Human Circulatory System – Organs, Structure and Function of Blood Circulation

Human circulatory system - Organs, Structure and Function of Blood Circulation
A ditch is one of the basic fluids of the human body, thanks to which organs and tissues receive the necessary nutrition and oxygen, are cleansed of toxins and decay products. This fluid can circulate in a strictly defined direction thanks to the circulatory system. In the article we will talk about how this complex works, due to which the blood flow is maintained, and how the circulatory system interacts with other organs.

The human circulatory system: structure and function

Normal life is impossible without effective blood circulation: it maintains the constancy of the internal environment, transports oxygen, hormones, nutrients and other vital substances, takes part in the purification of toxins, toxins, decay products, the accumulation of which would sooner or later lead to the death of an individual organ or the whole organism. This process is regulated by the circulatory system – a group of organs, thanks to the joint work of which, the sequential movement of blood through the human body is carried out.

Let’s look at how the circulatory system works and what functions it performs in the human body.

the cardiovascular system

The structure of the human circulatory system

At first glance, the circulatory system is simple and understandable: it includes the heart and numerous vessels through which blood flows, alternately reaching all organs and systems. The heart is a kind of pump that spurs the blood, ensuring its systematic flow, and the vessels play the role of guiding tubes that determine the specific path of blood movement through the body. That is why the circulatory system is also called cardiovascular, or cardiovascular.

Let’s talk in more detail about each organ that belongs to the human circulatory system.

Organs of the human circulatory system

Like any organismic complex, the circulatory system includes a number of different organs, which are classified depending on the structure, localization and functions performed:

  1. The heart is considered the central organ of the cardiovascular complex. It is a hollow organ formed predominantly by muscle tissue. The cardiac cavity is divided by septa and valves into 4 sections – 2 ventricles and 2 atria (left and right). Thanks to rhythmic successive contractions, the heart pushes blood through the vessels, ensuring its uniform and continuous circulation.
  2. Arteries carry blood from the heart to other internal organs. The farther from the heart they are localized, the thinner their diameter: if in the area of ​​the heart bag the average width of the lumen is the thickness of the thumb, then in the area of ​​the upper and lower extremities its diameter is approximately equal to a simple pencil.

Despite the visual difference, both large and small arteries have a similar structure. They include three layers – adventitia, media and intimacy. Adventitium – the outer layer – is formed by loose fibrous and elastic connective tissue and includes many pores through which microscopic capillaries pass through which feed the vascular wall, and nerve fibers that regulate the width of the artery lumen depending on the impulses sent by the body.

The median media includes elastic fibers and smooth muscles, which maintain the elasticity and elasticity of the vascular wall. It is this layer that regulates to a greater extent the blood flow rate and blood pressure, which can vary within an acceptable range depending on external and internal factors affecting the body. The larger the diameter of the artery, the higher the percentage of elastic fibers in the middle layer. According to this principle, vessels are classified into elastic and muscular.

The intima, or the inner lining of the arteries, is represented by a thin layer of endothelium. The smooth structure of this tissue facilitates blood circulation and serves as a conduit for nourishing the media.

As the arteries become thinner, these three layers become less pronounced. While adventitia, media, and intima are clearly distinguishable in large vessels, only muscle coils, elastic fibers, and a thin endothelial lining are visible in thin arterioles.

  1. Capillaries are the thinnest vessels of the cardiovascular system, which are an intermediate link between arteries and veins. They are localized in the most distant areas from the heart and contain no more than 5% of the total blood volume in the body. Despite their small size, capillaries are extremely important: they envelop the body in a dense network, supplying blood to every cell of the body. It is here that the exchange of substances between blood and adjacent tissues takes place. The thinnest walls of the capillaries easily pass oxygen molecules and nutrients contained in the blood, which, under the influence of osmotic pressure, pass into the tissues of other organs. In return, the blood receives the decay products and toxins contained in the cells, which are sent back through the venous channel to the heart and then to the lungs.
  2. Veins are a type of vessels that carry blood from internal organs to the heart. The walls of veins, like arteries, are formed by three layers. The only difference is that each of these layers is less pronounced. This feature is regulated by the physiology of the veins: there is no need for strong pressure from the vascular walls for blood circulation – the direction of blood flow is maintained due to the presence of internal valves. Most of them are found in the veins of the lower and upper extremities – here, with low venous pressure, without alternating contraction of muscle fibers, blood flow would be impossible. In contrast, large veins have very few or no valves.

In the process of circulation, part of the fluid from the blood seeps through the walls of the capillaries and blood vessels to the internal organs. This fluid, visually somewhat reminiscent of plasma, is lymph, which enters the lymphatic system. Merging together, the lymphatic pathways form rather large ducts, which in the region of the heart flow back into the venous bed of the cardiovascular system.


The human circulatory system: briefly and clearly about blood circulation

Closed circuits of blood circulation form circles along which blood moves from the heart to the internal organs and vice versa. The human cardiovascular system includes 2 circles of blood circulation – large and small.

The blood circulating in a large circle begins its path in the left ventricle, then passes into the aorta and through the adjacent arteries enters the capillary network, spreading throughout the body. After that, molecular exchange occurs, and then the blood, deprived of oxygen and filled with carbon dioxide (the end product during cellular respiration), enters the venous network, from there into the large vena cava and, finally, into the right atrium. This entire cycle in a healthy adult takes an average of 20-24 seconds.

The small circle of blood circulation begins in the right ventricle. From there, blood containing a large amount of carbon dioxide and other decay products enters the pulmonary trunk and then into the lungs. There, the blood is oxygenated and sent back to the left atrium and ventricle. This process takes about 4 seconds.

In addition to the two main circles of blood circulation, in some physiological conditions in humans, other pathways for blood circulation may appear:

  • The coronary circle is an anatomical part of the large and is solely responsible for the nutrition of the heart muscle. It begins at the exit of the coronary arteries from the aorta and ends with the venous cardiac bed, which forms the coronary sinus and flows into the right atrium.
  • The circle of Willis is designed to compensate for the failure of cerebral circulation. It is located at the base of the brain where the vertebral and internal carotid arteries converge.
  • The placental circle appears in a woman exclusively during the carrying of a child. Thanks to him, the fetus and placenta receive nutrients and oxygen from the mother’s body.

Functions of the human circulatory system

The main role played by the cardiovascular system in the human body is the movement of blood from the heart to other internal organs and tissues and vice versa. Many processes depend on this, thanks to which it is possible to maintain normal life:

  • cellular respiration, that is, the transfer of oxygen from the lungs to the tissues with the subsequent utilization of waste carbon dioxide;
  • nutrition of tissues and cells with substances contained in the blood coming to them;
  • maintaining a constant body temperature through heat distribution;
  • providing an immune response after the entry of pathogenic viruses, bacteria, fungi and other foreign agents into the body;
  • elimination of decay products to the lungs for subsequent excretion from the body;
  • regulation of the activity of internal organs, which is achieved by transporting hormones;
  • maintaining homeostasis, that is, the balance of the internal environment of the body.

The human circulatory system: briefly about the main thing

Summing up, it is worth noting the importance of maintaining the health of the circulatory system to ensure the performance of the whole body. The slightest failure in the blood circulation processes can cause a lack of oxygen and nutrients by other organs, insufficient excretion of toxic compounds, disruption of homeostasis, immunity and other vital processes. To avoid serious consequences, it is necessary to exclude the factors that provoke diseases of the cardiovascular complex – to abandon fatty, meat, fried foods, which clog the lumen of blood vessels with cholesterol plaques; lead a healthy lifestyle in which there is no place for bad habits, try, due to physiological possibilities, to go in for sports, avoid stressful situations and be sensitive to the slightest changes in well-being.