What best describes the anatomical structure of the humeral head in normal conditions?

The description of the humeral head as a sphere is accurate because the humeral head has a nearly spherical shape that allows it to articulate smoothly with the glenoid cavity of the scapula. This spherical structure is crucial for the functional range of motion in the shoulder joint, facilitating movement in multiple directions, such as flexion, extension, abduction, adduction, and rotation.

This spherical anatomy also plays a significant role in distributing forces during various shoulder activities, helping to maintain the joint's stability and integrity. A proper understanding of the spherical nature of the humeral head is essential in total shoulder arthroplasty, as it informs the design and implantation of the prosthesis to ensure optimal function and alignment with the glenoid.

In contrast, other shapes, such as flat, irregular, or concave, do not accurately represent the anatomy of the humeral head, which is specifically adapted to its role in a ball-and-socket joint.