The upper arm and shoulder form a complex network of bones, muscles, ligaments, and joints that provide structure and allow for a wide range of motion.
The structure of the upper arm and shoulder allows for a wide range of movements, including lifting, pulling, and pushing. However, this area can be prone to injury and conditions such as rotator cuff tears, shoulder impingement, and biceps tendonitis.
Here’s a breakdown of the key components:
Bones: The humerus is the long bone of the upper arm, extending from the shoulder to the elbow. The shoulder joint is formed where the humerus fits into the scapula (shoulder blade) in a socket called the glenoid fossa. The clavicle (collarbone) also plays a crucial role in the shoulder, connecting the scapula to the sternum (breastbone).
The shoulder is a complex joint system that includes three bones:
Muscles: The shoulder is composed of several muscles that provide movement and stability:
Ligaments: Ligaments are tough bands of tissue that connect bones to each other, providing stability to the joints. In the shoulder, the joint capsule is a group of ligaments that surround the shoulder joint. The rotator cuff tendons are particularly important for shoulder movement and stability. The biceps tendon attaches the biceps muscle to the shoulder and the elbow, allowing it to control arm rotation and flexion.
Several ligaments contribute to the stability of the shoulder:
Nerves: The brachial plexus is a network of nerves that originates from the neck and provides sensation and motor control to the shoulder, arm, and hand.
Blood Supply: The axillary artery, a continuation of the subclavian artery, and its branches supply blood to the shoulder and upper arm.
Fascial Compartments: The shoulder does not have true anatomical compartments like the lower limbs. However, it is divided into an anterior and posterior region by the scapula, with each region containing specific muscles.
The shoulder comprises three joints:
Bursa Sacs: The primary bursa in the shoulder is the subacromial bursa, located under the acromion. It reduces friction between the acromion and the rotator cuff tendons.
Kinesiology: The kinesiology of the shoulder involves a wide range of movements:
Understanding the anatomy and kinesiology of the shoulder is critical in diagnosing and treating shoulder pathologies, designing rehabilitation programs, and in preventing injuries.