Thumb

The thumb (Latin: pollex ) is the first and strongest of the five fingers of one hand and takes with the other fingers because of its movement possibilities a special position.

In contrast to the other fingers, he is anatomically only two phalanx bones, and proximal phalanx distalis. Functionally, but also the first metacarpal of the thumb metacarpal are belong counted. Its articulation by means of the thumb saddle joint allows for increased freedom of movement of the thumb. At the distal end of the metacarpal often there is a sesamoid bone.

Functional possibilities

All Old World monkeys have an opposable thumb. The opposition position of the thumb maintains the gripping and improves grip function key - an evolutionary leap in development of these primates to non- Old World monkeys and other mammals. Non- Old World monkeys can Thumb adduction only, not oppose. In primates with opponierbarem thumb muscles of the thumb is very differentiated pronounced and there are a total of nine individual muscles with different functions grouped around him. This limits the thumb significantly from the other fingers. Therefore, it is seen evolutionarily also no finger in the proper sense. Also responsible for the movement and sensitivity of the thumb areas of the brain are significantly larger than those of the other fingers. The thumb finger nail grows the slowest of all, and rolls if you can grow long enough it together into a spiral. Some people have the ability to bend back the end link of the thumb up almost at right angles. This property is not controlled by a single gene and is often mistakenly used as a simple example of the basis of heredity.

Anomaly

A notable anomaly of the thumb is the brachydactyly type D. Here, shortened the end link of the thumb and the associated fingernail. Shape and degree of severity can vary greatly, with women being affected more often than men. It occurs in addition to a two-sided and one-sided expression.

Word origin

Ahd. Dum ( o), MHG Dume. From the West Germanic word * Thuman, literally " particularly strong ( er) or strong (er) (finger) ", but also " thumb-width, inches ". On präindogermanisch * tum- due (cf. Latin tumere be " swollen " or tumor).

Expressions

Because of the particularity of the thumb under the fingers, numerous human expressions with the thumb have been formed:

• The rule of thumb
• Green Thumb for people with skill in dealing with plants,
• Fingers crossed, if you wish someone good starting a company,
• Turn thumbs or thumbs turn as an expression of boredom,
• Rule of thumb "about" as a synonym for,
• Thumb jump, estimating the distance with the help of his own thumb ( " over the thumb aiming ")
• As Tom Thumb a human figure is referred to in the fairy tale, which is no bigger than a thumb,
• Geldzähldaumen people (90 degrees) can bend over stretching out their Daumenendglieder have right angles (thumb reflection). Most passively by back pressure, but also actively by muscle power. Especially frequently it occurs in girls and women.
• Thumbs draufhaben: the symbolism is derived from the special function for the grasping.
• The thumb nail - in the English translation " thumbnail " - as the name for a preview image.