What are The Differences Between a Vein and an Artery?

Arteries and veins are a part of the circulatory system which carries blood between the heart, lungs, and all areas of the body. Arteries and veins are made up of different tissue, which each perform a specialized job to the other in different ways. The main difference between the two is that every artery carries blood away from the heart, while all veins carry blood towards the heart.

Diagram taken (then edited) from:

Tunica intima (Endothelial cells) – The tunica intima is the innermost layer of an artery or vein. It is made up of one layer of endothelial cells and is supported by an internal elastic lamina. The endothelial cells are in direct contact with the blood flow.

Elastin- Elastin is a protein in connective tissue that is elastic and allows many tissues in the body to resume their shape after stretching or contracting.

Tunica externa (smooth muscle) – The tunica externa, or adventitia, is the outer layer of a vein and artery. It is much thinner in veins than in arteries. This layer is relatively loose layer of fibrous, elastic connective tissue through which run small blood vessels, called vasa vasorum, that nourish the blood vessel walls.

Tunica externa (smooth muscle) –

Arteries:  It is made up of smooth muscle cells and elastic tissue. It lies between the tunica intima on the inside and the tunica externa (adventitia) on the outside.

Veins: The middle coat is composed of a thick layer of connective tissue with elastic fibers, intermixed, in some veins, with a transverse layer of muscular tissue. The white fibrous element is in considerable excess, and the elastic fibers are in much smaller proportion in the veins than in the arteries.

Serosa – Serosa is a smooth membrane consisting a thin layer of cells which secrete serous fluid. Serous membranes line and enclose several body cavities, known as serous cavities, where they secrete a lubricating fluid which reduces friction from muscle movement. Serosa is not to be confused with adventitia, a connective tissue layer which binds together structures rather than reducing friction between them.




An artery is an elastic blood vessel which transports blood away from the heart. Of the many arteries, there are two main arteries.

·         Pulmonary arteries

·         Systemic arteries


Pulmonary arteries:

These arteries pump blood from the heart to the lungs, which is where the blood picks up oxygen. The oxygen rich blood is returned to the heart via the pulmonary veins. Systemic arteries deliver blood to the rest of the body. The aorta is also an artery and is the main systemic artery, as well as being the largest artery in the body. It begins from the heart and branches out into smaller arteries which supply blood to the top region of the body via the Brachiocephalic artery. This artery extends from the aortic arch to the head, neck and arms and branches into the right common carotid artery and the right subclavian artery. (Refer to diagram of heart in Part 2)

Systemic Arteries:

Systemic Arteries are the collection of arteries which provide oxygenated blood from the heart to the body.



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A vein is also an elastic blood vessel which transports blood from different parts of the human body to the heart. Veins can be categorized into four main types:

·         Pulmonary Veins

·         Systemic Veins

·         Superficial Veins

·         Deep Veins

Pulmonary Veins carry oxygen rich (oxygenated) blood from the lugs to the left atrium of the heart. Systemic veins return the deoxygenated blood from the rest of the body to the right atrium of the heart. Superficial veins are found close to the surface of the skin, but are not located near a corresponding artery. Veins which are found deep within muscle tissue are the deep veins. They are located near a corresponding artery of the same type.

Veins are smaller than arteries and can range from 1 millimetre to 1-1.5 centimetres in diameter. The smallest of the veins found in our body are called venules. They receive blood from the arteries from the arterioles and capillaries. Venules branch into larger veins which carry the blood to the largest vein in the body, the vena cava (Refer to heart diagram from part 2) the blood is then transported from the superior and inferior vena cava to the right atrium of the heart.

source: wikipedia commons

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