The venous valves of the lower limbs
Alberto Caggiati Department of Anatomy University “La Sapienza”, Rome, Italy ABSTRACT Venous valves appear after the heart begins to beat and the primordial muscles begin to move the limb buds. The pressure gradient due to heart beats and muscle movements triggers the process of venous valve development. Prenatal, postnatal, and senile morphological and numerical rearrangements have been described. However, the signaling pathways related to venous valve morphogenesis have yet to be clearly demonstrated. The cusps of the venous valves consist of thin collagen half-moon–shaped folds covered by endothelium, which spring from the wall of the vein very close to each…