This is a pptx about the human GIT

1. Gastrointestinal Physiology-III

2. • Hydrochloric acid is secreted by
a. Peptic cells in the pyloric glands
b. Parietal cells in the pyloric glands
c. Parietal cells in the oxyntic glands
d. Peptic cells in the oxyntic glands

3. Secretory functions of the
gastrointestinal tract (continued)
4. Pancreatic secretion
Contains digestive enzymes, bicarbonate ions
etc.
Bicarbonate ions neutralize the acidic pH of
the chyme.
Cholecystokinin and secretin increase
pancreatic secretion.

4. • Digestive enzymes:
For digesting proteins:
Trypsinogen, chymotrypsinogen,
procarboxypolypeptidase (inactive forms)
For digesting carbohydrates:
Pancreatic amylase
For digesting fats:
Pancreatic lipase, cholesteryl esterase,
phospholipase
Secretory functions: Pancreas
(continued)

5. Secretory functions: Liver
5. Secretion of bile by the liver
Bile acids and lecithin help in emulsification and
absorption of fats. Bile provides the way to
dispose bile pigments and cholesterol. It also
helps neutralize the acidity of the chyme.
Gall bladder concentrates bile.
Cholecystokinin causes contraction of gall bladder
and relaxation of sphincter of Oddi.

6. Bilirubin formation and excretion

7. Secretory functions (continued)
6. Secretion of the small intestine
 alkaline mucus; water and electrolytes
 peptidase; sucrase, maltase, isomaltase,
lactase; intestinal lipase
7. Secretions of the large intestine
 mucus

8. Digestion in the gastrointestinal tract
• Digestion of carbohydrates, proteins and fats
involves hydrolysis in the presence of
enzymes.
1. Digestion of carbohydrates
 Carbohydrates of the diet: sucrose (a
disaccharide commonly called cane sugar),
lactose (a disaccharide in milk),
starches(polysaccharides)

9. Digestion: carbohydrates (continued)
In the mouth
Ptyalin in the saliva hydrolyses the starch into
maltose and other small polymers of glucose.
Action of ptyalin continues in the stomach
before the food becomes mixed with gastric
secretions.

10. Digestion: carbohydrates (continued)
In the small intestine
 Pancreatic amylase converts carbohydrates
into maltose and very small polymers of
glucose.
 Intestinal epithelial enzymes lactase, sucrase,
maltase split lactose, sucrose and maltose
into their constituent monosaccharides.

11. Digestion: carbohydrates (continued)
Lactose splits into a molecule of glucose and a
molecule of galactose.
Sucrose splits into glucose and fructose.
Maltose and other small polymers of glucose
split into glucose molecules.

12. Digestion: proteins
2. Digestion of proteins
In the stomach
Pepsinogen is activated by hydrochloric acid to
form pepsin.
Pepsin hydrolyses proteins into proteoses,
peptones and a few polypeptides.

13. Digestion: proteins (continued)
In the intestine
Pancreatic secretion: trypsinogen,
chymotrypsinogen, procarboxypeptidase
Intestinal secretion: peptidases
Trypsinogen is activated by enterokinase (or
previously formed trypsin) to form trypsin.

14. Digestion: proteins (continued)
Chymotrypsinogen and procarboxypeptidase
are activated by trypsin to form chymotrypsin
and carboxypeptidase respectively.
Activated pancreatic enzymes and intestinal
peptidases sequentially split partially digested
proteins into dipeptides, tripeptides and
amino acids.

15. Digestion: fats
3. Digestion of fats:
Fats in the diet: triglycerides, phospholipids,
cholesterol esters
In the intestine
Bile salts and lecithin facilitate splitting of fat
globules into minute particles on agitation
(emulsification of fat).

16. Digestion: fats (continued)
Emulsification of fat increases surface area for
enzymatic action.
 Pancreatic lipase and to some extent
intestinal lipase splits emulsified fat into fatty
acids and monoglycerides.

17. • Which of the following is not a pancreatic
enzyme?
a. Trypsin
b. Chymotrypsin
c. Lipase
d. Pepsin

18. • Digestion of the carbohydrates begins in the
a. Oral cavity
b. Stomach
c. Duodenum
d. Ileum

19. • Which of the following is incorrect?
a. Bilirubin is formed in macrophages.
b. Bilirubin is conjugated in hepatocytes.
c. Bile acids are derived from hemoglobin.
d. Cholecystokinin stimulates contraction of the
gall bladder.

20. Thank you