Posterior Triangle 3

Question 0

What does the SCM divide the neck into?

Answer 0

Posterior and anterior triangles

Question 1

What is the key muscle of the neck? What is is attached to? What does it do? What it’s innervation?

Answer 1

The sternocleidomastoid.
It’s attached to the mastoid process, sternum and clavicle.
It functions to tilt the head toward the shoulder of the same side and rotate the face to the opposite side. Together, both muscles protract (or draw forward) the head.
It’s innervated by the Cranial nerve XI.

Question 2

What are the 3 “compartments” that make up the neck?

Answer 2

1. Posterior: support-vertebral column, musculature for flexion/extension of neck
2. Anterior or median visceral: 2 anterior triangles, deep viscera (larynx/trachea and pharynx, and a neurovascular bundle
3. Posterior triangles (lateral cervicle regions): continuous with axilla, brachial plexus and subclavian a/v are here

Question 3

What are the 4 layers of cervical fascia?

Answer 3

1. Investing layer: roofs the posterior and anterior triangles, surrounds the entire neck
2. Pretracheal: forms sheath around thyroid
3. Prevertebral: forms fascial carpet over floor of post. triangle, surrounds support compartment (musc./vert.)
4. Carotid sheath: condensation of all 3 layers enclosing the verticle neurovascular bundle (common carotid a., internal jugular v., vagus n.)

Question 4

What are the boundaries of the posterior triangle?

Answer 4

Base: superior border of the clavicle
Anterior: posterior border of the SCM
Posterior: anterior border of trapezius
Roof: investing layer of cervical fascia
Floor: musculature and prevertebral fascia

Question 5

Which muscles divides the posterior triangle into 2 subtriangles? What are these triangles?

Answer 5

The inferior belly of omohyoid

1) occipital triangle: larger and superior
2) supraclavicular triangle : smaller and inferior

Question 6

Name an important structure in the supraclavicular triangle.

Answer 6

The subclavian artery

Question 7

The ventral rami of _________ plexus and _________ plexus can be found in the posterior triangle.

Answer 7

Cervical and brachial

Question 8

Where are the brachial and cervical plexus located? (What spinal cord levels?)

Answer 8

Cervical: C1-C4
Brachial: C5-C8/T1

Question 9

Which plexus is purely sensory?

Answer 9

Cervical

Question 10

Where is the brachial plexus located? What does it supply?

Answer 10

Floor of the triangle between the scalenus anterior and medius. It supplies sensory innervation for the upper limb.

Question 11

What does the cervical plexus supply innervation to? What are the 4 major nerves that make up this plexus? Which nerve can we see in lab?

Answer 11

It supplies sensory innervation to the neck and upper thorax.

1. Lesser occipital
2. Transverse cutaneous
3. Great auricular
4. Supraclavicular <~~~~

Question 12

Which 3 nerves/plexuses can be found in the post triangle?

Answer 12

Brachial plexus
Cervical plexus
Accessory nerve

Question 13

Where is the needle inserted in a cervical block?

Answer 13

1/2 way up the posterior border of the SCM

Question 14

Where is the accessory nerve found? What does it supply?

Answer 14

Crosses overtop of the levator scapulae

It supplies motor information to the SCM and trapezius.

Question 15

Name the muscles that make up the floor of the posterior triangle.

Answer 15

Scalenus anterior
Scalenus medius
Levator scapulae
Selenium capitis 
Semispinalis capitis

Question 16

Where does the phrenic nerve lie?

Answer 16

Crosses overtop the anterior scalene

Question 17

Where does the brachial plexus enter the axilla?

Answer 17

Cervicoaxillary canal

Question 18

Where do the scalene muscles arise from on the vertebrae? Insertion?

Answer 18

Transverse processes of cervical nerves

R1 and R2

Question 19

The accessory nerve lies _______ the fascial carpet.

Answer 19

Above

Question 20

What are the functions of the SCM?

Answer 20

Unilaterally acts to tilt the head to the same side and rotate the head to the opposite side.
Bilaterally acts to extend the head and to aid in respiration when the head is fixed.