The upper ends of the forearm bones articulate with each other in a:1. pivot joint2. ellipsoid joint3. saddle joint4. hinge joint

The upper ends of the forearm bones articulate with each other in a: 1. pivot joint 2. ellipsoid joint 3. saddle joint 4. hinge joint

To determine the correct answer, we need to understand the characteristics of each type of joint and compare them to the articulation of the forearm bones.

1. Pivot joint: This type of joint allows rotation around a central axis. It is commonly found in the neck and allows for the rotation of the head. However, the forearm bones do not rotate around a central axis, so a pivot joint is not the correct answer.

2. Ellipsoid joint: This type of joint allows movement in two planes, such as flexion and extension, as well as abduction and adduction. The articulation of the forearm bones does involve movement in multiple planes, so an ellipsoid joint is a possibility.

3. Saddle joint: This type of joint allows movement in two planes, similar to an ellipsoid joint. However, a saddle joint also allows for a greater range of motion and is typically found in the thumb. The forearm bones do not have the same range of motion as a saddle joint, so this is not the correct answer.

4. Hinge joint: This type of joint allows movement in only one plane, such as flexion and extension. The articulation of the forearm bones primarily involves flexion and extension, making a hinge joint the most likely answer.

Therefore, the correct answer is 4. hinge joint.