he carpometacarpal joint of the thumb.*1 pointA. Saddle jointB. Hinge jointC. Pivot jointD. Gliding joint

Break Down the Problem

1. Identify the types of joints.
2. Determine the characteristics of the carpometacarpal joint of the thumb.

Relevant Concepts

1. Saddle Joint: Allows movement in two planes, providing stability and flexibility.
2. Hinge Joint: Allows movement predominantly in one plane (flexion and extension).
3. Pivot Joint: Allows rotation around a single axis.
4. Gliding Joint: Allows limited movement in multiple directions but essentially allows gliding movements.

Analysis and Detail

1. The carpometacarpal joint of the thumb is responsible for the unique movement of the thumb, allowing it to cross over the palm.
2. This joint exhibits both flexion/extension and abduction/adduction, characteristic of a saddle joint.

Verify and Summarize

The thumb’s carpometacarpal joint supports complex movements including opposition, an ability unique to humans among primates.

Final Answer

A. Saddle joint is the correct answer, as it accurately describes the motion and structure of the carpometacarpal joint of the thumb.