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3 - HNN > Functional Anatomy of the Larynx > Flashcards

Functional Anatomy of the Larynx Flashcards

1
Q

Describe the location of the larynx

A
  • Larynx lies below the hyoid bone
  • Part of the respiratory system - begins at laryngeal inlet and continues as the trachea (at C6/lower border of cricoid cartilage)
  • Lies anterior to the laryngopharynx
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2
Q

What is the main function of the larynx

A

Provide a protective sphincter for the lower respiratory tract

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3
Q

Name the cartilages present in the larynx

A
  • Thyroid cartilage contains the laryngeal prominence (Adam’s apple)
  • Cricoid - only cartilage with a complete ring
    • Thyroid cartilage and trachea do not have back
  • Epiglottis - has ligaments attaching to thyroid cartilage
  • Arytenoid cartilage moves vocal cords
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4
Q

Describe the ligaments and membranes present in the larynx

A
  • Thyrohyoid membrane - between thyroid cartilage and hyoid
  • Cricothyroid ligament - between cricoid and thyroid cartilage
  • Cricotracheal membrane - between cricoid and trachea
  • Quadrangular membrane - epiglottis to arytenoid cartilage
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5
Q

State where synovial joints are present within the larynx

A
  • Between inferior horn of thyroid cartilage and cricoid

- Between cricoid and arytenoid cartilages

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6
Q

Describe what the aryepiglottic fold is

A
  • Aryepiglottic folds form margins of oval inlet of the larynx
  • Lie over the epiglottis and quadrangular membrane
  • Lined with mucous membrane - can be irritated leading to cough
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7
Q

Describe the location of the two types of vocal cords

A
  • Vestibular ligament/fold - false vocal cord
    • Thickened lower border of quadrangular membrane
  • Vocal ligament/fold - true vocal cord
    - Thickened upper border of cricothyroid ligament
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8
Q

Describe the 3 sections of the larynx

A
  • Supraglottis - part of the larynx above vocal cords
    • From epiglottis to vestibular folds
  • Glottis - vocal folds
  • Infraglottis - from vocal folds to cricoid cartilage
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9
Q

What epithelium lines the larynx

A
  • Larynx lined with pseudostratified ciliated columnar epithelium (part of respiratory tract)
  • Apart from vocal cords, which are lined with stratified squamous epithelium due to constant abrasion from air
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10
Q

Describe the laryngeal ventricle

A
  • Between vestibular and vocal folds is a small recess (laryngeal ventricle) which leads laterally and upwards into the saccule of larynx
  • Contains mucous glands that keep vocal folds moist
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11
Q

What do the intrinsic muscles of the larynx do

A
  • Act to alter the size and shape of the inlet or move position of vocal cords
  • Act to close the larynx during swallowing, protecting the respiratory tract
  • Act to open the larynx and allow movement of air during inspiration and expiration
  • Controls movement of vocal cords in phonation and in cough reflex
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12
Q

Describe the action of cricoarytenoid

A
  • Act to open (abduct) the vocal cords, while other intrinsic muscles act to close (adduct) vocal cord
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13
Q

Describe the innervation of the intrinsic muscles of the larynx

A
  • All supplied by recurrent laryngeal nerve of vagus

- Except cricothyroid muscle which is supplied by external branch of superior laryngeal nerve

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14
Q

Describe what the superior laryngeal nerve innervates within the larynx

A
  • Internal branch provides sensation in supraglottis region

- External branch provides motor to cricothyroid muscle

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15
Q

Describe the route of the recurrent laryngeal nerves

A
  • Left nerve loops under arch of aorta and right loops under right subclavian artery
  • Ascends in tracheo-oesophageal groove and has close relationship with inferior thyroid arteries supplying thyroid gland
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16
Q

Describe what the recurrent laryngeal nerves innervate within the larynx

A
  • Innervates all intrinsic muscles of larynx apart from cricothyroid
  • Provides sensation to infraglottic region
17
Q

Describe the equipment used to endoscopically view the larynx

A
  • Laryngoscope can be used to view vocal cords and allow for intubation (placement of a tube into subglottic region)
    • Plastic tube has a inflatable cuff to prevent gastric contents from entering trachea
      • Inflated after tube passes below the vocal cords
  • Nasoendoscope - flexible endoscope inserted via nasal cavity and pharynx to visualize larynx
18
Q

How can you orientate yourself when viewing the larynx endoscopically

A
  • Rima glottidis is the gap between the vocal folds

- Point anteriorly

19
Q

Describe the position of the vocal cords during inspiration and expiration

A

The vocal cords abduct

20
Q

Describe the position of the vocal cords during phonation

A
  • True vocal cords adduct
  • Expired air is forced through closely adducted vocal cords to vibrate a column of air
  • Position of arytenoid on cricoid cartilage determine position of true vocal cords and therefore size of aperture
21
Q

Describe how the cough reflex occurs in the larynx

A
  • During a cough, vocal cords powerfully adducted

- Intrathoracic pressure builds, then cords suddenly abduct

22
Q

How can pitch be altered by vocal cords

A
  • Pitch of sound can be altered by tension and length of true vocal cords
    • High-pitched sounds - vocal cords taut
    • Low-pitched sounds - vocal cords relaxed
  • Bilateral contraction of cricothyroid muscle increases length and tension in vocal cords
    • Tilts thyroid cartilage
      • Allows production of high pitched sounds
23
Q

What muscles of the larynx aid swallowing

A
  • Protects airways from food/fluid during swallowing
  • Contraction of aryepiglottic muscles act to narrow laryngeal inlet and pull epiglottis down
  • Assisted by elevation of larynx (through pharyngeal muscles and suprahyoid muscles)
  • Closure of vocal cords (glottis)
24
Q

Explain what a cricothyroidotomy is

A
  • Emergency access to provide patent airway
  • If a patient cannot be ventilated, such as anaesthetized or unconsciousness, access can be gained through cricothyroid membrane
25
Q

How can recurrent laryngeal nerves be damaged

A
  • Recurrent laryngeal nerves closely associated with inferior thyroid artery
    • Potentially injured during thyroid surgery
  • Also can be injured from aortic arch aneurysm, cancer involving apex of lung or disease/surgery involving larynx, oesophagus or thyroid
26
Q

Describe the presentation of a unilateral vocal cord palsy

A
  • Paralysed vocal cord assumes a paramedian position
    • Between fully abducted and fully adducted
  • Unilateral palsy may lead to hoarseness of voice and ineffective cough
    • Often contralateral side compensates in time
27
Q

Describe the presentation of the bilateral vocal cord palsy

A
  • Both vocal cords paralysed in paramedian position
  • Narrow glottis
  • Significant airway obstruction
  • Require emergency surgical airway such as crocothyroidotomy or tracheostomy
28
Q

Describe the presentation of an injury to the superior laryngeal nerve

A
  • Injury to superior laryngeal nerve leads to hoarseness of voice, especially when attempting high pitched sounds
  • Failure to innervate cricothyroid muscle
29
Q

How do conditions causing swelling of the larynx present

A

Patients present with stridor, raised respiratory rate, distress, hypoxia with possible cyanosis

30
Q

Give examples of conditions which could cause swelling of the larynx

A
  • Laryngitis
  • Laryngeal nodules
  • Laryngeal cancer
  • Croup - inflammation of upper respiratory tract due to viral infection
  • Epiglottitis - could lead to complete airway blockage
  • Laryngeal oedema - such as through allergic reaction
31
Q

What is the cervical plexus

A
  • Network of nerve fibres that supplies innervation to some of the structures of the neck and trunk
  • Located in the posterior triangle in the neck
  • Plexus is formed form the anterior rami of C1-C4 cervical nerves
32
Q

Describe the muscular and sensory branches from the cervical plexus

A
  • Muscular branches are located deep to the sensory branches
    • Supply muscles of the neck, back and diaphragm
    • Phrenic nerve arises from C3-C5 and innervates the diaphragm
    • Ansa cervicalis - loop of nerves formed by C1-C3
      • Gives off branches that supply 4 infrahyoid muscles including the omohyoid
      • Depress the hyoid bone - important in speech and swallowing
  • Sensory branches supply the skin of the neck, upper thorax, scalp and ear
    • These nerves enter the skin at Erb’s point (middle of the posterior border of the sternocleidomastoid)
33
Q

Outline the relationship between the blood supply of the thyroid and the nerves supplying the larynx

A
  • Recurrent laryngeal nerves run behind the thyroid gland to innervate the larynx
    • Can be damaged in thyroid enlargement or thyroid surgery
    • Runs closely with the inferior thyroid artery
  • External laryngeal nerve runs alongside the superior thyroid artery

3 - HNN (15 decks)

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