The palm has 5 bones , one to each of the 5 digits. These metacarpals have a head and a shaft. The bones of the distal row are : trapezium, trapezoid, capitate and hamate
The back of the hand is formally called the dorsum of the hand. The human hand consists of a broad palm with 5 digits, attached to the forearm by a joint called the wrist
Like other paired organs , each hand is dominantly controlled by the opposing brain hemisphere, and thus handedness, or preferred hand choice for single-handed activities such as writing with a pen, reflects a significant individual trait. They are the chief organs for physically manipulating the environment, using anywhere from the roughest motor skills to the finest , and since the fingertips contain some of the densest areas of nerve endings on the human body, they are also the richest source of tactile feedback so that sense of touch is intimately associated with human hands. The hands are the two intricate, prehensile, multi-fingered body parts normally located at the end of each arm of a human or other primate
Each finger, starting with the one closest to the thumb, has a colloquial name to distinguish it from the others:. The four fingers on the hand are used for the outermost performance; these four digits can be folded over the palm which allows the grasping of objects
Human hands contain 14 digital bones, also called phalanx bones: 2 in the thumb and 3 in each of the four fingers. These are:
The scientific use of the term hand to distinguish the terminations of the front paws from the hind ones is an example of anthropomorphism. 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 hands. The only true hands appear in the mammalian order of primates. Hands must also have opposable thumbs, as described later in the text
The human hand has 27 bones: the carpus or wrist account for 8; the metacarpus or palm contains 5; the remaining 14 are digital bones; fingers and thumb. The bones of proximal row are : scaphoid, lunate, triquetral and pisiform. The eight bones of the wrist are arranged in two rows of four. These bones fit into a shallow socket formed by the bones of the forearm
The thumb can be easily rotated 90°, on a level perpendicular to the palm, unlike the other fingers which can only be rotated approximately 45°. Opposable thumbs are identified by the ability to be brought opposite to the fingers, a muscle action known as opposition. The thumb is located on one of the sides, parallel to the arm. A reliable way of identifying true hands is from the presence of opposable thumbs
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. Humans have only two hands , which are attached to the arms. Also, some apes have toes that are longer than human fingers
Sesamoid bones are small ossified nodes embedded in the tendons to provide extra leverage and reduce pressure on the underlying tissue. Many exist around the palm at the bases of the digits; the exact number varies between different people
These muscles arise from the deep flexor and insert on the dorsal extensor hood mechanism. The intrinsic muscle groups are the thenar and hypothenar muscles , the interosseus muscles and the lumbrical muscles
The extrinsic muscle groups are the long flexors and extensors. They are called extrinsic because the muscle belly is located on the forearm. They can be subdivided into two groups: the extrinsic and intrinsic muscle groups. The movements of the human hand are accomplished by two sets of each of these tissues
The articulations are:
The hand can also form a fist, for example in combat, or as a gesture. Also of note is that the articulation of the human hand is more complex and delicate than that of comparable organs in any other animals. Without this extra articulation, we would not be able to operate a wide variety of tools and devices