Shoulder Complex Anatomy

Study Notes

The Shoulder Complex

The shoulder complex enables the hand to be placed in various positions to perform multiple tasks.
The shoulder (glenohumeral joint) is the most mobile joint in the body, allowing for a great deal of motion.

Bone Structure of Shoulder Joint

The scapula is a triangular-shaped bone located superficially on the posterior side of the thorax.
It is slightly concave anteriorly and glides over the convex posterior rib cage.
The scapula serves as an attachment site for 15 major muscles.
In the resting position, the scapula is located between the second and seventh ribs, with the vertebral border approximately 2-3 inches lateral from the spinous processes of the vertebra.

Scapula Attachments

The scapula provides attachment for the upper trapezius muscle laterally.
The superior medial aspect of the scapula provides attachment for the levator scapula muscle.
The most inferior point of the scapula, where the vertebral and axillary borders meet, determines scapular rotation.
The area between the superior and inferior angles medially provides attachment for the rhomboid and serratus anterior muscles.
The projection on the posterior surface of the scapula, running from the medial border laterally to the acromion process, provides attachment for the middle and lower trapezius muscles.
The projection on the anterior surface of the scapula provides attachment for the pectoralis minor muscle.
The broad, flat area on the superior lateral aspect of the scapula provides attachment for the upper trapezius muscle.
The slightly concave surface on the superior lateral side of the scapula articulates with the humerus above the axillary border and below the acromion process.

Clavicle

The clavicle is an S-shaped bone that connects the upper extremity to the axial skeleton at the sternoclavicular joint.
It serves as an attachment site for muscles.
It helps to transmit muscle force to the scapula.
It contributes to the range of motion of the shoulder complex through its articulations with the sternum and acromion.

Sternum

The sternum is a flat bone located in the midline of the anterior thorax.
It is divided into three parts: manubrium, body, and xiphoid process.
The manubrium provides attachment for the clavicle and the first rib.
The body provides attachment for the remaining ribs.
The xiphoid process is the inferior tip of the sternum.

Joints and Ligaments

The sternoclavicular joint is a synovial joint with a double gliding motion.
Motions occur in three planes and accompany the motions of the shoulder.
The joint capsule surrounds the joint and is reinforced by the anterior and posterior sternoclavicular ligaments.
The joint has a double attachment, similar to a double-hung hinge, allowing for motion in both directions.

Abnormal Scapula Orientation

Abnormal positions of the scapula in individuals with shoulder dysfunction can lead to abnormal orientation of the glenoid fossa and glenohumeral joint instabilities.
Patients with shoulder impingement syndrome often exhibit excessive anterior tilt of the scapula during shoulder abduction.

Description

This quiz covers the anatomy of the shoulder complex, including the scapula, clavicle, sternum, humerus, and rib. It also covers the joints involved, such as the sternoclavicular joint, acromioclavicular joint, and glenohumeral joint.