Mechanism of respiration 

Hello students and friends, today we are going to discuss the mechanism of respiration or how our lung helps in breathing. Here we will learn the steps involved in the mechanism of respiration and how respiration takes place.

What is breathing?

Breathing is a process that involves in and out of the air from the lungs. This process is carried out by various respiratory organs of our body. Inhalation of air is the process in which oxygen-rich air goes into the lungs and exhalation is the process in which carbon dioxide-rich air goes out from the body.

The breathing rate of a normal adult= 15-18 times per minute.

During heavy exercise= exceeds 25 times per minute.

Mechanism Of Breathing

Mechanism of breathing involves two processes:

1.  Inspiration
2.  Expiration

Inspiration

In the process of inspiration, there is the contraction of muscles that are attached to the outer side of the ribs. These muscles pull out the ribs and result in an expansion of the chest cavity.

Diaphram contracts and moves downwards resulting in expansion of the chest cavity and contraction of abdominal muscle takes place.

A partial vacuum is made within the thoracic cavity which sucks air into the lungs and fills the expanded alveoli.

Mechanism Of Inspiration

• It is an active process in which the intake of atmospheric air takes place.
• When the volume of the thoracic cavity (rib cage) increases and the air pressure decreases, inspiration takes place.
• The volume of the thoracic cavity(rib cage) increases due to the contraction of external intercostal muscles.
• Contraction of the diaphragm further increases the dimension of the chest cavity. Simultaneously expansion of lungs takes place.
• As the lungs expand pressure of the air inside the lungs gets decreased.
• The pressure equalizes and therefore the atmospheric air which is inhaled rushes inside the lungs.

Expiration

In the process of gaseous exchange, when the air is expelled out, expiration takes place.

During the process of expiration, the muscles which are attached to the ribs contract, and the muscles of the diaphragm and abdomen relax.

The volume of the chest cavity decreases so the pressure inside the lungs increases. When the pressure increases the air in the lungs is pushed out and expiration takes place.

Mechanism Of Expiration

• It is a passive process.
• Carbon dioxide is exhaled out in the process of expiration.
• Expiration occurs when the size of the thoracic cavity decreases and the pressure of the air outside increases.
• As the pressure gets increased, the external intercostal muscles relax and internal intercostal muscles contract.
• When muscles contract and relax, the ribs are pulled inwards and therefore the size of the chest cavity is reduced.
• Diaphragm gets to relax and the lung compressed.
• Consequently, the pressure of air increases, and therefore the air is forced out.

Mechanism of Respiration

It involves an exchange of gases and breathing mechanisms.

Exchange of Gases

1. Transport of Oxygen

• Oxygen within the blood is carried to the tissue by two forms-
• Oxyhaemoglobin- chemical composition of oxygen with haemoglobin(Hb), and solution of oxygen in plasma.
• The O2 in the blood combines with haemoglobin(Hb) when the concentration of oxygen is high in the blood.
• Oxyhaemoglobin, being unstable, dissociates to release oxygen. Low O2, low pH and high temperatures stimulate the dissociation process.

Internal Respiration

When the gaseous exchange takes place in the tissues, it is known as internal respiration.

Here, the oxygen carried in the form of oxyhaemoglobin gets dissociated to release oxygen.

This oxygen breaks down the glucose to release CO2, H2O, and energy. The energy is utilized by the body, while carbon dioxide is diffused from the tissues.

2. Transport of CO2 from Tissues to the Lungs

CO2 is transported by 3 mechanisms:

• Some CO2 dissolves in the water of plasma to form carbonic acid.
• Carbonic acid ionizes to form bicarbonate ions.
• The H+ ions are catalyzed by the enzyme carbonic anhydrase. 
• Bicarbonates ions combine with sodium(Na+) and potassium(K+) to form sodium bicarbonate and potassium bicarbonate.
• Some carbon dioxide(CO2) combines with haemoglobin for the formation of carbaminohemoglobin.
• At last, it is carried to the lungs and released out by the body through the method of expiration.

Respiratory Gas Transport

After the blood becomes oxygenated, and carbon dioxide is removed, the next phase is the transportation of oxygen-rich blood to the tissues. The cardiovascular system contributes to the transportation of gases. It consists of blood vessels and the heart.

The oxygenated blood leaves the lungs and enters the heart through the pulmonary veins(the only vein which carries oxygenated blood).

Then the blood is pumped to the rest of the body from the left ventricle through the aorta and its corresponding branches.

Hope you all find this helpful for you, if you have any query related to this topic or any other topic then you all are free to contact me via contact us or you can also ask your doubts on the comment box. Thank you! 

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