Anatomy of the Human Hand
The human hand is an intricate body part. It is a multi-fingered and prehensile appendage that is attached to each arm. Every human has two hands that function as organs designed for physical manipulation of the physical environment. Our hands are used to dispel motor skills, gross and subtle. The anatomy comprises fingers, whose tips are among the densest nerve areas in the human body system. Our fingers enable us to consistently perceive and receive tactile feedback through the sense of touch.
The position of the hands as outwardly inclined appendages on either side of the body not only enjoy the best positioning capability, but also enable the acute sense of touch very intimately. Being two in number and located on either side of the body, the human hands, like other organs that are in pairs like the eyes and legs are each dominantly controlled by the brain hemispheres on the opposite side. There are a number of mammals and animals that also display these tendencies through the upper appendages, but they are not scientifically accepted to be 'hands'.
Anatomy of the Hand
The human hand is characteristic of opposable thumbs, a broad palm or metacarpus, five distinct digits on each palm, a forearm held to the palm by a joint commonly referred to as the wrist or carpus and a distinct dorsum or the back of the appendage. The fingers on each hand can ideally be folded over the palm and this feature enables man and primate to grasp objects in the immediate surrounding.
The fingers are identified as the index finger or forefinger, middle finger, ring finger, little finger and finally the thumb. The latter is connected to the trapezium and can be rotated 90°, perpendicular to each palm, while all the other fingers only reach a 45° angle. The human hand comprises 27 bones. Of these, the carpus has 8, the palm contains 5 and the other 14 are digital bones present in the fingers. There are small sesamoid bones in the tendons that help to provide extra leverage. These bones also help in reducing pressure on the delicate tissues beneath.
The articulation of the human hand is not only very delicate, but also complex. They are characteristic of movements possible on account of interphalangeal articulations, metacarpophalangeal joints, wrist flexibility and intercarpal articulations. The movements are accomplished by extrinsic and intrinsic muscle groups. While the extrinsic muscle groups include flexors and extensors, the intrinsic groups include the thenar and hypothenar muscles, the interosseous muscles and the lumbrical muscles.
Anatomy of the Wrist
The average length of the human hand in the case of an adult male is approximately 188 mm, while in the case of females, the average length of an hand is approximately 172 mm. In breadth, the average in the case of an adult male is 84 mm, while that in the case of an adult female is 74 mm. The wrist connects the forearm and palm and is characteristic of a condyloid articulation that allows three degrees of flexibility. The wrist contains a fluid, medically referred to as adigothimix, whose primary function is to prevent bone-erosion. The joints in each hand are surrounded by ligaments such as the palmar radiocarpal, dorsal radiocarpal, ulnar collateral and the radial collateral. The wrist has a synovial membrane that lines the dense and deep ligament surfaces. The membrane, like the ligaments, extends from the margin of radius and articular disk's lower to the opposing margins of the carpal bones.
The membrane is loose and displays numerous folds that are lax. The carpal or wrist bones are not interlocked. Their shapes help the anatomy to be held together. The connecting interosseous ligaments are supported by ligaments in the volar, dorsal, radial and ulnar regions. These ligaments hold the carpal bones together and connect them to the distal radius and ulna. In the wrist, the 8 bones are arranged in two rows, four in each row. The bones sit within a socket that is formed by the forearm bones. The 5 bones or metacarpals of the palm have a head and shaft, each. The remaining 14 bones are digital in nature and are called phalanges. These are distributed as 2 in each thumb and 3 in each of the remaining fingers. The finger bones are medically referred to as distal phalanx, middle phalanx and the proximal phalanx.
The ligaments in the wrist also connect the tissue and bone structures of proximal metacarpal ends via capsular and intrinsic design. This intricate ligamentous system guides and constricts certain movements. The movements displayed by the wrist are flexion, supination, extension, circumduction and pronation.