NB4-3 - Triangles of the Neck

Question 1

Describe the layers of cervical fascia and the structures found within each layer.

Answer 1

1. Superficial fascia - a loose, fatty, subcutaneous layer that is just under the skin. It contains the platysma muscles
2. Deep fascias
   
   1. Investing (deep superficial) layer. It contains the SCM and Trapezius muscles
   2. Middle layers
      
      1. Infrahyoid (muscular) fascia. Contains the infrahyoid muscles
      2. Visceral Fascias
         
         1. Pretracheal Fascia - contains trachea and thyroid
         2. Buccopharyngeal Fascia - thicker continuation of the pretracheal fasica that lies behind the esophagus and spans the distance between the thyroid lobes.
   3. ​​Deep (prevertebral) layer encompases the vertebra and paravertebral musculature

Question 2

Which cervical fasic layers help to form the carotid sheath?

Answer 2

All of them

Question 3

Answer 3

A - infrahyoid (muscular) fascia of the deep middle layer

B - pretracheal fasica of the deep middle visceral layer

C - buccopharyngeal fascia of the deep middle visceral layer

D - Middle Layers of the Deep Fascia

E - Deep (prevertebral layer of the deep fascia

F - Superficial Fascia

G - Superficial (investing) layer of the Deep Fascia

H - Carotid Sheath

Question 4

What strucutres are contained within the carotid sheath

Answer 4

Common Carotid

Internal Jugular

Vagus Nerve

Question 5

Between which two components in the neck is the phrenic nerve found?

Answer 5

Anterior to the anterior scalene and deep to the prevertebral fascia

Question 6

List the two major triangles of the neck and their boundaries.

Answer 6

Anterior Triangle - posteriorly and inferiorly bound by the SCM, laterally bound by the investing fascia, superiorly bound by the mandible, anteriorly bound by the mid-sagittal line

Posterior Triangle - anteriorly bound by the SCM, inferiorly bound by the clavicle, posteriorly bound by the trapezius, superiorly bound by the occipital bone

Question 7

List the muscles that form the floor of the posterior triangle from most superior to most inferior.

Answer 7

1. Splenius Capitus
2. Levator Scapulae
3. Posterior Scalene
4. Middle Scalene
5. Anterior Scalene
6. Inferior Belly of Omohyoid

Question 8

List the various subdivisions of the posterior triangle, their boundaries, and their clinical significance.

Answer 8

• Occipital Triangle - region of the posterior triangle superior to the inferior belly of the omoyoid - no clinical significance
• Subclavian (supraclavicular) Triangle - region of the posterior triangle inferior to the inferior belly of the omohyoid - no clinical significance
• Carefree Triangle - region superior to where CN XI crosses the posterior triangle - no clinical significance
• Careful Triangle - region inferior to where CN XI crosses the posterior triangle - this region contains many branches of the supraclavicular nerves so extra caution should be taken when operating in this region

Question 9

List and describe the location of the cutaneous branches of the cervical plexus.

Answer 9

All nerves emerge from underneath the SCM, about halfway down its length

• Lesser Occipital - runs along the SCM’s posterior edge up to the occipital bone
• Great Auricular - crosses back over the SCM superioanteriorly headed up to the mastoid process
• Transverse Cervical - crosses back over the SCM anteriorly to the front of the neck
• Supraclavicular - heads almost straight down to the shoulder

Question 10

Answer 10

Question 11

Answer 11

Question 12

From where to the nerves of the cervical plexus arise?

Answer 12

The ventral rami of C1-C4

Question 13

The structures emerge through the scalene interval?

Answer 13

The Brachial Plexu

The Subclavian artery

Question 14

Answer 14

Question 15

List the subdivisions of the Anterior Triangle and their boundaries.

Answer 15

• Submental Triangle (only one) - bounded by the anterior bellies of the digastric and the hyoid bone
• Digastric Triangles - bounded by the anterior and posterior bellies of the digastric and the mandible
• Carotid Triangles - bounded by the posterior belly of the digastric, the superior belly of the omohyoid, and SCM
• Muscular Triangles - bounded by the superior belly of the omohyoid, SCM, and mid-sagittal line

Question 16

Answer 16

Question 17

List the muscles found within the muscular triangle, where they originate and insert, and what their primary functions are.

Answer 17

These are all considered to be infrahyoid (strap) muscles and they all serve to depress the hyoid bone.

• Sternohyoid - originates at sternum and inserts at the hyoid. Innervated by the ansa cervicalsi (a loop of nerves from the cervical plexus)
• Sternothyroid - deep to sternohyoid. Originates at sternum and inserts at thyroid cartilage. Innervated by the ansa cervicalis
• Thryohyoid - deep to sternohyoid. Originates at thyroid cartilage and inserts at the hyoid. Innervated by C1

Question 18

Describe the attachments of the omohyoid. What does the omohyoid do? What is it innervated by?

Answer 18

The inferior belly originates at the scapula (omo means shoulder), narrows down into a tendon just as it enters the neck, then becomes the superior belly which inserts at the hyoid bone. The middle tendonous region is attched to the clavicle by a fascial sling. The omohyoid serves to depress the hyoid (therefore considered a strap muscle) and is innervated by the ansa cervicales (a loop of nerves from the cervical plexus)

Question 19

What are the suprahyoid muscles? What do they do? What are they innervated by?

Answer 19

All of these muscles elevate the hyoid

• Mylohyoid - innervated by V3
• Anterior Digastric - innervated by V3
• Stylohyoid - innervated by CN VII
• Posterior Digastric - innervated by CN VII
• Geniohyoid - innervated by C1

Question 20

Answer 20

Question 21

Answer 21

D

Question 22

Label and way whether each branch provides motor or sensory innervation.

Answer 22

Question 23

Which nerves make up the ansa cervicalis?

Answer 23

Superior Branch - C1

Inferior Branch - C2 & C3

Question 24

Explain the relationship between the C1 spinal nerve, the ansa cervicalis, and the hypoglossal nerve.

Answer 24

C1 fibers will branch off the C1 spinal nerve and hitchhike with the hypoglossal nerve. Shortly after this merger, many of the fibers will exit the hypoglossal nerve to form the superior branch of the ansa cervicalis. The rest of the fibers will continue with the hypoglossal nerve and then branch off to innervate the thyrohyoid and geniohyoid muscles.

Question 25

Answer 25

Question 26

How can you easily find the ansa cervicalis on a cadaver?

Answer 26

Locate the infrahyoid muscles and follow one of the nerves from them back to the ansa cervicalis

Question 27

How can you distinguish between the ICA and ECA on a cadaver?

Answer 27

The ECA will give off branches in the neck while the ICA won’t

Question 28

Describe the course of CN XII starting with how it exits the sull.

Answer 28

CNXII exits the skull through the hypoglossal canal and descends medial to the ICA and IJV. It will then pass between the ICA and IJV and hook around the occipital artery. It will then pass deep to the the digastric, stylohyoid, and mylohyoid muscles on its way to the tongue.

Question 29

Answer 29

Question 30

Describe the location of the cervical sympathetic ganglia and which structures they innervate.

Answer 30

There are only three cervical ganglia per side (superior around C2 level and middle/inferior around C5/C6 level) and they are located anterior to the prevertebral muscles and posteromedial to the carotid sheath. They will suppy sympathetic innervation to the head, neck, hear, and upper limb.

Question 31

Answer 31

Question 32

What is the mnemonic to remember the branches of the ECA and how is it used?

Answer 32

The mnemonic is for the ECA branches from inferior to superior - Some Anatomists Love Freaking Out Poor Medical Students

Superior Thyroid, Ascending Pharyngeal, Lingual, Facial, Occipital, Posterior Auricular, Maxillary, Superficial Temporal

Question 33

Answer 33

Question 34

What is a pyramidal lobe?

Answer 34

It is a piece of ectopic thryoid gland that can sometimes be found somewhere along the thyroglossal duct

Question 35

Describe the arterial supply and venous drainage of the thyroid gland

Answer 35

Arterial Supply - Superior thyroid (from ECA), inferior thyroid (from thyrocervical trunk), thyroid ima (variable presence from subclavian)

Venous Drainage - superior thyroid (into IJV), middle thyroid (into IJV), inferior thyroid (into brachiocephalic)

Question 36

What nerve is closely associated with the thyroid gland and how

Answer 36

The recurrent laryngeal nerve runs just posterior to the thyroid gland in the trachoesophageal groove

Question 37

Answer 37

A

Question 38

Describe the pathway of lymphatic drainage from the superficial structures of the face, scalp, head, and neck.

Answer 38

Face, scalp, and head superficial structures will drain to the collar nodes first (occipital, mastoid (posterior auricular), parotid (pre-auricular), submandibular, submental) then to the deep cervical nodes which run along the IJV

Neck superficial structures will drain to the superficial cervical nodes which run along the EJV and then drain into the deep cervical nodes. will drain to the right and left jugular trunks which then drain to the right lymphatic duct and thoracic duct, respectively. Both will then drain into a subclavian vein

Question 39

What are and where are the clinically significant lymph nodes that drain the head and neck? Which specific areas do they drain? Why are they clinically significant?

Answer 39

Jugulo-digastric (tonsilar) node - located just anterior to the mastoid process and drains the tonsilar region (indirectly drains most of face and scalp)

Jugulo-omohyoid node - located just lateral to the thyroid and drains the tongue (indirectly drains most of head and neck)

Both these nodes are large and prominent and easy to palpate.