THE HUMAN

DIGESTIVE SYSTEM

Archana Das,

Tangla College,Tangla,

Assam

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.

THE HUMAN DIGESTIVE TRACT

9meters

THE HUMAN DIGESTIVE TRACT

MEASUREMENT

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.

SPECIALIZED REGIONS WHERE DIGESTION TAKES

PLACE

MOUTH

PHARYNX

ESOPHAGUS

STOMACH

SMALL

INTESTINELARGE

INTESTINE

ANUS

DIGESTIVE SYSTEM WITH OTHER ASSOCIATED

ORGANS

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.

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.

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

TWO PHASES OF DIGESTION

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

DIGESTION IN THE MOUTH

THE HUMAN TEETH INSIDE MOUTH

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

THE PERMANENT DENTAL SET OF MAN

Salivary glands secrete saliva.

This saliva contains the enzyme

called salivary amylase.

This salivary amylase enables

the chemical digestion of Starch

into Maltose & Dextrin

CHEMICAL DIGESTION IN THE MOUTH

HUMAN SALIVARY GLANDS

STARCH Maltose

Salivary amylase

HOW MOUTH’S CHEMICAL DIGESTION IS

DONE?

CARBOHYDRAT

ES

Saliva makes food slippery and kills the

germs by the action of Lysozyme.

THE PROCESS OF PERISTALSIS

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.

ESOPHAGUS ON CONDUCTING FOOD

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

DIGESTION IN THE STOMACH

THE STRUCTURE OF 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.

ENZYMATIC DIGESTION IN THE STOMACH

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

DIGESTION IN THE SMALL INTESTINE

THE THREE REGIONS OF THE SMALL INTESTINE

Most chemical digestion takes place in the

duodenum, the first layer of the small intestine.

THE LAYERS OF THE SMALL INTESTINE

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

THE LIVER

THE LIVER SECRETING BILE

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.

FUNCTIONS OF A LIVER

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.

THE PANCREAS

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

Trypsin and Chymotrypsin digest

polypeptides to dipeptides resulting to:

THE PANCREAS RELEASES DIGESTIVE

ENZYMES

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.

CHEMICAL DIGESTION IN THE SMALL INTESTINE

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

THE DIGESTED NUTRIENTS

PROTEINS Amino acids

FATS Fatty acids &

Glycerol

CARBOHYDRATES

Monosaccharides

proteases

CHEMICAL DIGESTION OF COMPLEX

MOLECULES

lipase

carbohydrases

SOME HORMONES THAT REGULATE

DIGESTIONHORMONE SOURCE TARGET

TISSUEACTION

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

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.

ABSORPTION

THE STRUCTURE OF THE VILLUS

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.

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.

THE LARGE INTESTINE ELIMINATES WASTE

THE STRUCTURE OF THE LARGE INTESTINE

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.

ELIMINATION OF WASTE

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.

TIPS FOR HEALTHY BODY

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.

YOUR BALANCE DIET SHOULD INCLUDE:

ARCHANA DAS

TANGLA COLLEGE, ASSAM

Thanks !