# 7th Class Science Respiration In Plants And Animals Human Respiratory System

## Human Respiratory System

Category : 7th Class

### Human Respiratory System

As we know our body cells require oxygen for survival. Therefore, our body has evolved a tubular path so that oxygen can reach to the body cells from the atmosphere. This path (consists of many organ) is called respiratory path or respiratory system, as the path is specialized for respiration. This path begins from the nose and ultimately leads to the body cells through lungs and heart. Nose is an outer organ of respiratory system, which can be called as the gate of respiratory path, as air enters through it. It has been evolved in hollow tubular shape so that air can enter through it automatically. This air reaches the lungs through nasal cavity, pharynx and wind pipe, where it enters into another system called as circulatory system.

Circulatory system is a net of blood vessels, which are laid throughout the body so that each cell could be supplied with required nutrients and energy.

Blood acts as a transportation medium. It receives material from one part of the body and transports it to the required cells. Lungs contain a number of blood vessels and allow only oxygen to be entered into it from the air, which comes through respiratory path. Blood receives this oxygen and transport it to all the body cells. Blood supplies digested food from the small intestine to the cells also. Thus blood provides the cells with both fuel (glucose) and oxygen so that cells can perform their function and life can be continued. Cells burn this digested food (glucose) and get energy. In this process some unwanted products are also formed in the body, which may be harmful for the cells. Blood again receives those unwanted substances from the cells and expelled them out of body in reverse way.

Look at the Following Picture of Respiratory System in a Human Body

Let understand the whole process with the help of following points:

First, the air enters through nose or mouth into pharynx, as both nasal and oral cavity opens into it.

Pharynx leads to two path. One goes to lungs and another to the stomach, named wind pipe and food pipe respectively

Air enters into lung through wind pipe.

Lung acts as a junction of two systems, respiratory system and circulatory system, where respiratory gasses (carbon dioxide and oxygen) are exchanged from one to another system.

Only oxygen is allowed to enter into circulatory system (blood stream).

Blood receives the oxygen and enters into heart.

Heart pumps this blood throughout the body so that each cell can be supplied with oxygen.

Cells receive this oxygen and perform oxidation (burning of glucose).

Carbon dioxide produced during oxidation inside the cells are expelled into circulatory system.

Blood receives this carbon dioxide and reaches to the heart.

Heart pumps this blood to the lungs.

In lungs, $C{{O}_{2}}$ enters into respiratory system from circulatory system.

Now this $C{{O}_{2}}$ is exhaled into air through the same path by which air is brought into lungs.

Entrance of Pathogen through Respiratory Path

Our respiratory path gives the way to bacteria and other harmful particles and microorganisms like shoot, molds, viruses etc., Although respiratory system has a defense mechanism against air born infections, still some toxic microorganisms enter in our body and spread diseases like influenza, pneumonia, etc.

Which one of the following gas is exhaled during respiration?

(a) Oxygen

(b) Carbon dioxide

(c) Nitrogen

(d) Helium

(e) None of these

Which one of the following organs can be called as the gate of the respiratory system?

(a) Nose

(b) Pharynx

(c) Windpipe

(d) Lungs

(e) None of these