Arteries are the blood vessels that transport oxygenated blood from the heart to tissues.
In contrast, the veins carry oxygen-depleted blood back to the heart from the tissues.
There are many anatomical and physiological similarities and differences between them.
The similarities include
- the presence of three layers of tissues in their walls,
- a hollow lumen to allow the flow of blood without any hindrance,
- distribution into deep tissues of the body, having branches, etc.
Main differences between arteries and veins
|1||Blood quality||Blood carried is oxygenated and rich in nutrients.||Blood carried is rich in CO2 and waste materials meant for expulsion from the body.|
|2||Body location||They are deep-seated in the body, away from the skin surface.||They are peripherally located in the body near to surface. Hence we can see blood vessels on the hands, face, legs, etc., just below the skin|
|3||The thickness of Vessel Walls||Arteries have a thicker wall (more tissue)||The veins have thin walls (less tissue)|
|4||Strength and tension||Arterial walls have more tensile strength, and when cut transversely, they remain open and do not collapse.||Vein’s walls are comparatively delicate, and when cut transversely, they collapse.|
|5||Stretch /distensible||Arteries are not distensible||Veins are distensible so that they can accommodate more blood.|
|6||Cutting of the vessel leads||The Blood spurt out as a stream with force.||Blood oozes out without a spurt and loosely.|
|7||Blood flow||Blood flows in a pulsatile manner corresponding to the heartbeat.||Blood flows uniformly without pulse|
|8||Flow pressure||Blood flows under the heart’s pumping pressure. So, pressure is high.||Blood flows due to the capillary force of action of the vein walls. The pressure is low, comparatively|
|9||Oxygen level||Oxygen levels are quite high in arterial blood||Oxygen level is low comparatively|
|10||Carbon-dioxide level||The CO2 level is quite low in arterial blood.||The CO2 level is high in venous blood,|
|11||Flow direction||From the heart to the tissues||From tissue to the heart.|
|12||Blood volume||Approximately 1/3rd of whole-body blood is present in arteries||2/3rd of whole-body blood is present in veins|
|13||Appearance Color||They are a dark reddish color||They are bluish red in color.|
|14||Valves||There are no valves in the artery vessels.||There are valves in the veins allowing blood to flow upward.|
|15||Diseases||Arteries are susceptible to diseases like angina pectoris, atherosclerosis||Susceptible to diseases like heart failure and varicose veins. Less susceptible to infections.|
|16||Gravitational force||Not affected by gravity to a large extent||Can be affected by gravity and hence chances of orthostatic hypotension.|
|17||Reservoir||Arteries have less blood||Veins have 2/3rd of blood in them at any point in time|
|18||Clinical and healthcare uses||To read pulse rate and blood pressure||To extract blood for diagnosis|
Detail on the differences in structure and functions.
- Arteries and veins are pipe-like vessels that carry blood in the body.
- These are two similar yet different types of blood vessels forming the parts of the circulatory system.
- In general, arteries carry away the blood pumped by the heart during systole.
- While veins carry blood from the body’s peripheral tissues back to the heart.
- Arteries carry from the heart through the aorta, which branches out as arterioles.
- These arterioles further branch out into capillaries.
- These capillaries are so minute and pass in between cells and deeper into most parts of tissues.
- Thus they supply the blood containing oxygen and nutrients to cells and tissues.
- As seen in the image above, these capillaries extend to converge into veins.
- They collect the waste and carbon dioxide from the cells and tissue surroundings to bring into the blood for excretion.
- These capillaries then converge to form a few venues that are a bit bigger in size.
- These venules further converge to form veins.
- These veins further converge to form the superior and inferior vena cava. These larger veins pour the collected deoxygenated blood into the heart.
- The heart sends the deoxygenated blood to the lungs through the pulmonary artery.
- And the oxygenated blood received through the pulmonary veins from the lungs is pumped into the arteries.
Thus arteries carry pure blood from the heart to the tissues while the veins return impure blood.
But interestingly, there are a few exceptions to this rule.
A pulmonary vein brings pure oxygenated blood from the lungs into the heart.
While a pulmonary artery carries impure blood (carbonated) from the heart to the lungs, these two are different from the rest of the blood veins and arteries only in terms of function.
Besides, there are also anatomical structural differences between them.
These differences are meant to keep them safe, perform their function efficiently, and minimize the heart’s workload.
Further, the body’s energy requirement to circulate the blood is minimized.
Anatomy and structure of arteries and veins.
- Arteries are thickly walled and deeply located in the body.
- They are also highly elastic due to circular and oblique muscles in their walls.
- This elasticity helps to convey the pulse from the heart until the blood reaches the cells and tissues.
- The blood in the arteries flows due to the pressure from the heart contraction.
- Hence, you can notice pulse in the arteries but not in the veins.
- Even a physician checks your pulse rate by holding the arteries of the wrists or carotid artery in the neck.
- The blood in arteries is reddish-brown and enriched with oxygen and nutrients.
- These are thin-walled blood vessels located superficially in the body.
- Hence, you can see dark-colored veins below the skin in the arms, hands, thighs, etc.
- The blood flows in them under the influence of capillary action. In humans, this blood flows against the gravitation force.
- So to prevent backflow, there are valves in the inner walls.
- These valves close down when the blood tends to flow downwards.
- Hence, the blood always moves in one direction in veins despite a lack of pulse.
- The blood in the veins is bluish red and has a high concentration of carbon dioxide, urea, and other excretory waste.
- Arteries receive blood due to pressure from the heart, while veins do not have that pressure.
- As seen in the differences above, arteries have thick walls as they have to bear the systolic pressure.
- Also, they have more muscle mass in the walls to propagate the pulse further due to elasticity.
- This helps the blood move fast from the vessel to the tissues. Hence we can measure heart pulse from the wrist artery.
- A further thick wall may minimize the chances of oxygen and nutrients diffusing to the surroundings.
- Their deep-seated location in the body may also prevent damage to them due to injury to the body.
- As their damage can destroy the organ receiving the blood faster.
- But for veins, there is another alternative called lymph vessels, which also carry waste from tissues.
- So damage can to them can be less severe.
- The only condition is there should be no hemorrhage.
- The pressure exerted by the blood on the walls of the arteries is higher than that of the veins.
- This is because the blood flows in the arteries due to the heart’s pumping action.
- This pumping action forces the blood to flow with speed leading to pressure in the arterial wall.
- Whereas in the veins, the flow is due to capillary forces between the vein walls and the blood.
Hence, blood pressure is monitored for the arteries and not the veins.
- Valves help in preventing the blood from flowing backward in the veins.
- The blood flows against gravity due to capillary action.
- Since there is a change in gravitational pressure when sitting and standing up, there is a chance of variation in the flow pressure.
So valves prevent the backflow of blood in veins. This is not required in arteries.
- The arteries are dark reddish due to oxygenated blood.
- While for veins, bluish-red is due to oxygenated blood.
- Arteries are thick and carry nutrition.
- So, nutrition-born disease occurs due to the accumulation of fat.
- While for veins, it is rare but occurs due to obstruction or physical damage to them.
Thus arteries and veins have functional and structural differences to suit the body’s needs.
Frequently asked questions and answers
Why are arteries deeper than veins?
They are located deeper for safety.
The arteries have oxygenated and nutrient-rich blood that flows under the influence of the heart pumping pressure.
If they are located superficially, any minor injury could lead to a huge loss of blood under pressure.
Veins have less blood comparatively, and even if there is a cut, the flow is slower, which can support blood clots (homeostasis).
Why are arteries thicker than veins?
Arteries are thicker than veins in order to maintain the pressure from the heart to the point of blood supply at the tips and deeper-most tissues.
The thickness gives elasticity to carry over the pulse.
Veins, on the other hand, transport blood by capillary action and their ability to dilate to accumulate blood.
So being thick will not help with dilation and capillary action.
Why are valves present in veins but not arteries
In the veins, the blood flows due to capillary force between the vein wall and the blood.
So this pressure is low, and there are chances for the blood to move backward under the influence of gravity of body movements.
Hence, the presence of valves prevents this and enables blood flow in one single direction.
In the arteries, the blood flow due to the pressure of the heart, and hence there is no chance for blood to move backward as there is the coming pulse that pushes blood in one direction. So they do not need and have valves.