3 - Upper limb 1 (2) (Exam 2)

• The levator scapulae rotates the scapula in the opposite direction to the trapezius.
• The rhomboideus major and minor stabilizes the shoulder, and rotates the inferior angle of the scapula.
• The latissimus dorsi is an adductor of the upper limb.

Muscles Arising From the Thoracic Wall

• The pectoralis major adducts the arm with the latissimus dorsi.
• The pectoralis major assists in medial rotation.
• The pectoralis minor pulls the scapulae forward.
• The pectoralis minor can reverse to raise ribs in respiratory distress when the shoulder girdle is fixed.
• The serratus anterior draws the scapulae forward during pushing and forward-reaching movements.
• The serratus anterior rotates the inferior angle of the scapula laterally turning glenoid cavity upwards when the arm is raised above the head.
• The subclavius steadies the clavicle.
• The sternocleidomastoid is primarily involved with tilting motions of the head.
• The clavipectoral fascia is a thickening of the deep fascia extending from the periosteum of the clavicle.
• The clavipectoral fascia encloses the subclavius m.
• The clavipectoral fascia fills the gap between the subclavius and the pectoralis minor as the costocoracoid membrane.
• The clavipectoral fascia splits to enclose the pectoralis minor.
• The clavipectoral fascia blends with the axillary fascia.

Muscles of the Scapular Region

• These muscles are located between the scapula and upper humerus.
• These muscles are key to shoulder stability and movement.
• The first four muscles form the rotator cuff. 
• The subscapularis stabilizes the head of the humerus in the shallow glenoid cavity.
• The subscapularis facilitates medial rotation of the humerus at the shoulder when the arm is at the side.
• The supraspinatus stabilizes and prevents the head of the humerus from slipping down off the glenoid cavity.
• The supraspinatus can abduct the arm with the deltoid.
• The infraspinatus rotates the arm laterally and stabilizes the shoulder joint.
• The teres minor stabilizes and produces lateral rotation of the arm.
• The tendons of the muscles of the rotator cuff surround the shoulder joint on all sides except inferiorly.
• The rotator cuff tendons keep the large head of the humerus applied to the shallow glenoid cavity.
• The teres major adducts and medially rotates the arm.
• The teres major can be considered a portion of the subscapularis that has migrated onto the dorsum of the scapula, as it has a similar nerve supply.
• The deltoid forms the "cap" of the shoulder and provides a wide range of actions at the shoulder.
• The anterior fibers of the deltoid flex the arm.
• The posterior fibers of the deltoid extend the arm back behind the body.
• The intermediate fibers of the deltoid are powerful abductors of the arm.

The Quadrangular and Triangular Spaces

• The configuration of the muscles below the shoulder allow a number of structures to pass from anterior to posterior regions of the axilla and arm.
• The quadrangular space transmits the axillary n. and posterior circumflex a.
• The triceps hiatus is medial to the shaft of the humerus.
• The triceps hiatus transmits the radial n. and profunda brachii a.
• The triangular space is inferior to the quadrangular space.
• The triangular space passes the circumflex scapular br. of the subscapular a.

Axillary Artery

• The axillary a. is a continuation of the subclavian a..
• The axillary a. begins at the lateral edge of R1.
• The axillary a. becomes the brachial a. as it passes the lower border of the teres major.
• The axillary a. is divided into 3 parts by the overlying pectoralis minor m.
• The number of the division is equivalent to the number of branches from that division
• Branches from the first part include the superior thoracic artery which supplies the pectoralis major & minor.
• Branches from the second part includethe thoracoacromial artery, a short trunk supplying the pectoral, acromial, clavicular, and deltoid regions
• Branches from the second part include the lateral thoracic artery which contributes substantially to the breast
• Branches from the third part include the subscapular artery.
• The subscapular artery is the largest branch of the axillary a. and gives rise to numerous muscular branches that form an anastomosis around the scapula.
• Branches from the third part include the anterior and posterior circumflex humeral aa. that form an anastomotic circle around the surgical neck of the humerus.
• The anterior circumflex humeral aa. is small.
• The posterior circumflex humeral aa. extends through the quadrangular space with the axillary n. to supply the shoulder joint and surrounding muscles.

An overview of muscles arising from the thoracic wall including the levator scapulae, rhomboideus major/minor, and latissimus dorsi. Descriptions of the function of the pectoralis major/minor, serratus anterior, subclavius, and sternocleidomastoid are provided. The clavipectoral fascia is also described.