Today we are discussing the humerus, the bone in your arm, which articulates proximally with the glenoid cavity of the scapula, as discussed yesterday. Distally, at the elbow, it articulates with your two forearm bones – the ulna and the radius (see image on the right). The head of the humerus is quite a bit larger than the glenoid cavity of the scapula, so the shoulder joint has maximized mobility but sacrificed some stability in the process, hence why it dislocates with the right force applied. The joint is reinforced by the four rotator cuff muscles, which attach from the scapula to the humerus.
Chances are you or someone you know has referred to your distal humerus as the “funny bone” due to a tingling sensation you get if you hit your inner elbow in just the right spot. The reason for that is because the ulnar nerve is running right behind the medial epicondyle of the humerus (see the labeled image below). The ulnar nerve courses very superficially, just under the skin, and the shock sensation comes from the momentary entrapment of the ulnar nerve against the medial epicondyle.
And that’s a wrap on your funny bone – tomorrow we explore the first of your two forearm bones, the ulna.
REFERENCES & MORE TO EXPLORE
The Humerus. TeachMe Anatomy Series. 2020
Humerus. Encyclopaedia Britannica. Anatomy & Physiology. 2020