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Difference between Arteries, Veins, and Capillaries

The human body is considered to be a complex structure. All the veins are interconnected, with blood flowing through them. Being a complex mechanism, the body also has some serious complications. These complications are present when the body undergoes pain, surgery, suffering, etc. But the human body has its own ways to filter out waste. Upon filtering out such waste, the body becomes healthy and active. Blood flow is the primary aspect of the human body. Without this flow, there cannot be a body. Be it humans or animals, blood flow is necessary. People with anemia, blood cancer, leukemia, etc., have to take care of themselves. Blood and cell structure are important for the body. So today, we will discuss about the three major aspects of a human body, i.e., arteries, veins, and capillaries. So, let us begin by understanding the definition of these terms.


Arteries are defined as the blood vessels that tend to carry the oxygen-related blood to the tissues. An artery is a muscular tube comprising of three layers. A kind of artery called the pulmonary artery carries low oxygenated blood to the lungs. Now, how many arteries are present in a human body? Well, there are twenty major arteries in the human body. These arteries extend to small arterioles. These arteries form an extensive network that carries blood to every body part.

Interestingly, the largest artery in the human body is called the aorta, which is divided into four major parts, i.e., abdominal aorta, thoracic aorta, ascending aorta, and aortic arch. This artery is present at the left ventricle. Thus, arteries serve as a channel for the transportation of blood.


Veins are defined as the vessels that support blood circulation to the heart. Veins transport the nutrients and oxygen in the body. Apart from this, water is also provided to the cells through veins. Unlike arteries, veins carry back the deoxygenated blood from the organs back to the heart. The deoxygenated blood is collected in small blood vessels called capillaries. There are three types of veins in the body, i.e., pulmonary veins, deep veins, and superficial veins. Every vein has its function to perform. The most prominent vein in the body is the inferior vena cava. The smallest vein in the body is the venule. From venules, the blood flows to the larger veins. It is interesting to note that the body is capable of forming new veins and vessels when one is blocked. The human body can form new blood vessels for the circulation of blood. Moreover, the veins can partially heal themselves after being cut. Thus, veins are capable of blood circulation in the body.


Capillaries are the tiniest vessels that serve as a link between the arteries and veins. The materials are exchanged between blood and tissues through capillaries. The size of capillaries ranges from 5-10 micrometers. Capillaries also have a cell wall called the endothelial wall, which is thick and supports blood circulation. The exchange of gases, water, nutrients between tissues and organs takes place in capillaries. The main function of the capillaries is to absorb oxygen and release it into the bloodstream during inhalation.

Similarly, during exhalation, carbon dioxide is released. Well, there is no count of capillaries in the human body as they are attached to several arteries and veins. They are interconnected. Still, there are around ten billion vessels in the body. The blood exits through these capillaries and returns to the heart. It is interesting to note that capillaries are not always opened. They open when the cells require blood. The brain is the only part of the body in which the capillaries remain open all the time. Now, there are some contrasting points between arteries, veins, and capillaries. So, let us take a look at them.

1. Arteries are defined as the blood vessels that carry oxygenated blood from the heart to the tissues. On the other hand, veins are defined as the vessels that carry deoxygenated blood from organs back to the heart. On the other hand, capillaries are defined as the smallest vessels that link arteries and veins.
2. Arteries carry blood to other organs of the body. Veins help in supporting blood circulation. Capillaries help in the transport of nutrients, gases, and water.
3. There are twenty major arteries in the human body. Veins stretch over from 60, 000 to 1,00,000 miles in the body. There are 10 billion capillaries in the body.
4. There are three significant types of arteries, i.e., elastic arteries, arterioles, and muscular arteries. There are three types of veins, i.e., deep veins, pulmonary veins, and superficial veins. There are three kinds of capillaries, i.e., continuous capillaries, sinusoid capillaries, and fenestrated capillaries.
5. The blood is carried from the heart to tissues. The blood is carried back from organs to the heart. The capillaries remain closed. They open when there is a requirement for blood.
6. The outer coat of the arteries is thin, while the middle layer is thick. The outer layer is thick, and the middle layer is thin. There are no outer or middle layers in capillaries.
7. The lumen of the artery is small. The lumen in the veins is large. The lumen in capillaries is small.
8. There are no semi-lunar valves in arteries. Semi-lunar valves are present. There are no semi-lunar valves present in capillaries.
9. The blood pressure is high in arteries. The BP is low in the veins. The blood pressure is always falling in capillaries.
10. The blood flow is rapid in the arteries. The flow of blood is slow in the veins. The blood flow is slow in capillaries.
11. The wall is thick in arteries. The wall is thin in veins. The walls are extremely thin in capillaries.
12. The three layers of arteries are:
  • Tunica Adventitia
  • Tunica Media
  • Tunica Intima
The three layers of veins are:
  • Tunica Adventitia
  • Tunica Media
  • Tunica Intima
Only one layer is present in capillaries called Tunica Intima.

So, these are some of the significant differences between arteries, veins, and capillaries. They are responsible for carrying out the blood circulation in the body. They ensure that enough blood is reaching all the organs of the body. Thus, arteries, veins, and capillaries are responsible for keeping the body fit and healthy by carrying blood from the heart to the tissues.

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