Hematosis is the exchange of respiratory gases.

In general, it is the gas exchange between organisms and the environment.

Where does hematosis occur?

Depending on where the hematosis occurs, aerobic respiration can be of the following types:

Aerobic cutaneous breathing , when hematosis occurs in the integument. This type of breathing is characteristic of terrestrial animals in humid environments. In this case, it is called tissue hematosis .

Tracheal aerobic breathing , when hematosis occurs in the trachea. It happens to insects.

Aerobic gill breathing , when hematosis occurs in the gills. It is typical of most aquatic animals. It is called branchial hematosis .

And if it occurs in the lungs, it is called pulmonary aerobic respiration , typical of land animals. In this case, gas exchange occurs in the pulmonary alveoli, being called pulmonary or alveolar hematosis .

How does hematosis occur?

Hematosis occurs when air, rich in oxygen, from the breath reaches the pulmonary alveoli .

Each lung has approximately 150 million alveoli.

The alveoli are structures in the form of sacs, located at the end of the bronchioles. They are covered by blood capillaries , in which blood circulates very close to the air that has been inhaled.

Upon reaching the alveoli, oxygen diffuses into the blood of the capillaries. Meanwhile, carbon dioxide, present in the blood of capillaries, diffuses into the alveoli.

Thus, hematosis occurs due to the diffusion of oxygen gas from the air of the alveoli to the blood of the capillaries . And the same happens with carbon dioxide, however, in reverse.

  • The blood that comes out of the lungs is rich in oxygen and is called arterial blood.
  • The blood that reaches the lungs is rich in carbon dioxide, being called venous blood.

When oxygen gas passes into the blood it enters red blood cells, where it binds with hemoglobin and forms oxyhemoglobin. In this form, oxygen gas passes throughout the body and reaches the blood capillaries of the tissues.

In tissues, O 2 dissociates from oxyhemoglobin and diffuses into the fluid that bathes cells.

The hematosis process in the pulmonary alveoli. The exchange of gases with the blood capillaries.

The cells use O 2 for cellular respiration. During this process, carbon dioxide molecules are created that diffuse into the fluid that bathes the cells and are absorbed by the blood capillaries.

Thereafter, CO 2 can remain in the plasma or associate with hemoglobin.

However, most of the CO 2 reacts with water inside the red blood cells and forms carbonic acid (H 2 CO 3 ), which dissociates into H + ions and bicarbonate ions (HCO  ).

Bicarbonate ions are essential to control blood acidity.

Learn more about the Respiratory System .

What is the importance of hematosis?

  • Ensures tissue oxygenation;
  • It allows for cellular respiration;
  • Produces bicarbonate ions that control blood acidity


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