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vein

Primary Information
Secondary Information

Definition

A vein is a blood vessel that carries blood back to the heart. Veins are typically blue because they carry deoxygenated blood, which is blood that has given up its oxygen to the tissues.

The walls of veins are thinner than the walls of arteries, and they have valves that help to keep the blood flowing in the right direction. The valves open when the blood is flowing and close when the blood is trying to flow backwards.

Veins are found all over the body. They are especially large in the legs and arms, where they help to return blood from the extremities back to the heart.

Veins can become varicose, which means they become enlarged and twisted. Varicose veins are often caused by standing or sitting for long periods of time.

Veins can also become blocked, which can cause blood clots. Blood clots can be dangerous, and they can even be fatal.

How can the word be used?

The leaves of the plant were veined with purple.

vein

Different forms of the word

Noun:

  • a blood vessel that carries blood away from the heart.
  • a streak or stripe of a different colour or material.

Verb: to form veins in something.

Etymology

The word "vein" comes from the Old English word "veina", which also means "a blood vessel that carries blood away from the heart".

The first recorded use of the word "vein" in English was in the 9th century.

Question

What are veins?

AQA Science Exam Question and Answer

Question:

Explain the function of veins in the circulatory system and how they differ from arteries. Provide an example of a specific vein in the human body and describe its role in returning blood to the heart.

Answer:

Veins are crucial components of the circulatory system that play a vital role in returning deoxygenated blood from various parts of the body back to the heart. Unlike arteries, which carry oxygen-rich blood away from the heart, veins transport oxygen-depleted blood towards the heart, completing the cycle of blood circulation.

A specific example of a vein in the human body is the superior vena cava. This large vein collects deoxygenated blood from the upper body, including the head, neck, and arms. It then delivers this blood to the right atrium of the heart, where it is subsequently pumped to the lungs for oxygenation.

The superior vena cava's role is essential for maintaining proper oxygen levels in the body. After oxygen-rich blood has been used by tissues, veins like the superior vena cava help collect and return the deoxygenated blood to the heart, allowing it to be oxygenated anew. This process ensures a continuous flow of oxygenated blood to body tissues, supporting metabolic processes and maintaining overall bodily functions.