Airway anatomy Flashcards
Name three functions of the nose?
- Warm
- Humidify
- Filter
What type of epithelium line the respiratory tract?
Nasal mucosa to bronchi - Pseudostratified columnar epitehlium with goblet cells
Bronchioles - simple cuboidal epithelium
Alveoli - Simple squamous epithelium
What is the function of the respiratory mucosa?
Formation of the mucociliary escalator and to ensure warming and near 100% humidification of air.
What are choanae?
Posterior nasal apertures or internal nostrils are two openings found at the back of the nasal passage between the nasal cavity and the throat.
Where is the widest part of the nasal airway?
Inferior to the inferior turbinate
What are the advantages of nasal intubation?
- leaves oral cavity clear for oral surgery
2. ICU patients - better tolerated.
What are the disadvantages of nasal intubation?
- More difficult
- Nose bleeds
- Mucosal injury with creation of a false passageway into the cranium.
- Long-term: infection in paranasal air sinuses
What two bones make up the hare palate and what is their orientation in the hard palate?
Anterior - palatine processes of the maxillary bone
Posterior - horizontal plates of the palatine bone.
From where does the soft palate originate?
Suspended from the posterior aspect of the hard palate and blends with the pharyngeal wall laterally and forms the uvula in its central portion
Why doesn’t a nasopharyngeal airway stimulate the gag reflex?
Contact with the palate, tonsil, posterior part of the tongue or the posterior pharyngeal wall elicit the gag reflex. If the NP airway does not extend beyond the tip of the soft palate, then the gag reflex will not be stimulated
What are the afferent and efferent nerves for the gag reflex?
Afferent - glossopharyngeal nerve
Efferent - vagus nerve
What makes up the pharynx
Nasopharynx
Oropharynx
Laryngopharynx
In what part of the pharynx do fish bones often lodge?
In the piriform fossae which are recesses within the laryngopharynx on either side of the posterior bulging larynx
Where are the adenoids located? What complications can occur regarding these structures.
Posterior to the nasal cavity on roof and posterior wall of the nasopharynx. They may become a site of bleeding following nasal intubation in children.
Obstructive sleep apnoea can occur with adenoid hypertrophy
What are the palatoglossal and the palatopharyngeal aches collectively known as and what structure lies between these two arches bilaterally?
The pillars of the fauces - between these structures are the palatine tonsils or ‘tonsils’
What are the clinical implications related to the palatine tonsils?
- Childhood hypertrophy - tonsillectomy indicated for OSA and recurrent infection
- Large tonsils may cause airway obstruction after induction of anaesthesia
Describe the sensory nerve supply to the tonsil and suggest the most efficient regional anaesthetic technique.
Sensory nerve supply is from branches of three different nerves:
- glossopharyngeal n.
- maxillary n.
- mandibular n.
Infiltration of local anaesthetic into the tonsillar bed is more effective than attempting nerve blockade
How is aspiration prevented during swallowing?
- Reflex closure of the laryngeal sphincter (vocal cords close)
- Reflex upward movement of the larynx behind the tongue
- Reflex inhibition of breathing
- Epiglottis may act as a lid to the larynx
What procedures remove the airway protective reflexes that occur in swallowing?
- General anaesthesia
- Application of topical anaesthetic to larynx
- Neurological injury
Where in the neck is the larynx located
Midline opposite the 3rd to the 6th cervical vertebrae closely related to the carotid arteries and jugular veins connecting pharynx to trachea
Name the three unpaired cartilages of the larynx
Thyroid cartilage
Cricoid cartilage
Epiglottis
Name the paired cartilages of the larynx
Arytenoid
Corniculate
Cuneiform
What is the function of the hyoid bone
Greater movement of tongue and larynx
What are three functions of the larynx
Breathing
Phonation
Protection of lower respiratory tract
How many types of cartilage are there? Name and define them.
There are 3 types of cartilage:
- Hyaline cartilage (most widespread: ribs, nose, larynx, trachea and is a precursor for bone)
- Fibrous cartilage (the only type of cartilage that contains type I collagen as well as the usual type 2: pubic symphysis and intervertebral discs)
- Elastic cartilage (elastic fibers - with elastin - and collagen 2 - eustachian tube and epiglottis)
Which cartilage in the larynx is hyaline cartilage
Thyroid
Cricoid
Arytenoids
Which cartilage in the larynx consist of elastic cartilage?
Epiglottis
Coniculate (paired - articulate with arytenoids at bases)
Cuneiform (paired - no attachment to other cartilage)
Name the extrinsic membranes and ligaments of the larynx
Thyrohyoid ligament
- lateral thyrohyoid lig.
- median thyrohyoid lig.
Cricothyroid ligment
- Median cricothyroid ligament
Tracheocricoid ligament
Name the intrinsic membranes and ligaments of the larynx
Elastic cone - paired - extends superiorly from the lateral aspects of the cricoid cartilage to the vocal lig.
Vocal ligament - extends from the the angle of the thyroid prominence to the vocal process of the arytenoid cartilage covered by the vocal folds (mucosa) - yellow elastic tissue.
Quadrangular membrane - square shaped layer of submucosa extending from lateral aspect of epiglottis to arytenoid cartilages - superior border defines the aryepiglottal fold
Vestibular ligament - formed by the thickened free edge of the inferior margin of the qaudrangular ligament enveloped by the vestibular fold
What is the narrowest part of the airway in the adult
Rima glottidis (space between the true vocal cords)
Space between vestibular folds is called the rima vestibuli
What is the function of the extrinsic muscles of the larynx
These muscles work with other muscles attached to the hyoid bone to move the larynx up and down during swallowing
What is the function of the intrinsic muscles of the larynx?
- Open vocal cords during inspiration
- close vocal cords and laryngeal inlet during swallowing
- Alter cord tension during phonation
What is the function of the posterior cricoarytenoid muscle and what is the nerve supply to this muscle
aBduction of the cords by pulling the posterior ends of the arytenoid cartilages together medially –> pivoting and abduction of the cords
The external division of the superior laryngeal nerve
What is the function of the lateral cricoarytenoids and transverse arytenoids?
aDduction of the cords by pulling the posterior aspect of the pivoting arytenoids away from each other
What is the function of the aryepiglottics and the thyroepiglottics
These close the laryngeal inlet during swallowing
What is the function of the cricothyroid muscles
To tilt the thyroid cartilage anteriorly to tense the cord for higher pitched phonation
What is the function of the thyroarytenoids and vocalis
Thyroarytnoids - relax the cords
Vocalis - fine adjustments of the cords
Which nerve is responsible for the sensory supply to the larynx above the vocal cords?
Superior laryngeal nerve (internal branch) (a branch of the vagus nerve)
The external branch provides the motor supply to the cricothyroid muscle
Which nerve is responsible for the sensory supply to the larynx below the level of the vocal cords?
Recurrent laryngeal nerve (also a branch of the vagus nerve)
Stimulation of which nerve might induce vagal reflexes during laryngoscopy
Internal branch of the superior laryngeal nerve which provides the sensory supply to the vallecula
Which nerve supplies all the intrinsic muscles of the larynx except the cricothyroid muscle
Recurrent laryngeal nerve
Describe the path of the right recurrent laryngeal nerve
The vagus nerve dips into the thorax first –> Under right subclavian artery to ascend into the larynx in the groove between the oesophagus and trachea
Describe the path of the left recurrent laryngeal nerve
The vagus nerve dips into the thorax first –> Under the aortic arch to ascend into the larynx in the groove between the oesophagus and the trachea
What happens when the superior laryngeal nerve is damages
- Hoarse voice (loss of tensor function of the cords - cricothyroid)
- Increase aspiration risk: less sensation above the cords
What happens with unilateral damage to the recurrent laryngeal nerve
- Hoarse voice with slight recovery - compensation of contralateral cord
- Ineffective cough (glottis cannot close completely - no adequate pressure build up)
- Increased risk of aspiration - infraglottic sensory loss
What happens if there is damage to both recurrent laryngeal nerves
Severe respiratory distress with stridor as the flaccid vocal cords flap together. Urgent intubation required with tracheostomy likely to follow
why should cricothyroidotomy only be used as a temporary airway?
Should be converted to tracheostomy within 72 hours to reduce risk of subglottic stenosis
