In contrast to the other fingers, it anatomically consists of only two phalanx bones , the phalanx proximalis and distalis . Functionally, however, the first metacarpal bone ( os metacarpale I ) can also be counted as belonging to the thumb. Its articulation by means of the thumb saddle joint enables increased freedom of movement of the thumb. There is often a sesamoid bone at the distal end of the first metacarpal .
All Old World monkeys have an opposable thumb. The opposing position of the thumb enables the fist to be closed and improves the grip function significantly - an evolutionary leap in development of these primates compared to New World monkeys and other mammals. New World monkeys can only adduct the thumb , not oppose it. In primates with an opposable thumb, the muscles of the thumb are very differentiated and a total of nine individual muscles with different functions are grouped around it. This clearly separates the thumb from the other fingers. Therefore, from an evolutionary point of view, it is not actually a finger. The brain areas responsible for the movement and sensitivity of the thumb are also significantly larger than those of the other fingers. The thumb fingernail grows the slowest of all and, if allowed to grow long enough, will curl into a spiral. Some people have the ability to bend the end of the thumb back almost at a right angle. This trait is not controlled by a single gene and is often mistakenly used as a simple example of the basics of inheritance.
History of the origin of the thumb joint
Up to 80% of women over the age of 40 are affected by rhizarthrosis . This is due to a growth disorder, which means that the saddle of the saddle joint in women is often inclined. The fact that rhizarthrosis is so common is related to the fact that the thumb joint in question - measured by the length of the history of human development - is relatively "young", namely eight million years. Only through this special joint did humans have the opportunity to hold objects properly and, for example, to play the flute. But because this joint was created very late in the history of human development and is therefore relatively "young", it is not yet perfectly developed and not as resilient as it would be desirable.
A notable abnormality of the thumb is brachydactyly type D. Here, the end phalanx of the thumb and the associated fingernail are shortened. The shape and degree of expression can vary, with women being more often affected than men. In addition to a bilateral expression, there is also a one-sided expression.
Ahd. Dum (o) , mhd. Dume . From the West Germanic word * thuman- , literally "particularly strong (he) or strong (he) (finger)", but also "thumb's width, inch". To be traced back to pre-Indo-European * tum- (compare Latin tumere “to be swollen” or tumor ).
Because of the peculiarity of the thumb under the human fingers, numerous expressions have been formed with the thumb:
- Rule of thumb
- Green thumb for people with skill in handling plants,
- keep your fingers crossed when you wish someone a good end to a company,
- Turn your thumbs or thumbs as an expression of boredom ,
- Pi of thumb "about" a synonym for,
- Jump of the thumb , estimate the distance with the help of your own thumb ( "look over the thumb" ),
- As Däumling in Wonderland a human figure is referred to, which is not greater than a thumb,
- Money counter thumbs have people who can bend their thumb phalanges at right angles (90 degrees) beyond the extension (thumb reflection). Mostly passively through counter pressure, but also actively through muscle power. It is particularly common among girls and women.
- Have your thumb on it : the symbolism is derived from the special function for grasping.
- "Thumbnail" - as a name for a thumbnail (only the size of a thumbnail ) .
- as a nickname or epithet , e.g. B. Ulrich with the thumb
- Saddle joint
- In the Allgäu Alps there is a 2280-meter-high mountain called Big Thumb .
In Beccles , a small town in Suffolk ( England ), which is held annually in the summer World Cup in the thumb-wrestling ( "World Thumb Wrestling Championship") instead. The British Paul Browse won the men's world championship for the fourth time in a row in 2019. His mother-in-law won the women's competition.
- Friderun Ankel-Simons: Postcranial Skeleton. In: Primate Anatomy (3rd edition), Academic Press, Burlington, 2007, p. 346, ISBN 978-0-12-372576-9 , doi : 10.1016 / B978-012372576-9 / 50010-3
- Hitchhiker's thumb: The myth http://udel.edu/~mcdonald/myththumb.html
- Sebastian Knoppik: When the rider slips off the saddle. Hildesheim hand surgeon Rieck provides information about special forms of osteoarthritis at the Sarstedt patient forum. In: "Leine Nachrichten" issue 21/2016 from January 26th, 2016 (supplement of the Hannoversche Allgemeine Zeitung).
- H. Piza-Katzer, A. Wenger: Congenital malformations of the hand. In: H. Towfigh, R. Hierner, M. Langer, R. Friedel (Eds.) Handchirurgie. Springer, Berlin / Heidelberg 2011, ISBN 978-3-642-11757-2 , pp. 514-516.
- Event website
- Sports show video of the decision