Stomach Physiology

1. Stomach-Physiology
Dr. Sai Sailesh Kumar G
Associate Professor
Department of Physiology
RDGMC

2. If there is no stomach.. can a
person survive?

3. Yes
you can say that artificially our body
can get the nutrients no need stomach!

4. BUT
Digestive system starts from stomach.
Lot of microbes are also present in the
stomach those are considered good for our
health.
Stomach gives us the space to accommodate
all foods.
 It has some enzymes which can start
protein digestion and also fat digestion.
 Food is sent to the intestines.

5. Anatomy
In adult life, stomach located T10 and
L3 vertebral segments.
Can be divided into anatomic regions
based on external landmarks
4 regions
Cardia, Fundus, Corpus (body), Antrum.

6. The Stomach

8. The stomach
The stomach is divided into
four regions:
1. The cardia, which surrounds
the opening of the esophagus
into the stomach.
2. The fundus of stomach, which
is the area above the level of
the cardial orifice.
3. The body of stomach, which
is the largest region of the
stomach.
4. The pyloric part, which is
divided into thepyloric
antrum and pyloric canal and
is the distal end of the
stomach.

9. The stomach
• Surfaces
• Antero-superior
Surface
• Postero-inferior
Surface

10. The stomach
• Openings:
– Gastroesophageal
: Toesophagus
– Pyloric: To
duodenum

11. The stomach
Sphincters
 The cardiac sphincter
(lower esophagus
sphincter) closes off
the top end of the
stomach.
 The pyloric sphincter
closes off the
bottom.

12. The stomach
• Thegreater curvature,
which isa
point of attachmentfor
the gastrosplenic ligament and
the greater omentum
• Thelesser curvature,
which isa
point of attachmentfor
the lesseromentum.

13. Stomach Innervations
The main innervations
are Left and Right
Vagus Nerves

14. Stomach Innervations
• Parasympathetic
innervation of
Stomach- VagusNerve
– 90%of fiber in vagal
trunk is afferent (info
transmitting from
stomach to CNS)
• Sympathetic
innervation of
Stomach- Splanchnic
Nerve
– Derived from
spinal segement
T5-T10

15. Gastric Mucous membrane
Gastric Mucous membrane contains three types
of gastric glands
1. Main gastric glands
2.Cardiac tubular glands
3.Pyloric or antral glands

18. Main gastric glands
 Maximum in number
 Located in the mucosa of body and fundus
 It has short duct and long alveoli
 Alveoli contains
1. Chief or peptic or zymogen cells ( secretes
pepsinogen)
2.Parietal or oxyntic cells (Secretes HCl and
intrinsic factor)

19. Chief cells
 Located in the deeper parts
 Typical protein-secreting.
 Basal cytoplasm- basophilic due the abundant
rER ,
 Apical cytoplasm- eosinophilic due to
presence of the secretory vesicles, zymogen
granules
 Zymogen granules contain enzyme precursors.

20. Parietal cells
 Has intracellular canalicular system
 Communicates with the lumen of the gland.
 Numerous microvilli
 In an active cell, the number of microvilli in the
canaliculi increases, and the tubulovesicular system is
reduced significantly or disappears..

21. CHIEFCELLVSPARIETALCELL

23. Pepsinogen
Secreted as inactive form-Pepsinogen
HCl converts inactive pepsinogen into active
pepsin
Pepsin has autocatalytic action ( small amount
of pepsin causes activation of pepsinogen into
pepsin)
Atropine inhibits pepsinogen secretion

24. Functions of pepsinogen
 Digestion of proteins to peptides: Pepsin hydrolyzes
peptide bonds between aminoacids. Optimal activity at
pH less than 4. Inactive at pH more than 5.
 Pepsin acts on caseinogen and converts into casein.
Casein combines with calcium salts and converts into
calcium caseinate which can be easily digested.

25. Functions of HCl
 Provides acidic environment for optimal pepsin
activity.
 Activates pepsinogen into pepsin
 Kills ingested bacteria (bactericidal)
 Helps in iron absorption
 Stimulates bile and pancreatic juice secretion.

26. Functions of Intrinsic factor
 Combines with Vitamin B12 and helps for its
absorption from small intestine.
 Note: Atrophy of gastric mucosa causes deficiency of
intrinsic factor and leads to pernicious anemia.

27. Mucus cells
 Present in surface of the gastric epithelium
 Secretes mucus and bicarbonates
 Mucus is alkaline in nature and also helps in
lubrication of food
 Mucus along with bicarbonates forms mucosal-
bicarbonate barrier

28.  The gastric mucosal barrier is the property of the
stomach that allows it to contain acid
 If the barrier is broken , then the acid diffuses back
into the mucosa and damage the stomach wall
 The gastric mucosal barrier is made up of 3
components.
1. compact epithelial cell lining with tight junctions
2. Gastric mucus covering (gel like coating )
3. Bicarbonate ions, secreted by the surface epithelial
cells.
The bicarbonate ions act to neutralize harsh acids

31. Cardiac tubular cells
Located in the gastric mucosa
immediately surrounding the esophagus.
Secretes mucus

32. Pyloric (Antral) glands
 Have long duct and short alveoli
 Deeper portion of pyloric glands has G cells or gastrin
cells that secretes gastrin
 G cells are flask shaped cells and has gastrin
granules.
 G cells secretes pro-gastrin which is converted into
gastrin by the action of HCl.
 G cells takes up amine precursors and decarboxylate
them. So they also called as APUD (Amino precursor
and uptake and decarboxylation)

33. Gastrin
 Occurs in three forms G-14, G-17 and G-34.
 Gastrin stimulates secretion of gastric acid and pepsin
 Gastrin increases HCl secretion directly by acting on
gastrin receptors and indirectly by stimulating ECL (
Entero chromaffin like cell).
 Activation of ECL increases release of histamine which
stimulates HCl secretion.

35. Gastrin
Gastrin stimulates growth of the mucosa
of the stomach, small intestine and large
intestine
Stimulates gastric motility
Stimulates contraction of gall bladder
Stimulates insulin and glucagon secretion

36. Factors increasing gastrin secretion
 Peptides and amino acids (products of protein
digestion)
 Pyloric antrum distention
 Vagal stimulation
 Calcium
 Epinephrine

37. Factors decreasing gastrin secretion
 Presence of Acid in the Antrum
 Secretin
 Gastric inhibitory peptide (GIP)
 Vasoactive intestinal peptide (VIP)
 Glucagon

38. Applied Physiology
 Penta gastrin is the synthetic gastrin used
for testing gastric secretory functions.
 Gastrin secreting tumors are called as
gastrinoma. It causes excessive secretion of
HCl and leads to peptic ulcer.

40. Enzymes in gastric Juice
Pepsinogen
Gelatinase
Gastric lipase
Lysozymes
Urease
Carbonic anhydrase