FUNCTIONAL ANATOMY INTESTINAL VILLI AND GLANDS PROPERTIES AND COMPOSITION OF SUCCUS ENTERICUS FUNCTIONS OF SUCCUS ENTERICUS FUNCTIONS OF SMALL INTESTINE REGULATION OF SECRETION OF SUCCUS ENTERICUS METHODS OF COLLECTION OF SUCCUS ENTERICUS APPLIED PHYSIOLOGY

1. Physiological Activities in
Small Intestine
Pandian M
Dept. of Physiology
D.Y. Patil Medical College, Kop

2. 1. FUNCTIONALANATOMY
2. SMALL INTESTINAL SECRETIONS
3. MOTILITY OF SMALL INTESTINE
4. FUNCTIONS OF SMALL
INTESTINE
5. APPLIED ASPECTS

4. FUNCTIONAL ANATOMY
• Gross anatomical considerations
• Structural characteristics of small
intestine

5. Gross anatomical considerations
• The small intestine is divided into three regions.
• The duodenum, the shortest region, is
retroperitoneal.
• It starts at the pyloric sphincter of the stomach
• Extends 25 cm (10 in.) until it merges with the
jejunum.
• Duodenum means “12”; it is so named because
it is about as long as the width of 12 fingers.

6. Contd….
• The jejunum is 1 m (3 ft) long and extends to
the ileum. Jejunum means “empty,” which is
how it is found at death.
• The final and longest region of the small
intestine, the ileum (twisted),
• measures about 2 m (6 ft) and joins the large
intestine at a smooth muscle sphincter called
the ileocecal sphincter.

7. Structural characteristics of small
intestine
• Most digestion and absorption of nutrients occur in a
long tube called the small intestine.
• Its length alone provides a large surface area for
digestion and absorption,
• that area is further increased by circular folds, villi,
and microvilli.
• The small intestine begins at the pyloric sphincter of
the stomach, coils through the central and inferior
part of the abdominal cavity,

9. Contd….
• eventually opens into the large intestine.
• It averages 2.5 cm (1 in.) in diameter; its
length is about 3 m (10 ft) in a living
person
• about 6.5 m (21 ft) in a cadaver due to the
loss of ………??? after death.

10. Histology of the Small Intestine
• The wall of the small intestine is composed of the same four layers
• that make up most of the GI tract: mucosa, submucosa, muscularis,
• and serosa

15. 2. SMALL INTESTINAL SECRETIONS
The intestinal juice also called succus entericus
comprises
the intestinal secretions which include:
Aqueous component (water and electrolytes),
-especially those present in the crypts of
Lieberkuhn.
- 2 L of secretion is produced per day by these cells,
- the chemical composition is almost similar to ECF
except that it is slightly more alkaline (pH 7.5–8.6).
-This fluid is colourless, slightly cloudy due to
admixture of mucus, shedded epithelial cells and
cholesterol.

16. • Intestinal enzymes:-
-Brush border of epithelial cells covering the
villi
-which secrete intracellular digestive enzymes
Peptidases, Disaccharidases, Intestinal lipases,
Enterokinase or ??

17. • Mucus:-
1. Brunner’s glands
- thick alkaline mucoid Secretion
protective role preventing HCl and chyme
from damaging the duodenal mucosa.
• 2. Goblet cells also secrete a lot of mucus, which
protects the intestinal mucosa and lubricates the
chyme.

18. REGULATION OF SECRETION
OF SUCCUS ENTERICUS
• Secretion of succus entericus is regulated by
both nervous and hormonal mechanisms.

20. Stimulation of
parasympathetic nerves
vasodilatation
↑se SUCCUS
ENTERICUS
↑se SUCCUS ENTERICUS
Stimulation of
sympathetic nerves
vasoconstriction

21. • But, role of these nerves in the regulation of
intestinal secretion in physiological conditions is
uncertain.
• the local nervous reflexes play impt role
increasing the secretion of intestinal juice.
• Its also called local myenteric reflexes,
• When chyme enters the small intestine,
• the mucosa is stimulated by tactile stimuli or
irritation.
• It causes the development of local nervous
reflexes, (local hormone VIP is also reported to
increase its secretion). which stimulate the glands
of intestine.

23. HORMONAL REGULATION
• When chyme enters the small intestine,
• intestinal mucosa secretes enterocrinin,
secretin and cholecystokinin,
• which promote the secretion of succus
entericus by stimulating the intestinal glands.

24. Secretion of Brunner’s gland is increased
by:
• Vagus stimulation,
• Direct tactile stimulation or irritation of
the duodenal mucosa and
• Secretin.

25. METHODS OF COLLECTION OF
SUCCUS ENTERICUS
• In human beings, the intestinal juice is
collected by using multilumen tube.
• IN ANIMALS
1.It is called Thiry loop or Thiry fistula.
2.Thiry-Vella loop is the modified Thiry
loop.

28. 3. MOTILITY OF SMALL INTESTINE
• There are 3 types of movements:-
1. Rhythmic segmental contractions or
pendular movements and
2. Peristalsis
3. Tonic Contraction

29. 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.

30. • 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 & concentric contraction
• also called rhythmic segmentation contractions
• Here the food divided & mixed with digestive juice
again & again and finally formed Chyme

32. time

33. 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

34. 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

35. ❸ the strength of contrn m 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

36. 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

37. Pendular Movement

39. 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

40. 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

41. 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

42. 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

43. 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.
• 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.

44. 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

45. 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

47. 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.

48. 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.

49. 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

50. 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

51. THANK YOU . . .