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Head And Neck > 10.1 Functional Anatomy Of The Larynx > Flashcards

10.1 Functional Anatomy Of The Larynx Flashcards

1
Q

Where is the larynx located?

A

Between the hyoid bone (laryngeal inlet) and lower border of the cricoid cartilage

(vertebral level C4-C6)

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2
Q

What are the functions of the larynx?

A

Ventilation
Airway protection
Cough reflex
Production of sound (phonation)

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3
Q

How does the larynx protect the airway?

A

Prevents ingested food and liquid entering the lungs

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4
Q

What is the function of a cough?

A

important protective mechanism to expel rapidly any substances that have inadvertently found their way into the airways

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5
Q

What structures are involved with phonation?

A 
Larynx
Pharynx
Oral cavity
Lips
Teeth
Tongue
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6
Q

What are the subdivisions of the larynx?

A

Supraglottis
Glottis
Subglottis

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7
Q

What cartilages form the structural framework of the larynx?

A

Epiglottis
Thyroid cartilage
Arytenoid cartilage
Cricoid cartilage

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8
Q

What is the thyrohyoid membrane?

A

Membrane that attaches the thyroid cartilage (superior larynx) to the hyoid bone

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9
Q

Where does the cricothyroid membrane run?

A

Upwards from the cricoid cartilage, deep to the thyroid cartilage.
Attaches anteriorly to the inner surface of the thyroid cartilage
Attaches posteriorly to the arytenoid cartilages

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10
Q

What forms the vocal ligament?

A

The thickened upper margin of the cricothyroid membrane

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11
Q

What is the function of the vocal ligament?

A

To give shape and structure to the true vocal cord

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12
Q

What is laryngospasm?

A

Sudden spasm of the vocal cords

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13
Q

What is a cricothyroidotomy?

A

Puncturing the cricothyroid membrane anteriorly to allow rapid emergency access into the infraglottic area of the larynx, below the vocal chords . Provides a temporary solution in acute laryngeal obstruction, at or above the vocal chords.

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14
Q

What more definitive treatment can be given over a cricothyroidotomy?

A

A tracheotomy

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15
Q

What does the epiglottis attach to?

A

Hyoid

Back of the thyroid cartilage (thyroglottic ligament)

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16
Q

What is the epiglottis made out of?

A

Elastic cartilage

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17
Q

How does the the epiglottis attach to the arytenoid?

A

The aryepiglottic folds created by the upper border of the quadrangular membrane

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18
Q

What forms the aditus of the larynx?

A

The epiglottis and aryepiglottic folds

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19
Q

What is the laryngeal prominence?

A

The midline of the thyroid cartilage where the two lateral plates meet.

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20
Q

Describe the shape of the cricoid cartilage?

A

Signet ring shaped, only complete ring of cartilage throughout the respiratory tract

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21
Q

What is the function of the cricotracheal membrane?

A

To attach the cricoid cartilage to the trachea

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22
Q

Where are the arytenoids?

A

Sit on top of the cricoid cartilage, one on each side.

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23
Q

What structure sits behind the larynx?

A

The laryngopharynx

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24
Q

Where is the laryngeal inlet?

A

Opening from the laryngopharynx into the larynx. Found posteriorly and inferiorly to the posterior part of the tongue

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25
Q

What is the piriform fossa?

A

A recess on the posterolateral aspect of either side of the larynx

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26
Q

What is the function of the piriformis fossa?

A

Allows food/fluids to travel down into the oesophagus after being redirected away from the laryngeal inlet by the epiglottis.

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27
Q

What pathology can be involved with the piriformis fossa?

A

Sit for ingested food / foreign bodies to become lodged - choking
Pharyngeal cancers - can grow in recess to reasonable size before influencing swallowing

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28
Q

Describe the structure of the thyroid cartilage

A

Consists of 2 lateral lamina that fuse anteriorly to form a v shape. Extend superiorly to form superior horn and inferiorly to form the inferior horn in the midline

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29
Q

What are the synovial joint of the larynx?

A

Cricothyroid

Cricoarytenoid

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30
Q

How is the larynx suspended?

A

By the thyrohyoid membrane attaching to the hyoid bone

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31
Q

Where does the thyroid gland lie?

A

Below the cricoid cartilage.

Isthmus runs across the upper tracheal rings

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32
Q

What forms the false vocal cord?

A

The inferior border of the quadrangular membrane

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33
Q

What structure gives rise to the true vocal cord?

A

The superior free border of the cricothyroid membrane

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34
Q

Where is the supraglottis?

A

Laryngeal vestibule - From the upper border of the epiglottis / laryngeal inlet, down to include the false vocal cord/ inferior border of the quadrangular membrane

35
Q

Where is the glottis?

A

From just below the false vocal cords to 1cm below the true vocal cords
Narrowest section of the larynx but includes the vocal cords

36
Q

Where is the infralarynx/ subglottis?

A

From 1 cm below the true vocal cords to the inferior margin of the cricoid cartilage

37
Q

What lines the larynx?

A

Mucous membrane

38
Q

What is the saccule of the larynx?

A

A small lateral and upwards outpouching of mucous membrane between the false and true vocal cords. One on either side.

39
Q

What is the function of the saccule of the larynx?

A

Contains mucous glands to keep the true vocal cords moist as the true vocal cords are not lined with mucus membrane

40
Q

What type of epithelium lines the larynx?

A

Pseudostratified ciliated columnar epithelium with goblet cells

41
Q

What epithelium lines the true vocal cords?

A

Stratified squamous epithelium

42
Q

Why do the vocal cords have a different type of epithelium to the rest of the larynx?

A

Have stratified squamous epithelium - true vocal cords are very mobile and are subject to abrasion of air.

43
Q

How is the larynx viewed clinically?

A

With a laryngoscope

Flexible nasoendoscopy

44
Q

What is the rima glottidis?

A

The space between the 2 true vocal cords, varies in width during phonation.

45
Q

What anatomical landmark can be used to orientate a laryngoscopic view of the larynx?

A

The point of the rima glottidis points anteriorly.

46
Q

Why would be need to visualise the larynx laryngoscopically?

A

Intubation

To visualise the anatomy of larynx and pharynx if suspecting pathology

47
Q

What is intubation?

A

placement of an endotracheal tube into subglottic region (i.e. below vocal cords)

48
Q

What is the vallecula?

A

A small recess between the epiglottis and the posterior root of the tongue. Where the tip of laryngoscope can be placed when intubating

49
Q

What is a flexible nasoendoscopy?

A

A flexible endoscope that is inserted via nasal cavity and pharynx to then visualise the larynx. Can be used on a conscious patient

50
Q

What are the 2 main functions of intrinsic muscles of the larynx?

A

To change the size/shape of the laryngeal inlet

Tension/position of the vocal cords

51
Q

How do the intrinsic muscles of the larynx function during swallowing?

A

Close the laryngeal inlet and vocal cords

Protect respiratory tract from ingested food/fluid

52
Q

How do the intrinsic muscles of the larynx function during inspiration and expiration?

A

Open vocal cords and laryngeal inlet

Allow movement of air

53
Q

How do the intrinsic muscles of the larynx act during phonation?

A

Partially adducted vocal cords

54
Q

How do intrinsic muscles act during the cough reflex?

A

Closely adducted, closing the trachea whilst be build up intrathoracic pressure.
Snapped open during the cough to allow air to be rapidly expelled

55
Q

How does the laryngeal inlet shut?

A

Epiglottis tips down

  • passively as the tongue pushes back onto it a we swallow
  • muscles in the aryepiglottic folds contract
56
Q

Only one intrinsic muscle of the larynx acts to widen the rima glottidis/ adduct the vocal cords. Which is it?

A

Posterior cricoarytenoid

57
Q

How do we alter the size of the rima glottidis?

A

By rotating the arytenoid cartilages on the cricoid

58
Q

What innervates most of the instrinsic muscles of the larynx?

A

Recurrent laryngeal nerve of vagus (CN X)

1 on each side (right and left)

59
Q

Which instrinsic muscle of the larynx is not innervated by the recurrent laryngeal nerve of vagus?

A

The cricothyroid muscle

60
Q

What innervates the cricothyroid muscle?

A

External branch of the superior laryngeal nerve (CN X)

61
Q

During phonation what happens to the vocal cords?

A

VC closely adducted.
Expired air is forced through closely adducted vocal cords
VC vibration creates sound waves

62
Q

How do the vocal cords move in the cough reflex?

A 
– inspire and fill lungs with air
– vocal cords then aDducted
– expiratory muscles contract
– intrathoracic pressure builds
– then cords suddenly aBducted
– explosive outflow of air!
63
Q

If the movement of one vocal cord is impaired, what will be effected?

A

Inability to met the other vocal cord in the midline

  • impaired phonation
  • impaired cough
64
Q

How does tension of the vocal cords affect the pitch of phonation?

A

High pitched sounds = vocal cords are taut

Low pitched sounds = vocal cords less taut

65
Q

How do we change the pitch of our voice?

A

By changing the tension of the vocal cords.

Varied by contraction of the cricothyroid muscle, contraction increases tension.

66
Q

Where is the cricothyroid cartilage located?

A

On the outside of the larynx

Runs from the anterior of the cricoid cartilage onto the outer surface of the thyroid cartilage

67
Q

What is the action of the cricothyroid muscle?

A

Tilts thyroid cartilage forwards on the cricoid cartilage. Increases tension in vocal cords allowing for higher pitch

68
Q

What innervates the cricothyroid muscle?

A

External branch of the superior laryngeal nerve (CN X)

69
Q

What structure is the external branch of the superior laryngeal nerve closely associated to?

A

Superior thyroid artery.

70
Q

When might innervation to the cricothyroid muscle be reduced?

A

During thyroid surgery.
Superior thyroid artery lies very close to the external branch of the superior laryngeal nerve. Injury results in hoarseness of voice, especially when attempting higher pitched sounds

71
Q

What part of the airway is shared by our respiratory and digestive system?

A

Oropharynx

72
Q

Describe the movement of the larynx during swallowing.

A

Hyoid bone elevated and moved anteriorly by suprahyoid muscles
Larynx moves up and forward
Tongue pushes epiglottis posteriorly and aryepiglottic muscles contract
– Narrowing laryngeal inlet
– Bringing epiglottis from a vertical to a
more horizontal position
Closure (adduction) of vocal cords (closes glottis)

73
Q

What is the role of the suprahyoids and longitudinal pharyngeal muscles during swallowing?

A

Suprahyoids = contract the anteriorly and superiorly displace hyoid and bone
Longitudinal pharyngeal muscles = contract to anteriorly displace larynx

74
Q

Describe the sensory innervation of the larynx

A

Vagus nerve (CN X)

  • Internal Superior laryngeal nerve - sensory supraglottis
  • recurrent laryngeal nerve - sensory to the subglottis and glottis
75
Q

Describe the motor innervation of the larynx

A

Vagus nerve (CN X)

  • external superior laryngeal to the cricothyroid muscle
  • recurrent laryngeal to the intrinsic muscles of the larynx
76
Q

Describe the path of the superior laryngeal branch

A

CN X exits cranium via jugular foramen. Passes into the carotid sheath, travelling inferiorly.
Superior laryngeal branch arises in the neck.
Internal branch pierces through the thyrohyoid membrane to enter larynx.
External branch does not enter the larynx and innervates the cricothyroid muscle.

77
Q

Describe the path of the recurrent laryngeal nerve to the larynx

A

Recurrent laryngeal nerves arise inferiorly and ascend to innervate intrinsic muscles of the larynx

right = arises in neck, hooks underneath right subclavian artery to ascend to larynx in a groove between the oesophagus and the trachea (trachealoesophagus groove)

Left = arises in the thorax. Hooks under the arch of the aorta. Ascends to larynx in the trachealoesophagus groove.

78
Q

What structures have a close anatomical relationship with the recurrent laryngeal nerves?

A

Thyroid gland

Inferior thyroid arteries

79
Q

When are the recurrent laryngeal nerves vulnerable to injury?

A

In thyroid surgery (close to inferior thyroid arteries)
Aortic arch aneurysm ( left RLN)
Cancer involving apex of the lung (right RLN)
Disease or surgery involving the larynx, oesophagus or thyroid

80
Q

Describe the symptoms of unilateral recurrent laryngeal nerve lesion?

A

Unilateral vocal cord palsies
- hoarse voice, ineffective cough
Contralateral side compensates over time (crosses midline to meet vocal cord on affected side)

81
Q

What is the position of a paralysed vocal cord?

A

Paramedian position - partially abducted/ adducted

82
Q

How does a bilayer recurrent laryngeal nerve lesion present?

A

Both vocal cords paralysed and in paramedian position
Narrow glottis
Significant airway obstruction

83
Q

How are bilateral recurrent laryngeal nerve palsies treated?

A

Emergency surgical airway - access below vocal cords.

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