Respiration in Human Beings | Mechanism of Respiration in Human Beings

Human respiratory system

Respiratory system in human beings serves to provide fresh oxygen to all body cells and remove harmful carbon dioxide from the body.


The well labelled diagram of the human respiratory system


In human beings many organs take part in the process of respiration. We call them organs of the respiratory system.

The parts of the human respiratory system and their respective functions are as follows

Nose/ nostrils

Air is taken into the body through the nostrils. It is lined by fine hairs and mucus which helps to filter the air entering through it.

Nasal passage

Air entering the nostrils leads to the nasal passage. The nasal passage is separated from the mouth cavity buy a hard Bony plate so that we can breathe in air even when we are eating food. Mucus is secreted by the glands inside the nasal passage.


The part of the throat between the mouth and windpipe is called the pharynx. From the nasal passage air enters into the pharynx. It passes air into the larynx.

Larynx or the sound box

Larynx is located in the neck region and in front of the trachea. It also produces sound. 

Trachea or the windpipe

The trachea is a tube which is commonly known as windpipe. The air passes from the pharynx and goes into the trachea. Incomplete rings of cartilage keeps track open allowing the passage of air to the lungs. Trachea doesn’t collapse even when there is no air in it because it has supported by rings of soft bones called cartilage.


The trachea runs down the neck and divides into two smaller tubes called bronchi at its lower end after entering the thoracic cavity. The two bronchi are connected to the two lungs. The singular of bronchi is bronchus.


Each bronchus divides in the lungs to form a large number of smaller tubes called bronchioles. Each bronchiole finally terminates into  many tiny air sacs at their ends.


The pouch like air sacs at the end of the smallest bronchioles are called alveoli. A large number of alveoli increases the surface area for the exchange of gases. The walls of alveoli are very thin and they are surrounded by very thin blood capillaries. It is in the alveoli that oxygen is taken into the body and carbon dioxide is eliminated. There are millions of alveoli in the lungs. Human alveolar surface when spread can cover area of 80 square meters.


These are 12 pairs of bones that form a cage in the thoracic region.Lungs and heart a safer place. Movement of intercostal muscles attached to ribs help in breathing.


These are primary organs for respiration, which are located on the two sides of heart. This transport O2 from the atmosphere into the blood and release CO2 from blood to atmosphere. They are enclosed by the protective membrane called pleura.


The diaphragm is a sheet of muscles below the lungs. It helps in breathing in and breathing out. Diaphragm is the partition between the thorax and the abdomen and forms the base of chest cavity. When we breathe in air, the diaphragm and muscles attached to the ribs contract due to which of the chest cavity expands. The expansion movement of the chest increase the volume inside the chest cavity.

Mechanism of gaseous exchange in humans.

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