<P> There is a considerable variation to this general pattern, except for the little finger and volar surface of the index finger . For example, in some individuals, the ulnar nerve supplies the entire ring finger and the ulnar side of the middle finger, whilst, in others, the median nerve supplies the entire ring finger . </P> <P> The glabrous (hairless) skin on the front of the hand, the palm, is relatively thick and can be bent along the hand's flexure lines where the skin is tightly bound to the underlying tissue and bones . Compared to the rest of the body's skin, the hands' palms (as well as the soles of the feet) are usually lighter--and even much lighter in dark - skinned individuals, compared to the other side of the hand . Indeed, genes specifically expressed in the dermis of palmoplantar skin inhibit melanin production and thus the ability to tan, and promote the thickening of the stratum lucidum and stratum corneum layers of the epidermis . All parts of the skin involved in grasping are covered by papillary ridges (fingerprints) acting as friction pads . In contrast, the hairy skin on the dorsal side is thin, soft, and pliable, so that the skin can recoil when the fingers are stretched . On the dorsal side, the skin can be moved across the hand up to 3 cm (1.2 in); an important input the cutaneous mechanoreceptors . </P> <P> The web of the hand is a "fold of skin which connects the digits". These webs, located between each set of digits, are known as skin folds (interdigital folds or plica interdigitalis). They are defined as "one of the folds of skin, or rudimentary web, between the fingers and toes". </P> <P> The ratio of the length of the index finger to the length of the ring finger in adults is affected by the level of exposure to male sex hormones of the embryo in utero . This digit ratio is below 1 for both sexes but it is lower in males than in females on average . </P>

How many bones in human hands and feet