Posterior Triangle of the Neck and Fascial Layers

Question 1

Superficial Fascia of the Neck

Answer 1

Immediately deep to skin (subcutaneous tissue)
- Comprised of loose connective tissue & fat
- Thinner than other areas of the body

Question 2

Platysma m.

Answer 2

Platysma m. in the subcutaneous tissue
- Similar to scalp and facial expression mm.
- Innervated by CN VII (facial)

Question 3

Deep Fascia Layers of the Neck

Answer 3

Deep to superficial fascia; dense, organized connective tissue layer, devoid of fat
- Envelops most body structures deep to skin & subcutaneous tissue
- Compartmentalizes structures of the neck
o Investing fascia
o Prevertebral fascia
o Carotid sheath, alar fascia
o Pretracheal fascia, buccopharyngeal fascia

Question 4

Investing Fascia

Answer 4

Most superficial of deep fascia layers; encircles the entire neck
- Surrounds trapezius m. and SCM
- Superior and inferior terminations are the same as the trapezius and sternocleidomastoid m. attachments (clavicle)

Question 5

Prevertebral Layer of Deep Cervical Fascia

Answer 5

Tubular sheath for prevertebral mm.
Contents: longus colli, longus capitius, scalenes, and deep cervical mm.
Attachments:
- Cranial base (superiorly)
- Endothoracic fascia (inferiorly)
- ALL at T3 (centrally)
- Axillary sheath that surrounds brachial plexus, axillary vessels, and cervical sympathetic trunk (laterally) *IMPORTANT if infection in the area, can affect surrounding plexus

Question 6

Carotid sheath of Deep Cervical Fascia

Answer 6

Tubular fascia, extends from base of cranium to the root of the neck
Contents: common and internal carotid aa., IJV, CN X, some deep cervical lymph nodes, carotid sinus n., sympathetic nn.
Attachments:
- Blends with investing and pre-tracheal fascia (anteriorly)
- Blends with prevertebral layer of fascia (posteriorly)
- Cranial base (superiorly)
- Middle mediastinum of thorax (inferiorly)

Question 7

Pretracheal fascia

Answer 7

Limited to anterior neck
Muscular part: encloses infrahyoid mm (in purple)
Visceral part: thyoids gland, trachea, esophagus (in blue)- continuous posteriorly and superiorly with buccopharyngeal fascia of pharynx (green)
Attachments: hyoid bone (superiorly), blends with fibrous pericardium of heart (inferiorly), continuous with carotid sheath (laterally)

Question 8

Alar Fasia of Deep Cervical Fasia

Answer 8

Thin layer to prevertebral fascia, further subdivides retropharyngeal space
Attachments:
- Posterior side of buccopharygeal fascia (midline)
- Cranium (superiorly)
- Level of C7/T2 (inferiorly)
- Extends laterally and terminates in carotid sheath/prevertebral fascia

Question 9

Retropharyngeal Space

Answer 9

Located posterior to buccopharyngeal fascia and anterior to alar fascia
- Permits movement of pharynx, esophagus, larynx, trachea relative to vertebral column during swallowing
Attachments:
- Cranial base (superiorly)
- Carotid sheath (laterally)
- Superior mediastinum (inferiorly, about T1,T2)

Question 10

Prevertebral “Danger” Space

Answer 10

Between alar & prevertebral fascia
- Infections here can spread from skull base down into posterior mediastinum to the level of the diaphragm
- Nortorious for inferior spread of infections here

Question 11

Posterior Cervical Triangle

Answer 11

Wraps around to lateral side of neck, contains platysma m.
Boundaries: posterior border of SCM (anterior), anterior border of Trapezius m. (posterior), middle 1/3 of clavicle (inferior), investing layer of deep cerical fascia (roof); splenius capitus, levator scapulae, middle and posterior scalene mm. covered by prevertebral fascia (floor)
Contents:
- Platysma m.
- Neurovasculature: EJV, cutaneous nn., Motor nn., transverse cervical & suprascapular aa.
- Deep muscles

Question 12

Sternocleidomastoid m.

Answer 12

O: mastoid process
I: Sternal head: anterior surface of manubrium of sternum
Clavicular head: superior surface of medial 1/3 clavicle
Inn: Accessory n. (CN XI)
Action:
Unilateral: ipsilateral neck flexion & rotates superiorly to contralateral side
Bilaterally: extend neck, flex cervical vertebrae (bring chin to manubrium), extend superior and flex inferior cervical vertebrae (thrust chin forward with level head)
Assists in respiration (elevate manubrium and clavicle

Question 13

Trapezius m.

Answer 13

O: midline
I: lateral 1/3 clavicle, acromion, spine of scapula
Inn: Accessory n. (CN XI)
Action: Descending part: elevates
Ascending part: depresses
Middle/all part together: retracts
Descending and ascending: rotate glenoid cavity superiorly

Question 14

Posterior Triangle Contents

Answer 14

• Platysma m.
• Neurovasculature: EJV, cutaneous nn., Motor nn., transverse cervical & suprascapular aa.
• Deep muscles

Question 15

Lesser Occipital Nerve

Answer 15

C2
Runs superiorly along posterior border of SCM, crosses over portion of occipital a.
- Supplies neck and scalp posterior to auricle

Question 16

Greater auricular n.

Answer 16

C2-C3
Ascends vertically on surface of SCM, runs with EJV superiorly toward ear
– Supplies lobe & skin posterior to auricle
– Also supplies angle of mandible to mastoid process

Question 17

Transverse Cervical N.

Answer 17

C2-C3
Runs transversely across middle of SCM
- Supplies skin of anterior cervical triangle & lateral neck

Question 18

Supraclavicular nn.

Answer 18

C3-C4
Generally 3 main branches: medial, intermediate & lateral (post.) nn.
Run superficial to clavicle & deep to platysma
- Supply skin of clavicular region

Question 19

Accessory N

Answer 19

CN XI
Emerges from jugula foreamen of skull, runs diagonally through triangle deep to investing fascia
- Supplies both SCM & trapezius mm.

Question 20

Phrenic N.

Answer 20

C3-C5
Located deep to prevertebral fascia, descends vertically along anterior scalene m., crossed anteriorly by transverse cervical a. & suprascapular a.
- Enters thorax between subclavian v. & a.
- Travels along pericardial sac to supply diaphragm

Question 21

Transverse Cervical and Suprascapular Arteries

Answer 21

• Both arise from the thyrocervical trunk
• Transverse cervical a. supplies trapezius m.
• Supplies rhomboid and levator scapulae mm. as dorsal scapular a.
• Suprascapular a. supplies supraspinatus and infraspinatus mm.

Question 22

3 Scalene mm.

Answer 22

Inn: Ventral rami C3-C8 nn.
Action: Tilt neck laterally

Question 23

Interscalene Triangle

Answer 23

Elongated triangle deep to posterior cerivcal trinagle
- Formed by anterior scalene, middle scalene & 1st rib
- Brachail prexus roots & subclaian a. pass through the triangle
- Subclavian v. passes anterior to anterior scalene m.
- Thoracic outlet syndomre can happen in this area (cancer, pregnancy), leading to compression to nerve and blood vessel