The upper arm is connected to the shoulder joint by the head of the humerus, which fits into the glenoid cavity of the scapula (shoulder blade).
Understanding the Shoulder Joint Connection
The shoulder joint, also known as the glenohumeral joint, is a ball-and-socket joint. This means the round head of the humerus (the long bone of the upper arm) sits within a cup-like socket on the scapula. This articulation allows for a wide range of motion in the arm, including flexion, extension, abduction, adduction, internal rotation, and external rotation.
- Humerus: The upper arm bone, featuring a rounded head at its proximal end.
- Scapula (Shoulder Blade): The flat, triangular bone that forms part of the shoulder girdle. The glenoid cavity, a shallow socket on the scapula, receives the humeral head.
- Glenoid Cavity: The shallow socket on the scapula that articulates with the humeral head. It's important to note that the glenoid cavity itself is relatively shallow, contributing to the shoulder's great range of motion but also making it prone to instability.
The stability of the shoulder joint is not solely reliant on the bony articulation but also involves a complex interplay of muscles, tendons, ligaments, and the surrounding soft tissues. These structures work together to hold the humeral head securely in the glenoid cavity while allowing for the extensive range of movement.
The reference material states: "The shoulder joint connects the upper arm to the shoulder blade. This is where the round head of the upper arm bone (head of the humerus) rests in the shoulder socket (glenoid) at the side of the shoulder blade." This accurately describes the primary connection between the upper arm and shoulder.
