• Describe the structures present in this area including: skin, muscles, connective tissue (tendons/ligaments/etc), bone and nerves. Describe these structures with specific anatomical terms so you can discuss how they work together
• Use directional terms to describe the comparative locations such as superior to, inferior to, anterior, etc.

The shoulder is a fascinating joint with a complex anatomy and made up of different structures. It has the greatest range of motion of all the joints in the body, which in turn makes it a joint susceptible to many pathologies.

The shoulder is made up of several joints that must work together to give a harmonious global movement. The shoulder joint complex or shoulder joint is made up of:

Humerus

Clavicle

Scapula (or shoulder blade)

Breastbone

These 4 bones form 5 joints, which must have a harmonious and congruent movement for the correct execution of their different movements:

Scapulohumeral joint

Subdeltoid joint

Acromioclavicular joint

Sternocostocalvicular joint

Scapulo-thoracic joint

Bursae are structures that are in all joints of the body. Its function is to reduce friction or friction between the structures that make up a joint. On the shoulder in particular, they are located:

on the tendons and muscles of the rotator cuff and acromion; and between the rotator cuff and the deltoid muscle.

The shoulder muscles involved in the movements you perform are:

Angular scapulae or levator scapulae, coracobrachialis, deltoid, latissimus dorsi, sternocleidomastoid, infraspinatus, supraspinatus, teres major and minor, rhomboids major and minor, subclavian, subscapular, trapezius, diaphragm, serratus major, omohyoid, long bicep triceps, pectoralis major, etc; in addition to the endothoracic fasciae.

The stability of the shoulder derives from the short rotator muscles of the humerus in the inferior aspect; supraspinatus on upper side; infraspinatus and teres minor on posterior side; and the subscapularis on the anterior side. The joint capsule is supported by two musculotendinous layers: the inner, the rotator cuff; and the external one, formed by the deltoid plus the teres minor

The normal movements of the shoulder are quite wide: abduction goes from 0 to 180 degrees and is given by the rotator cuff (supraspinatus, infraspinatus, teres minor, subscapularis) plus the deltoid, plus the long portion of the biceps; the adduction ranges from 0 to 45 degrees and is given by the pectoralis major, latissimus dorsi and deltoid; Rotation, both external and internal, is 0 to 90 degrees depending on the rotator cuff, latissimus dorsi, and deltoid; the flexion ranges from 0 to 180 degrees and is given by the pectoralis major, the deltoid, and the long and short portion of the biceps; the extension, from 0 to 60 degrees, depends on the deltoid and the pectoralis.

The tendons are in charge of connecting the muscles with the bones. The biceps tendon runs from the biceps muscle, across the front of the shoulder, to insert into the top of the glenoid, joining here with the labrum.

The rotator cuff tendons are the next layer that we find in the shoulder joint. These constitute a total of four tendons that connect the deepest layer of muscles with the humerus.

All nerves to the arm and hand pass through the shoulder and enter the arm through the front and bottom of the armpit. The main nerves that go to the arm are:

Ulnar nerve

Median nerve

Radial nerve

Musculocutaneous Nerve

Axillary Nerve

Through the nerves, the motor signals that activate the muscle plate are sent and the sensory signals are also received through the skin and sensors that carry information to the brain.

In addition to important nerves, the arteries and veins that supply the arm, forearm and hand also pass through the shoulder. The axillary artery travels below the armpit, its branches reaching the humeral head and other structures around the shoulder.