The human digestive system is made up of a long digestive tract that stretches from the mouth to the anus. Food is broken down mechanically and chemically by different organs along the tract. Mechanical digestion begins in the mouth by teeth. Chemical digestion starts in the mouth by saliva and continues in the stomach by gastric juices and in the small intestine by enzymes from the pancreas, liver, and intestinal walls. Nutrients are absorbed in the small intestine and undigested waste is eliminated in the large intestine and anus. Proper digestion relies on balanced diet, chewing, drinking water, and exercise.

1. THE HUMAN
DIGESTIVE SYSTEM
Archana Das,
Tangla College,Tangla,
Assam

2. THE HUMAN DIGESTIVE TRACT
The human digestive tract is
a long, highly coiled, muscular
tube that stretches from mouth
to anus.
From mouth to the anus, the
human food tube or the
digestive tract is about 9
meters long.

3. THE HUMAN DIGESTIVE TRACT
MEASUREMENT
9meters

4. SPECIALIZED REGIONS WHERE DIGESTION TAKES
PLACE
1. Food processing begins in the mouth.
2. The bite food is then swallowed and is moved
through the pharynx to the esophagus.
3. Then, food is mechanically and enzymatically
digested in the stomach.
4. Most enzymatic digestion takes place in the
small intestine.
5. The large intestine then eliminates wastes
through anus.

5. SPECIALIZED REGIONS WHERE DIGESTION TAKES
PLACE
MOUTH
PHARYNX
ESOPHAGUS
STOMACH
SMALL
INTESTINE
LARGE
INTESTINE
ANUS

6. DIGESTIVE SYSTEM WITH OTHER ASSOCIATED
ORGANS

7. DIGESTION AS IT OCCURS….
1. Food processing begins in the mouth.
2. The bite food is then swallowed and is moved
through the pharynx into the esophagus.
3. Then, food is mechanically and enzymatically
digested in the stomach.
4. The liver secretes bile.
5. The pancreas secretes digestive enzymes.

8. DIGESTION AS IT OCCURS….
6. Most enzymatic digestion takes place in the
small intestine.
7. Nutrients are digested as they move the
digestive tract.
8. Nerves and hormones regulate digestion.
9. Absorption takes place mainly through the villi of
the small intestine.
10. The large intestine eliminates wastes leading to
the opening for the elimination of wastes called
anus.

9. TWO PHASES OF DIGESTION
MECHANICAL PHASE – involves
the breaking up of food into small
pieces, pushing the food down the
food tube, and mixing with it digestive
juices
CHEMICAL PHASE – involves the
further breaking up of the larger
molecules of food into smaller
molecules by the action of digestive
enzymes

10. DIGESTION IN THE MOUTH
MECHANICAL DIGESTION starts in
the mouth where four kinds of teeth
tear the food into pieces:
Four kinds of teeth:
1. INCISORS – thin-edged for cutting
food
2. CANINES – are pointed used for
tearing
3. MOLARS & PREMOLARS –
specialized for crushing and grinding

11. THE HUMAN TEETH INSIDE MOUTH

12. THE PERMANENT DENTAL SET OF MAN
TEETH UPPER
JAW
LOWER
JAW
TOTAL
Incisors 2 ; 2 2 ; 2 8
Canine 1 ; 1 1 ; 1 4
Premolars 2 ; 2 2 ; 2 8
Molars 3 ; 3 3 ; 3 12
TOTAL: 32

13. CHEMICAL DIGESTION IN THE MOUTH
Salivary glands secrete saliva.
This saliva contains the enzyme
called salivary amylase.
This salivary amylase enables
the chemical digestion of Starch
into Maltose & Dextrin

14. HUMAN SALIVARY GLANDS

15. HOW MOUTH’S CHEMICAL DIGESTION IS
DONE?
CARBOHYDRAT
ES
Salivary amylase
STARCH Maltose
Saliva makes food slippery and kills the
germs by the action of Lysozyme.

16. THE PROCESS OF PERISTALSIS

17. ESOPHAGUS ON CONDUCTING FOOD
ESOPHAGUS – The canal that connects
throat to the stomach.
EPIGLOTTIS – It closes the opening to
the nostrils during swallowing
PERISTALSIS – A mechanism that
pushes chewed food (bolus) and mixes it
with digestive juices in stomach
ANTI-PERISTALSIS – results vomiting
which prevents body from harmful
substances that are ingested.

18. DIGESTION IN THE STOMACH
It is a bag-like structure where
protein part of food is digested.
Once food enters, the folds of
stomach wall called Rugae, it
starts secreting HCl

19. THE STRUCTURE OF THE STOMACH

20. ENZYMATIC DIGESTION IN THE STOMACH
The Parietal Cells of Gastric glands
secret HCl and turns food into acidic
THE CHIEF CELLS secrete pepsinogen,
an inactive enzyme precursor). When
pepsinogen comes in contact with the
acidic gastric juice, it becomes pepsin
the main digestive enzyme of the
stomach.

21. DIGESTION IN THE SMALL INTESTINE
Digestion is completed in the small
intestine and nutrients are absorbed
by villi through its wall.
The small intestine is about 5 to 6
meters in length and has 3 regions.
1. Duodenum
2. Jejunum
3. Ileum

22. THE THREE REGIONS OF THE SMALL INTESTINE
Most chemical digestion takes place in the
duodenum, the first layer of the small intestine.

23. THE LAYERS OF THE SMALL INTESTINE

24. THE LIVER
LIVER – The largest internal organ
of the body and also one of the most
complex organs which lies in the
upper right. The liver secretes BILE
BILE – It is the fluid secreted by the
liver which emulsifies fats

25. THE LIVER SECRETING BILE

26. FUNCTIONS OF A LIVER
Secrets BILE and helps to maintain
homeostasis by removing or adding
nutrients to blood.
Converts excess glucose to
glycogen and stores it.
Converts excess amino acids to fatty
acids and urea
Stores iron and certain vitamins.
Detoxifies alcohol and other drugs
and poisons.

27. THE PANCREAS
PANCREAS is an elongated gland
that secretes both digestive enzymes
and hormones. They help to regulate
the level of glucose in the blood. The
enzymes secreted by the pancreas
are:
Trypsin and Chymotrypsin.

28. Trypsin and Chymotrypsin digest
polypeptides to dipeptides resulting to:
PANCREATIC
LIPASE
Degrades fats
PANCREATIC
AMYLASE
Breaks down almost all types
of carbohydrates except
cellulose disaccharides
RIBONUCLEAS
E and
DEOXYRIBONUCLE
ASE
Split RNA and DNA to free
nucleotides

29. THE PANCREAS RELEASES DIGESTIVE
ENZYMES

30. CHEMICAL DIGESTION IN THE SMALL INTESTINE
1. Bile and digestive enzymes are released into
the duodenum.
2. They act on the Chyme (a semi fluid mass of
digested food expelled by the stomach into the
duodenum)
3. Then enzymes produced by the epithelial cells
lining the duodenum digest the major types of
nutrients.

31. THE DIGESTED NUTRIENTS
Chyme moves through the
digestive tract by peristalsis.
Nutrients in the chyme come into
contact with enzymes that digest
them.
1. Carbohydrates are digested to
monosaccharides
2. Proteins are digested to amino acids.
3. Fats are digested to fatty acids
and glycerols

32. CHEMICAL DIGESTION OF COMPLEX
MOLECULES
proteases
PROTEINS Amino acids
lipase
FATS Fatty acids &
Glycerol
carbohydrases
CARBOHYDRATES
Monosaccharides

33. SOME HORMONES THAT REGULATE
DIGESTION
HORMONE SOURCE TARGET
TISSUE
ACTION
Gastrin Stomach
(mucosa)
Stomach
(gastric
glands)
Stimulates gastric
glands to secrete
pepsinogen
Secretin Duodenum
(mucosa)
Pancreas
Liver
Signals secretion to
Stimulate bile
secretion
Cholecystoki
nin (CCK)
Duodenum
(mucosa)
Pancreas
Gall bladder
Stimulates release of
digestive enzymes
Gastric
Inhibitoy
Peptide (GIP)
Duodenum
(mucosa)
Stomach Decreases stomach
churning

34. ABSORPTION
ABSORPTION is the process by
which nutrients are taken up by
cells of the food tube.
Absorption takes place through
the villi of the small intestine.
Digested food like amino acids,
sugars, fatty acids & glycerol
diffuse into the cells of the villi.

35. THE STRUCTURE OF THE VILLUS

36. THE PROCESS OF ABSORPTION
Most of the digested food diffuse into
capillaries and reach the blood, while fatty
acids and glycerol diffuse into the lymph.
Through diffusion, digested food reaches the
blood and lymph and undergoes a process
called circulation.
The circulating fluids distribute the digested
food to all the cells of the body.

37. THE LARGE INTESTINE ELIMINATES WASTE
Undigested food passes
through the large intestine.
It is called “large” because its
diameter is greater than that of
the small intestine.
The large intestine is 1.3m in
length.

38. THE STRUCTURE OF THE LARGE INTESTINE

39. ELIMINATION OF WASTE
ELIMINATION is the
process of getting rid of
digestive wastes
materials that have not
been absorbed from the
digestive tract and did
not participate in
metabolic activities.

40. TIPS FOR HEALTHY BODY
Have a balance diet.
Eat proper amount of food.
Chew food well and eat
slowly to facilitate digestion.
Drink plenty of water.
Balance your food with
activities such as exercise.

41. YOUR BALANCE DIET SHOULD INCLUDE:
Vegetables and fruits
Milk and milk products
Meat including fish
Cereals such as rice
Other healthy foods
Always Remember:
The greatest wealth is your
Health.

42. Thanks !
ARCHANA DAS
TANGLA COLLEGE, ASSAM