Blood vessels

Blood vessels

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Blood vessel: conduction of blood by the body

Introduction (what they are)

The circulatory system is formed by arteries, veins and lymphatic vessels, which aim to carry fluids through the body. It is divided into:

- Cardiovascular system: formed by the veins, arteries and heart, which nourish and capture blood from tissues.

- Lymphatic system: contains lymph inside, and unidirectional sense, to allow the output of fluid from tissues. Its content flows into the venous system.

From such differentiation, it is possible to explain the aspects involved and the peculiarities of blood vessels.

Composition and operation

Blood vessels are closed structures that specialize in conducting blood throughout the body.

To have a better understanding of the subject, it is important to note that there are two types of circulation in the body:

- Pulmonary circulation: restricted to the heart and lungs, so that the carbon-rich blood can be exchanged for oxygenated in the pulmonary alveoli.

- Systemic circulation: From the heart, oxygen-rich blood is distributed to the tissues, which return carbon dioxide.

From this concept, the vessels are differentiated into:

1 - Arteries

They are highly resistant structures, with the function of distributing oxygen-rich blood throughout the body - thus referring to systemic circulation.

In the pulmonary circulation, the arteries have the function of taking the blood with CO2 that reached the heart to the lungs.

Histologically speaking, they contain 3 layers:

- Intimate tunic: It is the innermost layer, which is in direct contact with the blood. It is formed by an elastic tissue called the endothelium.

- Medium tunic: This is a highly resistant layer composed of smooth muscle. It is responsible for constriction and dilation of the vessel.

- Adventitic tunic: is the outermost portion, formed by connective tissue.

2 - Veins

Unlike arteries, these are vessels that collect CO2-rich peripheral blood and carry it to the heart. In the pulmonary circulation, on the other hand, they are structures that carry oxygenated blood to the heart to be distributed throughout the body.

Although they also have 3 layers, their structure is more malleable and fragile than the arteries, due to the lower thickness of the middle layer, formed by muscles.

They are characteristic because they have valves that help the blood overcome the force of gravity. To better understand, think that the blood in the feet must rise to the heart. For this, there is such mechanism that prevents the reflux of blood, besides the aid of the musculature.


- Atherosclerosis is a disease that affects the arteries through the deposition of fats, which eventually result in calcification and stiffening of the vessels.

- Upon reaching the tissues, the arteries become thinner and thinner, called arterioles. Later, the capillaries are formed, which are extremely thin structures where blood exchange occurs.

- Malfunction of venous valves can result in blood accumulation and consequently varicose vein formation.