Brachial Plexus and Axilla Anatomy Flashcards

Comprehensive vocabulary flashcards covering the brachial plexus, axilla boundaries, axillary artery branches, cords, and lymph node classifications based on the lecture materials.

Brachial Plexus Sequence

The five-step anatomical sequence of the brachial plexus: Roots $\rightarrow$ Trunks $\rightarrow$ Divisions $\rightarrow$ Cords $\rightarrow$ Branches (mnemonic: "Read That Damn Cadaver Book").

Superior Trunk

The trunk of the brachial plexus formed by the union of the $C5$ and $C6$ roots.

Middle Trunk

The trunk of the brachial plexus formed as a direct continuation of the $C7$ root.

Inferior Trunk

The trunk of the brachial plexus formed by the union of the $C8$ and $T1$ roots.

Musculocutaneous Nerve

A terminal branch from the lateral cord ($C5-C7$) that pierces coracobrachialis, supplies the BBC muscles (Brachialis, Biceps brachii, Coracobrachialis), and continues as the lateral cutaneous nerve of forearm.

Axillary Nerve

A terminal branch from the posterior cord ($C5, C6$) that passes through the quadrangular space with the posterior circumflex humeral artery to supply the deltoid and teres minor muscles and sensory area over the lateral shoulder ("regimental badge" area).

Radial Nerve

A terminal branch from the posterior cord ($C5-T1$) that travels through the spiral groove of the humerus to supply all extensor muscles of the upper limb and sensory areas of the posterior arm, forearm, and dorsum of the hand.

Median Nerve

A nerve formed by two roots from the lateral and medial cords ($C5-T1$) that supplies most anterior compartment forearm muscles, the LOAF hand muscles, and skin over the palmar aspect of the lateral 3½ fingers.

Ulnar Nerve

A terminal branch of the medial cord ($C7, C8, T1$) passing behind the medial epicondyle that supplies the FCU, medial half of FDP, all intrinsic hand muscles except LOAF, and skin over the medial 1½ fingers.

Long Thoracic Nerve

A nerve arising from roots $C5-C7$ that supplies the serratus anterior muscle; injury results in winging of the scapula.

LOAF Muscles

The intrinsic hand muscles innervated by the median nerve: Lateral 2 lumbricals, Opponens pollicis, Abductor pollicis brevis, and Flexor pollicis brevis.

Erb-Duchenne Palsy

An upper brachial plexus injury ($C5, C6$ roots) caused by traction, presenting with "waiter's tip deformity" (arm adducted and medially rotated, elbow extended, forearm pronated).

Klumpke's Palsy

A lower brachial plexus injury ($C8, T1$ roots) caused by hyperabduction, presenting with claw hand and Horner's syndrome (ptosis, miosis, anhidrosis) due to $T1$ root avulsion.

Saturday Night Palsy

Compression of the radial nerve in the spiral groove causing wrist drop and dorsum of hand sensory loss while sparing triceps motor function.

Crutch Palsy

Compression of the radial nerve in the axilla causing wrist drop, where unlike Saturday night palsy, the triceps muscle may also be affected.

Axilla

A pyramid-shaped space between the upper arm and chest wall that serves as a passageway for neurovascular structures and houses major axillary lymph nodes.

Cervico-axillary Canal

The apex/inlet of the axilla, bounded anteriorly by the posterior surface of the clavicle, posteriorly by the superior border of the scapula, and medially by the outer border of the 1st rib.

Axillary Artery

The direct continuation of the subclavian artery starting at the outer border of the 1st rib and ending at the lower border of teres major, divided into 3 parts by pectoralis minor.

Superior Thoracic Artery

The single branch from the first part of the axillary artery supplying upper serratus anterior, pectoral muscles, and 1st and 2nd intercostal spaces.

Thoracoacromial Artery

A wide branch from the second part of the axillary artery that pierces clavipectoral fascia and splits into clavicular, acromial, deltoid, and pectoral branches.

Lateral Thoracic Artery

A branch of the second part of the axillary artery running on the medial wall of the axilla that provides the main arterial supply to the breast.

Subscapular Artery

The largest branch of the axillary artery (arising from the third part), which divides into the circumflex scapular artery and thoracodorsal artery.

Quadrangular Space

An anatomical space bounded by teres minor, teres major, long head of triceps, and humerus; transmits the axillary nerve and posterior circumflex humeral artery.

Lateral Cord

A cord of the brachial plexus formed by the anterior divisions of the superior and middle trunks ($C5, C6, C7$), lying lateral to the axillary artery.

Medial Cord

A cord of the brachial plexus formed by the anterior division of the inferior trunk ($C8, T1$), lying medial to the axillary artery.

Posterior Cord

A cord of the brachial plexus formed by the posterior divisions of all three trunks ($C5-T1$), lying posterior to the axillary artery.

Pectoral (Anterior) Group

Axillary lymph nodes along lateral thoracic vessels draining the majority of the breast (75%), often the first group involved in breast cancer metastasis.

Level I Axillary Lymph Nodes

Surgical classification for axillary lymph nodes located inferolateral to the pectoralis minor muscle.

Level II Axillary Lymph Nodes

Surgical classification for axillary lymph nodes located deep to the pectoralis minor muscle, including the central group.

Level III Axillary Lymph Nodes

Surgical classification for axillary lymph nodes located medial and superior to the pectoralis minor muscle (Apical group).

Sentinel Lymph Node Biopsy

A procedure targeting the initial node(s) receiving lymph drainage from a tumor (often in Level I) to assess metastatic spread in breast cancer.

Axillary Sheath

A fascial enclosure surrounding the axillary artery, axillary vein, and brachial plexus, used as the target site for brachial plexus block administration.