External Respiration

Respiration in Humans

human respiratory system

For the convenience of study, the respiratory process in humans can be divided into the following two parts:

1: External Respiration, 2: Internal Respiration

1: External Respiration

For the convenience of study, external respiration is also divided into the following stages.

A: Breathing

The removal of impure air by taking purified air from the atmosphere by respiratory organs is called apoptosis. This action is completed in the following two steps-

a) Inlahation

In this activity, pure air reaches inside the lungs through respiratory organs. In this process, the diaphragm and internal intercostal muscles are narrowed, causing the diaphragm to come down and the lower ribs to extend outward and upward, increasing the volume of the thoracic cavity. In this way, the atmospheric pressure in the lungs is reduced and the air from the atmosphere passes into the lungs through the nasal passages and the respiratory tract.


external respiration

b) Exhalation

In this activity, air comes out of the lungs. Under this process, relaxation of external intercostal muscles and diaphragm reduces the volume of the thoracic cavity, which increases the pressure on the lungs and the air in it exits through the nasal passage.

B: Gaseous exchange in lungs

Gaseous exchange in the lungs is done by diffusion action. The air that is inhaled in the lungs is relatively high in oxygen while the blood in the blood vessels located in the lungs has a high amount of carbon dioxide. Therefore, carbon dioxide from the blood vessels in the lungs and oxygen from the lungs diffuse automatically into the blood vessels.

gaseous exchange in lungs

C: Transportation of Oxygen

The oxygen transported from the lungs to the blood reacts with the red-colored hemoglobin present in the red blood cells (RBC) of the blood to form temporary additive oxyhemoglobin. This oxyhemoglobin, upon reaching the tissues through the blood, disintegrates and releases oxygen, which causes oxygen to diffuse and reach the cells.

Hemoglobin: Hemoglobin is a complex protein that is formed from iron-containing pigment heme and globin protein. It is found in red blood cells in all vertebrates.

gaseous transportation

D: Transportation of carbon dioxide

Carbon dioxide produced by oxidation of food substances in cells reaches the lungs in the following 3 ways-

a) In the form of Carbonic Acids

About 5 to 7% of carbon dioxide dissolves in blood plasma to form Carbonic acids. On reaching the blood in the lungs, this action is done in the reverse direction and carbon dioxide diffuses and passes out of the body through the lungs.

b) In the form of carboxyhemoglobin

About 10 to 23% of carbon dioxide reacts with the hemoglobin present in the red blood cells (RBC) of blood to form a temporary additive carboxyhemoglobin. Upon reaching the lungs, it breaks down and releases carbon dioxide.

c) In the form of bicarbonates

About 70 to 85% of carbon dioxide flows by blood in the form of bicarbonate of sodium and potassium. When these bicarbonate compounds reach the lungs, carbon dioxide diffuses into the lungs through a special process called the chloride shift.

The Capacity of Lungs for External Respiration:

We can understand the strength of lungs under the following terms –

Strength of lungs

a) Functional Residual Air

About 2500 ml of air is always filled in our lungs, it is called Functional Residual Air.

b) Tidal Air

Normally we fill and release about 500 ml of air in each breath. This is called Tidal Air.

c) Inspiratory Capacity

We can take a maximum of 3500 ml of air at a time through long breathing, it is 3000 ml more than the Tidal Air, it is called Inspiratory Capacity.

d) Total Lung Capacity

A total of 6000 ml of air can be filled into the lungs at a time by mixing the Inspiratory Capacity and Functional Residue Air. This is called total lung capacity.

e) Vital Capacity of Lung

A maximum of 4500 ml of air can be ejected from the total lung capacity at a time. This is called the Vital Capacity of the Lung.

f) Residual air

When the air of the vital capacity is removed from the total lung capacity, 1500 (6000-4500 = 1500) ml air remaining in the lungs is called residue air.

g) Dead space air

Out of 500 ml of flowing air, 150 ml remains in the bronchi and bronchioles. This is called dead place air.

It is difficult to understand too much subject material gathered in one go, so I will try to explain the internal respiration effectively in the next article.

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