Veins

Veins are blood vessels that return deoxygenated blood from the peripheral tissues back to the heart.

They are highly compliant, low-pressure capacitance vessels that accommodate approximately two-thirds of the total blood volume in the body and serve as a functional blood reservoir.

Veins are anatomically classified as superficial (located between the dermis and muscle fascia), deep (located deep to the muscle fascia and accompanying major arteries), and perforator veins (which connect superficial and deep systems).