Hand bones

A hand is a prehensile, multi-fingered appendage located at the end of the forearm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs. A few other vertebrates such as the koala (which has two opposable thumbs on each 'hand' and fingerprints extremely similar to human fingerprints) are often described as having 'hands' instead of paws on their front limbs. The raccoon is usually described as having 'hands' though opposable thumbs are lacking.Illustration of Hand and Wrist Bones.Bones of the left hand. Volar surface.Bones of the left hand. Dorsal surface.Static adult human physical characteristics of the hand.Cuban doctor checks the hand of a patient. Sara, Guinea-Bissau, liberated zones, 1974Hard hands of a young girl in Algeria.A picture of an ordinary hand A hand is a prehensile, multi-fingered appendage located at the end of the forearm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs. A few other vertebrates such as the koala (which has two opposable thumbs on each 'hand' and fingerprints extremely similar to human fingerprints) are often described as having 'hands' instead of paws on their front limbs. The raccoon is usually described as having 'hands' though opposable thumbs are lacking. Some evolutionary anatomists use the term hand to refer to the appendage of digits on the forelimb more generally — for example, in the context of whether the three digits of the bird hand involved the same homologous loss of two digits as in the dinosaur hand. The human hand normally has five digits: four fingers plus one thumb; these are often referred to collectively as five fingers, however, whereby the thumb is included as one of the fingers. It has 27 bones, not including the sesamoid bone, the number of which varies between people, 14 of which are the phalanges (proximal, intermediate and distal) of the fingers and thumb. The metacarpal bones connect the fingers and the carpal bones of the wrist. Each human hand has five metacarpals and eight carpal bones. Fingers contain some of the densest areas of nerve endings in the body, and are the richest source of tactile feedback. They also have the greatest positioning capability of the body; thus, the sense of touch is intimately associated with hands. Like other paired organs (eyes, feet, legs) each hand is dominantly controlled by the opposing brain hemisphere, so that handedness—the preferred hand choice for single-handed activities such as writing with a pencil, reflects individual brain functioning. Among humans, the hands play an important function in body language and sign language. Likewise the ten digits of two hands, and the twelve phalanges of four fingers (touchable by the thumb) have given rise to number systems and calculation techniques. Many mammals and other animals have grasping appendages similar in form to a hand such as paws, claws, and talons, but these are not scientifically considered to be grasping hands. The scientific use of the term hand in this sense to distinguish the terminations of the front paws from the hind ones is an example of anthropomorphism. The only true grasping hands appear in the mammalian order of primates. Hands must also have opposable thumbs, as described later in the text. The hand is located at the distal end of each arm. Apes and monkeys are sometimes described as having four hands, because the toes are long and the hallux is opposable and looks more like a thumb, thus enabling the feet to be used as hands. The word 'hand' is sometimes used by evolutionary anatomists to refer to the appendage of digits on the forelimb such as when researching the homology between the three digits of the bird hand and the dinosaur hand. An adult human male's hand weighs about a pound.