Question

Valves are present in the veins, Explain.

Answer 1

Hint: The veins are the blood vessels that aid in transportation of deoxygenated blood lacking nutrients towards the heart. In the leg veins of a healthy person, these valves are one-way thus allowing the flow of blood only towards the heart that the flow is restricted to only one direction.

Complete answer:
The circulatory system comprises both the arteries and the veins. The oxygenated blood is carried by arteries from heart to other parts of body while the veins carry deoxygenated blood towards the heart. The valves are present in the veins, known as the bicuspid valves which are characterized by a pair of flap-like structures. This structure helps in regulating the flow of blood. The pair of flaps consists of tissues which are elastic in nature. The main function of these valves is to direct the flow of blood in one direction that is towards the heart.

Blood can flow freely in the upwards direction that is towards the heart in conditions when the valves are open and in other conditions when the valves are closed, the flow of blood back to the legs is prevented. The major percentage of blood is carried towards the heart from the legs through deep veins. The pressure of blood flow is not high in veins therefore the blood can flow back if valves were not there. Also, the valves present in veins assist the flow of blood against the gravity that is in upward direction.

Note: In comparison to veins, arteries are the blood vessels that bring nutrient rich oxygenated blood from the heart to the other parts of the body. The valves are not required by arteries because the heart pumps the blood out with such a pressure that backflow is not possible hence the flow is always directed in one direction.