Synonym: DigitusThe hand has a total of five fingers (Digiti), of which the thumb (Pollex) is the first. It is followed by the index finger (index) and the middle finger (digitus medius), which is also the longest of all fingers. The fourth finger is called the ring finger (digitus anularius), followed by the so-called little finger (digitus minimus).
Each of these fingers consists of several finger bones (Ossa digitorum manus), in anatomy they are called phalanx, which means “fighting row”. Each individual finger has exactly three phalanges, but the thumb is an exception, with only two phalanges. Starting from the metacarpal bones (Os metacarpi), the first phalanx (phalanx proximalis) is an elongated bone whose body resembles the structure of a cylinder divided lengthwise.
The term “proximalis” or “proximal” means translated “pointing towards the trunk of the body”. On one side, this part of the finger has a small canal in which parts of the tendons of some flexor muscles (flexors) are located. At the end of the finger bone, a small bulge can be seen where the head (caput) of the respective metacarpal connects.
The length of this first phalanx is different for each of the five fingers. The longest bone is found in the middle finger, followed by the index and ring fingers. The second phalanx (phalanx media) differs from the first phalanx only in its shorter length and special structure of the joint connection with the first phalanx.
The thumb is a special exception here because it does not have a middle phalanx. The third phalanx bones, which are furthest away from the trunk, are connected to the phalanx media by joints and also serve to support the fingernails. Each phalanx has three sections, a base (facing the trunk), a head (facing away from the trunk) and a body.
There are five basic finger joints per hand, which from an anatomical point of view are so-called ball joints. In these articulated bony connections, the outwardly curved (convex) joint head of the metacarpals is connected to the inwardly curved (concave) joint sockets of the first phalanges. In most of the five metacarpophalangeal joints, however, the rotational movement (rotation) is very limited.
The capsule is elastic and is reinforced by extremely resistant lateral ligaments. For this reason, abduction is hardly possible in a bent finger position. The basic joints of the fingers are therefore anatomically ball joints, but functionally they are so-called egg joints.
