Metacarpal bones
The middle hand bones (lat. Ossa metacarpi) consist of five tubular bones. They are each divided into a base, a shaft and a head. The metacarpal bones form the connection between the carpal bones and the finger bones.
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Anatomy
Anatomy of the metacarpal bones
The metacarpals are five tubular bones positioned between the carpal bones and the phalanges. They form the basic bony structure of the metacarpus. For the anatomical designation of the five bones, they are numbered from lateral to medial:
The os metacarpale primum (os metacarpale I) has a connection to the thumb bones as well as to the large polygon.
The longest metacarpal bone is the os metacarpale secundum (os metacarpale II). It is connected to the large and small polygon and carries the bones of the index finger.
Through the os metacarpale tertium (os metacarpale III) the head bone and the middle finger bones are connected to each other.
The ring finger is carried by the os metacarpale quartum (os metacarpale IV). This metacarpal bone articulates with the capitate bone and the hamate bone.
The last metacarpal bone, the os metacarpale quintum (os metacarpale V), is connected to the hooked bone and carries the bones of the little finger.
The individual bones are divided into three structures. The base ossis metacarpus has a cubic shape and is connected to the distal surfaces of the carpal bones. The base, the proximal end piece, is significantly thicker than the shaft that follows it. The long shaft of the metacarpal bones is called the corpus ossis metacarpi. It has an approximately triangular cross-section. The side of the metacarpal bones facing the phalanges is called caput ossis metacarpi and has a cartilaginous surface which is convex.
The shortest of these tubular bones is the os metacarpale I. The adjacent os metacarpale II is the longest metacarpal bone. As a result, the length of the individual metacarpal bones decreases towards the ulna.
Function
The metacarpals form the bony base of the palm. Since the metacarpus is made up of individual tubular bones that run in a ray-like manner, the elasticity of the hand is given. The slightly splayed position of the os metacarpale I allows the thumb to protrude significantly.
Development
The metacarpals are each formed by an epiphysis and a diaphysis. The ossification of the shafts of the metacarpals takes place from the ninth week of embryonic development. The fusion of the pineal nuclei with the shaft sections does not take place until between the ages of 16 and 18.
