Posterior Triangle of the Neck Flashcards
boundaries of posterior triangle of neck?
contents?
Anterior = post. border of SCM
Posterior = anterior border of trapezius
Base = clavicle
Contents = external jugular vein, roots of brachial plexus, accessory nerve, cervical + supraclavicular nodes
label with roots
which sensory nerves of the cervical plexus lie in the posterior triangle?
function?
lesser occipital nerve - passes from beneath sternocleidomastoid to ascend in neck towards suboccipital region
supraclavicular nerves - supply skin in lateral side of neck + clavicle
Auricular nerve - passes from beneath sternocleidomastoid to cross anterior surface of this muscle accompanied by external jugular vein
label cutaneous supply
label veins of posterior triangle
external jugular vein found? Pathway?
Internal jugular vein?
Anterior jugular vein?
External jugular = anterior to SCM (post triangle)
external jugular vein crosses the anterior surface of sternocleidomastoid to pass into posterior triangle + cross the anterior surface of posterior belly of omohyoid to reach subclavian vein
Internal jugular = posterior to SCM (ant triangle)
Anterior jugular = midline, may be absent
which nerve passes between sternocleidomastoid and trapezius in the neck?
accessory nerve (supplies both sternocleidomastoid + trapezius)
which strap muscle is found in both the anterior and posterior triangles of the neck?
Omohyoid
The posterior belly of omohyoid crosses the posterior triangle so the muscle is found in both triangles of the neck
which vessels cross posterior triangle immediately posterior to omohyoid?
the transverse cervical and suprascapular vessels
phrenic nerve found where in posterior triangle of neck?
roots of brachial plexus? pathway?
phrenic nerve found on anterior surface of anterior scalene
roots of brachial plexus passes between middle + anterior scalene
arise from C5-T1 and cross through posterior triangle to pass under the clavicle and into the axilla
phrenic nerve crosses the anterior surface of anterior scalene muscle in the root of the neck before passing into the thorax
sternocleidomastoid attachments?
innervation?
what crosses sternocleidomastoid?
mastoid process to —> clavicle + sternum
motor innervation = accessory nerve (CN XI)
proprioception = cervical plexus C2, C3
external jugular vein + great auricular nerve crosses SCM
levator scapulae
label + innervation
Photograph A shows the boundaries of the posterior triangle (white dotted triangle) and the external jugular vein crossing the anterior surface of sternocleidomastoid, the muscle that separates the two triangles.
Photograph B shows some of the neurovascular structures present in the posterior triangle. The cutaneous nerves from the cervical plexus supply the skin of the neck. The supraclavicular nerves fan out across the posterior triangle and onto the skin above the clavicle – they are shown by the white dotted line. The spinal accessory nerve (CN IX) crosses the posterior triangle as it supplies both sternocleidomastoid and trapezius with motor innervation.
Photograph A shows sternocleidomastoid reflected and a deeper dissection of the posterior triangle. The area contained within the white dotted oval lies lateral to the carotid sheath and contains the anterior and middle scalene muscles, the phrenic nerve and the roots of the brachial plexus.
Photograph B shows a closer view of this area. The phrenic nerve runs across the anterior surface of scalenus anterior (anterior scalene) as it passes from the C3,4, and C5 roots in the neck towards the thoracic inlet; where it passes into the thoracic cavity to supply the diaphragm.
The roots of the brachial plexus lie between anterior and middle scalene (scalenus medius). They will then leave the posterior triangle by passing under the clavicle to reach the axilla and supply the upper limb with innervation.
The floor of the posterior triangle is muscular and contains the scalene muscles, levator scapulae and splenius capitis (in that order from anterior to posterior). The anterior and middle scalene muscles were shown on the previous slide, the posterior scalene muscle (scalenus posterior) lies partially hidden by the middle scalene muscle. The scalene muscles arise from the transverse processes of the cervical vertebrae and attach to rib 1 (anterior and middle) and rib 2 (posterior). The scalene muscles act to flex the neck (bilateral) and are innervated by nerves from the anterior cervical rami between C3 and C7.
Levator scapulae passes from the transverse processes of the first four cervical vertebrae to the superior angle/medial border of the scapula. It acts to elevate the scapula or laterally flex the neck to the same side. It is innervated by C3, C4 and C5 via the dorsal scapular nerve.
Splenius capitis acts to extend the neck and is innervated by the cervical dorsal rami nerves. It will be described further during the suboccipital region presentation.
