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

1. Large Intestine
Pandian M
Dept. of Physiology
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
1. ABSORPTIVE FUNCTION
2. FORMATION OF FECES
3. EXCRETORY FUNCTION
4. 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. The general causes of diarrhea are:
1. 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:-
1. Rhythmic segmental contractions or
pendular movements and
2. Peristalsis
3. 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 Ca2+ 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

18. time

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

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

21. ❸ the strength of contrn 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

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

24. 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

25. 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

26. 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

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

28. 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.

29. • 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.

30. 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
H2O
• Gastrin produces relaxtn & Secretin causes contrn
• These agent show opposite effects on cardiac
sphincter

31. Tonic contraction
• These’re relatively prolonged contractn that isolate
one segment of intestine from another
• Along with segmental contrn, permits longer
contact of chyme with enterocytes and promotes
absorptn

33. 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
(a)& (b) ↓ intestinal motility to cause adynamic
ileus.

34. 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.

35. 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 stimuln ↑ contrn of the valve

36. 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.

37. 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.

38. 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.

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

40. THANK YOU . . .