Phalanges
The finger bones (lat. Ossa digitorum manus) are formed by 14 tubular bones. These are the phalanges of the fingers and serve as supporting elements. Each finger has three phalanges, except the thumb. The thumb has only two phalanges, the phalanx media is missing. Thus the fingers correspond to the basic structure for phalanges of mammals (2-3-3-3-3).
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Anatomy
The phalanges consist of 14 tubular bones. These represent the phlanges of the hand. They are the end phalanges of the hand and therefore connect distally to the five middle hand bones. The individual bone elements are divided between the individual fingers. All fingers consist of three phalanges, except the thumb which consists of only two phalanges.
Because of this subdivision, the phalanges are called differently. The finger elements close to the body are the palanx proximalis. The distal ones are called the phalanx distalis. Between these are the phalanx media. The phalanx media is missing on the thumb, so it consists only of the proximal phalanx and distal phalanx.
The individual phalanges can also be structurally subdivided according to their affiliation to the tubular bones. Each bone element is divided into the head, the shaft and the base.
The head is called caput phalangis and represents the distal end of the bone. It is flattened at the distal phalangis where no other bone is adjacent.
The proximal end of the tubular bone is called the base phalangis. In the phalanx proximalis, this part has a concave base which is connected to the respective metacarpal bone.
Between the base and the head of the phalanges is the shaft, the corpus phalangis. It is a somewhat narrower area and has a columnar-like shape.
The proximal phalanx is also called the phalanx of the finger and is the longest of the three bone links. Its base meets the corresponding metacarpal. The distal end articulates with the phalanx media in each finger. The thumb is an exception to this rule. There the phalanx proximalis is directly connected to the phalanx distalis.
The phalanx media is located in the middle of the phalange row. It is medium in size and its base has a larger diameter than the distal end. At the head of this phalange there are two small bony elevations. The proximal end connects to the phalanges. The distal end is followed by the distal phalanx.
The distal limb of the entire upper extremity is the distal phalanx. It is always the shortest of the phalanges. The base articulates with the phalanx media, except at the thumb where it is directly connected to the phalanx distalis.
Function
A series of finger joints are formed by the individual phalanges. This is how the large range of movement of the fingers is created. Furthermore, the phalanges serve as basic support structures for the fingers. The end phalanx is also the basis for the fingernail above it.
Movements
The high number of finger joints formed by the bones produces a large range of movement in the finger area. The joints between the individual types of phalanges can perform extension and flexion over a degree of freedom. The thumb can perform abduction and adduction in addition to flexion and extension due to its position in a saddle joint. Here, the thumb is placed opposite the other fingers so that the targeted interaction between thumb and other fingers can be performed. Powerful and precise grips are thus possible.
Development
The phalanges are formed both by the diaphysis in the embryonic period and by the epiphysis after birth. The primary bone nuclei are formed before birth. The secondary ones follow around the twelfth month of life. Around the age of 16 or 17 the epiphyseal fugues close.
