecture

– Physiological Anatomy of Pancreas – Composition of Pancreatic secretions – Hormones of GIT – Autonomic control of GIT

movements of small and large intestine

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