Larynx Flashcards
What are the functions of the larynx?
Airway protection - prevents food / fluid ect.. entering airways
Ventilation - movement of air into / out of the lungs
Cough reflex - rapidly expel everything inadvertently entering airway
Production of sound
What is the larynx?
A ‘Tube’ created by a series of ligaments / membranes, cartilage and muscles.
It lies behind the hyoid bone.
It begins at laryngeal inlet and continues as the trachea at C6 / lower border of cricoid cartilage.
What is the route of inspired air?
Oral cavity or nasopharynx
Oropharynx
Larynx
Trachea
What is the route of food?
Oral cavity
Oropharynx
Laryngopharynx
Oesophagus
What things make up the larynx?
Three single cartilages:
Thyroid, cricoid, epiglottis
Three paired cartilages:
Arytenoid, Carnicuate, Cuneiform
Numerous membranes and ligaments connecting cartilages (and to hyoid) to help give shape to larynx:
- Thyrohyoid membrane
- Criothyroid membrane
- Cricotracheal membrane
- Quadrangulat membrane
What is a cricothyroidotomy?
Cut cricothyroid membrane for emergency access to the airway,
This is used rarely when a patient cannot be intubated or ventilated.
What does the quadrangular membrane do?
Forms the aryepiglottic fold which form the margins of oval inlet of the larynx.
Free lower margin forms edge of false vocal cord (vestibular ligament).
What is the vestibular ligament?
The free lower edge of the quadrangular membrane. It makes the vestibular folds which are the false vocal cords.
What is your vocal ligament?
True vocal cords
What makes up supraglottis, glottis and infragrottis?
Supraglottis (laryngeal vestibule) - Epiglottis to false vocal cords
Glottis (narrowest part) - vocal cords
Infraglottis (or subglottis) - vocal cords to bottom cricoid cartilage / start of tracheal.
What type of epithelium lines the larynx?
Pseudostratified ciliated columnar epithelium
EXCEPT: vocal cords - squamous epithelium.
How can you view the larynx?
Endotracheal tube
Nasoendoscopy
What are the main actions of the laryngeal muscles?
Alter size and shape of inlet
Alter size / position of vocal cord
This means that they:
- Close laryngeal inlet and vocal cords during swallowing
- Open vocal cords and allow for movement of air during inspiration and expiration
- Use movement of vocal cords in phonation and in cough reflex.
What does posterior cricoarytenoid do?
Keeps vocal cord open.
It is the ONLY muscle to do this! (all others close vocal cords)
What innovates the intrinsic laryngeal muscles?
All supplied by the recurrent laryngeal nerve of the vagus.
EXCEPT cricothyroid which is supplied by an external branch of the superior laryngeal nerve.
What happens to vocal cords during insiparation / expiration?
Abduct - glottis wide open
Vocal cords abduct to greater extent during deep breathing.
What happens to vocal cords during phonation?
Adduct - expired air is forced through closely adducted vocal cords to vibrate a column of air.
What happens to vocal cord during coughing?
During a cough, vocal cords are powerfully adducted, intrathoracic pressure builds then cords suddenly abducted.
How do you change the pitch of sound?
Pitch of sound is determined by vocal cord tension.
Pitch of sound can be altered by tension and length of the vocal folds.
High pitch - taught vocal folds
Low pitch - folds relaxed
What does cricothyroid do?
Bilateral contraction increases length and tension in vocal folds.
it is the only muscle of the larynx found outside the larynx and to be innervated by an external branch of the superior laryngeal nerve.
What happens to the larynx during swallowing?
Protect airways from food / fluid during swallowing
Contraction of aryepiglottic muscles act to narrow laryngeal inlet and pull down epiglottis.
Assisted by elevation of larynx (pharyngeal muscles and suprahyoid muscles pull larynx UP and FORWARD)
Closure of vocal cords (glottis)
What do suprahyoids and longitidinal pharyngeal muscles do?
They act to elevate and anteriorly displace the larynx. This helps ensure potency of pharynx so food / fluid can be directed into it.
Describe the nerve supply to the larynx
Superior laryngeal nerve:
Internal -Sensory, supraglottic
External - Motor, cricothyroid
Recurrent laryngeal nerve -sensory to subglottic, motor to intrinsic muscles
Describe the route of superior laryngeal nerve
Branch of the vagus]Gives rise to internal and external branches.
Internal - sensory
External -motor to cricothyroid
Describe the route of the recurrent laryngeal nerve?
Recurrent laryngeal nerve arises distally from vagus, then loops under right SCA and on left, arch of aorta.
Ascends in tracheostomy’s-oesophageal groove.
Close anatomical relationship with thyroid gland and inferior thyroid arteries supplying the gland,
How could you injure the recurrent laryngeal nerve?
Thyroid surgery - in close relations inferior thyroid artery.
Aortic arch aneurysm (left)
Lung apex cancers (right)
Disease or surgery involving larynx, oesophagus or thyroid
What happens if you get a unilateral vocal cord palsy?
Hoarseness of voice or ineffective cough as the contralateral side compensates in time (it crosses the midline to meet the vocal cords on the affected side that have assumed a paramedian position).
What happens if you have a bilateral vocal cord lesions?
Both vocal cords paralysed in paramedian position
Narrow glottis
Significant airway obstruction… emergency surgical airway!
What conditions can affect the larynx?
Laryngitis
Laryngeal nodules
Laryngeal cancer
Croup (acute respiratory distress in children)
Epiglottitis (acute respiratory distress in children)
Laryngeal oedema - allergic reaction.
How will a patient with a compromised airway present?
Stridor
Raised respiratory rate
Distress
Hypoxia +/- cyanosis
