Anatomy of the neck

Question 1

What is a key aim of surgery

Answer 1

Removing what you need to remove whilst preserving what you need to preserve- removing tissues will result in a loss of function

Question 2

Where does the neck run from

Answer 2

The neck is a tube providing continuity from the head to the trunk. It extends anteriorly from the lower border of the mandible to the upper surface of the manubrium of the sternum, and posteriorly from the superior nuchal line on the occipital bone of the skull to the intervertebral disc between the CVII and TI vertebrae.

Question 3

Summarise the functions of the neck

Answer 3

Structural – support and move head
inside prevertebral fascia

Visceral functions (thyroid gland, parathyroid gland, oesophagus and trachea) 
inside or associated with pretracheal fascia

Conduit for blood vessels & nerves
inside or associated with carotid sheaths

Question 4

What are the different compartments bounded by

Answer 4

Deep fascia (largely collagen)
Separates tissues, organs and muscles into planes- good for maintaining the integrity of the different tissues (holds them together)- the spread of different diseases is confined to certain compartments.

Question 5

Describe the different compartments of the neck

Answer 5

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The visceral compartment is anterior and contains parts of the digestive and respiratory systems, and several endocrine glands.
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The vertebral compartment is posterior and contains the cervical vertebrae, spinal cord, cervical nerves, and muscles associated with the vertebral column.
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The two vascular compartments, one on each side, are lateral and contain the major blood vessels and the vagus nerve [X].

Question 6

Describe the superficial fascia in the neck

Answer 6

The superficial fascia in the neck contains a thin sheet of muscle (the platysma), which begins in the superficial fascia of the thorax, runs upward to attach to the mandible and blend with the muscles on the face, is innervated by the cervical branch of the facial nerve [VII], and is only found in this location.

Question 7

What is the deep cervical fascia split into

Answer 7

Deep to the superficial fascia, the deep cervical fascia is organized into several distinct layers (Fig. 8.156). These include:
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an investing layer, which surrounds all structures in the neck;
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the prevertebral layer, which surrounds the vertebral column and the deep muscles associated with the back;
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the pretracheal layer, which encloses the viscera of the neck; and
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the carotid sheaths, which receive a contribution from the other three fascial layers and surround the two major neurovascular bundles on either side of the neck.

Question 8

Which structures does the investing layer of fascia surround

Answer 8

The investing layer completely surrounds the neck

Question 9

Describe the passage of the investing fascia

Answer 9

Attaching posteriorly to the ligamentum nuchae and the spinous process of the CVII vertebra, this fascial layer splits as it passes forward to enclose the trapezius muscle, reunites into a single layer as it forms the roof of the posterior triangle, splits again to surround the sternocleidomastoid muscle, and reunites again to join its twin from the other side.

Anteriorly, the investing fascia surrounds the infrahyoid muscles

Question 10

Describe the attachments of the investing fascia

Answer 10

The investing fascia is attached:
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superiorly to the external occipital protuberance and the superior nuchal line,
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laterally to the mastoid process and zygomatic arch, and
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inferiorly to the spine of the scapula, the acromion, the clavicle, and the manubrium of the sternum.

Question 11

Which structures pierce the investing fascia

Answer 11

The external and anterior jugular veins, and the lesser occipital, great auricular, transverse cervical, and supraclavicular nerves, all branches of the cervical plexus, pierce the investing fascia.

Question 12

Describe the prevertebral layer

Answer 12

The prevertebral layer is a cylindrical layer of fascia that surrounds the vertebral column and the muscles associated with it (Fig. 8.158). Muscles in this group include the prevertebral muscles, the anterior, middle, and posterior scalene muscles, and the deep muscles of the back.

Question 13

Describe the attachements of the prevertebral fascia

Answer 13

The prevertebral fascia is attached posteriorly along the length of the ligamentum nuchae, and superiorly forms a continuous circular line attaching to the base of the skull. This circle begins:
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anteriorly as the fascia attaches to the basilar part of the occipital bone, the area of the jugular foramen, and the carotid canal;
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continues laterally, attaching to the mastoid process; and
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continues posteriorly along the superior nuchal line ending at the external occipital protuberance, where it associates with its partner from the opposite side.
Anteriorly, the prevertebral fascia is attached to the anterior surfaces of the transverse processes and bodies of vertebrae CI to CVII.

Question 14

Describe the longitudinal fascial space created by the prevertebral fascia

Answer 14

The prevertebral fascia passing between the attachment points on the transverse processes is unique. In this location, it splits into two layers, creating a longitudinal fascial space containing loose connective tissue that extends from the base of the skull through the thorax

Question 15

Describe the fascial extension of the prevertebral fascia

Answer 15

There is one additional specialization of the prevertebral fascia in the lower region of the neck. The prevertebral fascia in an anterolateral position extends from the anterior and middle scalene muscles to surround the brachial plexus and subclavian artery as these structures pass into the axilla. This fascial extension is the axillary sheath.

Question 16

Describe the pretracheal layer

Answer 16

The pretracheal layer consists of a collection of fascias that surround the trachea, esophagus, and thyroid gland (Fig. 8.158). Anteriorly, it consists of a pretracheal fascia that crosses the neck, just posterior to the infrahyoid muscles, and covers the trachea and the thyroid gland. The pretracheal fascia begins superiorly at the hyoid bone and ends inferiorly in the upper thoracic cavity. Laterally, this fascia encloses the thyroid gland and more posteriorly is continuous with fascia that surrounds the esophagus.

Question 17

Posterior to the trachea, what is the pretracheal fascia referred to as

Answer 17

Posterior to the pharynx, the pretracheal layer is referred to as the buccopharyngeal fascia and separates the pharynx from the prevertebral layer (Fig. 8.159).
The buccopharyngeal fascia begins superiorly at the base of the skull and merges with fascia covering the esophagus that then continues inferiorly into the thoracic cavity.

Question 18

What is the name given to the fascia between the posterior aspect of the oesophagus and the anterior part of the prevertebral fascia?

Answer 18

Buccopharyngeal fascia

Question 19

Describe the carotid sheath

Answer 19

Each carotid sheath is a column of fascia that surrounds the common carotid artery, the internal carotid artery, the internal jugular vein, and the vagus nerve as these structures pass through the neck (Fig. 8.158).
It receives contributions from the investing, prevertebral, and pretracheal layers, though the extent of each component’s contribution varies.

Question 20

What is a key consequence of the fascial spaces

Answer 20

Between the fascial layers in the neck are spaces that may provide a conduit for the spread of infections from the neck to the mediastinum.

Question 21

Describe the pretracheal space

Answer 21

The first is the pretracheal space between the investing layer of cervical fascia (covering the posterior surface of the infrahyoid muscles) and the pretracheal fascia (covering the anterior surface of the trachea and the thyroid gland), which passes between the neck and the anterior part of the superior mediastinum.

Question 22

Describe the retropharyngeal space

Answer 22

The second is the retropharyngeal space between the buccopharyngeal fascia (on the posterior surface of the pharynx and esophagus) and the prevertebral fascia (on the anterior surface of the transverse processes and bodies of the cervical vertebrae), which extends from the base of the skull to the upper part of the posterior mediastinum.

Question 23

Describe the third fascial space

Answer 23

The third space is within the prevertebral layer covering the anterior surface of the transverse processes and bodies of the cervical vertebrae. This layer splits into two laminae to create a fascial space that begins at the base of the skull and extends through the posterior mediastinum to the diaphragm.

Question 24

Summarise the hyoid

Answer 24

Freely moving bone in the neck
Surrounded by a collection of muscles- go to underside of chin
Muscles from larynx, thyroid cartilage and hyoid move downwards- strap muscles- concerned with elevation and depression of the larynx during swallowing as well as helping to open the mandible

Question 25

Why do we need cervical ganglia

Answer 25

No sympathetic outflow in the cervical spinal cord- BUT we need sympathetic innervation to the face and head- thus we have the cervical ganglia

Question 26

Where does the hyoid bone sit

Answer 26

Superior to the thyroid cartilage (adam’s apple)

U-shaped bone consisting of supra- and infra-hyoid muscles.

Question 27

Where do the two plates of thyroid cartilage meet

Answer 27

Anteriorly.

Question 28

What important structures are at each of the following levels:

Answer 28

C1	open mouth
C2	superior cervical ganglion
C3	body of hyoid
C4	upper border of thyroid cartilage
	bifurcation of common carotid artery- into internal (supplying brain) and external (supplying face) 
C6	cricoid cartilage
	middle cervical ganglion
C7	inferior cervical ganglion

Question 29

Where does the cricoid sit

Answer 29

Inferior to the thoracic cartilage
Important for voice
But also clinically as an emergency access to the airways
passageway between thyroid and cricoid cartilage- can be penetrated (i.e by a pen) to open up obstructed airway in a patient who is unable/struggling to breathe.

Question 30

Summarise the function of the sternocleidomastoid muscle

Answer 30

Turn head over shouldr

Left muscle- contracts to loom over right shoulder.

Question 31

What are the boundaries of the anterior triangle of the neck

Answer 31

The anterior triangle of the neck is outlined by the anterior border of the sternocleidomastoid muscle laterally, the inferior border of the mandible superiorly, and the midline of the neck medially

Question 32

How can the anterior triangle be further subdivided

Answer 32

Submandibular triangle
submental triangle
muscular triangle
carotid triangle

Question 33

Describe the submandibular triangle

Answer 33

The submandibular triangle is outlined by the inferior border of the mandible superiorly and the anterior and posterior bellies of the digastric muscle inferiorly.

Question 34

Describe the submental triangle

Answer 34

The submental triangle is outlined by the hyoid bone inferiorly, the anterior belly of the digastric muscle laterally, and the midline.

Question 35

Describe the muscular triangle

Answer 35

The muscular triangle is outlined by the hyoid bone superiorly, the superior belly of the omohyoid muscle, and the anterior border of the sternocleidomastoid muscle laterally, and the midline.

Question 36

Describe the carotid triangle

Answer 36

The carotid triangle is outlined by the superior belly of the omohyoid muscle anteroinferiorly, the stylohyoid muscle and posterior belly of the digastric superiorly, and the anterior border of the sternocleidomastoid muscle posteriorly.

Question 37

What can the muscles of the anterior triangle be divided into

Answer 37

Supra- and infrahyoid muscles

Question 38

What are the suprahyoid muscles

Answer 38

Muscles superior to the hyoid are classified as suprahyoid muscles and include the stylohyoid, digastric, mylohyoid, and geniohyoid.

Question 39

What are the infrahyoid muscles

Answer 39

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Muscles inferior to the hyoid are infrahyoid muscles and include the omohyoid, sternohyoid, thyrohyoid, and sternothyroid.

Question 40

Describe the stylohyoid muscle

Answer 40

The stylohyoid muscle arises from the base of the styloid process and passes anteroinferiorly to attach to the lateral area of the body of the hyoid bone (Fig. 8.163). During swallowing it pulls the hyoid bone posterosuperiorly and it is innervated by the facial nerve [VII].

Question 41

Describe the two bellies of the digastric muscle

Answer 41

The digastric muscle has two bellies connected by a tendon, which attaches to the body of the hyoid bone (Fig. 8.163):
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The posterior belly arises from the mastoid notch on the medial side of the mastoid process of the temporal bone.
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The anterior belly arises from the digastric fossa on the lower inside of the mandible.

Question 42

Describe the two actions of the digastric muscle

Answer 42

The tendon between the two bellies, which is attached to the body of the hyoid bone, is the point of insertion of both bellies. Because of this arrangement, the muscle has multiple actions depending on which bone is fixed:
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When the mandible is fixed, the digastric muscle raises the hyoid bone. (posterior belly)
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When the hyoid bone is fixed, the digastric muscle opens the mouth by lowering the mandible (anterior belly)

Question 43

Describe the innervation of the digastric muscle

Answer 43

Innervation of the digastric muscle is from two different cranial nerves.
The innervation of the posterior belly of the digastric muscle is by the facial nerve [VII], whereas the anterior belly of the muscle is innervated by the mandibular division [V3] of the trigeminal nerve [V].

Question 44

Describe the mylohyoid muscle

Answer 44

The mylohyoid muscle is superior to the anterior belly of the digastric and, with its partner from the opposite side, forms the floor of the mouth (Fig. 8.163). It originates from the mylohyoid line on the medial surface of the body of the mandible and inserts into the hyoid bone and also blends with the mylohyoid muscle from the opposite side.

Question 45

Describe the function and innervation of the mylohyoid muscle

Answer 45

This mylohyoid muscle supports and elevates the floor of the mouth and elevates the hyoid bone. It is innervated by the mandibular division [V3] of the trigeminal nerve [V].

Question 46

Describe the geniohyoid muscle

Answer 46

The geniohyoid muscle is superior to the floor of the oral cavity and is not generally considered a muscle of the anterior triangle of the neck; however, it can be regarded as a suprahyoid muscle. It is the final muscle in the suprahyoid group (Fig. 8.163). A narrow muscle, it is superior to the medial part of each mylohyoid muscle. The muscles from each side are next to each other in the midline.
The geniohyoid arises from the inferior mental spine of the mandible and passes backward and downward to insert on the body of the hyoid bone.

Question 47

Describe the function and innervation of the geniohyoid muscle

Answer 47

It has two functions depending on which bone is fixed:
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Fixation of the mandible elevates and pulls the hyoid bone forward.
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Fixation of the hyoid bone pulls the mandible downward and inward.
The geniohyoid is innervated by a branch from the anterior ramus of C1 carried along the hypoglossal nerve [XII].

Question 48

Summrise the infrahyoid muscles

Answer 48

The four infrahyoid muscles are related to the muscular triangle (Fig. 8.162). They attach the hyoid bone to inferior structures and depress the hyoid bone. They also provide a stable point of attachment for the suprahyoid muscles. Because of their appearance, they are sometimes referred to as the “strap muscles.”

Question 49

Describe the sternohyoid muscle

Answer 49

The sternohyoid muscle is a long, thin muscle originating from the posterior aspect of the sternoclavicular joint and adjacent manubrium of the sternum (Fig. 8.164). It ascends to insert onto the body of the hyoid bone. It depresses the hyoid bone and is innervated by the anterior rami of C1 to C3 through the ansa cervicalis

Question 50

Summarise the omohyoid muscle

Answer 50

Lateral to the sternohyoid muscle is the omohyoid muscle (Fig. 8.164). This muscle consists of two bellies with an intermediate tendon in both the posterior and anterior triangles of the neck:

The omohyoid depresses and fixes the hyoid bone. It is innervated by the anterior rami of C1 to C3 through the ansa cervicalis.

Question 51

Describe the inferior belly of the omohyoid muscle

Answer 51

The inferior belly begins on the superior border of the scapula, medial to the suprascapular notch, and passes forward and upward across the posterior triangle ending at the intermediate tendon.

Question 52

Describe the superior belly and intermediate tendon of the omohyoid muscle

Answer 52

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The superior belly begins at the intermediate tendon and ascends to attach to the body of the hyoid bone just lateral to the attachment of the sternohyoid.
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The intermediate tendon is attached to the clavicle, near its medial end, by a fascial sling.

Question 53

Describe the attachments of the thyrohyoid muscle

Answer 53

The thyrohyoid muscle is deep to the superior parts of the omohyoid and sternohyoid (Fig. 8.164). Originating at the oblique line on the lamina of the thyroid cartilage it passes upward to insert into the greater horn and adjacent aspect of the body of the hyoid bone.

Question 54

Describe the function and innervation of the thyrohyoid muscle

Answer 54

The thyrohyoid muscle has variable functions depending on which bone is fixed. Generally, it depresses the hyoid, but when the hyoid is fixed it raises the larynx (e.g., when high notes are sung). It is innervated by fibers from the anterior ramus of C1 that travel with the hypoglossal nerve [XII].

Question 55

Describe the sternothyroid muscle

Answer 55

Lying beneath the sternohyoid and in continuity with the thyrohyoid, the sternothyroid is the last muscle in the infrahyoid group (Fig. 8.164). It arises from the posterior surface of the manubrium of the sternum and passes upward to attach to the oblique line on the lamina of the thyroid cartilage.
The sternothyroid muscle draws the larynx (thyroid cartilage) downward and is innervated by the anterior rami of C1 to C3 through the ansa cervicalis.

Question 56

Summarise the origins of the right and left common carotid arteries

Answer 56

The right common carotid artery originates from the brachiocephalic trunk immediately posterior to the right sternoclavicular joint and is entirely in the neck throughout its course.
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The left common carotid artery begins in the thorax as a direct branch of the arch of the aorta and passes superiorly to enter the neck near the left sternoclavicular joint.

Question 57

Outline the course of the right and left common carotid arteries

Answer 57

Both right and left common carotid arteries ascend through the neck, just lateral to the trachea and esophagus, within a fascial compartment (the carotid sheath). They give off no branches as they pass through the neck.
Near the superior edge of the thyroid cartilage each common carotid artery divides into its two terminal branches—the external and internal carotid arteries