Head and Neck: General Organisation

Question 1

How many bones make up the skull and cervical vertebrae?

Answer 1

Skull - 22 bones, divided into neurocranium and viscerocranium
Cervical vertebrae - 7

Question 2

What are the 3 important muscles making up the neck?

Answer 2

Platysma
Sternocleidomastoid
Trapezius

Question 3

What are the actions and innervation of the platysma?

Answer 3

Very superficial sheet-like muscle, located in the superficial fascia
- draws corners of mouth inferiorly and skin of neck superiorly

Supplied by the facial nerve (CN VII) (7)

Question 4

What are the attachments, actions and innervation of the sternocleidomastoid?

Answer 4

Arises from the mastoid process and has 2 heads attaching to the clavicle and sternum

• unilateral action: lateral flexion of neck, rotating chin superiorly
• bilateral action: flexion of neck, extends the atlanto-occipital joint

Supplied by the accessory nerve (CN XI) (11)

Question 5

What are the attachments, actions and innervation of the trapezius?

Answer 5

Arises from the nuchal ligament and spinous processes of vertebrae and inserts on the lateral 1/3 of the clavicle, acromion and spine of scapula
- action is to elevate and rotate scapula (abduction of arm over 90 degrees), and shrug

Supplied by the accessory nerve (CN XI) (11)

Question 6

What are the borders of the anterior triangle of the neck?

Answer 6

Inferior margin of mandible
Midline of neck
Anterior margin of sternocleidomastoid

Question 7

What are the borders of the posterior triangle of the neck?

Answer 7

Posterior margin of sternocleidomastoid
Anterior margin of trapezius
Clavicle

Question 8

List the facial planes of the neck

Answer 8

Superficial cervical fascia

Deep cervical fascia: investing layer, carotid sheath, pre-tracheal fascia, pre-vertebral fascia

Question 9

What does the investing layer contain?

Answer 9

Forms a complete collar around the neck - contains everything except trapezius, sternocleidomastoid and platysma

Question 10

What does the carotid sheath contain?

Answer 10

Contains the carotid artery (the internal carotid remains in the sheath of the external carotid leaves), the internal jugular vein which is most lateral and the vagus nerve

Question 11

What does the prevertebral fascial layer contains?

Answer 11

Contains the cervical vertebrae with the prevertebral and paravertebral muscles

Question 12

What does the pretracheal layer contain?

Answer 12

The thyroid, trachea, oesophagus and 2 infrahyoid muscles

Has a thickened area at the back called the buccopharyngeal fascia

Question 13

What is the importance of the retropharyngeal and pretracheal space?

Answer 13

Retropharyngeal space is located behind the pretracheal fascial layer and infront of the prevertbral layer
The pretracheal space is located between trachea and thyroid
– although rare, infection in these spaces can pass down and cause mediastinitis

Question 14

What is the innervation of the muscles of facial expression and the muscles of mastication?

Answer 14

Muscles of facial expression - facial nerve (CN VII) (7)

Muscles of mastication - trigeminal nerve (CN V) (5)§

Question 15

What is the action of the trigeminal nerve?

Answer 15

Motor innervation to muscles of mastication (mandibular branch)
Sensory to the face and scalp - has 3 branches: opthalmic, maxillary, mandibular

Question 16

Why is the relationship between the facial nerve and the parotid gland important?

Answer 16

The facial nerve passes through the parotid gland therefore parotid pathology can cause paralysis of that side of the face by compressing the nerve

Question 17

What are the actions of the orbital and palpebral part off the orbicularis oculi?

Answer 17

The orbital part is under voluntary control - tightly closes the eye
The palpebral part is under involuntary control - gently closes the eye eg blinking and sleeping

Question 18

What is the action of the levator palpebrae superioris?

Answer 18

Opens the eye

Question 19

What is the action of the occipitofrontalis muscle?

Answer 19

Raises the eyebrows and creases the forehead

Question 20

What is the action of the orbicularis oris?

Answer 20

Closes mouth and puckers the lips

Question 21

What is the action of the buccinator muscle?

Answer 21

Aids in smiling, whistling and suckling

Also keeps cheer against teeth during mastication

Question 22

What is the role of the zygomaticus muscle?

Answer 22

It is the smiling muscle - draws corners of mouth superiorly

Question 23

What is the action of the lateral and medial pterygoids?

Answer 23

Lateral pterygoid: lies superiorly to medial, and is a muscle of mastication

Medial pterygoid: closes jaw, assists mastication

Question 24

What is the action of the masseter?

Answer 24

Muscle of mastication - elevates the mandible (stronger than the medial pterygoid)

Question 25

What is the action of the temporalis?

Answer 25

Closes the mouth - a powerful muscle of mastication

Question 26

What is the action of the sternocleidomastoid?

Answer 26

Bilaterally: flexes the neck
Unilaterally: pulls the chin towards the shoulder

Question 27

What is the action of the trapezius?

Answer 27

Shrugs the shoulders

Rotates the scapula so the arm can abduct beyond 90 degrees (with the serratus anterior)

Question 28

What are the layers of the scalp?

Answer 28

S - Skin
C - dense Connective tissue
A - epicranial Aponeurosis 
L - Loose connective tissue
P - Periosteum

Question 29

Why do scalp lacerations bleed profusely?

Answer 29

• the skin is unable to constrict the wound due to the pull of the occipitofrontalis muscle
• the blood vessels are adhered to the dense CT so unable to constrict to minimise blood loss
• the blood supply to the scalp is made up of many anastomoses

Question 30

How can scalp infections spread?

Answer 30

Pus and blood can spread easily through the loose connective tissue layer and can spread to meninges via emissary veins