Artery

Vein

1. It has thicker and more muscular wall.

2. It has a narrow lumen.

3. It lacks valves.

4. It carries blood away from the heart.

1. It has thinner and less muscular wall.

2. It has a wider lumen.

3. It has valves to prevent back flow of blood.

4. It carries blood towards the heart

Pulmonary artery

Pulmonary vein

1. It carries deoxygenated blood from right auricle (atrium) to lungs for oxygenation.

1. It carries oxygenated (pure) blood from lungs to left auricle (atrium) for circulation.

5.5 liters of blood is present in a healthy adult. The main components of blood are plasma and 3 types of blood cells, viz, red blood cells, white blood cells and platelets.
Blood plasma makes 55% of total blood volume. It has 90% water and remaining 10% of protein, fat, minerals and carbohydrates. Three functions of plasma are as follows.
  1. It balances the flow and amount of water in the body.
  2. It dissolves and transports nutrients obtained from intestine.
  3. It takes carbon dioxide produced in the cells to lungs for excretion.
The artery that takes blood from the heart to the lungs for oxygenation is called pulmonary artery. Only this artery carries impure (deoxygenated) blood while all other arteries carry pure (oxygenated) blood.
Artery is thick-walled and carries blood pumped by heart to different parts of the body. Due to this reason, blood flows under high pressure in artery. Vein is thin-walled and carries blood from tissues towards the heart under very low pressure. As blood flows under high pressure in artery and low pressure in vein bleeding is dangerous from artery than that from vein.
Artery carries oxygenated blood pumped by the heat to different parts of the body under high pressure. But the deoxygenated blood is collected by veins to the heart under low pressure. That's why the wall of artery is thicker than vein to withstand high pressure of blood.
Blood flows under low pressure in veins. So, there is a chance of back flow of blood. To prevent this back flow of blood, veins have valves. As blood flows under high pressure in arteries, there is no risk of back flow. That's why arteries do not have valves.
Arteries and veins have many layered walls. But, capillaries have single layered wall that allow easier passage of substances. Because of this reason, exchange of substances between blood and cells takes place when the blood is flowing through the capillaries.
There are two types of blood circulation in humans. They are pulmonary circulation and systematic circulation. The circulation of blood between the heart and lungs for oxygenation is called pulmonary circulation where as the circulation of blood between the heart and all parts of the body for supplying the requirements and removing the wastes is called systematic circulation.
When blood flows through arteries, it exerts pressure to the arterial walls. The pressure experienced by arterial walls is called blood pressure. Its unit is mm of Hg.
Pressure experienced by arterial walls when the heart muscles contract (systole) is called systolic blood pressure. Its average value is 120 mm of Hg. Pressure experienced by arterial walls when the heart muscles relax (diastole) is called diastolic blood pressure. Its average value is 80 mm of Hg.
If a person has blood pressure 140/100 mm Hg, it means that person has systolic blood pressure (maximum arteriol blood pressure) 140 mm Hg and diastolic blood pressure (minimum arteriol pressure) is 100 mm Hg.
Blood pressure of a man is 130/90 mm of Hg. It means that the arterial walls in that man experiences a pressure equal to 130 mm of Hg when the heart (especially the ventricles) is contracting and a pressure equal to 90 mm of Hg when the heart (especially the ventricles) is relaxing.
Sphygmomanometer is used to measure blood pressure. The factors that affect the blood pressure of a person are- time of the day, mental condition, age, sex, physical condition, etc.
The contraction and relaxation of heart muscles pump the blood. The combined term of one contraction and one relaxation of the heart muscles is called heart beat.
The rate of heart beat depends upon sex, age and work. During heavy work and exercises, high fever, under stress and fear, the rate of heart beat increases. Likewise, the heart beat is rapid in children and during old age.
The force exerted by blood against the wall of a vessel is called blood pressure. It is greater in arteries than in vein.
It means the person has normal blood pressure i.e. systolic blood pressure is 120 mm of Hg and diastolic blood pressure is 80 mm of Hg.
The instrument used to measure blood pressure is sphygmomanometer.
Bleeding from artery is dangerous because oxygenated blood flows with a high pressure in the arteries.
The blood flowing through artery is scarlet in colour, while that flowing through veins is purple or brownish in colour. It is because the blood flowing through artery is oxygenated blood while the blood flowing through vein is deoxygenated blood.
The differences between artery and vein are as follows:
Artery Vein
  1. Arteries carry blood from the heart to the body parts.
  2. Arteries have thick walls
  3. There are no valves in the arteries.
  1. Veins carry blood from body parts to the heart.
  2. Veins have comparatively thin walls
  3. There are valves in the vein.
The differences between pulmonary artery and pulmonary vein are as follows: -
Pulmonary artery Pulmonary vein
  1. It carries impure blood.
  2. It carries blood from right ventricle to the lungs.
  1. It carries pure blood.
  2. It carries blood from lungs to the left auricle.
There are three types of blood vessels in human body which are as follows: -
  1. Veins: - It collects the impure blood from different parts of the body through capillaries to the heart.
  2. Arteries: - It carries the blood from the heart to different parts of the body.
  3. Capillaries: - It exchanges the proteinous substances, gases, etc between the blood and the cells at different parts.
The pulmonary artery carries deoxygenated blood (impure blood) from right ventricle to the lungs. The pulmonary vein carries oxygenated blood from the lungs to the left auricle.
Arteries are deep seated whereas veins are superficial. It is because blood flows at high pressure in the arteries and at low pressure in the veins. To balance the pressure in and out of the blood vessels, they are found at different depth in our body.
Veins have valve because valves prevent the back flow of blood. It may happens because, blood flows at low pressure with low speed in them. Arteries don't have valves because they carry pure blood from the heart. The blood flows at high pressure and high speed in arteries. Hence, they have no valves.