01 / Location & anatomical relationships
On the side of your hand, near the wrist.
02 / Structure & organization
The thumb has two phalanges and a highly mobile first carpometacarpal joint between the trapezium and first metacarpal. Thenar muscles contribute to opposition, which combines several movements to bring the thumb pad toward the fingers.
03 / Function
This movement helps you grip objects such as a pencil.
04 / Mechanism
A special joint at its base allows the thumb to move across the palm. It can meet the fingertips for a precise pinch or wrap around an object for a strong grip. Small hand muscles control these movements.
Part of a bigger picture
The thumb belongs in our arms & hands collection. Explore the nearby parts to see how this area of the body fits together.
Explore arms & hands →FOR DEEPER STUDY
Connect structure with function
Opposition is more than simple flexion. The orientation of the thumb makes precise pad-to-pad contact possible and distinguishes many human hand grips.
Check your understanding
Locate the thumb in relation to its neighbors. Explain how the structural features described above support its function, then distinguish it from a nearby structure with a different role.
Keep learning
Continue with OpenStax Anatomy and Physiology for system-level study. This atlas is educational and has not undergone independent medical peer review.