Larynx Anatomy Flashcards by Ronit Hardasani

Where is the Larynx?

What are 4 of its functions

Between Hyoid bone and Trachea (C4-C6 level)

Ventilation (Most important)
Airway protection
Phonation (sound production)
Allows us to cough

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Outline the structure of the Larynx very briefly

What are it’s Subdivisions?

Consist of Cartilages and 1 Bone, held together by Membranes, Ligaments and Muscles

Supraglottis
Glottis
Infraglottis

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What structures form the Structural framework/ Scaffolding of the Larynx?

Epiglottis
Thyroid cartilage
Cricoid cartilage
Arytenoid cartilage

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What is the Thyroid cartilage attached to superiorly and how?

Attached to Hyoid bone by the Thyrohyoid Membrane

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Describe the Cricothyroid Membrane/ ligament

Runs upwards from Cricoid cartilage but deep to Thyroid cartilage, giving a Free Upper Margin
FUM attaches anteriorly to Thyroid cartilage and posteriorly to Arytenoid cartilages

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What is the Vocal Ligament?

Gives shape and structure to what we see as the true vocal cord

The thickened upper margin of the Cricothyroid membrane

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Which horn of thyroid cartilage articulates with the cricoid cartilage?

Inferior horn (Synovial joint)

Thus 2 connections between Thyroid and Cricoid cartilages, the CT Membrane and Synovial joint

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Part of the Cricothyroid Membrane can be palpated anteriorly.

Why is this significant clinically?

In Acute Laryngeal Obstruction, the Cricothyroid Membrane can be punctured to allow a patient to breathe

(Cricothyroidotomy, allows rapid access to infraglottic area of Larynx, but is a temporary solution)

(Infraglottic= Below vocal cords)

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Suggest 2 examples of Acute Laryngeal Obstuction

Laryngospasm

- Tongue swelling

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The leaf-shaped Epiglottis attaches to the Hyoid bone and the back of the Thyroid Cartilage (thyroglotticligament)

What are the Aryepiglottic folds?
What gives them their shape?

Connections between sides of Epiglottis and the Arytenoids
Quadrangular membrane

(The folds are the upper margin of the membrane)

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What structures form the entrance/ Aditus to the Larynx?

Epiglottis + Aryepiglottic folds

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What is the Laryngeal Prominence?

Where the 2 lateral plates of they thyroid cartilage meet in the midline (Adam’s apple)

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Describe the signet-ring shaped Cricoid cartilage

Only complete ring of cartilage in the Respiratory Tract
Attached to Trachea by Cricotracheal membrane
Arytenoids sit on top of the Cricoid cartilage posteriorly, one on each side

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Passing from the Arytenoids to the back of the Thyroid cartilage are 2 Mucosal Folds.

Name them and say what they form/ contain

Upper;

Vestibular Fold (Lower free border of Quadrangular membrane)
Forms the False Vocal Cord on each side

Lower;

True Vocal Cord (Upper free border of Cricothyroid Membrane)
Contains the Vocal Ligament

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What is the space between the Vestibuar Fold and True Vocal Cord called?

Rima Glottidis

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The Vestibular Fold and True Vocal Cord separate the Larynx into what 3 compartments?

Supraglottis/ Vestibule (Between Laryngeal inlet to Vestibular fold (False vocal cords))
Glottis (Narrowest part)
Infraglottis (Between True vocal cords and trachea)

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What is the Saccule of the Larynx?

What does it do?

A lateral outpouching of the mucous membrane between the True and False vocal cords
Contains mucous glands whose secretions keep the true vocal cords moist

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How is the Saccule of the Larynx connected to the Glottis?

Via the Layngeal Ventricle on either side

What epithelia line the true vocal cords?

Stratified squamous

Rest of larynx has pseudostratified ciliated columnar

Describe how an Endotracheal (ET) tube is inserted for intubation

Passes through Oral cavity, Oropharynx, Larynx and through Vocal Cords
Sits on upper part of trachea
Has a small balloon/ cuff that is inflated to ensure tube stays in place

When inserting a Laryngoscope, where can the tip be placed?

Into the Vallecula (a recess behind the root of the tongue)

The Arytenoid cartilages are moved by the Intrinsic Larynx muscles to alter the size and shape of the Rima Glottidis.

How do the vocal cords appear in an anaesthetised patient about to be intubated?

Relatively abducted

List 3 key roles of the Intrinsic Larynx muscles

Open glottis in inspiration
Close vestibule and vocal cords during swallowing
Alter tone of the true vocal cords in phonation and coughing

Which 2 groups of muscles support the larynx in its function?

Infra and Suprahyoid muscles (Depress and elevate the Hyoid and Larynx)

Name the only Intrinic Larynx muscle that is found outside of the larynx What does it do?

Cricothyroid muscle - Tenses + slightly adducts the true vocal cords by its tilting action of the Thyroid cartilage on the Cricoid cartilage - Allows higher pitched sounds to be made

How is the Cricothyroid muscle’s innervation different to that of the other Intrinsic Larynx muscles

Other Intrinsic Larynx Muscles; - Recurrent Laryngeal Nerve (CN X) Cricothyroid Mucsle; - External Laryngeal Nerve (branch of Superior Laryngeal)

Other than Cricothyroid, the Intrinsic Larynx Muscles make up an encircling sheet. What do they do?

- Act to move the Arytenoid Cartilage at the Cricoarytenoid Joint - This allows opening and closing of the Rima Glottidis, by Abducting and Adducting the True Vocal Cord

Other than Cricothyroid, most Intrinsic Larynx Muscles act to Adduct the true vocal cords. Which one doesn’t? What does it do?

- Posterior Cricoarytenoid, one on each side | - Rotates the Arytenoids outwards, Abducting the True Vocal Cords

What would happen to the true vocal cords without the action of Posterior Cricoarytenoid? (Runs from Cricoid to Arytenoid cartilage)

True vocal cords would be permanently adducted and block airflow

What is the action of the Intrinsic Larynx Muscles that attach to the Epiglottis?

Contract to pull down on sides of Epiglottis so that it covers the the Laryngeal Inlet

In terms of sensory innervation, what do the Internal and Recurent Laryngeal Nerve innervate? (Branch of Superior Laryngeal)

Internal; - Laryngeal mucosa above the vocal cords (Supraglottis) and the Glottis Recurrent; - Laryngeal mucosa below the vocal cords

What vessels accompany the Superior and Recurrent Laryngeal Nerves

Superior and Inferior Thyroid arteries

How many pairs of Suprahyoid muscles are there? What is their innervation?

- 4 pairs - Branches of Cranial nerves (E.g Digastric who’s posterior belly is a boundary of the Carotid Triangle)

How many pairs of Infrahyoid (‘Strap’) muscles are there? What is their innervation?

- 4 pairs - Branches from C1-C3 (E.g Omohyoid, whose superior belly forms a boundary of the Carotid Triangle)

How does the Larynx move when swallowing? | What muscles do this?

- Elevated and displaced anteriorly by Suprahyoid and Longitudinal Pharyngeal muscles

What are 3 benign causes of a hoarse voice?

- Infection - Inflammation - Singer’s nodules (Vocal cord nodules)

What does Unilateral Complete injury to the Recurrent Laryngeal Nerve cause? How does this present?

Causes vocal cord on affected side to; - Become immobile and take a Neutral/ Paramedian position between Abduction and Adduction - Other side’s vocal cord compensates well but may be some Hoarseness and a Cough (breathing issues not usually present)

What happens in Bilateral Complete injury to the Recurrent Laryngeal Nerves? How does this present?

- Both vocal cords take up a Paramedian position - Rima Glottidis becomes extremely narrow - Affects ability to speak - Significant breathing difficulties (Airflow obstruction)

The RLN has a long course, especially on the left where it loops under the Aortic Arch and ascends in the Tracheo-Oesophageal Groove. Suggest 3 neck/ chest pathologies that can affect/ injure the RLN

- Aortic Arch Aneurysm (Left RLN) - Apical Lung Tumours - Disease or surgery of Larynx/ Oesophagus/ Thyroid

How can Larynx Carcinomas present? What is often the earliest sign of lesions involving the Vocal Cords?

- Voice and/ or airway problems | - Hoarseness of voice

Why is the Prognosis favourable if a Laryngeal Cancer is small and involves the glottis?

The glottis has very minimal lymphatic drainage

Laryngeal cancers in the Supra and Infraglottis have a poor prognosis due to having higher lymph drainage. Which lymph nodes do they drain to?

Supraglottis; - Neck nodes Infraglottis; - Paratracheal nodes

What does the Inferior free border of the Quadrangular membrane give rise to? What does the Superior free border of the Cricothyroid Membrane give rise to?

False vocal cords True vocal cords