Posterior Triangle & Brachial Plexus I Flashcards
Innervation of Sternocleidomastoid
Accessory nerve (CN XI)
Innervation of Trapezius
Accessory nerve (CN XI)
Innervation of Platysma
Facial Nerve
Innervation of Subclavius
Nerve to Subclavius
Innervation of Omohyoid
Ansa cervicalis
Innervation of Anterior Scalene
C4–6
Innervation of Middle Scalene
C3-8
Innervation of Posterior Scalene
C5-7
Action of Sternocleidomastoid
Bilaterally: flex head, raise thorax
Unilaterally: turns face toward opposite side
Action of Trapezius
Elevates, retracts, and rotates scapula; lower fibers depress scapula
Action of Platysma
Tenses skin of neck
Action of Subclavius
Anchors and depresses clavicle
Action of Omohyoid
Steadies hyoid bone and depresses hyoid
Action of Anterior Scalene
Elevates 1st rib, bends neck
Action of Middle Scalene
Elevates 1st rib, bends neck
Action of Posterior Scalene
Elevates 2nd rib, bends neck
What does the Phrenic Nerve sit on top of? Innervate?
Anterior Scalene Muscle
“C3,4,5 keeps the Diaphragm alive!”
Boundaries of the posterior triangle?
A. Anterior border: Sternocleidomastoid m.
B. Posterior border: Trapezius m.
C. Inferior border: Clavicle
D. Roof: Investing fascia, Platysma, Superficial fascia, skin.
E. Floor: Deep (Prevertebral) fascia over scalene muscles.
F. Subdivided by Omohyoid m. into Occipital triangle superiorly, and Omoclavicular or Supraclavicular triangle inferiorly
Cutaneous components of cervical plexus and what do they innervate?
Transverse cervical n.: From ventral rami of C2-3; Cutaneous nerve to throat.
Great auricular n.:From ventral rami of C2-3; Cutaneous to area around ear.
Lesser occipital n.:From ventral rami of C2 (and sometimes C3); Cutaneous to skin near mastoid process.
Supraclavicular n.:From ventral rami of C3-4; Splits into three branches - anterior, middle and posterior (also called medial, intermediate and lateral); Cutaneous to area over clavicle.
Layers of fascia in neck?
A. Superficial Cervical Fascia - fat, cutaneous nerves, vessels, platysma.
B. Investing Fascia - envelopes all structures of the neck except the platysma.
Attaches to the ligamentum nuchae and C7 spinous process posteriorly.
Splits to enclose the trapezius and sternocleidomastoid mm.
C. Infrahyoid Fascia – envelops and isolates movements of strap muscles.
D. Carotid Sheath – envelops Carotid a, Internal Jugular v. & Vagus n.
E. Prevertebral Fascia - invests vertebral column and associated muscles.
F. Pretracheal Fascia - encapsulates trachea, esophagus and thyroid gland.
Relationship of anterior scalene muscle to subclavian V/A & brachial plexus?
Subclavian vein is superficial to anterior scalene m. Subclavian artery and brachial plexus run between anterior and middle scalene muscles.
Subclavian artery and its branches
“VITamin C and sometimes D”
Part 1: proximal to anterior scalene m.
Vertebral a. – Biggest, dives back to supplies brainstem & circle of Willis
Internal Thoracic a. – opposite direction of vertebral. anterior chest wall & breast
Thyrocervical Trunk - immediately splits into four branches
Part 2: under/deep to anterior scalene m.
Costocervical Trunk: 2 branches
Deep cervical, Supreme Intercostal
Part 3: distal to anterior scalene m.
Dorsal Scapular a. – highly variable origin, often absent (“sometimes
D”)
Important pressure point to stop bleeding in upper extremity?
Compressing subclavian artery against first rib is important pressure point to stop severe bleeding in upper extremity
.
When, and to what, are the subclavian a. & v renamed to?
As Subclavian a & v cross first rib, renamed to Axillary a & v.
