Question

why are valves are present in heart and veins

Answer 1

$\huge{\mathfrak{HEYA\:MATE\:!!}}$

Answer...

The valves are present in heart and veins to prevent back flow when blood flows at high pressure.

$\mathscr{\large{Hope\:helps\:}}!! \\ \\ {GRACIAS!!}$

$\huge{\red{\ddot{\smile}}}$

Answer 2

the valves are present bcoz to prevent the backflow of the blood into atria when the ventricles contract to pump blood out of the heart to the rest of the body.This is bcoz when the ventricles contract the valves close automatically so the blood may not go back into atria