Question

Why are valves present in veins but not in arteries?

Answer 1

Hint: Valves are the gate which opens only in one direction that liquid can if entered through that valve can not leave through the same valve. For example, Tricuspid and Bicuspid valves present at Atrium and ventricle.

Complete answer:
We are aware that the Veins and Arteries are the part of the Blood Circulation System of the Organisms.
• Arteries and veins transport nutrition through blood to various parts of the body and also carry waste from various parts of the body.
• Usually Veins collect deoxygenated blood from different organs and transport it to the heart and Arteries transport oxygenated blood from heart to various parts of the body.
• Deoxygenated Blood from veins first enters the Right Atrium and then atrium contracts and blood enters the right ventricle, when ventricle contract blood goes to Lungs through Pulmonary arteries where it gets Oxygenated.
• This Oxygenated blood is carried away from lungs to heart via Pulmonary Veins. Here also it first enters the Left Atrium and when Atrium contracts it enters the left ventricle. Contraction of ventricles causes the oxygenated blood to reach various other body parts through Arteries.
• It is important to note that Arteries always carry blood away from the heart (pulmonary arteries to lungs and Aorta to tissues) therefore there is a pressure in them which does not allow backflow of blood.
• But veins always carry blood to the heart (vena cava from tissues and pulmonary veins from lungs) and there is no such pressure so when the heart contracts there is possibility that blood can flow back through veins.
• Therefore to prevent this backflow there are valves present in the veins.

Note: Veins t carry deoxygenated blood, except the pulmonary veins which carry oxygenated blood, similarly pulmonary arteries carry deoxygenated blood. Also note that due to the pressure created by the heart in arteries they can burst, so to prevent that the walls of arteries are thick.