What are the major differences between arterial blood flow and venous blood flow?
Arteries carry oxygenated blood from the heart to all parts of body. They supply oxygen rich blood to brain, lungs, liver, kidneys, muscles and other vital organs.
Veins transport oxygen-poor (hypoxic) blood back to heart through capillaries in various tissues. These capillary beds provide energy for cells.
The main function of arteries is to carry oxygenated blood away from the heart to all parts of body. Veins have a role in supplying oxygen-rich blood to brain, lungs, liver, kidneys, muscles and other vital organs.
How do arteries work?
Arteries are made up of many small vessels called capillaries. Each capillary carries oxygenated or hypoxic blood from one place to another with little resistance. The capillaries are lined with specialized cells called endothelial cells. These endothelium cells allow the blood to pass easily through them.
When there is too much oxygen in the bloodstream, it becomes difficult for the blood to move freely through these capillaries. There is no room left for extra oxygen molecules because they cannot get past the walls of the capillary bed. These endothelial cells swell, increasing the size of the capillaries and allowing more space for extra oxygen. The skin becomes flushed.
Arteries are thick, hard-walled and elastic. They have three layers, an external elastic fibrous layer called tunica externa, a middle layer called tunica media which is made up of cardiac muscle and in between these two layers is an internal lining called tunica intima which is very thin and delicate. Arteries are elastic and muscular tubes which carry blood away from the heart. The walls of arteries contain special cells called smooth muscle cells. These cells are capable of contracting and relaxing.
They can also dilate or narrow the size of arteries, depending on what is required at a particular time.
What happens in veins?
The main difference between veins and arteries is in how they transport blood to and from the heart. While arteries transport oxygenated blood from the heart to all parts of the body, veins carry deoxygenated blood back to the heart. Blood in veins is said to be flowing in the reverse direction compared to that of arteries.
Veins are thinner than arteries because they have to carry less blood. They contain one thick elastic layer and an inner lining called tunica intima. The tunica intima is made up of delicate endothelial cells. Veins are thinner and have less muscle compared to arteries.
What is the major difference between veins and arteries?
The major difference between veins and arteries is that the former carry deoxygenated blood towards the heart, while the latter carry oxygenated blood away from it. Arteries are also thicker compared to veins.
Arteries carry oxygenated blood away from the heart to all parts of the body while veins carry deoxygenated blood back to the heart
Arteries have thick muscular walls and contractile cells that help in narrowing and widening its diameter to adequately supply blood to different parts of the body. They contain smooth muscle cells, which help adjust the diameter of the artery.
Arteries also have elastic fibres in their tunica media that allow the artery to recoil, if increased pressure is suddenly released on it. Apart from this, arteries are covered by a thick fibrous layer called Tunica externa. This fibrous layer is made up of irregularly arranged collagenous fibres which help the artery retain its shape and sustain any kind of physical trauma or stress.
In arteries, the tunica intima is made up of a single layer of flat endothelial cells that completely cover the inside surface of the artery. These endothelial cells prevent any type of substances from entering into the blood stream. They also produce a lubricating fluid that allows the blood to flow freely inside the artery. If a tear or hole appears in the tunica intima, then blood can escape into the tissue that surrounds the artery. This causes a haematoma.
Arteries are able to maintain a strong force of blood flowing through them. They can adjust the diameter of the artery, so that more blood can reach parts of the body that require a greater supply, such as when you are exercising and your muscles need extra oxygen.
Arteries do not contain any valves to stop the flow of blood in the wrong direction. However, some arteries do contain an inner layer of elastic fibres that help it prevent the back flow of blood.
Arteries also have an external elastic membrane, which helps the artery deal with any trauma and stress that can damage it.
Veins on the other hand, do contain one or more types of one-way valves to make sure blood flows in the right direction. They ensure that blood travels towards the heart. Veins also have an inner layer of elastic fibres which help them cope with any increased pressure in the veins and prevent the backward flow of blood. These elastic fibres are arranged in a crisscross pattern.
What are the differences between arteries and veins?
Arteries contain tunica media, which is made up of smooth muscle cells and elastic fibres.They also contain tunica externa, which is a thin layer of collagen arranged irregularly.
The veins do not contain tunica media or tunica externa.
Arteries contain tunica intima, which is a single layer of flat endothelial cells. They also have a layer of elastic fibres, which are arranged in a crisscross pattern.
The veins do not have tunica intima or elastic fibres.
Arteries have an external elastic membrane for protection, while veins do not have this.
Arteries contain contractile cells to help increase the diameter of the artery and more blood can flow through it.
The veins do not have any contractile cells in them.
None of the elastic fibres in the tunica media or tunica externa are arranged in a specific order or orientation. However, in the tunica intima, the elastic fibres are parallel to each other.
In the tunica media, there are a few elastin fibres that are arranged parallel to each other. In the tunica externa, the collagen fibres are more arranged in an irregular manner.
Arteries contain a small number of internal elastic fibres that help them expand to allow more blood to pass through them efficiently. These internal elastic fibres of arteries are parallel to each other.
The veins contain a large number of internal elastic fibres that help them expand to allow more blood to pass through them efficiently. These internal elastic fibres of the veins are arranged in a specific order and orientation.
In a cross-section of the tunica media, the tunica externa, and the tunica intima, it will look like an English ‘A’.
In a cross-section of the tunica media, the tunica externa, and the tunica intima, it will look like a capital ‘A’.
Arteries display a range of structural differences to veins. The tunica media of arteries contain smooth muscle and elastic tissue. This tunica media is surrounded by the tunica externa, which is made up of collagen.
Arteries are elastic and strong as they have a tunica media and tunica externa. The tunica media is made up of smooth muscle and elastic tissue. The tunica externa is made up of collagen fibres.
The tunica media and the tunica externa are arranged to give the artery strength and flexibility.
The tunica intima of the arteries is less complex than that of the veins.
Sources & references used in this article:
Arteries and veins: making a difference with zebrafish by ND Lawson, BM Weinstein – Nature Reviews Genetics, 2002 – nature.com
Macroscopic and microsurgical varicocelectomy: what’s the intraoperative difference? by X Liu, H Zhang, X Ruan, H Xiao, W Huang, L Li… – World journal of …, 2013 – Springer
Theory of the use of arteriovenous concentration differences for measuring metabolism in steady and non-steady states by KL Zierler – The Journal of clinical investigation, 1961 – Am Soc Clin Investig