Neck

From IKE

Contents 1 Posterior triangle 1.1 Boundaries 1.2 Blood supply 1.2.1 Subclavian artery 1.2.2 Subclavian vein 1.2.3 External jugular vein 1.3 Innervation 1.3.1 Cutaneous branches of the cervical plexus 1.3.2 Phrenic nerve (C3-C5) 1.3.3 Accessory nerve (CXI) 1.3.4 Brachial plexus 2 Resources

Posterior triangle

Boundaries

• posterior border of the stern-cleido-mastoid
• anterior border of the trapezius and clavicle
• The floor of the triangle consists of several muscles
• Three, known as prevertebral muscles, are important as landmarks
• They are, from superior to inferior
  1. levator scapulae
  2. scalenus medius
  3. scalenus anterior

Blood supply

Subclavian artery

• enters the triangle deep to the scalenus anterior muscle
• Its course in the posterior triangle is short, soon crossing the lateral border of the first rib to enter the upper limb

Subclavian vein

• a continuation of the axillary vein at the lateral border of the first rib
• It has a short course in the posterior triangle before passing superficial to the scalenus anterior
• Within the triangle, it receives the external jugular vein.

External jugular vein

• there is considerable individual variation in the arrangement of the superficial veins of the neck
• The most prominent are the external jugular veins
• Each crosses the sterno-cleido-mastoid in the superficial fascia to enter the posterior triangle
• here it pierces the investing fascia and drains into the subclavian vein

Innervation

Cutaneous branches of the cervical plexus

• anterior primary rami of spinal nerves C1-C4
• A number of branches pierce the investing fascia posterior to the sternocleidomastoid to become superficial
• They radiate throughout the anterior and lateral parts of the neck and over the shoulder, on to the thorax
• One branch, the great auricular nerve (C2,C3), extends up over the lower jaw on to the lower part of the face

Phrenic nerve (C3-C5)

• a branch primarily from the cervical plexus
• It crosses the anterior surface of the scalenus anterior, deep to the sternocleidomastoid, to enter the thorax

Accessory nerve (CXI)

• enters the posterior triangle from beneath the sterno-cleido-mastoid, which it supplies
• It crosses the triangle, superficial to the levator scapulae, to supply the trapezius

Brachial plexus

• the roots of the plexus emerge from between scalenus anterior and medius, while the trunks lie in the lower part of posterior triangle

Resources

• Gross anatomy head and neck notes (PDF)