TBL24 - Bones and Fascial Sheaths of the Neck

Question 1

What four parts characterize the vertebrae of C3 to C7? What is unique about the long spinous process of C7?

Answer 1

1) Small bodies, relatively large vertebral foramina, and the transverse foramina in the transverse processes characterize vertebrae C3 to C7
2) The long spinous process of C7 is typically the most prominent spinous process of the vertebral column

Question 2

What does C1 (atlas) consist of and what do these structures connect? What does the skull rest on?

Answer 2

1) C1 (atlas) consists of anterior and posterior arches that connect two lateral masses, which contain transverse foramina
2) The skull rests on the superior articular facets on the superior surfaces of the lateral masses

Question 3

Where does the facet for the dens lie on? Where does the dens project from? What holds the dens against the facet? What does the dens function as?

Answer 3

1) The facet for the dens lies on the anterior arch of C1
2) The peg-like dens projects superiorly from the body of C2 (axis)
3) The transverse ligament of the atlas holds the dens against the facet
4) Thus, the dens serves as a pivot around which the atlas turns (e.g., the “no” movement) and carries the skull

Question 4

What is found on the transverse processes of C2?

Answer 4

The transverse processes of C2 contain transverse foramina

Question 5

How does a burst fracture of C1 typically occur, and why does it not necessarily result in spinal cord injury?

Answer 5

1) Because the taller side of the lateral mass is directed laterally, vertical forces (as would result from striking the bottom of a pool in a diving accident) compressing the lateral masses between the occipital condyles and the axis drive them apart, fracturing one or both of the anterior or posterior arches
2) If the force is sufficient, rupture of the transverse ligament that links them will also occur
3) The resulting Jefferson or burst fracture in itself does not necessarily result in spinal cord injury, because the dimensions of the bony ring actually increase
4) Spinal cord injury is more likely, however, if the transverse ligament has also been ruptured

Question 6

Does the U-shaped hyoid bone articulate with another bone and where is it placed in relation to vertebrae C3? What is it an attachment for?

Answer 6

1) The U-shaped hyoid bone, which is anterior to vertebrae C3, does not articulate with another bone
2) The hyoid bone is an attachment site for anterior neck muscles

Question 7

What invests and compartmentalizes structures in the neck? What is the name of the fatty fascial layer and where does it lie between?

Answer 7

1) Structures in the neck are invested in and compartmentalized by several layers of fascia
2) The fatty superficial cervical fascia lies between the dermis and the investing layer (green) of the deep cervical fascia that encircles the neck

Question 8

Where does the thin, broad platysma muscle reside? What is the appearance of this muscle when it tenses?

Answer 8

1) The thin, broad platysma muscle resides in the superficial fascia of the anterior neck
2) When the muscle tenses, vertical skin ridges appear conveying tension or stress

Question 9

Why are the skin and edges of the platysma carefully sutured during repair of neck wounds?

Answer 9

1) Paralysis of the platysma, resulting from injury to the cervical branch of the facial nerve, causes the skin to fall away from the neck in slack folds
2) Consequently, during surgical dissections of the neck, extra care is necessary to preserve the cervical branch of the facial nerve
3) When suturing wounds of the neck, surgeons carefully suture the skin and edges of the platysma
4) If this is not done, the skin wound will be distracted (pulled in different directions) by the contracting platysma muscle fibers, and an ugly scar may develop

Question 10

What sheaths does the investing fascia of the deep cervical fascia surround? What muscles does the investing fascia enclose?

Answer 10

1) The investing fascia surrounds the pretracheal and prevertebral fascial sheaths
2) It also encloses the trapezius and sternocleidomastoid (SCM) muscles

Question 11

Anterolaterally, what bones does the investing fascia extend from and to?

Answer 11

Anterolaterally, the investing fascia extends from the inferior border of the mandible and the hyoid bone to the clavicle and sternal manubrium

Question 12

What does the slipperiness that the three deep cervical fascial layers provide to structures of the neck function for and what are two examples of this function?

Answer 12

The three deep cervical fascial layers provide slipperiness that allows structures of the neck to move and pass over one another, as when turning the head or swallowing

Question 13

What three structures does the visceral (posterior) part of the pretracheal fascia enclose? What muscles does the thin muscular (anterior) part of the pretracheal fascia enclose?

Answer 13

1 The visceral (posterior) part of the pretracheal fascia encloses the thyroid gland, trachea, and esophagus
2) The thin muscular (anterior) part of the pretracheal fascia encloses the infrahyoid muscles, which include the sternothyroid and sternohyoid muscles

Question 14

The muscular part of the pretracheal fascia extends from and to what bones? Where is the visceral part of the pretracheal fascia continuous with the buccopharyngeal fascia and where does the buccopharyngeal fascia attach to?

Answer 14

1) The muscular part of the pretracheal fascia extends from the hyoid bone to the sternal manubrium
2) The visceral part of the pretracheal fascia is continuous superiorly and posteriorly with the buccopharyngeal fascia of the pharynx that attaches to the base of the skull

Question 15

Where does the visceral part of the pretracheal fascia extend inferiorly posterior to and what does it blend with in this region?

Answer 15

The visceral part of the pretracheal fascia extends inferiorly posterior to the manubrium into the middle mediastinum where it blends with the fibrous pericardium

Question 16

What are the carotid sheaths, what are they interconnected by, and where do they extend from and to? Name the two vessels and nerve contained within the sheaths. What do the carotid sheaths communicate with freely and what can this possibly allow for?

Answer 16

1) The carotid sheaths are tubular fascial sleeves interconnected by the alar fascia and extending from the cranial base to the root of the neck
2) Internal jugular vein, Common carotid artery, & Vagus nerve
3) The sheaths, which communicate freely with the mediastinum inferiorly and cranial cavity superiorly, provide potential pathways for spread of infection

Question 17

What does the tubular prevertebral fascial layer surround? What is the prevertebral fascial sheath fixed to superiorly? Inferiorly, what does it fuse with and where?

Answer 17

1) The tubular prevertebral fascial layer surrounds the cervical vertebral column and associated deep back muscles
2) The prevertebral fascial sheath is fixed to the cranial base superiorly
3) Inferiorly, it fuses with the anterior longitudinal ligament in the thoracic region of the spine

Question 18

What is the retropharyngeal space located between and what is it subdivided by? What is the space closed by superiorly and on each side? What does the space open into inferiorly?

Answer 18

1) The retropharyngeal space is located between the buccopharyngeal and prevertebral fasciae and subdivided by the alar fascia
2) The space is closed superiorly by the base of the cranium and on each side by the carotid sheaths
3) The space opens inferiorly into the superior mediastinum

Question 19

What does the retropharyngeal space create a possibility for?

Answer 19

The retropharyngeal space creates another potential pathway for the spread of infection

Question 20

Where can infections between the investing fascia and muscular part of the pretracheal fascia spread?

Answer 20

If an infection occurs between the investing layer of deep cervical fascia and the muscular part of the pretracheal fascia surrounding the infrahyoid muscles, the infection will usually not spread beyond the superior edge of the manubrium of the sternum

Question 21

Where can infections between the investing fascia and visceral part of the pretracheal fascia spread?

Answer 21

If, however, the infection occurs between the investing fascia and the visceral part of pretracheal fascia, it can spread into the thoracic cavity anterior to the pericardium

Question 22

What are the symptoms of a retropharyngeal abscess?

Answer 22

1) Pus from an abscess posterior to the prevertebral layer of deep cervical fascia may extend laterally in the neck and form a swelling posterior to the SCM
2) The pus may perforate the prevertebral layer of deep cervical fascia and enter the retropharyngeal space, producing a bulge in the pharynx (retropharyngeal abscess)
3) This abscess may cause difficulty in swallowing (dysphagia) and speaking (dysarthria)