Session 10 Flashcards
(21 cards)
Functions of the larynx
Ventilation (movement of air into/out of lungs)
Airway protection -preventing food/fluid etc entering airways
Important role in cough reflex -rapidly expel anything inadvertently entering airway
Role in production of sound (phonation)
What is the larynx?
‘Tube’ created by ligaments, membranes, cartilages and muscles
• Suspended from and lies below the hyoid bone
• Part of the respiratory system (transmits air into/out of lower resp. tract)
• Begins at laryngeal inlet and ends at lower border of cricoid cartilage (C6)
• Continues as the trachea
Larynx Lies Anterior to the Laryngopharynx
Framework of Larynx
Cartilages, Membranes and Ligaments
Synovial joints between the cartilages (cricothyroid [A] and cricoarytenoid [F])
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Surface Anatomy of layrnx
Certain Cartilages and Membranes are Palpable
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Cricothyroidotomy
Provides emergency access to airway, beneath vocal cords
On the very rare occasion a patient cannot be intubated or ventilated e.g swelling to vocal cords, access can be gained into airway via cricothyroid membrane (below vocal cords)
Framework of Larynx
Formation of the laryngeal inlet and aryepiglottic folds
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Lining of larynx
Larynx is lined with a mucous membrane
Internal Anatomy is Shaped By Folds Formed by Ligaments/ Membranes & Cartilages
Between vestibular and vocal folds is a small recess (ventricle) - leads laterally and upwards into the saccule (or sinus); contains mucous glands that keep (true) vocal folds moist
Mucosal folds internally divide larynx into three regions: supraglottis, glottis and infraglottis
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What type of epithelium lines the larynx?
panopto
With the exception of the true vocal cords which are lined with
Label the Laryngoscopic View of Larynx e.g. during intubation
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Intuation witheiglottis
Vocal cords must be viewed for intubation: placement of an endotracheal tube into subglottic region (i.e. below vocal cords)
Flexible nasoendoscopy: insert flexible endoscope via nasal cavity and pharynx to then visualise larynx
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Intrinsic Laryngeal Muscles
• Broadly have two main actions, to alter – Size/shape of laryngeal inlet – Tension/position of vocal cords
1) Swallowing – Close laryngeal inlet and vocal cords – Protecting respiratory tract
2) Inspiration and expiration – Open vocal cords (and laryngeal inlet) – Allowing movement of air
3) Phonation and cough reflex – ……………… vocal cords
Of all the intrinsic muscles of the larynx…only one aBducts the vocal cords (widens the glottis) - posterior cricoarytenoid
Move cartilages relative to one another playing a key role in vocal cord movement
• Arytenoids position on cricoid determines position of true vocal cords and therefore size of aperture (rima glottidis/glottis)
• All muscles supplied by recurrent laryngeal nerve of vagus (CN X) – Right vocal cord muscles = right recurrent laryngeal nerve – Except cricothyroid muscle (external branch of superior laryngeal nerve)
Vocal Cord Movements
- Inspiration and expiration – VC aBduct
- Phonation– VC closely aDduct – Expired air forced through closely adducted vocal cords – VC vibration creates sound waves
• Cough (explosion of compressed air) – inspire and fill lungs with air – vocal cords then aDducted – expiratory muscles contract – intrathoracic pressure builds – then cords suddenly aBducted – explosive outflow of air!
Both vocal cords have to meet in midline (aDduct) to allow for phonation and cough
If movement of one vocal cord impaired (e.g. injury to nerve supplying muscles involved in its movement) phonation and cough will be impaired
What is the patient doing?
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pan
What determines pitch of sound during phonation?
Pitch of Sound Determined by Vocal Cord Tension
• High-pitched sounds → vocal cords taut
• Low-pitched sounds → vocal cords less taut
• Bilateral contraction of cricothyroid muscle increases tension in vocal cords – Found on outside of larynx – Innervated by external branch of superior laryngeal nerve (branch of CN X)
Action of Cricothyroid Muscle
Tilts Thyroid Cartilage forward on Cricoid Increasing Tension in Vocal Cords Important for Reaching Higher Pitch
Cricothyroid muscle is innervated by CN X, specifically external branch of superior laryngeal nerve
Injury to nerve (closely related to superior thyroid artery) leads to hoarseness of voice especially when attempting higher pitched sounds
Larynx During Swallowing
protects the airway from food and fluid
• 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 of vocal cords (glottis)
- Suprahyoids and longitudinal pharyngeal muscles play an important role during swallowing
- Act to elevate and anteriorly displace the larynx • Helps ensure patency of pharynx so food/fluid can be directed into it
Vagus Nerve (CN X) Innervation to Larynx
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Nerve Supply to Larynx - Superior Laryngeal Nerve
Relationship between superior thyroid artery and external laryngeal nerve
• Superior laryngeal nerve is a branch of the vagus
• Gives rise to an internal and external branch
• Internal branch: purely sensory (supraglottic and glottic areas- i.e. includes VC)
• External branch: motor to cricothyroid
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Nerve Supply to Larynx - Recurrent Laryngeal Nerve (RLN)
• Recurrent laryngeal nerve arises distally from vagus
• Passes anteriorly to then loops under right SCA and on left, the arch or aorta
• Ascends in tracheo-oesophageal groove
• Close anatomical relationship with thyroid gland and inferior thyroid arteries supplying the gland
• Innervates all intrinsic muscles of larynx (except cricothyroid)
• And provides sensory of and below vocal cords (infraglottic region)
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Vocal Cord Palsies
Injury to Recurrent Laryngeal Nerve
• Recurrent laryngeal nerves is close relation of inferior thyroid artery – Potentially injured during thyroid surgery
• Other anatomical relations of RLN during its journey (on left and right side) – Aortic arch aneurysm (left RLN) – Cancer involving apex of lung (right RLN) – Disease or surgery involving larynx, oesophagus or thyroid
• RLN supplies intrinsic muscles of larynx responsible for vocal cord movements
• Unilateral RLN lesions lead to unilateral vocal cord palsies – →hoarse voice, ineffective cough
Unilateral vs Bilateral RLN Injuries
• Paralysed vocal cord assumes a paramedian position – Between fully abducted and fully adducted
• Unilateral palsy may lead to hoarseness of voice +/ineffective cough – Often contralateral side compensates in time (crosses midline to meet vocal cord on affected side)
• Bilateral lesions – Both vocal cords paralysed and in paramedianpostion – Narrow glottis – Significant airway obstruction…emergency surgical airway
Conditions Affecting the Larynx
• Laryngitis (inflammation of the vocal cords) • Larnyngeal nodules • Laryngeal cancer • Croup (read more) • Epiglottitis (read more) • Laryngeal oedema e.g. allergic reaction
Certain conditions causing swelling of the larynx can threaten the airway Patient with a compromised upper airway will present with stridor, raised respiratory rate, distress, hypoxia +/- cyanosis
