Hand and Foot

The Hand contains a total of 27 bones and is the most flexible part of the human skeleton. Like other higher primates, humans possess nails instead of claws and have a thumb that can be rotated to oppose the other digits, enabling them to manipulate objects delicately and precisely. Higher primates other than humans, however, also use hands for locomotion; the development of an upright posture and consequent use of the hands for manipulation alone probably took place concurrently with the increase in brain size in humans. Shown here are some of the major muscle and tendon systems for moving the bones of the thumb and other digits.

The human foot differs from the feet of other higher primates in that it is used solely for locomotion, so that the big toe is no longer opposable to the other digits as it is in the great apes. Instead the bones of the feet have evolved in a way that enables humans to stride, and toes other than the big toe begin to show signs of degeneration. The heel bone bears most of the weight of the body and helps to form the longitudinal arch of the foot, along with the transverse arch formed by the metatarsal bones. If the ligamens between the bones weaken, the result is flatfoot, in which all instead of only part of the sole rests on the ground.


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