4. Muscles of the breast and the arm

Biceps Brachii *

A large muscle that lies on the front of the upper arm between the shoulder and the elbow. Both heads of the muscle arise on the scapula and join to form a single muscle belly which is attached to the upper forearm. While the biceps crosses both the shoulder and elbow joints, its main function is at the elbow where it supinates the forearm and flexes it (to a lesser extent).

Clavipectoral Fascia

A strong fascia situated under cover of the clavicular portion of the pectoralis major. Has a small hole through which the cephalic vein passes.

Winged Scapula

A winged scapula (scapula alata) is a skeletal medical condition in which the shoulder blade, or shoulder bone, protrudes from a person's back in an abnormal position. The most common cause of scapular winging is serratus anterior paralysis. This is typically caused by damage to the long thoracic nerve.

Posterior Circumflex Humeral Artery **

Arises from the third part of axillary artery at the lower border of the subscapularis, and runs posteriorly with the axillary nerve through the quadrangular space. It winds around the neck of the humerus and is distributed to the deltoid muscle and shoulder-joint, anastomosing with the anterior humeral circumflex and deep artery of the arm. It supplies the teres major, teres minor, deltoid, and (long head only) triceps muscles.

Ant. Thoraco-appendicular muscles (שרירי החזה)

Between anterior thoracic wall and pectoral girdle. Pectoralis major Pectoralis minor Subclavius Serratus Anterior

Musculocutaneous Nerve

Branches out from the lateral cord of the brachial plexux, its fibers being derived from C5, C6 and C7. It leaves the axilla and enters the arm by passing through the coracobrachialis muscle. It passes diagonally down the arm in the plane between the biceps brachii and brachialis muscles. After giving rise to motor branches in the arm, it emerges laterally to the tendon of the biceps brachii muscle at the elbow, penetrates deep fascia, and continues as the lateral cutaneous nerve of the forearm. The musculocutaneous nerve provides: • motor innervation to all muscles in the anterior compartment of the arm (coracobrachialis, biceps brachii and brachialis). • sensory innervation to skin on the lateral surface of the forearm.

Triangular Space **

Has the following boundaries: Inferior: the superior border of the teres major; Lateral: the long head of the triceps; Superior: Teres minor Contents: Circumflex Scapular Artery

Triangular Interval

Has the following boundaries: superior: teres major medial : long head of the triceps brachii lateral: lateral head of the triceps. Contents: deep brachial artery and radial nerve.

Quadrangular Space **

Has the following boundaries: superior: the teres minor (inferior margin). inferior: the teres major (superior margin) medially: the long head of the triceps brachii laterally: the surgical neck of the humerus anteriorly: the subscapularis Contents: Axillary nerve and the posterior circumflex humeral artery

Radial Nerve

It originates from the brachial plexus, carrying fibers from the ventral roots of spinal nerves C5, C6, C7, C8 & T1. Supplies the posterior portion of the upper limb. It innervates the medial and lateral heads of the triceps brachii muscle of the arm, as well as all 12 muscles in the posterior osteofascial compartment of the forearm.

Triceps Brachii

Long, lateral and medial head.

Short head of biceps **

Origin of Short Head: Apex of the coracoid process of the scapula. Insertion: Tuberosity of the radius and aponeurosis of the biceps brachii.

Brachialis

Origin: Anterior aspect of humerus and adjacent intermuscular septae. Insertion: Tuberosity of the ulna. Innervation: Musculocutaneous nerve Function: flexor of the forearm at the elbow joint. Stronger than the bicipital.

Pectoralis minor **

Origin: Anterior surfaces and superior borders of ribs Ill to V. Insertion: Coracoid process of scapula. When we affix the scapula, the origin and insertion of the muscle switch (After running). Innervation: Medial pectoral nerve. Function: Scapular depression and stabilization. Also protracts the scapula.

Coracobrachialis **

Origin: Apex of coracoid process. Insertion: linear roughening on midshaft of humerus on medial side. Innervation: Musculocutaneous nerve Function: adduction of the arm at the glenohumeral joint.

Long Head of Triceps **

Origin: Infraglenoid tubercle on scapula Insertion: common tendon of insertion with medial and lateral heads on the olecranon process of ulna Innervation: Radial nerve Function: extension of the forearm at the elbow joint and adduction of the arm at the should joint.

Long head of biceps **

Origin: Supraglenoid tubercle of the scapula. Insertion: Tuberosity of the radius and aponeurosis of the biceps brachii. It

Lateral Head of Triceps **

Origin: posterior surface of humerus Insertion: common tendon of insertion with medial and long heads on the Innervation: Radial nerve Function: extension of the forearm at the elbow joint.

Medial Head of Triceps **

Origin: posterior surface of humerus Insertion: common tendon of insertion with medial and long heads on the Innervation: Radial nerve Function: extension of the forearm at the elbow joint.

Serratus Anterior **

Originates as a number of muscular slips from the lateral surfaces of ribs I to IX and the intervening deep fascia overlying the related intercostal spaces. The muscle forms a flattened sheet, which passes posteriorly around the thoracic wall to insert primarily on the costal surface of the medial border of the scapula. The serratus anterior performs protraction of scapula. It also keeps the costal surface of the scapula closely opposed to the thoracic wall. The serratus anterior is innervated by the long thoracic nerve, which is derived from the roots of the brachial plexus.

Circumflex Scapular Artery **

Part of the triangular space. A branch of the subscapular artery. It curves around the axillary border of the scapula, traveling through the anatomical triangular space. It enters the infraspinatous fossa under cover of the Teres minor, and anastomoses with the transverse scapular artery (suprascapular) and the descending branch of the dorsal scapular artery.

Axillary Nerve **

The axillary nerve or the circumflex nerve is a nerve of the human body, that originates from the brachial plexus (upper trunk, posterior division, posterior cord) at the level of the axilla (armpit) and carries nerve fibers from C5 and C6. The axillary nerve travels through the quadrangular space with the posterior circumflex humeral artery and vein. The axillary nerve supplies three muscles in the arm: deltoid, triceps and teres minor. It also carries sensory information from the shoulder joint, as well as the skin covering the inferior region of the deltoid muscle.

Pectoralis major **

The largest and most superficial of the pectoral region muscles. lt directly underlies the breast and is separated from it by deep fascia and the loose connective tissue of the retromammary space. The pectoralis major has a broad origin that includes the anterior surfaces of the medial half of the clavicle, the sternum, and related costal cartilages. The muscle fibers converge to form a flat tendon, which inserts into the lateral lip of the bicipital groove of the humerus. The posterior fibers flex the shoulder. The middle fibers medialy rotate the arm. The inferior fibers adducts the arm. When all the fibers contract they cause horizontal adduction. Innervation: Medial and lateral pectoral nerves.

Lateral Antebrachial Cutaneous Nerve

The termination of the musculocutaneous nerve. A sensory nerve that reaches the lateral part of the forearm.