Current Affairs 4th Class

Category : 4th Class

                                                          Functioning of Human Body

All human beings require energy for doing various kinds of activities. They get this energy from food that they eat. The food we eat cannot be used by our body directly. It has to be broken down into a simpler form. Our body has a system for breaking down the food into a simpler form. This system is called digestive system.

Digestive System

The process of digestion takes place in the following steps:

• First we eat food which goes into the mouth. Our mouth has teeth for chewing and cutting the food into smaller pieces. Thus, the process of digestion begins in the mouth.
• In the mouth, a digestive liquid called saliva mixes with food to make it a fine paste. Saliva breaks down food into starch and soluble sugar.
• Food then passes into the stomach through the food pipe. The stomach is a hollow, muscular bag-like structure. In the stomach, the food again mixes with some more digestive juices for further break down into simpler form.
• From the stomach, the food passes into long coiled tube called the small intestine its wall produces more digestive juices.
• Liver and pancreas also pour their juices into the small intestine. These juices help to digest the food completely.
• Digested food is then absorbed by a network of blood vessels present in the small intestine. The absorbed food is then carried to different parts of the body.
• Small intestine is not able to digest water and roughage. Therefore, they are passed into the large intestine. The blood in the walls of the large intestine absorbs the water and carries it to the kidneys.
• The semi-solid waste is then thrown out from the body through the anus.

Digestive System of Human Body

Parts of Teeth

A tooth has three parts. Crown, neck and root.

Crown: Crown is that part of tooth that we can see.

Neck: Neck is below the crown.

Root: through roots, tooth is fixed in the jaw. The gum covers the root.

The outer hard layer which covers the tooth is called enamel. Enamel is the hardest thing in a human body. Dentine is below it. The core of the tooth is called pulp. Pulp is soft and has blood vessels and nerves in it. The nerves are connected to the gum through a hole in the root.

Types of Teeth

There are four kinds of teeth in our mouth which are as follows:

Incisors

The teeth which have sharp straight edges are called incisors. These are four in number in each jaw. They are present in front of the jaw. They help to cut or bite the food.

Canines

Canines are located on either side of incisors. They are sharp pointed teeth. These are used for tearing something hard. In each jaw, there are two canines.

Premolars

They are next to the canines which are broad and flat. They help in cracking hard food. Therefore, they are also called cracking teeth. There are four premolars in each jaw.

Molars

They are used for grinding the food. Thus, they are also called grinding teeth. They are broader than premolars. There are six molars in each jaw.

Tooth Decay

When we eat food, small bits of food get stuck between the teeth. On these bits, germs begin to grow. When we do not clean our teeth properly, a yellowish covering starts appearing which is called plaque. This is a sign of presence of germs. The germs release some juices to digest the stocked food in teeth. These juices slowly harm the tooth.

Sometimes a hole called cavity appears in the inner part of the teeth. The food that we eat goes into the cavity. If we don't go to the dentist, the decay can even harm the neighbouring teeth. The germs present in the tooth cause pain and toothache.

Microbes

Microbes are very small organisms which cannot be seen through naked eye. They can be seen through microscope only. Disease causing microbes are called germs. There are kinds of microbes which are as follows:

Bacteria: Bacteria are microbes made up of one cell only. They can cause diseases like typhoid, tuberculosis, etc.

Viruses: Viruses are smaller than bacteria and cause diseases like common cold, influenza, etc.

Fungi: =Fungi grow on dead plants and animals. They cause diseases like ringworm and athlete’s foot.

Protozoans: Protozoans are also single-cell microbes and cause diseases like malaria and dysentery, etc.