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In human anatomy, the metacarpal bones or metacarpus, also known as the "palm bones", are the appendicular bones that form the intermediate part of the hand between the phalanges and the carpal bones (wrist bones), which articulate with the forearm. The metacarpal bones are homologous to the metatarsal bones in the foot.
These joints are of the condyloid kind, formed by the reception of the rounded heads of the metacarpal bones into shallow cavities on the proximal ends of the proximal phalanges. [1] Being condyloid, they allow the movements of flexion, extension, abduction, adduction and circumduction (see anatomical terms of motion) at the joint. [1]
The intermetacarpal joints are in the hand formed between the metacarpal bones. The bases of the second, third, fourth and fifth metacarpal bones articulate with one another by small surfaces covered with cartilage. The metacarpal bones are connected together by dorsal, palmar, and interosseous ligaments.
The joints are: In the wrist there is the radiocarpal joint between the radius and carpus. Between the carpal bones are the intercarpal articulations and the midcarpal joint. The carpometacarpal joint connects the carpal bones to the metacarpus or metacarpal bones which are joined at the intermetacarpal articulations.
The metacarpal bone of the index finger has two centres of ossification: a primary centre in the shaft and a secondary centre in the head. This contrasts to the first metacarpal bone where the secondary centre is found in the base. The ossification process begins in the shaft during prenatal life, and in the head between 11th and 22nd months. [4]
The carpometacarpal (CMC) joints are five joints in the wrist that articulate the distal row of carpal bones and the proximal bases of the five metacarpal bones.. The CMC joint of the thumb or the first CMC joint, also known as the trapeziometacarpal (TMC) joint, differs significantly from the other four CMC joints and is therefore described separately.
The fourth metacarpal bone (metacarpal bone of the ring finger) is shorter and smaller than the third. The base is small and quadrilateral; its superior surface presents two facets, a large one medially for articulation with the hamate , and a small one laterally for the capitate .
The third metacarpal bone (metacarpal bone of the middle finger) is a little smaller than the second.. The dorsal aspect of its base presents on its radial side a pyramidal eminence, the styloid process, which extends upward behind the capitate; immediately distal to this is a rough surface for the attachment of the extensor carpi radialis brevis muscle.