MadSci Network: Anatomy

Re: How many bones, muscles, and tendons are in your hand?

Date: Thu Jan 8 15:53:30 2004
Posted By: Paul Odgren, Assistant Professor, Dept. of Cell Biology
Area of science: Anatomy
ID: 1072754864.An

Dear Sarah,

Interesting question. 

There are 26 bones, including 7 in the wrist and 19 in the fingers and 
thumb (four for each finger and three for the thumb) in a normal adult 
hand. In children, it takes until about age 6 or 7 for all the wrist bones 
to fully form and become hardened. The number of tendons and muscles is 
higher, but also much harder to put exact numbers on. Your wrist is chock 
full of muscles and tendons that control the hand and fingers, and there 
are many that are in the hand, plus some that are partly in both. For 
every finger and the thumb, there are at least three pairs of what are 
called “flexors” (or “abductors”) and “extensors,” i.e., muscles with 
tendons connected to them that curl (flexors) or open (extensors) the 
fingers and thumb. Some bend the digit at the first knuckle, as when you 
point at something and move your index finger up or down, and some curl 
the rest of the finger or thumb, as when you make a fist. Then there are 
muscles that move the fingers sideways, as when you spread your hand. Many 
of the muscles and tendons split at either end and connect to two 
different fingers, and there may be more than one name for different 
parts. All together, 4 fingers plus one thumb is 5, times at least 3 
motions is 15, times 2 directions is 30, plus quite a few others that are 
involved in things like cupping the hand or compressing the palm when you 
move the thumb toward the little finger. The muscles for the sideways 
motions and for compressing the palm are in the hand itself, and all the 
tendons are at least partly within the hand. Roughly speaking, there are 
about 40 tendons and 20 muscles within the hand, and another 20 muscles in 
the wrist that connect to the hand and fingers through tendons. 

I hope this answers your question.

Paul Odgren, Ph.D.
Department of Cell Biology
University of Massachusetts Medical School, Worcester

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