Posterior Triangle of Back

Question 0

List the boundaries of the posterior triangle (posterior, anterior, inferior/base, floor, roof)

Answer 0

Posterior: trapezius
Anterior: sternocleidomastoid
Inferior: clavicle
Floor: musculature and prevertebral fascia
Roof: investing layer of deep cervical fascia

Question 1

What is the key muscle of the neck? What is it’s innervation? What does this muscle divide the neck into?

Answer 1

The sternocleidomastoid muscle, innervated by CNXI, divides neck into two triangles (anterior and posterior)

Question 2

What structure divides the posterior triangle into two subtriangles? Name them

Answer 2

The inferior belly of the omohyoid muscle divides it into the large superior occipital triangle and the lower supraclavicular triangle.

Question 3

List at least one important structure in the lower of these two triangles (occipital & supraclavicular)

Answer 3

The subclavian artery

Question 4

The ventral rami of which two plexuses can be found in the posterior triangle?

Answer 4

The brachial and cervical plexuses.

Question 5

What are the root values (spinal cord levels involved in the formation) of each plexus? What do they supply?

Answer 5

Cervical plexus- C1-C4, sensory innervation to neck & upper thorax
Brachial plexus- C5-T1, motor & sensory to upper limb

Question 6

Which is purely sensory– cervical or brachial plexus?

Answer 6

Cervical

Question 7

What are the root values (spinal cord levels involved in the formation) of each plexus?

Answer 7

inferior to superior- scalenus anterior, scalenus medius, levator scapulae, splenius capitis, semispinalis capitis.

Question 8

Between which two muscles is the brachial plexus located?

Answer 8

Scalenus anterior and scalenus medius.

Question 9

Where is the scalenus posterior located?

Answer 9

posterior to the scalenus medius

Question 10

Name the nerve that can be found lying superficial to the scalenus anterior?

Answer 10

Phrenic

Question 11

Name the nerve superficial to the levator scapulae?

Answer 11

CN XI

Question 12

Posterior compartment contains what and and required for what?

Answer 12

contains vertebral column and musculature required for flexion/extension of the neck. It is specialized for support

Question 13

Anterior compartment of neck

Answer 13

Divided into 2 anterior triangles. It includes the larynx/trachea and pharynx. Contains a neurovascular bundle

Question 14

Superior and inferior attachments of SCM?

Answer 14

Superior- mastoid process

Inferior- sternum & clavicle

Question 15

Function of sternocleidomastoid muscle?

Answer 15

unilaterally tilt head toward the shoulder of the same side, rotating the face to the opposite side. bilaterally protract the head

Question 16

What are the boundaries of the neck?

Answer 16

Superior- superior nuchal line, mastoid process, inferior border of mandible
Inferior- clavicle & sternum
Posterior- trapezius
Anterior- midline

Question 17

What are the four layers of deep cervical fascia of the neck?

Answer 17

• Investing layer (roof of post/ant triangles)
• Pretracheal layer (sheath around thyroid)
• Prevertebral layer (surrounds vertebra & musculature)
• Carotid sheath (all 3 layers, encloses neruovascular bundle of neck)

Question 18

Which cervical fascia layer is the fascial carpet?

Answer 18

The prevertebral layer

Question 19

What muscle divides the posterior triangle in two? What are the names of these two things?

Answer 19

The inferior belly of the omohyoid muscle divides the posterior triangle into the larger superior occipital triangle and the lower smaller supraclavicular triangle.

Question 20

What are the four nerves of the cervical plexus?

Answer 20

Lesser occipital, transverse cutaneous, great auricular, supraclavicular

Question 21

What are the muscles of the posterior triangle floor?

Answer 21

1) semispinalis capitis
2) splenius capitis
3) levator scapulae
4) scalenus medius
5) scalenus anterior