<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> <P> A number of genetic disorders affect the hand . Polydactyly is the presence of more than the usual number of fingers . One of the disorders that can cause this is Catel - Manzke syndrome . The fingers may be fused in a disorder known as syndactyly . Or there may be an absence of one or more central fingers--a condition known as ectrodactyly . Additionally, some people are born without one or both hands (amelia). </P> <P> There are several cutaneous conditions that can affect the hand including the nails . </P> <P> The autoimmune disease rheumatoid arthritis can affect the hand, particularly the joints of the fingers . </P>

How many ligaments are in the human hand