Answer :
Final answer:
Valves in the veins of the lower limbs assist in maintaining unidirectional blood flow towards the heart, even under lower pressure. They prevent backflow of blood as they open when skeletal muscles contract, thus ensuring blood does not pool in the lower limbs.
Explanation:
Valves present in the veins of lower limbs play a vital role in ensuring unidirectional blood flow towards the heart. Particularly, when blood passes from capillaries into veins, the pressure exerted by heart contractions on the blood diminishes significantly. Veins and venules withstand lower pressure as compared to arteries due to their thinner walls and larger diameters.
Crucially, the valves in our limbs (especially lower limbs) facilitate the steady, upward flow of blood against gravity. When surrounding skeletal muscles contract, such as during walking, these valves prevent the backflow of blood towards the feet.
Skeletal muscle contraction squeezes nearby veins, causing blood to flow upward, opening valves above the contracting muscles. This prevents blood from pooling in lower limbs, which otherwise could lead to conditions like edema – the accumulation of excess tissue fluid around cells.
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