H and N 1.5

Question 1

What is the origin of the Sternothyroid muscle?

Answer 1

arises from the posterior surface of the manubrium of the sternum and the edge of the 1st costal cartilage

Question 2

What is the insertion of the Sternothyroid muscle?

Answer 2

attaches to the oblique line of the lamina of the thyroid cartilage

Question 3

What is the action of the Sternothyroid muscle?

Answer 3

depresses the larynx after the larynx has been elevated for swallowing

Question 4

What is the innervation of the Sternothyroid muscle?

Answer 4

• C2 and C3 from the ansa cervicalis

- Part of infrahyoid muscles

Question 5

What does the omohyoid muscle consist of?

Answer 5

Inferior and superior belly

Question 6

Where does the superior belly of the omohyoid muscle arise from?

Answer 6

uperior belly begins at the intermediate tendon and passes vertically

Question 7

Where does the inferior belly of the omohyoid muscle arise from?

Answer 7

The inferior belly arises from the superior border of the scapula, near the suprascapular notch and passes to the intermediate tendon

Question 8

Where do the superior and inferior belly of the omohyoid muscle insert?

Answer 8

1. The superior belly passes vertically and inserts into the lower border of the hyoid bone
2. The inferior belly of the muscle inserts into the intermediate tendon deep to the sternocleidomastoid muscle

Question 9

What is the action of the omohyoid muscle?

Answer 9

Omohyoid muscle depresses the hyoid bone after the bone has been elevated. It also retracts and steadies the hyoid bone

Question 10

What is the innervation of the omohyoid muscle?

Answer 10

C1, C2, and C3 by a branch of the ansa cervicalis

Question 11

How does the omohyoid muscle work with other infra hyoid muscles?

Answer 11

• The omohyoid acts with the other infrahyoid muscles to depress the larynx and hyoid bone after these structures have been elevated during swallowing, speaking, or mastication (chewing)
• The omohyoid is an unusual “strap” muscle because it arises from the scapula in the shoulder region

Question 12

Where does the thyrohyoid muscle arise from?

Answer 12

arises from the oblique line of the lamina of the thyroid cartilage

Question 13

Where does the thyrohyoid muscle attach?

Answer 13

to the inferior border of the body and the greater horn of the hyoid bone

Question 14

What is the action of the thyrohyoid muscle?

Answer 14

Thyrohyoid muscle depresses the hyoid bone and, if the hyoid bone is fixed, draws the thyroid cartilage superiorly

Question 15

What is the innervation of the thyrohyoid muscle?

Answer 15

C1 via the hypoglossal nerve (CN XII)

Question 16

What fibres are the thyrohyoid muscles supplied by?

Answer 16

• The thyrohyoid muscle is supplied by fibers of the 1st cervical nerve that happen to travel with the last cranial, or hypoglossal, nerve (CN XII)
• The thyrohyoid muscle is also 1 of the infrahyoid, or “strap,” muscles

Question 17

What can trauma to the neck result in?

Answer 17

1. Trauma to the neck may damage the ansa cervicalis (C1-C3) and its branches, leading to paralysis of the infrahyoid and suprahyoid muscles
2. Because these muscles are critical in the process of swallowing, dysphagia (difficulty in swallowing) may ensue.

Question 18

Where does the stylohyoid muscle arise from?

Answer 18

arises from the styloid process of the temporal bone

Question 19

Where does the stylohyoid muscle attach?

Answer 19

to the body of the hyoid bone

Question 20

What is the action of the stylohyoid muscle?

Answer 20

elevates and retracts the hyoid bone in an action that elongates the floor of the mouth

Question 21

What is the innervation of the stylohyoid muscle?

Answer 21

Facial nerve

Question 22

Where is the stylohyoid muscle perforated?

Answer 22

near its insertion by the tendon of the 2 bellies of the digastric muscle

Question 23

Is the stylohyoid muscle part of the styloid process?

Answer 23

1. The stylohyoid is 1 of the 3 muscles arising from the styloid process, each innervated by a different cranial nerve
2. The other 2 muscles are the stylopharyngeus (CN IX) and the styloglossus (CN XII).

Question 24

How does the stylohyoid muscle help stabilise the hyoid bone?

Answer 24

1. The stylohyoid is 1 of several muscles that help stabilize the hyoid bone, which is important in movements of the tongue and in swallowing, speaking, and mastication (chewing)
2. If this process is compromised, these movements become more difficult and/or painful to execute

Question 25

What are the two bellies of the digastric muscle? Where do they arise from?

Answer 25

1. The posterior belly is the longest, and it arises from the mastoid notch of the temporal bone
2. The anterior belly arises from the digastric fossa of the mandible

Question 26

Where does the digastric muscle bellies insert?

Answer 26

The 2 bellies end in an intermediate tendon that perforates the stylohyoid muscle and is connected to the body and greater horn of the hyoid bone

Question 27

What is the action of the digastric muscle?

Answer 27

elevates the hyoid bone and, when both muscles act together, helps the lateral pterygoid muscles open the mouth by depressing the mandible

Question 28

What is the innervation of the digastric muscle?

Answer 28

1. The anterior belly of the digastric muscle is innervated by the mylohyoid nerve, a branch of the mandibular division of the trigeminal nerve
2. The posterior belly is innervated by the facial nerve

Question 29

What are the digastric muscles assisted by?

Answer 29

• They are important in swallowing and mastication (chewing)
• The digastric muscles are important for opening the mouth symmetrically and are assisted by the lateral pterygoid muscles

Question 30

Where does the Cricothyroid muscle arise from?

Answer 30

arises from the anterolateral part of the cricoid cartilage

Question 31

Where does the Cricothyroid muscle insert?

Answer 31

inserts into the inferior aspect and inferior horn of the thyroid cartilage

Question 32

What is the action of the Cricothyroid muscle?

Answer 32

tretches and tenses the vocal folds

Question 33

What is the innovation of the Cricothyroid muscle?

Answer 33

External branch of the superior laryngeal nerve of the vagus

Question 34

Where is the Cricothyroid muscle derived from embryonically?

Answer 34

• is derived embryologically from the 4th through 6th pharyngeal (branchial) arches
• All of these laryngeal muscles are innervated by the vagus nerve

Question 35

How is the innervation of the Cricothyroid muscle special?

Answer 35

1. The cricothyroid muscle is innervated by the small, external branch of the superior laryngeal nerve of the vagus
2. Most of the superior laryngeal nerve continues as an internal branch that pierces the thyrohyoid membrane to provide sensory innervation above the vocal folds

Question 36

What happens if there is damage on 1 side to the superior laryngeal nerve?

Answer 36

1. Damage on 1 side to the superior laryngeal nerve, a branch of the vagus nerve (CN X), will paralyze the ipsilateral cricothyroid muscle
2. Consequently, the voice will be affected because the ipsilateral vocal fold cannot be fully stretched and tensed
3. Additionally, the ipsilateral laryngeal mucosa above the level of the vocal folds will be anesthetized (the superior laryngeal nerve is sensory to the laryngeal mucosa above the vocal folds), somewhat compromising the protective gag reflex that would normally keep foreign objects from being aspirated into the larynx

Question 37

Where do the Oblique and transverse arytenoid muscles arise from?

Answer 37

arise from the arytenoid cartilages

Question 38

Where do the Oblique and transverse arytenoid muscles attach?

Answer 38

attach to the opposite arytenoid cartilage

Question 39

What is the action of the Oblique and transverse arytenoid muscles?

Answer 39

1. The muscles close the inlet of the larynx by adducting the arytenoid cartilages
2. This narrows the rima glottidis, the space between the vocal folds

Question 40

What is the innervation of the Oblique and transverse arytenoid muscles?

Answer 40

Recurrent laryngeal nerve of the vagus

Question 41

What happens to some muscle fibres of the oblique arytenoid?

Answer 41

Some muscle fibers of the oblique arytenoid continue superiorly as the aryepiglottic muscle

Question 42

What happens to the vocal cords during quiet respiration?

Answer 42

1. The vocal folds are controlled by the laryngeal muscles, all of which are innervated by the vagus nerve (CN X)
2. During quiet respiration, the vocal folds are gently abducted to open the rima glottidis (space between the folds)

Question 43

What happens to the vocal cords during forced inspiration?

Answer 43

In forced inspiration (taking a rapid, deep breath), the folds are maximally abducted by the posterior cricoarytenoid muscles, further enlarging the rima glottidis.

Question 44

What happens during phonation of the vocal cords?

Answer 44

1. During phonation, the folds are adducted and tensed to create a reed-like effect (similar to a reed musical instrument), causing vocal fold mucosal vibrations that produce sound that is then modified by the upper airway (pharynx, oral cavity, tongue, lips, nose, and paranasal sinuses).
2. Closure of the rima glottidis occurs when holding your breath or when lifting something heavy (the Valsalva maneuver), and the folds are completely adducted.

Question 45

Where does the posterior cricoarytneoid muscle arise form?

Answer 45

Arises from the posterior surface of the laminae of the cricoid cartilage

Question 46

Where does the posterior cricoarytneoid muscle insert?

Answer 46

Attaches to the muscular process of the arytenoid cartilage

Question 47

Where is the posterior cricoarytenoid muscle action?

Answer 47

• Abducts the vocal folds and widens the rima glottidis, the space between the vocal folds
• Only muscles that abduct the vocal cords

Question 48

How is the posterior cricoarytenoid muscle innervated?

Answer 48

Recurrent (inferior) laryngeal nerve of the vagus

Question 49

What happens if there is damage to the recurrent laryngeal nerve during neck surgery?

Answer 49

1. Damage to the recurrent laryngeal nerve during neck surgery (e.g., resection of the thyroid gland) can cause the vocal folds to adduct, causing hoarseness or closure of the rima glottidis, or both.
2. This occurs because the posterior cricoarytenoid muscles are the only laryngeal muscles that abduct the vocal folds and keep the rima glottidis open