Pyramid-shaped space. Located between the upper arm and chest wall. Serves as a pathway for neurovascular structures

Conduit for nerves and blood vessels connecting the neck/thorax to the upper limb

Apex: Connected to the neck Base: Armpit Walls (4): Anterior wall. Posterior wall. Medial wall. Lateral wall

Upwards and medially towards the root of the neck called Cervicoaxillary canal

Anteriorly: Clavicle. Posteriorly: Upper border of the scapula. Medially: Outer border of the first rib.

Axillary fascia and Skin of the arm pit

Pectoralis major Pectoralis minor Subclavius muscles Clavipectoral fascia

Subscapularis Latissimusdorsi Teres major muscles

Wide and formed by: Serratus anterior. Upper 4-5 ribs & Intercostal muscles

Narrow and formed by: Coracobrachialis Biceps brachii Bicepital groove of the humerus

Neurovascular Bundle: * Enclosed within the "axillary sheath" (a connective tissue sheath). Brachial Plexus: * Cords (lateral, medial, posterior). * Branches (e.g., musculocutaneous, median, ulnar, radial, axillary nerves). Axillary Blood Vessels: * Axillary artery and its branches. * Axillary vein and its tributaries. Lymphatic System: * Axillary lymph nodes (various groups). * Axillary lymphatic vessels. Supporting Tissues: * Axillary fat. * Loose connective tissue.

* A strong connective tissue sheet. Superiorly: * Splits to enclose the subclavius muscle. * Attaches to the clavicle. Intermediate: * Splits to enclose the pectoralis minor muscle. Inferiorly: * Continues as the suspensory ligament of the axilla. * Merges with the axillary fascia forming the floor of the armpit.

Origin: Half of Clavicle, sternum, upper ribs. Insertion: Humerus (bicipital groove). Nerve: Pectoral nerves. Action: Adducts, medially rotates, and flexes arm.

Origin: 1st costal cartilage. Insertion: Inferior clavicle. Nerve: Nerve to subclavius (brachial plexus). Action: Depresses and stabilizes clavicle.

Origin: 3rd, 4th, and 5th ribs. Insertion: Coracoid process. Nerve: pectoral nerve (medial cord of brachial plexus). Action: Pulls the shoulder downward and forward. Elevates the ribs of origin

Origin: Subscapular fossa (scapula). Insertion: Lesser tubercle (humerus). Nerve: Upper and lower subscapular nerves. Action: Medial rotation and shoulder stabilization.

Origin: Iliac crest, lumbar fascia, lower thoracic vertebrae, lower ribs. Insertion: Bicipital groove of humerus. Nerve: Thoracodorsal nerve. Action: Extends, adducts, and medially rotates arm.

Origin: Lower lateral scapula. Insertion: Medial bicipital groove of humerus. Nerve: Lower subscapular nerve. Action: Adducts and medially rotates arm.

Origin: Outer surface of upper 8 ribs. Insertion: Medial scapular border (inferior angle). Nerve: Long thoracic nerve. Action: Protraction and rotation of scapula.

Continuation of the subclavian artery. Begins at the lateral border of the 1st rib. Ends at the lower border of the teres major. Continues as the brachial artery. Closely related to brachial plexus cords. Enclosed with them in the axillary sheath. Axillary sheath is continuous with the prevertebral fascia. Divided into 3 parts by the pectoralis minor muscle.

Lateral 1st rib to upper pectoralis minor. Relations: Anterior: Pectoralis major, fascia, skin, cephalic vein. Posterior: Long thoracic nerve. Lateral: 3 Brachial plexus cords. Medial: Axillary vein.

Behind pectoralis minor. Relations: Anterior: Pectoralis minor/major, fascia, skin. Posterior: Posterior cord (brachial plexus). Lateral: Lateral cord (brachial plexus). Medial: Medial cord (brachial plexus), axillary vein.

Extends from the lower border of pectoralis minor to the lower border of teres major. Relations: Anterior: Pectoralis major, medial root of the median nerve. Posterior: Subscapularis, latissimus dorsi, and teres major. Lateral: Coracobrachialis, biceps, humerus. Medial: Ulnar nerve, axillary vein, medial cutaneous nerve of the arm.

Superior Thoracic: * Supplies first 2 intercostal spaces

Thoracoacromial: * Has clavicular, pectoral, deltoid, and acromial branches. Lateral Thoracic: * Runs with the long thoracic nerve and supplies muscles

Subscapular: * Divides into the thoracodorsal and circumflex scapular branches Anterior Humeral Circumflex: * Passes around the surgical neck of the humerus. Posterior Humeral Circumflex: * Runs with the axillary nerve through the quadrangular space and anastomoses with the anterior humeral circumflex branch.

* Enlargement of 1st part of the axillary artery. * May compress brachial plexus trunks. * Causes pain and anesthesia in affected nerve areas.

* Nerves control blood flow in arm arteries. * Raynaud's: Nerves over-constrict finger arteries, risking tissue death. * Surgery (sympathectomy) cuts these nerves, widening arteries. * This improves blood flow, preventing tissue damage

* Can occur spontaneously. * Associated with excessive, unusual shoulder movements.

* Starts: Teres major border (brachial/basilic veins). * Position: Medial to axillary artery. * Ends: 1st rib (becomes subclavian vein). * Receives: Tributaries matching artery branches and cephalic vein

* Supplies sensory, motor, and sympathetic innervation to the upper limb (skin, joints, muscles, blood vessels, sweat glands). * Formed in the posterior triangle of the neck. * Composed of the anterior rami of C5, C6, C7, C8, and T1 spinal nerves.

ROOTS (ventral rami) TRUNKS DIVISIONS CORDS BRANCHES

C5, c6 upper trunk C7 middle trunk C8, T1 lower trunk

Upper trunk, anterior and posterior Middle trunk, anterior and posterior Lower trunk, anterior and posterior

AA, lateral cord A, medial cord Ppp, posterior cord

* Lateral: Anterior divisions of upper and middle trunks. * Medial: Anterior division of lower trunk. * Posterior: All posterior divisions

* Roots: Between anterior and middle scalene muscles. * Trunks: Posterior triangle of the neck. * Divisions: Behind the clavicle. * Cords: Axilla, with specific relationships to the axillary artery: * Lateral cord: Lateral to the second part of the axillary artery. * Medial cord: Medial to the second part, crossing behind the first part. * Posterior cord: Posterior to the second part.

* Lateral cord: Musculocutaneous nerve. * Medial cord: Ulnar nerve. * Posterior cord: Radial and axillary nerves. * Median nerve: Formed by branches from both lateral and medial cords.

Roots Dorsal scapular nerve (C5) Long thoracic nerve (C5, 6, and 7) Upper trunk Nerve to subclavius (C5 and 6) Suprascapular nerve (supplies the supraspinatus and infraspinatus muscles) Lateral cord Lateral pectoral nerve Musculocutaneous nerve Lateral root of median nerve Medial cord Medial pectoral nerve Medial cutaneous nerve of arm and forearm Ulnar nerve Medial root of median nerve Posterior cord Upper and lower subscapular nerves Thoracodorsal nerve Axillary nerve Radial nerve

Rare: Full nerve damage. Common: Partial damage (stretch, pressure, cuts). Results: Weakness, numbness in arm

Damage: Upper brachial plexus (C5-C6). Nerves: Suprascapular, axillary, musculocutaneous. Cause: Stretch injury (birth, fall). Result: "Waiter's tip" arm, weak shoulder/biceps, numb arm.

Damage: Lower brachial plexus (C8-T1). Nerves: ulnar and median nerves, long thoracic nerve. Cause: Excessive arm abduction (traction injury). Result: "Claw hand" (hyperextended MCP, flexed IP joints). Paralysis of small hand muscles. Sensory loss: medial arm, forearm, hand.

Nerve: Long thoracic nerve. Muscle: Serratus anterior. Causes: Blows/pressure to the neck. Surgical procedures (e.g., radical mastectomy). Results: "Winged scapula" (scapula protrudes). Difficulty raising arm overhead. Vertebral border and inferior angle of the scapula protrude posteriorly.

Nerve: Axillary nerve (C5-C6). Origin: Posterior cord of brachial plexus. Causes: Crutch pressure Shoulder dislocation. Humeral neck fracture. Vulnerable at the quadrangular space. Results: Deltoid and teres minor paralysis. Sensory loss over the lateral deltoid area.

* Lymphangitis (Infection): Cause: Upper limb infection. First nodes affected: Lateral (humeral) group. * Metastatic Cancer: Apical group involvement. May adhere to axillary vein (requiring vein excision). Apical node enlargement can cause cephalic vein obstruction.