posterior triangle of the neck Flashcards
what are the borders of the posterior triangle of the neck?
anterior border: posterior border of SCM
posterior border: anterior border of trapezius
base: clavicle
what are the contents of the posterior triangle of the neck?
external jugular vein
roots of the brachial plexus
accessory nerve
cranial and supraclavicular lymph nodes
what is the course of the lesser occipital nerve?
it passes from beneath the SCM to ascend the neck towards the suboccipital region
what do supraclavicualr nerves supply?
the skin on the lateral side of the neck and clavicle
explain the course of the great auricular nerve
it passes from beneath the SCM to cross the anterior surface of SCM accompanied by the external jugular vein
which veins form the external jugular vein?
the external jugular vein is formed by the union of the posterior auricuarl vein w/ the posterior division of the retromandibular vein
explain the course of the external jugular vein
it crosses the anterior surface of SCM to pass into the posterior triangle and cross the anterior surface of the posterior belly of omohyoid to reach the subclavian vein deep in the root of the neck
what nerve supplies trapezius and SCM w/ motor innervation?
the spinal accessory nerve
which muscle is found in both triangles of the neck?
omohyoid
the posterior belly of omohyoid crosses the posterior triangle
which 3 small vessels cross the posterior triangle immediately posterior to omohyoid?
transverse cervical artery
supra scapular artery
suprascapular vein
what nerve roots are seen in the posterior triangle of the neck?
the roots of the brachial plexus and the phrenic nerve
what are the nerve roots of the phrenic nerve?
C3,C4,C5
explain the course of the phrenic nerve
it descends into the neck and crosses the anterior scalene muscle in the root of the neck before passing into the thorax
explain the course of the roots of the brachial plexus
the roots of the brachial plexus arise from C5-T1 and cross through the posterior triangle of the neck to pass under the clavicle and into the axilla
what are the muscles of the posterior triangle of the neck?
sternocleidomastoid
trapezius
omohyoid
scalane muscles
levator scapulae
splenuius capitis
which triangle does SCM lie in?
it forms the borders between the triangles of the neck so technically doesn’t lie in either triangle
explain the distribution of SCM
it is a v large muscle that attaches to the mastoid process of the temporal bone and crosses the neck to attach to both the clavicle and the sternum
what is the innervation of SCM?
motor innervation: spinal accessory nerve (CN11)
proprioception: cervical plexus (C2,3)
what does lateral flexion of SCM do?
brings the head closer to the shoulder
what does extension of SCM do?
pulls the head backwards
what does flexion of SCM do?
pulls the chin towards the body wall
does trapezius lie in the posterior triangle?
no, it forms the posterior boundary of the posterior triangle so does not lie w/in the triangle itself
what forms the muscular floor of the posterior triangle?
omohyoid, scalene muscles, levator scapulae and splenius capitis
what is the function of omohyoid?
depresses the hyoid bone
what is the innervation of omohyoid?
it is innervated by ansa cervicalis
what are the two functions of splenius capitis?
elevate the scapula
laterally flex the neck if the shoulder is in a fixed position
what is the innervation of levator scapulae?
innervated directly by C3,C4 and C5 via the dorsal scapular nerve
which nerve crosses the anterior scalene?
the phrenic nerve
where in relation to the scalenes do the roots of the brachial plexus lie?
between anterior and middle scalenes
what are the functions of the scalene muscles?
flex the neck (bilateral)
tilt the head to the same side (unilateral)
elevate the upper ribs
what is the innervation of the posterior scalene?
anterior rami of C5-C7
what is the innervation of the anterior scalene?
anterior rami of C4-C7
what is the innervation of the middle scalene?
anterior rami of C3-C7
