Comparison Table: Arteries and Veins Structure, Function, and Features
All the living organisms need food, water, and oxygen to survive, which needs to be transported to different body parts. In addition to this, the waste in our body needs to be taken to a specific part, from where it can be removed. Well, do you know how it is done?
The heart and blood vessels form the essential components of our circulatory system and make the transportation of substances possible.
Now, the blood alone performs both the functions of transporting the essential substance as well as the waste material. It is categorized mainly in two types of vessels, namely arteries and veins, both having many noteworthy functions.
What are Arteries and Veins?
Arteries are thick-walled blood vessels that carry oxygen-rich blood from the heart and distribute it into all the parts of the body.
Veins perform the reverse task, so they are defined as thin-walled blood vessels carrying the blood from all the parts of the body to the heart.
Note- Basically, apart from the many differences between arteries and veins, the similarity in each of these arteries and veins is they have three layers: an inner lining( called the tunica intima), a middle layer made of smooth muscle and elastic fiber ( tunica media), and an external layer made of fibrous connective tissue and collagen fibers ( tunica externa).
The middle layer, I,e.tunica media, is thinner in a vein.
Types of Arteries
There are three types of arteries, all composed of the three layers mentioned above.
Elastic Arteries- They are also called conducting arteries and have a thick middle layer to facilitate the stretching in response to the pulses of the heart.
Muscular Arteries- Also called distributing arteries, they are medium-sized blood vessels. They are meant to draw blood from the elastic arteries and spread to the resistance vessels.
Arterioles- These are the smallest division of arteries that transport blood from the heart into the capillary networks.
Types of Veins
Deep Veins- These veins are positioned within the muscle tissue and have a corresponding artery adjacent to it.
Superficial Veins- No corresponding arteries are placed with them, and they are comparatively closer to the surface of the skin.
Pulmonary Veins- Each lung has two sets of these veins. They transport oxygenated blood from the lungs to the heart.
Systemic Veins- They are present all over the body from the legs to the neck and transport deoxygenated blood.
Apart from veins and arteries function, is there any other difference between the arteries and veins? The answer is big, yes! Let’s explore those contrasts-
Let’s Know More to Find out the Differences Between Arteries and Veins
FAQs on Arteries vs Veins: The Main Differences
1. What is the primary function of arteries and veins in the circulatory system?
The primary function is blood transport, but in opposite directions. Arteries are blood vessels that carry oxygenated blood away from the heart to all parts of the body. In contrast, veins are blood vessels that carry deoxygenated blood from the body tissues back to the heart for purification.
2. What are the main differences between arteries and veins?
The main differences between arteries and veins are based on their function, structure, and blood flow characteristics. Key distinctions include:
- Direction of Blood Flow: Arteries carry blood away from the heart, while veins carry blood towards the heart.
- Type of Blood: Arteries generally carry oxygenated blood (except the pulmonary artery), while veins carry deoxygenated blood (except the pulmonary veins).
- Wall Thickness: Arteries have thick, muscular, and elastic walls to handle high pressure. Veins have thinner, less muscular walls.
- Valves: Veins have valves to prevent the backflow of blood. Arteries do not have valves as the high pressure from the heart's pumping action prevents backflow.
- Lumen Size: The lumen (internal cavity) of an artery is narrower, while the lumen of a vein is wider.
3. Why are the walls of arteries much thicker and more elastic than the walls of veins?
The walls of arteries are thicker and more elastic to withstand the high pressure and powerful surges of blood pumped directly from the heart. The elastic fibres allow the artery to expand with each heartbeat and then recoil, which helps to push the blood forward. Veins, on the other hand, operate under much lower pressure as they are just returning blood to the heart, so they do not require such thick, muscular walls.
4. Why do veins have valves while arteries do not?
Veins have one-way valves to ensure that blood flows in a single direction—towards the heart. Since blood in veins is at a very low pressure and often flows against gravity (e.g., from the legs), these valves are crucial to prevent backflow. Arteries do not need valves because the blood is pushed through them with immense force from the heart's contractions, which naturally prevents it from flowing backward.
5. Why is the blood in arteries bright red, while the blood in veins is dark red?
The colour difference is due to the amount of oxygen bound to haemoglobin in the red blood cells. Arterial blood is rich in oxygen, and when oxygen binds to haemoglobin, it forms oxyhaemoglobin, which is bright red. Venous blood has given up much of its oxygen to the body's tissues and contains more carbon dioxide. The resulting deoxygenated haemoglobin is darker, giving venous blood a deep, dark red colour.
6. How do capillaries fit into the circulatory system with arteries and veins?
Capillaries are the critical link between arteries and veins. Arteries branch into smaller vessels called arterioles, which then lead into vast networks of capillaries. These are extremely thin, single-cell-thick vessels that permeate every tissue of the body. It is here that the actual exchange of oxygen, nutrients, and waste products occurs between the blood and the body cells. After this exchange, the capillaries merge into small venules, which then join to form larger veins that carry the deoxygenated blood back to the heart.
7. Are there any exceptions to the rule that arteries carry oxygenated blood and veins carry deoxygenated blood?
Yes, there is a major exception related to the pulmonary circuit. The pulmonary artery is the only artery that carries deoxygenated blood from the right ventricle of the heart to the lungs for oxygenation. Conversely, the pulmonary veins are the only veins that carry oxygenated blood from the lungs back to the left atrium of the heart. This is a key concept in understanding double circulation.
8. Why is blood for a blood test usually drawn from a vein and not an artery?
Blood is drawn from a vein for several practical reasons. First, veins are located closer to the surface of the skin, making them much easier to access than arteries, which are situated deeper within the body for protection. Second, the blood pressure in veins is significantly lower, so the puncture site bleeds less and clots faster. Drawing blood from a high-pressure artery would be more dangerous and difficult to manage. The most commonly used vein is the median cubital vein in the arm.
9. What is the aorta, and what is its significance?
The aorta is the largest artery in the human body. Its significance lies in its role as the main distributor of oxygenated blood. It originates from the left ventricle of the heart and extends down into the abdomen, branching off into smaller arteries that supply oxygen-rich blood to the entire body. Its thick, elastic walls are essential for handling the high-pressure blood being ejected from the heart.
10. Beyond carrying blood, what are some key similarities between arteries and veins?
While their differences are more pronounced, arteries and veins do share some fundamental similarities.
- Three-Layered Wall Structure: Both are composed of three layers of tissue: the outer tunica externa (connective tissue), the middle tunica media (smooth muscle and elastic fibres), and the inner tunica intima (endothelial cells).
- Part of the Circulatory System: Both are integral components of the circulatory system, working together to ensure continuous blood flow.
- Presence of a Lumen: Both have a hollow central cavity, known as the lumen, through which blood flows.
