VASCULAR SYSTEM: A REVIEW

Differences Between Arteries (Structural and Functional)

August 10, 2016 by Ranga.nr

Arteries: blood vessels that carry blood away from the heart to tissues. 

Veins: blood vessels that carry blood back to the heart from the tissues. 

SIMILARITIES BETWEEN VEINS & ARTERIES

Both have three layers of tissues in their walls: 1) 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

Arteries and veins are two similar yet different types of blood vessels that make up the circulatory or vascular system.

DIFFERENCES IN STRUCTURE & FUNCTION

Arteries carry away the blood pumped by the heart during systole.

Veins carry blood from the periphery of the body back to the heart.

From the heart, arteries start from the aorta, which branches out as arterioles.

These arterioles further branch out into capillaries.

CAPILLARIES

Capillaries are so minute that they pass in between cells and deeper into most parts of tissues. They supply the blood containing oxygen and nutrients to each cell and tissue.  

As seen in the image above, 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.

Capillaries then converge to form a few venues that are a bit bigger in size.

VENULES

Venules further converge to form veins.

These veins further converge to form the superior and inferior vena cava. 

VEINS POUR DEOXYGENATED BLOOD INTO THE HEART

Larger veins pour deoxygenated blood that has collected into the heart. 

 

DEOXYGENATED BLOOD: FROM HEART TO LUNGS

The heart sends the deoxygenated blood to the lungs through the pulmonary artery.  

OXYGENATED BLOOD: FROM LUNGS TO ARTERIES

And the oxygenated blood received through the pulmonary veins from the lungs is pumped into the arteries.

Arteries carry pure blood from the heart to the tissues while the veins return impure blood. But there are a few interesting 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, so 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 also to minimize the workload on the heart. Further, the energy requirement of the body to circulate the blood is minimized.

ANATOMY & STRUCTURE OF ARTERIES & VEINS

ARTERIES: CARRY BLOOD FROM THE HEART TO THE REST OF THE BODY

Arteries are thickly walled and located deeper in the body. They're 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 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.

VEINS: CARRY IMPURE BLOOD BACK TO THE HEART

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 in-spite of 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.

ARTERY THICKNESS

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 in 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 to diffuse to the surroundings.

LOCATION OF ARTERIES IN THE BODY

Their deep-seated location in the body may also be to prevent damage to them in 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.

PRESSURE & BLOOD FLOW: THE HEART PUMPS BLOOD THRU THE ARTERIES; CAPILLARIES PUMP BLOOD THROUGH THE VEINS

The pressure exerted by the blood on the walls of the arteries is higher than that of the veins because the blood flows in the arteries due to the pumping action of the heart.

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.

VALUE OF VALVES

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.

COLOR

The arteries are dark reddish due to oxygenated blood. While for veins, bluish-red is due to oxygenated blood.

DISEASE

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.