Each person needs to know about the features of his body. All basic questions regarding anatomy are difficult to answer right away. Therefore, now only one will be affected. And he sounds like this: "In which vessels does gas exchange take place?" Not only the question is interesting, but also the topic to which it relates, and therefore it should now be considered in a little more detail.
Briefly about the process
Before you talk about in which vessels gas exchange takes place, it is necessary to discuss the specifics of the process itself. Based on the name, it can be understood that it is customary to denote the exchange of gases between the body and the environment.
The process is elementary. Oxygen (without interruptions) enters the body from the environment, which is consumed by all tissues, organs and cells. And he, in turn, back emits carbon dioxide formed in the process, as well as some other metabolic products.
This process is necessary for almost all organisms. Because without it, the normal metabolism of energy is not possible.
Lung capillaries
These are the vessels in which gas exchange takes place. Although it is impossible to say so unambiguously, because the gas exchange functions, as well as blood oxygenation, are carried out with the participation of vessels of the entire small circle of blood circulation.
The branches of the pulmonary artery have very thin walls. The entire vascular system is very malleable, it stretches easily. It receives a fairly large amount of blood from the right ventricle (about 6 liters per minute).
And this is considering the low pressure in the small circle (approximately 15-22 mm Hg). This fact is due to very small resistance. It is ten times smaller than in vessels belonging to a large circle of blood circulation.
Features of the structure of blood vessels
A network of alveolar capillaries cannot be compared with anything. And telling about the vessels in which gas exchange takes place, one simply cannot but touch upon the specifics of their structure. Features can be distinguished in such a list:
- Capillary segments are very small.
- All of them are abundantly interconnected, as a result of which a looped network is formed.
- Individual capillary segments very densely fill all units of the alveolar surface area.
- Blood flow rate is very low. Why? Because the walls of the alveoli have such a dense capillary network that some physiologists consider it to be a continuous layer of moving blood.
So, where the gas exchange takes place is clear. What about the sizes? The surface area of the studied capillary network is close to the alveoli (approximately 80 m 2 ). And it contains about 200 ml of blood.
If we talk about alveolar blood capillaries, then their diameter varies from 8.3 to 9.9 microns. In red blood cells, it is smaller - 7.4 microns. What does it mean? The fact that red blood cells are very tightly adjacent to the capillary walls. This feature of blood supply creates excellent conditions for efficient and rapid gas exchange, which results in the normalization of the gas composition of arterial blood and alveolar air.
Process description
Based on the foregoing, we can understand where gas exchange occurs. But how exactly? It is worth trying to answer this question.
First you need to understand that the key task of the lungs is to carry out the gas exchange process, and not just to distill the air. And in them the inhaled composition changes. Here the circulatory system is already included in the process. Namely - capillaries. They permeated all the alveoli.
Once in them, oxygen is sent to the walls of the capillaries. Why? Because in the blood and in the air that is contained in the alveoli, different pressure. In venous blood it is much lower. That is why oxygen flows from the alveoli into the capillaries. But the pressure of carbon dioxide is greater in the blood than in the alveoli. What, in turn, means this? The fact that carbon dioxide is transported directly from the venous blood into the lumen of the alveoli.
Then oxygen joins the hemoglobin contained in red blood cells, and in this form moves through the body. As a result, arterial blood enriched with oxygen is formed.
Interaction with the heart system
What happens next? Blood is transported to the heart, which then distills it to tissue cells. After that, it is delivered through vessels to all cells of the body.
The process does not end there. Entering the cells, the blood "gives" all the oxygen, absorbing carbon dioxide, which is a product of life.
After that, the reverse process begins. It goes along such a path: tissue capillaries - veins - heart - lungs. Arriving at the final destination, venous blood saturated with carbon dioxide is again transported to the alveoli. After that, she with the rest of the air goes out. And carbon dioxide, just like oxygen, is transported with hemoglobin.
Process intensity
Talking about in which vessels gas exchange occurs in the lungs, it is worth noting an interesting nuance. The fact is that this process (and, consequently, the subsequent energy expenditure) becomes less intense if the body temperature decreases. At first, this was revealed in cold-blooded creatures, and then it was possible to prove a similar dependence in warm-blooded mammals. Man, of course, applies to them too.
The same is observed in conditions of artificial or natural hypothermia. But with an increase in body temperature, when a person becomes sick or overheats, gas exchange, on the contrary, increases.
What happens in the lungs?
It is worth returning to this question. How gas exchange occurs in the vessels and which path the oxygen-enriched blood then makes is clear. But what exactly happens in the lungs?
They carry out excretory function. It manifests itself in the removal of more than 200 volatile substances formed in the body or falling into it from the outside. Carbon dioxide, exogenous substances (ethyl ether and alcohol), acetone, methane, nitrous oxide and fluorotan - all of these are, to one degree or another, removed from the blood through the lungs.
In addition to conditioning, this organ also has a protective function. Microorganisms ingested during inhalation and then settled on the walls of the alveoli capture and destroy the alveolar macrophages.
It is also worth recalling that immunoglobulins, interferon, specific leukocyte antibodies and lysozyme are formed in the lungs - those elements that play an important role in protecting the body from various infectious agents.
Oxygen value
In which blood vessels gas exchange occurs and how this process is generally carried out, is clear. Now it’s worth talking about the importance of oxygen for the human body.
This is an organogen element. In the body it contains up to 65%. And this is about 40 kilograms, if we take into account the average person.
A key function of oxygen is to participate in all redox reactions that take place in the body. Thanks to him, the body can utilize proteins, fats and carbohydrates with the extraction of energy for their needs.
According to studies, 1.8 to 2.4 grams of oxygen is consumed per minute.
Conclusion
In conclusion of the topic regarding the question in which vessels gas exchange occurs in the lungs and tissues, I would like to say that this process is perhaps the most stable in the body.
Its constancy is always maintained, even if the partial pressure of O 2 in the environment changes, the functioning of the respiratory system, etc. And this happens due to the presence of adaptive reactions of systems that are involved in gas exchange. They, by the way, are controlled by the central nervous system.