Anatomy Lecture 5: Axilla, Brachial Plexus

First Part of Axillary Artery

The section of the axillary artery located proximal to the pectoralis minor muscle, starting at the lateral border of the first rib, which gives off the superior thoracic artery.

apex of axilla

1^st rib, clavicle, & scapula

base of axilla

Skin, subcutaneous tissue, & axillary fascia

anterior wall of axilla

Pectoralis major, pectoralis minor, subclavius, pectoralis fascia, & clavipectoral fascia

pectoralis fascia

loose connective tissue that wraps around the pectoralis major

clavipectoral fascia

loose connective tissue that wraps around the pectoralis minor and subclavius

posterior wall of axilla

Teres major, latissimus dorsi, subscapularis & scapula

medial wall of axilla

Thoracic wall & serratus anterior

lateral wall of axilla

Intertubercular sulcus of humerus

Superior Thoracic Artery

The single artery branching off the first part of the axillary artery.

Second Part of Axillary Artery

The section of the axillary artery located deep to the pectoralis minor muscle, giving off the thoracoacromial and lateral thoracic arteries.

Thoracoacromial Artery

One of the two arterial branches arising from the second part of the axillary artery.

Lateral Thoracic Artery

One of the two arterial branches arising from the second part of the axillary artery.

Third Part of Axillary Artery

The section of the axillary artery extending from the distal border of the pectoralis minor muscle to the inferior border of the teres major muscle, which gives off the subscapular, anterior circumflex humeral, and posterior circumflex humeral arteries.

Subscapular Artery

A major branch of the third part of the axillary artery that bifurcates into the circumflex scapular and thoracodorsal arteries.

Anterior Circumflex Humeral Artery

A branch of the third part of the axillary artery that runs along the front of the surgical neck of the humerus

Posterior Circumflex Humeral Artery

A branch of the third part of the axillary artery that runs along the back of the surgical neck of the humerus

Circumflex Scapular Artery

A branch of the subscapular artery that moves posteriorly to go through the triangular space

Thoracodorsal Artery

A branch of the subscapular artery that accompanies the thoracodorsal nerve to supply the latissimus dorsi muscle.

Cephalic Vein

A superficial vein of the upper limb that courses laterally and drains into the axillary vein.

Basilic Vein

A superficial vein of the upper limb that courses medially and joins the brachial vein to form the axillary vein.

Axillary Vein

A deep vein formed by the union of the basilic vein and brachial vein, which eventually receives the cephalic vein to become the subclavian vein.

brachial vein

A deep vein that joins with the basilic vein to become the axillary vein

perforating branches

veins that connect superficial veins to deeper veins

Pectoral (Anterior) Lymph Nodes

Lymph nodes that drain the anterior thoracic wall and breast.

Subscapular (Posterior) Lymph Nodes

Lymph nodes that drain the posterior thoracic wall and scapula.

Humeral (Lateral) Lymph Nodes

Lymph nodes that drain the upper limb.

Central Lymph Nodes

Lymph nodes that receive lymphatic drainage from the pectoral, subscapular, and humeral lymph node groups.

Apical Lymph Nodes

Lymph nodes that receive lymphatic drainage from all other axillary node groups (central, pectoral, subscapular, and humeral).

Subareolar Plexus

A lymphatic plexus into which drainage from the breast's glandular tissue, areola, and nipple first passes.

Breast Lymphatic Drainage

A physiological pathway where, after going to the Subareolar Plexus, approximately 75% of lymphatic drainage from the breast flows into the axillary lymph nodes and the rest goes the the parasternal nodes or inferior nodes of the upper abdomen

Parasternal Lymph Nodes

Lymph nodes that connect to lymphatic channels, allowing for lymphatic drainage of both sides of the chest.

Roots of Brachial Plexus

Formed by the anterior rami of spinal nerves C5–T1.

Trunks of Brachial Plexus

Three major nerve bundles (superior, middle, and inferior) formed by the union of the brachial plexus roots.

Divisions of Brachial Plexus

Three pairs of anterior and posterior nerve pathways (six divisions total) formed when each of the three trunks divides.

Cords of Brachial Plexus

Three major nerve cords (lateral, medial, and posterior) named in relation to their position relative to the axillary artery and formed by the junction of the divisions.

Terminal Branches of Brachial Plexus

The five major peripheral nerves (musculocutaneous, axillary, radial, median, ulnar) that arise from the cords to serve key roles in the upper limb; marks the end of the brachial plexus

Dorsal Scapular Nerve C5

A branch arising directly from the C5 root that provides motor innervation to the levator scapulae, rhomboid minor, and rhomboid major muscles.

Long Thoracic Nerve C5-C7

A nerve arising from the C5–C7 roots that provides motor innervation to the serratus anterior muscle.

Nerve to Subclavius C5-C6

A branch arising from the superior trunk of the brachial plexus that provides motor innervation to the subclavius muscle.

Suprascapular Nerve C5-C6

A branch arising from the superior trunk of the brachial plexus that provides motor innervation to the supraspinatus and infraspinatus muscles.

Lateral Pectoral Nerve C5-C7

A branch of the lateral cord that provides motor innervation to the clavicular head of the pectoralis major muscle.

Musculocutaneous Nerve C5-C7

A terminal branch of the lateral cord providing motor innervation to the flexor arm muscles and sensory innervation as the lateral antebrachial cutaneous nerve in the forearm.

lateral root of median nerve

part of the lateral cord that contributes C5-C7 fibers to the median nerve

Medial Pectoral Nerve C8-T1

A branch of the medial cord that provides motor innervation to both the sternocostal head of the pectoralis major and pectoralis minor muscles.

Medial Brachial Cutaneous Nerve C8-T1

A branch of the medial cord providing sensory innervation to the medial side of the arm.

Medial Antebrachial Cutaneous Nerve C8-T1

A branch of the medial cord providing sensory innervation to the medial side of the forearm.

Ulnar Nerve C8-T1

A terminal branch of the medial cord providing sensory and motor innervation to the forearm and hand.

medial root of median nerve

part of the medial cord that contributes C8-T1 fibers to the median nerve

Median Nerve C5-T1

A major terminal nerve formed by the union of the lateral and medial roots from the lateral and medial cords, providing sensory and motor innervation to the forearm and hand.

Upper Subscapular Nerve C5-C6

A branch of the posterior cord providing motor innervation to the subscapularis muscle.

Lower Subscapular Nerve C5-C6

A branch of the posterior cord providing motor innervation to both the subscapularis and teres major muscles.

Thoracodorsal Nerve C6-C8

A branch of the posterior cord providing motor innervation to the latissimus dorsi muscle.

Axillary Nerve C5-C6

A terminal branch of the posterior cord providing motor innervation to the deltoid and teres minor muscles, and sensory innervation to the proximal arm.

Radial Nerve C5-T1

A terminal branch of the posterior cord providing sensory and motor innervation to the forearm and hand.

C6

The spinal nerve that covers the thumb.

C7

The spinal nerve that that covers the index and middle fingers.

C8

The spinal nerve dermatome area that covers the sensation of the ring and little fingers.

Suprascapular Nerve Entrapment

A clinical condition associated with rotator cuff damage, shoulder dislocation, or fractures that causes shoulder pain in overhead athletes and can lead to muscle wasting of the supraspinatus and infraspinatus.

Winged Scapula

A clinical presentation resulting from damage to the long thoracic nerve and subsequent paralysis of the serratus anterior muscle, making the medial border of the scapula abnormally prominent.

Surgical Neck Fracture of Humerus

A humeral fracture location that puts the closely associated axillary nerve at risk of damage.

Shaft Fracture of Humerus

A humeral fracture location that puts the closely associated radial nerve at risk of damage.

Supracondylar Fracture of Humerus

A humeral fracture location that puts the closely associated median nerve at risk of damage.

Medial Epicondyle Fracture of Humerus

A humeral fracture location that puts the closely associated ulnar nerve at risk of damage