Fingers Don’t Contain Muscles

female-rock-climber
 We all have pet-peeves that occasionally happen around us- windshield wipers on when there isn’t enough rain to support lubrication, your husband leaving his dirty laundry on the floor, etc. One of mine is supposed experts in their field saying things about their field that just aren’t true, like a doctor claiming you only use 10% of your brain. In fact, you use all of your brain unless you have brain damage.  (This “brain” myth, incidentally, made it on the list of “Top 7 Medical Myths Even Doctors Believe”- a list compiled by the British Medical Journal after surveying over 1000 doctors.  For the other 6 items, see the BonusFacts below.)

More to the point of this article, I recently had a rock climbing instructor who told me and two other students, “You need to strengthen the muscles in your fingers.” Being someone who knows a little something about anatomy, I wanted
to tell him that would technically be impossible, though not wanting to be a Melvin, I chose to remain silent… at the time. Of course, after the class, I dropped some finger knowledge on my instructor- namely, that fingers don’t contain muscles, at least not ones used to move fingers as he was talking about. (Technically fingers contain many tiny arrector pili muscles, but these have nothing to do with movement of fingers, but rather are attached to hair follicles and can make the hairs on your fingers stand out straight.)
So if there are no muscles in our fingers to move them, what gives all those action movie stars the ability to one-hand a dangling bad guy off a roof? Short answer: magic… err, tendons and ligaments.
Long answer: Each finger consists of three bones (phalanges). They’re named based on where they are in relation to the palm of your hand. There’s the proximal phalange (closest to the palm), the middle phalange, and the distal phalange (farthest from the palm). The first knuckle is called the metacarpophalangeal joint (MCP). (Say that after drinking 3 beers and watch the laughter ensue!) The second knuckle is the proximal inter-phalangeal joint (PIP) and the last knuckle is the distal inter-phalangeal joint (DIP).
In our bodies, tendons generally connect muscle to bone, and ligaments generally connect bone to bone. The tendons that control the bones in our helpful little protrusions are attached to 17 muscles in the palm of your hand and 18 in your forearm- none of which are in your fingers. The muscles that close your hand are known as flexors, and the ones that open your hand are known as extensors. Some are small and help control each individual finger.
The muscles that control your fingers in the palm are known as intrinsic, and the muscles in your forearm are known as extrinsic. The two main extrinsic flexors are the flexor digitorum superficialis and the flexor digitorum profundus. The three main extrinsic extensors are the extensor digitorum, the extensor indicies and the extensor digiti minimi. The muscles in the palm of your hand can be broken down into 4 types, known as interossei, thenar, hypothenar, and lumbricals.
While you probably won’t remember the names of the muscles that control your fingers, you can at least feed your inner-Melvin knowing none of them actually reside there.  This is probably for the best considering the sheer size of the muscles, if they did reside in your fingers, would probably make range of motion almost nothing unless someone had exceptionally weak fingers.

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