Final answer:
The head of the radius is the anatomical structure that articulates with the capitulum of the humerus, and this articulation is a key component of the elbow joint.
Step-by-step explanation:
The anatomical structure that articulates with the capitulum of the humerus is the head of the radius. The capitulum, a rounded knob-like structure on the distal end of the humerus, facilitates articulation with the proximal end of the radius, specifically at its disc-shaped head. This joint is part of the elbow, allowing for the movement of the forearm. The head of the radius sits adjacent to the radial notch of the ulna at the proximal radioulnar joint, which allows for the rotation of the forearm. Although the ulna also interacts with the humerus at the elbow joint, it articulates through its trochlear notch with the trochlea of the humerus, not the capitulum