The deep finger flexor
Flexor digitorum profundus · musculus flexor digitorum profundus
The forearm muscle that curls the very tips of your fingers.
What it does
This deep muscle lies against the forearm bones and sends four tendons all the way to the fingertips. It is the only muscle that bends the last joint of the fingers, so it does the hard work of gripping, hanging on and making a tight fist.
Surprising fact
Its tendons pass straight through a slit in the tendons of the superficial flexor in each finger, a neat arrangement that lets both work in the same tight space.
Why it matters
Rock climbers hang from their fingertips using this muscle, and the pulleys that hold its tendons against the finger bones are a common climbing injury.
Nearby
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Sources
Drafted with AI help; awaiting a human fact-check against these sources.
Open in the 3D atlas · Suggest a correction · Not medical advice.
3D models: Z-Anatomy & BodyParts3D (CC BY-SA 4.0 / 2.1 JP). Card text CC BY 4.0.