Metacarpus

The metacarpal bone ( metacarpal bones, MC ) form the basis of the metacarpal bone. These are broken down to bones, in a base ( base metacarpi ), a body ( corpus metacarpal ) and the direction of finger bones lying head (caput metacarpi ).

Metacarpal bone of the human

In humans, there are a total of five metacarpals, which are arranged almost in parallel. The second and third metacarpal bones are longest, which first is the shortest. The spaces between the metacarpal bones ( Spatia interosseous metacarpal ) are filled interossei of the musculi.

The broad base of the metacarpal bone has a cubic basic form. Your hyaline curved inward ( concave ) surfaces of cartilage associated with the distal row of carpal bones (ossa carpi ) of the wrist ( carpus ), in conjunction and in their totality form the carpometacarpal joints, the first of which is called the carpometacarpal joint. The base of the third metacarpal bone carries a styloid process ( styloid process ), where the extensor carpi radialis brevis muscle attaches.

The shaft has a triangular cross-section. In the basic anatomical position - also called anatomical neutral position ( palms facing forward ) - shows the tip of the triangle to the front, the base for the back of the hand. This site is in the distal portion of metacarpal bone an almost perfectly level surface over which the tendons of the flexor run. The other two sides, that the medial and lateral side of the metacarpal bones are curved inward. Here the musculi interossei put on. Front collide in a Knochengrat.

The head of the metacarpal bone has an outwardly curved (convex ) Cartilage surface whose expansion in the front - rear ( anteroposterior ) direction is larger than in the horizontal ( transverse ) direction. This cartilage surfaces forming the joint head of the metacarpophalangeal joints. On both sides of the bowl, small nodules found ( tubercles ). From here, the five fingers of the hand rays have their origin. The metacarpal is guided and stabilized by taut bands in the lateral direction, the lateral ligaments ( collateral ligaments ) are each attached to the tubercle of the metacarpophalangeal joints. Borne by the head of the first metacarpal palm side, two small articular facets that are used to connect with the sesamoid bones of the abductor pollicis brevis or flexor pollicis brevis.

Comparative Anatomy

In the course animals it comes with reducing the number of front-toes also to regressions and / or mergers of bone in the metacarpal area. Thus, in a powerful horses metacarpal (MC III " Röhrbein " ) is only formed, which is flanked on both sides by a thin metacarpal (MC II and IV " splint bones ").

Birds have only one metacarpal bone, which is adherent to the lower row of carpal bones and is referred to as Carpometacarpus (→ bird skeleton).