Posterior Triangle of the Neck

Question 1

Answer 1

Question 2

boundaries of posterior triangle of neck?

contents?

Answer 2

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

Question 3

label with roots

Answer 3

Question 4

which sensory nerves of the cervical plexus lie in the posterior triangle?
function?

Answer 4

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

Question 5

label cutaneous supply

Answer 5

Question 6

label veins of posterior triangle

Answer 6

Question 7

external jugular vein found? Pathway?
Internal jugular vein?
Anterior jugular vein?

Answer 7

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

Question 8

Answer 8

Question 9

which nerve passes between sternocleidomastoid and trapezius in the neck?

Answer 9

accessory nerve (supplies both sternocleidomastoid + trapezius)

Question 10

Answer 10

Question 11

Answer 11

Question 12

which strap muscle is found in both the anterior and posterior triangles of the neck?

Answer 12

Omohyoid

The posterior belly of omohyoid crosses the posterior triangle so the muscle is found in both triangles of the neck

Question 13

which vessels cross posterior triangle immediately posterior to omohyoid?

Answer 13

the transverse cervical and suprascapular vessels

Question 14

Answer 14

Question 15

phrenic nerve found where in posterior triangle of neck?

roots of brachial plexus? pathway?

Answer 15

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

Question 16

Answer 16

phrenic nerve crosses the anterior surface of anterior scalene muscle in the root of the neck before passing into the thorax

Question 17

sternocleidomastoid attachments?
innervation?
what crosses sternocleidomastoid?

Answer 17

mastoid process to —> clavicle + sternum

motor innervation = accessory nerve (CN XI)
proprioception = cervical plexus C2, C3

external jugular vein + great auricular nerve crosses SCM

Question 18

movements of SCM?

Answer 18

lateral flexion, rotation, extension + flexion

Question 19

Answer 19

Question 20

innervation trapezius?

function?

Answer 20

Innervation = accessory nerve, cervical plexus C3, C4 (proprioception)

ascending part depresses scapula, transverse part retracts scapula, descending part elevates scapula, rotates glenoid cavity

holds scapula in position when weightlifting

Question 21

muscular floor of posterior triangle?
function + innervation?

Answer 21

omohyoid, splenius capitis, levator scapulae + scalene muscles

omohyoid - depresses hyoid bone
ansa cervicalis

splenius capitis - extends neck, rotates
dorsal rami of middle cervical

Question 22

Answer 22

Question 23

Answer 23

Question 24

Levator scapulae attachments?
function?
innervation?

Answer 24

from transverse processes of atlas, axis, C3 + C4 to —> medial scapular border between superior angle and medial end of scapular spine

function = elevate shoulder (with trapezius), shoulder fixed can laterally flex neck to the same side

innervation = direct C3, 4 + C5 via dorsal scapular nerve

Question 25

Answer 25

levator scapulae

Question 26

scalene attachments? | function?

Answer 26

From transverse processes of C3-6 (anterior), C2-7 (middle) and C4-6 (posterior) to ---> rib 1 (scalene tubercle = anterior; and behind subclavian artery groove = middle) and rib 2 (posterior) innervation = flex neck (bilateral), tilt head to same side (unilateral) and elevate upper ribs

Question 27

label + innervation

Answer 27

Question 28

what crosses anterior scalene? | what lies between anterior + middle scalene?

Answer 28

Anterior scalene is crossed by the phrenic nerve The roots of the brachial plexus lie between anterior and middle scalene

Question 29

Answer 29

Question 30

Answer 30

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.

Question 31

Answer 31

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.

Question 32

Answer 32

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.