Muscles and fascia of the neck and mouth

Question 0

Name the superficial and cutaneous muscles of the neck (3) with attachments, action, and innervation

Answer 0

1.) Platysma
Superior attachment: Inferior border of mandible.
Inferior attachment: Fascia of pecs.
Action: Draws mouth inferiorly and widens it.
Innervation: Facial nerve (CN VII)

2.) Sternocleidomastoid (SCM)
Superior attachment: Lateral surface of mastoid process
Inferior attachment –> Sternal head: Anterior surface of manubrium. Clavicular head: Superior surface of medial third clavicle.
Action: Assists in pump-handle action of deep respiration. Tilts, flexes and extends neck.
Innervation: CN XI (accessory)

3.) Trapezius
Superior attachment: Nuchal ligament
Inferior attachment: Lateral third of clavicle, acromion. 
Action: Scapula
Innervation: CN XI (accessory)

Question 1

What is enclosed within the carotid sheath?

Answer 1

p. 988 Moore
1. ) Common and internal carotid arteries
2. ) Internal jugular vein
3. ) Vagus nerve (CN X)
4. ) Carotid sinus nerve
5. ) Sympathetic nerve fibers

Question 2

List the suprahyoid muscles of the neck (4) with origin and insertion, action, and innervation.

Answer 2

1.) Mylohyoid
Origin: Mylohyoid line of mandible
Insertion: Raphe and body of hyoid
Action: Elevates hyoid, floor of mouth, and tongue during speaking.
Innervation: Nerve to mylohyoid, branch of inf. alveolar (CN V3)

2.) Geniohyoid
Origin: Inferior mental spine of mandible
Insertion: Body of hyoid
Action: Pulls hyoid anterosuperiorly, shortens floor of mouth.
Innervation: C1 via hypoglossal (CN XII)

3.) Stylohyoid
Origin: Styloid process of temporal bone.
Insertion: Body of hyoid
Action: Elevates and retracts hyoid, elongating floor of mouth.
Innervation: Stylohyoid branch of facial nerve (CN VII)

4.) Digastric
Anterior belly:
Origin: Digastric fossa of mandible
Insertion: Horn of hyoid
Action: Working with infrahyoids, depresses mandible against resistance, elevates and steadies hyoid during swallowing and speaking.
Innervation: Nerve to mylohyoid (CN V3, inferior alveolar)

Posterior belly
Origin: Mastoid notch of temporal bone
Insertion: Horn of hyoid
Action: Working with infrahyoids, depresses mandible against resistance, elevates and steadies hyoid during swallowing and speaking.
Innervation: Digastric branch of facial nerve.

Question 3

List the infrahyoid muscles of the neck (4) with origin and insertion, action, and innervation.

Answer 3

1.) Sternohyoid
Origin: Manubrium and clavicle
Insertion: Hyoid
Action: Depresses hyoid after elevation during swallowing.
Innervation: C1-C3 branch of ansa cervicales

2.) Omohyoid:
Origin: Scapula
Insertion: Inferior hyoid border
Action: Depresses, retracts, and steadies hyoid
Innervation: C1-C2 branch of ansa cervicales

3.) Sternothyroid
Origin: Posterior manubrium
Insertion: Thyroid cartilage
Action: Depresses hyoid and larynx.
Innervation: C2-C3 branch of ansa cervicales

4.) Thyrohyoid
Origin: Thyroid cartilage
Insertion: Greater horn of hyoid
Action: Depresses hyoid and elevates larynx
Innervation: C1 via hypoglossal (CN XII)

Question 4

p.351 BRS

List the muscles of mastication with origin, insertion, innervation, and action.

Answer 4

1.) Masseter
Origin: Lower border and medial surface of zygomatic arch.
Insertion: Lateral surface of coronoid process, ramus, and angle of mandible.
Action on mandible: Elevates and retracts.
Innervation: Trigeminal (V3)

2.) Medial pterygoid
Origin: Maxilla, lateral pterygoid plate, palatine bone. 
Insertion: Angle and ramus of mandible.
Action mandible: Elevates, protracts.
Innervation: V3

3.) Lateral pterygoid
Origin: Infratemporal and pterygoid surface of sphenoid.
Insertion: Neck of mandible, temporomandibular joint.
Action on mandible: Depresses and protracts.
Innervation: V3

4.) Temporalis
Origin: Temporal fossa
Insertion: Coronoid process and ramus of mandible. 
Action: Elevates and retracts.
Innervation: V3

Question 5

1. ) Which muscles open the jaw?

2. ) Which muscles close the jaw?

Answer 5

p. 351 BRS
1. ) Lateral pterygoid
2. ) Temporalis, masseter, medial pterygoid.