Axilla Flashcards by Kirsten Bayles

Axilla

“Axillary region”
Area that lies underneath the glenohumeral joint
At the junction of the upper limb and the thorax
Passageway by which neurovascular and muscular structures can enter and leave the upper limb.

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Cutaneous innervation of Axilla

Intercostobrachial nerve (T1)
Intercostal nerve (T2-T4)

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Borders of Axilla

Anterior: anterior axillary fold
Posteror: posterior axillary fold
Medial: lateral thoracic wall with serrates ant.
Lateral: humerus, coracobrachialis, biceps
Apex: junction of walls at scapula & clavicle (superomedial)
Floor: axillary fascia

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Clavipectoral Fascia

Covers proximal neuromuscular structures of the axillary region

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Major components of axilla

1) Serratus anterior
2) Axillary lymph nodes
3) Axillary artery
4) Axillary vein
5) Axillary fascia
6) Cords of brachial plexus
7) Brachial Plexus

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Axillary lymph nodes

Communicate with pectoral lymph nodes from the breast, neck, head, and upper limb, and with nodes from the other side of the body

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Axillary Artery

Continuation of subclavian artery
From Rib I to lower border of Teres major
Determines nomenclature for brachial plexus cords
Has three parts: Part 1, Part 2, Part 3

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Part 1 of Axillary Artery

Supreme Thoracic A.
Arises from anterior surface of the axillary a.
Supplies first intercostal space
Descends from behind the axillary v.

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Part 2 of Axillary Artery

Thoracoacromial Trunk
Branches from anterior surface of axillary a.
Arises deep to pec major
Usually arises medial to pec minor
Divides into:
DELTOID, PECTORAL, ACROMIAL, & CLAVICULAR ARTERIES (to SC joint)

Lateral Thoracic A.
Descends along the lateral border of pec minor
Supplies serratus anterior and mammary gland

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Part 3 of Axillary Artery

Posterior Humeral Circumflex A.

Anterior Humeral Circumflex A.

Supscapular A.
Thoracodorsal A.
Scapular Circumflex A.

Shoulder Anastomosis
(among thoracic-acromial branch)

Scapular Anastomosis

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How do veins compare to arteries?

Arteries: carry oxygenated blood away from the heart to the body
Veins: carry oxygen-poor blood back from the body to the heart.

Not an exact match
Partially due to development
Veins are usually BIGGER (carry 70% of blood at a time)
Branches look so varied in the body!

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Posterior Humeral Circumflex A.

Component of Part 3 of Axillary A.
Travels medial to surgical neck of humerus
Runs posteriorly 
Travels with anterior humeral circumflex
Supplies deltoid, teres minor, GH joint

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Anterior Humeral Circumflex A.

Component of Part 3 of Axillary A.
Passes deep to coracobrachialis & Biceps brachii
Runs anterior to surgical neck of humerus
Supplies shoulder joint

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Subscapular A.

Component of Part 3 of Axillary A.
Largest branch of Axillary A.
Arises at level of the subscapularis muscle along the posterior border of axillary A.
Has two sub-portions:
Thoracodorsal A.
Scapular Circumflex A. (larger, supplies shoulder joint and muscles)

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Major veins of arm

Cephalic vein - on lateral side of arm
Basophilic vein - on medial (base) side of arm
Both are very long veins

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Axillary Vein

Formed by union of:
basilic vein & various brachial veins
Empties into subclavian vein

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Axillary Fascia

Continuous with deep back fascia, pectoral fascia, and brachial fascia
Forms floor of axilla

Cords of Brachial Plexus

Named for proximity to axillary artery

3 cords: Medial, Lateral, & Posterior

Brachial Plexus Schematic**

Netter Plate 430/418

Brachial Plexus

Ventral Rami of C5-T1 (5 Levels)
Ventral Rami of these spinal n. emerge through the intervertebral foramina

Many components:
Roots
Trunks
Divisions
Cords

Brachial Plexus:

Roots

FIVE!
Travel deep to scalene anterior muscle
Travel superficial to scalene medius muscle

Deep to scalene anterior, the roots form trunks.
Between scalene ant. and medius are found: brachial plexus trunks
subclavian a. and vein.
axillary a. and vein
Nerves that come off of the roots:
Dorsal scapular N.
Long thoracic N.

Brachial Plexus:

Trunks

THREE
Upper - Combination of C5 & C6 (2 roots)
N. to Subclavius muscle
Suprascapular N.

Middle - Root of C7 (1 root)

Lower - Combination of C8 & T1 (2 roots)

Brachial Plexus:

Divisions

THREE ANTERIOR & THREE POSTERIOR
Every trunk has an anterior and posterior division
Divisions combine to form cords

Brachial Plexus:

Cords

THREE
Found in axilla itself, deep to the pec minor muscle
Named for their relation to axillary artery:
Medial
Lateral
Posterior

Brachial Plexus: | Terminal Branches

EVERY CORD HAS TWO | All cords end where branches depart.

Medial Cord

C8 & T1 Formed by anterior division of lower trunk ONLY Medial pectoral n. (C8 and T1) Ulnar n. (C8 and T1) Medial brachial cutaneous (C8 and T1) Medial antebrachial cutaneous (C8 and T1) Medial cord contribution to median nerve

Lateral Cord

``` C5, C6, C7 Formed by anterior divisions of upper and middle trunks. Lateral pectoral nerve (C5-C7) Musculocutneous nerve (C5-C7) Median Nerve (C5-T1) or (C6-T1) ```

Posterior Cord

``` C5-T1 Formed by posterior divisions of all trunks Upper Subscapular N. (C5-C6) Lower Subscapular N. (C5-C6) Thoracodorsal N. (C6-C8) Axillary N. (C5-C6) Radial N. (C5-T1) ```

Ulnar Nerve | of Brachial Plexus

Part of medial cord in brachial plexus. C8 & T1 Most medial nerve in arm Main role: Intrinsic hand movement Also supplies some of wrist and digital flexors Cutaneous to medial part of the hand (palmar and dorsal sides)

Medial Brachial Cutaneous N. | of Brachial Plexus

Part of medial cord in brachial plexus. C8 & T1 Cutaneous from the medial aspect of the arm (anterior & posterior sides)

Medial Antebrachial Cutaneous N. | of Brachial Plexus

Part of medial cord in brachial plexus. C8 & T1 Cutaneous from the medial aspect of forearm (anterior & posterior sides)

Radial N.

Part of lateral cord in brachial plexus. C5-T1 Main role: elbow, wrist, and digital extensors Cutaneous skin over extensor compartment of the arm, forearm, and part of hand

Levels in the Brachial Plexus per branch

Roots: one Trunks: two Cords: two-five Branches: may have any # of levels

Common Injuries of Brachial Plexus: | Stretching of the Neck

Result in Upper Brach. Plex. Injuries (C5 and C6 roots or upper trunk) Ex: Falls on shoulder, stretch of head from shoulder, breached births Deficits: Affect deltoid, biceps, brachial, brachioradialis = extended elbow, medially rotated arm Erb Palsy, Erb Duschennes Palsy, Upper Radicular Syndrome

Common Injuries of Brachial Plexus: | Stretching of the Upper Limb Superiorly

Result in Lower Brach. Plex. Injuries (C8 and T1 roots or lower trunk) Ex: Breaking a fall, difficult births Mainly felt in areas supplied by the Ulnar N. Chronic semi-extension of Chris, paralysis of hand, claw hand

"Cervical Nerve"

Rarely occurs Found at C7 Mainly affects the Ulnar N.

Radial Nerve Injuries

Occur at radial groove or near elbow Result in wrist drop Diaphysial fractures, humeral fractures Weakens extensors

Median Nerve Injuries

``` Occur in the carpal tunnel Thumb opposition lost Thumb stuck to palm in a "simian hand" Large disruption of sensory supply to hand (repetitive use syndrome) ```

Ulnar Nerve Injuries

Occurs at eblow or at wrist | "Results in claw hand or palpal blessing hand"

Long Thoracic Nerve Injuries

Right on serratus Crutch injuries Winged scapula

Axillary Nerve Injuries

Crutch injuries Also Surgical neck fractures Deltoid is compromised, so paraesthesia of shoulder Proximal arm weakness

Thoracic Outlet/Thoracic Inlet Syndrome

"Catch all" Neurovascular compression syndrome Uncategorable abnormality of the axillary a. or inferior trunk May result from cervical ribs, enlarged lymph nodes, vascular compression, particular weakness, etc. *Usually involves the artery if inferior trunk involved Signs: cold, weak, cyanosis in hands