Digestive System of Human Body|Why need a Digestive System?

Digestive System of Human Body

Why need a Digestive System?

Every cell in our body does work. 

Work requires energy, which is supplied by the food we eat. 

Food also supplies the small molecules that are the building blocks for cell maintenance, growth, and function.

Digestion breaks down food into materials the body can use.

1. Your sense receptors work together with your brain to make you hungry

Saliva increases  (you produce more than  1 litre/day), and helps
digest food while it is mechanically torn, cut,  crushed, and ground in your mouth.

2. The passages of your digestive system are lined with involuntary muscles that contract in waves to squeeze food along.

3. Your stomach stores food so that you need not eat continuously.

It also breaks down food with acid and enzymes.

4. The salivary glands,  pancreas, liver, and gallbladder secretes and store digestive juices.

5. The small intestine is where  most of the chemical digestion
and nutrient absorption into the bloodstream takes place.

6. The large intestine reclaims water and releases waste.


When swallowing, muscles move the epiglottis down to close the opening to the trachea, so that food and drink do not enter the lungs. 

The soft palate also moves up, so that food does not go up the nasal passage.

The stomach does not have one fixed shape.
Everyone’s internal organs are slightly different

The shape and position of your stomach also depend on how much food it contains, and whether you are standing or lying down.

Role of The Intestinal Wall in the Digestive System

In order to increase its surface area, the intestinal wall is folded, and each fold is lined with villi. This way, more cells come into contact with nutrients in the digested food. 

Nutrients enter the epithelial cells that line the villi, either by diffusion or active transport. 

They are then absorbed by capillaries and lymph vessels.

Capillaries transport the nutrients to larger blood vessels, then to the portal vein, which goes to the liver. 

Then the nutrients go to the heart, to be pumped to the rest of the body.

Role of Mouth  in the Digestive System

The mouth starts mechanical and chemical digestion of food with the help of teeth, tongue, and saliva.

 Salivary glands:

Salivary glands produce saliva, which helps lubricate food for easier swallowing; contains antibacterial agents and the enzyme amylase, which breaks down starch.


Entering  of food triggers its swallowing reflex


The oesophagus is a muscular tube that squeezes food along to the stomach.


stores, mixes, and digests food with the gastric juice it produces, which consists of mucus, enzymes, and hydrochloric acid, producing acid chyme.


The blood carrying nutrients from the small intestine passes through the liver, which filters it and breaks down and synthesizes proteins, breaks down carbohydrates into glucose and glycogen, produces bile.


The gallbladder collects bile from the liver and discharges it into the small intestine, where it helps digest fat.


Pancreas a gland that produces digestive enzymes and an alkaline solution that neutralizes the acid chyme that comes from the stomach; it also secretes the hormone, insulin.

Small intestine

Small Intestine is a 6-metre long tube in which most of the chemical digestion occurs; nutrients are absorbed from here into the bloodstream.

Large intestine:

The Large intestine absorbs water from the food wastes that have
not been digested in the small intestine; also absorbs some important vitamins that are produced by the large numbers of bacteria it harbours.


Rectum stores faeces (which consist mainly of indigestible plant fibres, bacteria, and water) until they can be eliminated from the body through the anus.

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