At veins, like arteries and capillaries, are blood vessels and, with the heart, are part of ourCardiovascular system. The veins are vessels that act in this system promoting the return of the blood, from the different parts of the body, to the heart. We'll describe more about these important blood vessels below.
Read too:The types of circulation existing in vertebrates
Vein characteristics
Veins are blood vessels that ensure the transport of blood from the tissues to the heart. These vessels have a varied diameter, and it is possible to observe veins with a diameter between 1 mm and 9 mm. Veins located close to the heart have a larger diameter.
Like arteries, veins have a wall formed by three layers or tunics: the intima, media, and adventitia. THE intimate tunic it is a thin layer and is found more internally in the vein. THE middle tunic it is rich in muscle cells and is the middle layer of the vein. already the adventitious tunic it is the outermost layer and stands out for being rich in collagen and fibers. In veins, the latter is the most developed.
The walls of the veins are not as developed as those of the arteries, as blood flows through them under high pressure. In the veins, however, blood flows at a lower blood pressure. Due to this low pressure, it is necessary the presence of mechanisms that guarantee the blood flow in the correct direction and prevent its return. To avoid these events, the veins have valves that prevent blood reflux.
In addition, it is important to highlight that the blood flow in the veins is directly related to the gravity. This is due to the fact that this force acts by “pulling” the blood downward, preventing its efficient return to the heart. The valves act to ensure unidirectional blood flow, but they are not the only structures involved in this - the contraction of the smooth musculature of the vein wall and the contraction of our skeletal muscles are fundamental to guarantee it.
Skeletal muscles contract according to our commands as they are voluntary contraction muscles. When we move, they behave like this and ensure the compression of the veins, which helps with blood flow. Knowing this, it's clear why it's important not to stand too long or sit too long.
Know more:Arteries, Veins, and Capillaries—The Three Basic Types of Blood Vessels!
Superficial veins and deep veins
Veins can be classified into two major groups:
Superficial veins: are located closer to our skin, and can even be viewed.
Deep veins: they are located more internally and may be alone or accompanied by arteries. The veins that accompany the arteries are called satellites.
Examples of important veins in the human body
Discover, below, some important veins present in our body:
Pulmonary Veins: ensure the transport of oxygen-rich blood from the lungs to the heart, more precisely to the left atrium.
Upper and lower vena cava: flow into the right atrium. All veins in the systemic circulation flow into the vena cava. They are considered to be the main veins in the body.
Femoral vein: ensures that blood from the lower limbs is taken to the vena cava. It's a vein close to the groin and has a lot of blood flow.
External and internal jugular vein: ensures the drainage of blood in the head region.
Saphenous veins: superficial and located in the legs, they are connected to the deep system.
Also access:How blood is produced - location, process and components
Varicose veins
At varicose veins they are a relatively common situation that occurs due to malfunction of the valves present in the veins. Valve failure causes blood to accumulate in these blood vessels, making them dilated. This continuous dilation causes the veins to lose their elasticity. Blood flowing improperly in the veins causes more and moredilation and reflux. These dilated and tortuous veins are what we call varicose veins.
Varicose veins occur mainly in the lower limbs and in individuals who stand for a long time. They have some characteristic symptoms, such as:
Burning sensation in the legs;
Swelling;
Fatigue in the legs;
Cramps;
Presence of bluish and visible veins.
The treatments for this situation depend on each case, the most common being: a chemical sclerotherapy (use of drugs that prevent blood circulation at the site), the surgery, it's the intravenous laser (using a laser that is emitted by a fiber).
