Digestive System in brief Functions of Digestion GI Tract, its components and functions GI Enzymes and their role in digestion Disorders of Digestion

1. DIGESTIVE SYSTEM
- CHAITRA CHINMAYEE M K

2. Functions of Digestive System:-
•Digestion of food: Complex food substances are broken down into
simpler forms for absorption for the energy requirements of the body
• Excretory function: The undigested food along with harmful
substances is excreted out of the body
• Immunity: Various digestive juices have anti-bacterial secretions to
play a role in the body’s immunity

3. The Gastro-Intestinal
Tract
. GI tract is a continuous tube about 10m
long extending from the mouth to the
anus and other accessory digestive
glands.
. It consists of the mouth, oral cavity,
esophagus, stomach, small intestine, large
intestine and anus.
.Accessory structures include the teeth,
tongue, salivary glands, liver, gallbladder
and pancreas

4. Mouth & Oral Cavity
• It contains teeth, tongue and
salivary glands.
•Food is broken down by
mechanical digestion, by the
teeth by chewing.
• Food particles are mixed
with saliva secreted by
salivary glands, and broken
into softer small particles for
easier passage into the
esophagus.
• The tongue helps in tasting
the food, chewing and
swallowing the food.

5. Salivary Glands
• There are 3 pairs of salivary
glands called parotid,
submandibular, and sublingual
gland which secrete saliva into the
oral cavity.
•Saliva helps moisten the food
during chewing, partially digest
starch and help cleanse the teeth.
• Saliva consists of 99.5% water,
the remaining 0.5% is dissolved
substances enzymes, hormones,
bicarbonate ions and many other
electrolytes.

6. Esophagus
• It is a long muscular tube
about 25cm long.
• It conducts partially digested
food from the oral cavity to the
stomach.
• The movement of esophagus
is called Peristalisis
• Peristalisis is a wave like
movement of the muscle to
push the food through the
tube.

7. Stomach
• The stomach is a J shaped
muscular bag
• It’s capacity in an average
adult is 1200-1500 mL
•The main function of the
stomach is digestion of
complex food substances
like carbohydrates, fats and
proteins.
• The stomach stores the
food for about 4-5 hours
for proper digestion of its
contents.

8. The Gastric Juice
The stomach secretes gastric juice which contains:
i. Mucus - it protects the wall of the stomach from
highly acidic gastric juice and lubricates the food
particles.
ii. Pepsinogen – it is a proenzyme for protein
digestion.
iii. Hydrochloric Acid – it provides acidic medium for
the enzymes to act and converts inactive
pepsinogen into pepsin which helps in protein
digestion.
iv. Renin(in infants) – helps in digestion of milk
proteins
v. Lipases - in small quantities for partial digestion of
fat

9. Liver and Gall Bladder
• Liver is the largest gland in
our body, an accessory
digestive gland.
• It secretes bile juice,
which is stored and
concentrated in the gall
bladder
• The bile is poured into the
small intestine along with
the secretions of the
pancreas.

10. The Bile Juice
• The bile juice helps in metabolism
and absorption of fats and fat soluble
vitamins.
• It contains bile salts, bile pigments,
cholesterol which helps in digestion
of fats.

11. Pancreas
• It is also an accessory
digestive gland.
• It secretes pancreatic
juice which has a major
role in digestion of
carbohydrates, fats and
proteins.
• It is poured into the
small intestine along
with bile juice.

12. The Pancreatic Juice
• It is secreted by the pancreas
• It contains:
i. Trypsinogen
ii. Chymotrypsinogen
iii. Procarboxypeptidase
iv. Amylase – converts Polysaccharides into
Disaccharides(Carbohydrate digestion)
v. Lipase – converts Fats into Di and Monoglycerides
vi. Nucleases – converts Nucleic acid into Nucleotides
and nucleosides
Converts Protein,
peptones into
dipeptides

13. The Small Intestine
• It is a muscular tube about
6m long.
• It is made up of 3 parts:
i. Duodenum – 25cm
ii. Jejunum – 2.5m
iii. Ileum – 3.5m
• The complete digestion of
food particles takes place
in the small intestine
• It not only helps in
digestion but also in
absorption of the digested
food particles.

14. The Intestinal Juice
• It is secreted by the intestinal cells
• It contains:
i. Disaccharidases – Disaccharides to
monosaccharides(Carbohydrate digestion)
ii. Dipeptidases – Dipeptides to amino acids(Protein
digestion)
iii. Lipases – Di and monoglycerides into fatty acids
and glycerol(Fat digestion)
iv. Nucleosidases – Nucleosides into sugars and
nitrogen bases
v. Enterokinase – It activates trypsinogen, a
pancreatic enzyme

15. Large Intestine
• It is about 1.5m long
• It is divided into:
i. Ceacum and Appendix
ii. Colon – ascending,
transverse, descending
and sigmoid
iii. Rectum
iv. Anal canal
• Its major role in digestion
is absorption of water and
excretion of undigested
food

16. Absorption of Digested food
• It is the process by which the end
products of digestion are absorbed into the
blood.
• The end products of digestion like
glucose, amino acids, fatty acids and
certain electrolytes like sodium, chloride,
bicarbonate, along with water is absorbed
and the rest is excreted as faeces through
the anus.

17. Disorders of Digestive System
• The most common infections are bacterial and viral
infections like that caused by tape worm, round
worm, hook worm, etc.
• Jaundice: The infection of the liver causes the
deposition of bile pigments, and causes the
yellowing of skin and eyes
• Vomiting: The throwing of stomach contents back
through the mouth, due to over
eating/contamination of food/other infections of
stomach

18. Disorders of Digestive
System(cont’d)
•Constipation: Irregular excretion of faeces and
its retention in the large intestine.
• Indigestion: The food is not properly digested
leading to a feeling of fullness. This is due to
over-eating/anxiety/food poisoning.
•Diarrhoea: The abnormal frequency of
increased liquidity of faeces