Superficial Muscles of the Thorax

Muscles of the Anterior Chest

The anterior chest contains several key muscles that contribute to movements of the arm and stabilization of the shoulder girdle. These muscles are essential for upper limb mobility and support.

• Pectoralis major: Responsible for arm adduction, bringing the arm toward the body's midline. It also assists in flexion and medial rotation of the humerus.

• Pectoralis minor: Functions in thoracic wall elevation and helps stabilize the scapula by drawing it anteriorly and inferiorly against the thoracic wall.

• Serratus anterior: Facilitates protraction of the scapula, moving it forward around the rib cage. This muscle is crucial for the upward rotation of the scapula during arm elevation.

• Subclavius: Acts to stabilize the pectoral girdle by anchoring and depressing the clavicle.

Example: The pectoralis major is heavily engaged during push-ups and bench press exercises.

Muscles of the Shoulder & Posterior Back

Shoulder and Back Muscles

The shoulder and back muscles are involved in complex movements of the scapula and humerus, providing both mobility and stability to the upper limb.

• Trapezius: Elevates and depresses the shoulder, and also retracts and rotates the scapula.

• Rhomboids (major and minor): Retract the shoulder by pulling the scapula toward the vertebral column.

• Levator scapulae: Elevates the scapula, assisting in shoulder shrugging.

• Latissimus dorsi: Adducts the arm, extends and medially rotates the humerus; important in movements such as pulling and climbing.

• Teres major: Responsible for arm medial (internal) rotation and adduction.

• Teres minor: Responsible for arm lateral (external) rotation; part of the rotator cuff group.

• Supraspinatus: Initiates arm abduction and stabilizes the shoulder joint.

• Infraspinatus: Responsible for arm lateral rotation and stabilization of the shoulder joint.

• Subscapularis: Responsible for arm medial rotation and stabilization of the shoulder joint.

Example: The rotator cuff muscles (supraspinatus, infraspinatus, teres minor, subscapularis) work together to stabilize the shoulder during overhead activities.

Rotator Cuff Muscles

The rotator cuff is a group of four muscles that stabilize the glenohumeral (shoulder) joint and allow for a wide range of arm movements.

• Supraspinatus: Abducts the arm.

• Infraspinatus: Laterally rotates the arm.

• Teres minor: Laterally rotates the arm.

• Subscapularis: Medially rotates the arm.

Example: Injury to the rotator cuff muscles can result in shoulder pain and limited range of motion, commonly seen in athletes who perform repetitive overhead movements.

Key Anatomical Landmarks

Several anatomical landmarks are important for identifying muscle attachments and understanding their functions:

• Clavicle: Serves as an attachment for the subclavius and pectoralis major.

• Spine of scapula: Attachment site for the trapezius and deltoid muscles.

• Humerus: Receives insertions from pectoralis major, latissimus dorsi, teres major, and rotator cuff muscles.

Additional info: The coordinated action of these muscles is essential for complex upper limb movements such as throwing, lifting, and reaching.