Digestive System | Introduction, Types & Diseases

By | March 28, 2020

What is Digestive System?

What is Digestion: Your digestive system is a tube 10 meters long which begins in the mouth and ends at the anus. The only way that carbohydrates, fats, and proteins can pass through the walls of this tube into the blood vessels is if they are made into smaller molecules. The process of breaking down food into smaller molecules is known as Digestion.

Everything you eat is made of molecules, but the molecules found in carbohydrates, fats, and proteins are large. They have to be taken to every part of the body by the blood system. But because these energy-giving and body-building foods are large molecules, they can’t enter the blood vessels as they are. The whole vore Digestion process is described below :

Anaerobic Digestion is basically a chain of biological procedures in which various microorganisms degrade or break biodegradable material. The whole process takes place in the absence of oxygen. The end product of this procedure is Biogas. Biogas is used for the combustion process which is used to generate electricity and heat.

Digestive System Diagram:

Digestive System

Components of Food:

All the food we eat falls into five basic categories:

1. Carbohydrates:

Carbohydrates: such as sugars and starches, give us energy.

2. Proteins

Proteins are bodybuilding foods that are part of every cell in your body. They are also needed to repair damaged parts of the body.

3. Fats

Fats are stored as a layer of insulation under the skin. Fat produces twice as much energy per gram as carbohydrates and about a quarter of the energy we use each day comes from fats.

4. Minerals

Minerals describe a whole collection of elements, including calcium and phosphorus, needed to build bones and teeth, sodium and potassium†to keep nerves functioning properly, and tiny quantities of other minerals that help to keep us healthy.

5. Vitamins

Vitamins are essential to your health, but again, they are only needed in tiny quantities. A lifetime’s supply of all the vitamins you need only weighs about 250 g.

For a healthy diet, we also need fiber to help the passage of food through the digestive system and water to help dissolve the food and to make up for the water the body loses when breathing, sweating, excreting, etc.

Digestive System

Human Digestive System

Digestive System

Steps of Digestion

Digestive System

Mechanical Digestion

The digestive process Involves:

  1. A mechanical breaking down of the food, e.g. by chewing it.
  2. A chemical breaks down the food using acids and chemicals known as enzymes.
  3. Enzymes speed up the chemical reactions of digestion. They can carry out only one job.
  4. Enzymes that break down starch cannot break down fats or proteins.
  5. Absorption of the small molecules that the body can use.
  6. Removal of the insoluble waste materials from the body.

Chemical Digestion

  • The first part of the digestive process is quickly chewing the food into small pieces before it is swallowed.
  • The food is mixed with saliva or spit which contains an enzyme called amylase.
  • Amylase starts to break down the starch in the food into a type of soluble sugar†called maltose.
  • The chewed food is pushed down the gullet or esophagus by waves of muscular contraction, like a series of squeezes until it reaches the stomach.
  • Food will go from your mouth to your stomach, even if you stand on your heads.
  • Food is stored in the stomach for a few hours. The stomach can hold about 1.5 liters of food.
  • The food is mixed with gastric juice, which is made by the walls of the stomach. Gastric juice contains hydrochloric acid which kills most bacteria in the food.
  • It also gives the best conditions for enzymes, called protease to begin breaking down proteins in the food.
  • The food is churned around in the stomach for up to f six hours after a large meal.
  • Food is slowly squashed and squeezed along the small intestine, at about 2.5 cm a minute. The small intestine is 7 meters long and about 3 cm in diameter. As the food is pushed through from the stomach into the small intestine, a little at a time, Bile is squirted onto it.
  • Bile is made by the liver and is stored in the gall bladder until it needed. Bile emulsifies (breaks up) fats.
  • It is also alkaline to make the conditions right for the enzymes in the small intestine.
  • The walls of the small intestine produce enzymes that digest proteins, carbohydrates, and fats.
  • The pancreas produces three more enzymes which also digest proteins, carbohydrates, and fats.
  • The walls of the small intestine are not smooth but are covered with millions of finger-like projections called villi.
  • The villi are perfect for absorbing food because they give the small intestine a much larger surface area. They have a thin outer layer of cells and a dense network of blood capillaries.

Digestive System

The Absorption Process:

Nearly all of the absorption of the food into the blood system takes placeí in the small intestine. The digested foods are transported to the liver and the liver controls what happens to them:

  1. Glucose is needed for respiration. A constant supply of glucose circulates in the blood.
  2. If there is too much glucose, the liver converts some into insoluble glycogen. This can be changed back into glucose when it is needed. Excess carbohydrates are converted into fats.
  3. Amino acids, formed by the digestion of proteins, cannot be stored. They are used for the growth and repair of the body. Excess amino acids are changed to a substance called urea, which is then excreted.
  4. In the large intestine, water and mineral salts are removed from the undigested food and absorbed into the blood. Food often contains cellulose†(from plant cell walls) which we cannot digest. This and any remaining undigested material is passed on to the rectum where it is stored as feces until it is passed out of the anus.
  5. About two-thirds of the feces are water and about half of the rest is bacteria, mainly dead bacteria. The bacteria line the intestines and scientists believe they may play an important part in producing certain vitamins and helping the body to fight disease.

Digestive System

Digestive System Function

Digestive System

Problems with the Digestive System

Germs get into the digestive system when you eat infected food. This is called food poisoning. Foods can be infected when you buy them, or while they are being prepared at home. Not washing the hands before preparing food and after using the toilet, dirty work surfaces and utensils, loose hanging hair, and sneezing near food can all lead to germs getting into food.


Indigestion is usually caused by eating food too quickly and not chewing it enough. The stomach produces extra gastric juice, with the result that the stomach contains a lot of acids. If the person belches, some of the acids come up the gullet, causing a burning sensation, which is sometimes called Ďheartburní. Indigestion can usually be cured by taking a tablet or drink which contains an alkali that will neutralize the acid.

A person who constantly has too much acid in his stomach may get an ulcer. This is when the acid starts to eat into the wall of the stomach, which then becomes raw and painful. Ulcers seem to be most common in middle-aged and elderly people, and often seem to be brought on by overwork and worry.


Infected food can be vomited from the stomach quite soon after it is eaten. More often, the germs are busy breeding and multiplying in your digestive system before you begin to feel ill. White blood cells rush to destroy the germs and the liquid food is rushed through the digestive system and out of the rectum. That’s why you can see why diarrhea is often called Ďthe runs.

Diarrhea stops when the infection clears up. During the attack, a great deal of water and important mineral salts and vitamins may be lost. Diarrhea is a serious illness in babies as they quickly become dehydrated (dried out) and ill. The lost water must be replaced and the baby was taken to a doctor if diarrhea lasts more than a day. Extra hygiene is very important, otherwise, the infection can spread to other people in the house.


Part of the food you eat, including the fiber, cannot be broken down by the digestive system. It travels to the rectum where it forms feces. The feces are passed out of the anus by powerful muscles. People have very different lavatory habits. Some people go four times a day, once a day, every four days or anything in between.

If feces are not passed out according to your usual pattern, they may become thick, hard, and dry. This is because the waste stays in the large intestine for longer and has more than the usual amount of water absorbed from it. The thick, hard, and dry faces are uncomfortable or even painful to pass.

Constipation is not serious and worry can make it worse. It is important to go to the toilet at the same time each day and when you have plenty of time. If nothing happens after, say, ten minutes do not worry. Try again the next day. Drink up to three liters of water a day and make sure you have enough fiber in your diet. This improves the tone of the muscles of the rectum and keeps the feces bulky and soft.

Make sure you have plenty of exercises since there is no better way to improve muscle tone. Try to avoid laxatives. These are medicines to soften the feces. They work, but there is a risk that may cause powerful muscles of the rectum to lose their muscle tone and become lazy. You then need a stronger laxative to help you to go to the lavatory.

Digestive System