Airway Anatomy Flashcards
components of upper airway
- nose
- mouth
- pharynx
- hypopharynx
- larynx
components of lower airway
- trachea
- bronchi
- bronchioles
- terminal bronchioles
- respiratory bronchioles
- alveoli
two openings of human airway
nose and mouth; separated anteriorly but join posteriorly by the pharynx
nose
- one of the openings to the human airway
- leads to the nasopharynx
- warms/humidifies inspired gases
- primary pathway for normal breathing unless obstruction (secretions, tumor, polyps, etc)
- nasal breathing resistance almost 2x that of mouth breathing
mouth
- leads to oropharynx
- mouth breathing used with HIGH flow rates (like in exercise)
pharynx
- u-shaped fibromuscular structure
- extends from posterior aspect of the nose to the level of the cricoid cartilage
three components of the pharynx
- nasopharynx
- oropharynx
- hypopharynx
nasopharynx
-lies anterior to C1
-bound superiorly by base of skull and inferiorly by soft palate
-contains nasal septum, turbinates, and adenoids
tonsillar lymphoid structures impede airflow here
oropharynx
-lies at the level of C2-C3
-bound superiorly by soft palate and inferiorly by epiglottis
-opens into the mouth anteriorly through the anterior and posterior tonsillar pillars
tongue is a major source of oropharyngeal obstructions due to decreased genioglossus muscle tone (like what happens when you give you anesthetic agents)
hypopharynx
- lies posterior to the larynx and leads to the esophagus
- bound by superior border of epiglottis and inferior border of cricoid cartilage at C5-C6
- upper esophageal sphincter lies at lower edge of hypopharynx and acts as a barrier to regurg in conscious patient
Waldeyer’s Tonsillar Ring
lymphoid tissue ring in the pharynx that is extremely vascular so at a high risk for bleeding, especially with nasal intubation
Waldeyer’s Tonsillar ring components
- pharyngeal tonsils (aka adenoids) located in nasopharynx
- palatine tonsils (aka tonsils) located in oropharynx
- lingual tonsils located at base of tongue
tubal tonsils
- located bilaterally posterior to eustachian tubes at opening of nasopharynx
- develop from accumulation of lymphoid tissue
larynx
- C3-C6 level in adults
- C2-C4 in infants and children
- descents to C4-C5 by age 5
- organ on phonation and a valve to protect the lower airways
larynx location
- extends from epiglottis to lower level of cricoid cartilage and sits at junction of the airway and the esophagus
- attached anteriorly by the epiglottis, posteriorly by mucous membrane which extends between arytenoid cartilage and laterally by the aryepiglottic folds (aka false cords)
structure of layrnx
- cartilaginous skeleton held together by ligaments, muscles, cartilages, and one bone (hyoid)
- house vocal cords, which extend in an anterior posterior plane from thyroid to arytenoid cartilages
nine cartilages of larynx
- epiglottic
- thyroid
- cricoid
- arytenoid (2)
- cuneiform (2) (lateral)
- corniculate (2) (middle)
epiglottis
- sits at base of tongue
- separates hypopharynx from larynx and hangs over laryngeal opening
- fibrous cartilage with mucous membrane covering that reflects up to the pharyngeal surface of the tongue and makes the glossoepiglottic fold
- on either side of this fold is the valleculae
- protects against aspiration by covering glottis when swallowing
- broad/leaf shaped
- VASCULAR area (bleeding risk)
- can be traumatized and swell
arytenoids
- paired cartilages
- pyramidal
- posterior
- cords attach to them
- most commonly seen paired cartilages on laryngoscopy
vestibular folds
- aka false cords
- narrow bands of fibrous tissue on each side of the larynx that are found first inside the laryngeal cavity opening
vocal cords
-pale, white, ligamentous structures that attach to the thyroid anteriorly and the arytenoids posteriorly
glottic opening
- triangular fissure between the vocal cords
- narrowest portion of an adult airway
- avg width of 6-9 mm (can be stretched to 12 mm)
thyroid cartilage
- “adam’s apple”
- anterior neck/thyroid notch
- largest cartilage of the larynx
- vocal cords attached anteriorly
cricoid cartilage
- only complete ring cartilage (tracheal rings are NOT complete rings of cartilage)
- sits at C6
- narrowest part of the airway in a child (may have trouble passing tube beyond the cords)
- site for Sellick’s maneuver - compresses esophagus between cricoid cartilage and cervical spine to prevent aspiration
thyrohyoid membrane
- connects thyroid cartilage with the hyoid bone
- internal branch of SLN (superior laryngeal nerve) penetrates the membrane at the level of the cornu of the hyoid
cricothyroid membrane
- relatively avascular (why it is an ideal location for LA injection during awake intubation)
- translaryngeal injection
- emergency airway site
- thyroid cartilage is attached to the cricoid cartilage anteriorly by the cricothyroid membrane
trachea
- begins at C6 at inferior border of the cricoid cartilage and extends to carina
- approximately 10-15 cm in length
- cricoid - only complete cartilagenous ring of the trachea
- remainder of trachea composed of 16-20 incomplete rings anteriorly
- bifurcates to R and L mainstem bronchi at level of T5
R bronchus angle
25-30 degrees
L bronchus angle
45 degrees
pediatric airway
- larynx positioned higher in neck
- tongue larger relative to mouth size
- epiglottis larger, stiffer, angled more posteriorly
- head and occiput larger relative to body size
- short neck
- narrow nares
- cricoid ring is narrowest region (as opposed to glottic opening)
role of airway muscles
adduct, abduct, regulate tension, or physically move the larynx
what do the intrinsic muscles do?
open, close and control tension of the vocal cords
what do the extrinsic muscles do?
connect larynx with the hyoid bone and other structures and serve to move the larynx as a whole (elevating and depressing) during phonation, swallowing, and breathing
what are the intrinsic muscles?
- posterior cricoarytenoid
- lateral cricoarytenoid
- arytenoids
- cricothyroid
- thyroarytenoid
action of posterior cricoarytenoid
abducts (opens) the vocal cords an opens the glottis
action of lateral cricoarytenoid
adducts (closes) the vocal cords
action of arytenoids
adducts (closes) the vocal cords
action of cricothyroid
- produces cord tension, closure, and elongates vocal cords
- can result in total and profound glottic closure called laryngospasm
action of thyroarytenoid
shortens and relaxes the vocal cords
what are the extrinsic muscles?
- sternohyoid
- sternothyroid
- thyrohyoid
- omohyoid
- stylohyoid
- mylohyoid
action of sternohyoid
draws hyoid bone inferiorly
action of sternothyroid
draw thyroid cartilage caudad
action of thyrohyoid
draws hyoid bone inferiorly
action of omohyoid
draws hyoid bone caudad
action of stylohyoid
elevates larynx
action of mylohyoid
elevates larynx
what innervates anterior septum and lateral walls of nose?
- opthalmic division of trigeminal nerve (CN V)
- specifically anterior ethmoidal nerve
what innervates posterior septum of nose?
- maxillary division of trigeminal nerve (CN V)
- specifically nasopalatine nerves and sphenopalatine ganglion
SNS stimulation of nose results in…
vasoconstriction and shrinkage of nasal tissues
PSNS stimulation of nose results in…
engorgement of blood vessels and increases likelihood of bleeding with airway manipulation (aka what we see in anesthesia)
what innervates tonsils, roof of pharynx, and underside of soft palate?
glossopharyngeal nerve (CN IX)
what innervates anterior 2/3 of tongue?
lingual nerve (mandibular division of trigeminal nerve CN V)
what innervates posterior 1/3 of tongue?
glossopharyngeal nerve (CN IX)
Facial Nerve CN VII
- supplies muscles of facial expression
- taste to anterior 2/3 tongue
- small amount of afferent conduction to oropharynx
- motor control of stylohyoid laryngeal muscle
- salivary glands (PSNS stim increases saliva production)
Hypoglossal Nerve (CN XII)
- provides motor innervation to most muscles of the tongue
- damage to this nerve can relax the tongue, causing it to fall back and obstruct the airway
Vagus Nerve (CN X)
- innervates airway below epiglottis
- separates into superior laryngeal nerve (SLN) and recurrent laryngeal nerve (RLN)
- these two branches provide innervation for all muscles of the larynx
superior laryngeal nerve (SLN)
- 2 branches
- internal branch (SENSORY SIS) - provides sensation to larynx from epiglottis to vocal folds (sensation ABOVE vocal cords); sensory specifically to lower pharynx, underside of epiglottis, and larynx above the cords
- external branch (MOTOR SEM)- a motor nerve; motor innervation to cricothyroid muscle (so involved in laryngospasm)
recurrent laryngeal nerve (RLN)
SENSORY - provides sensation to larynx BELOW vocal cords
MOTOR
-on R, leaves vagus at level of subclavian artery and loops up
-on L, leaves vagus at level of the aortic arch and loops up
-runs in the groove alongside the trachea
-innervates all muscles of the larynx EXCEPT for cricothyroid muscle (innervated by SLN)
SLN damage
- unilateral = minimal effects
- bilateral = hoarseness, vocal tiring
RLN damage
- unilateral = hoarseness
- bilateral acute = stridor, respiratory distress from unopposed tension of the circothyroid muscle
- bilateral chronic = aphonia
vagus nerve injury
- affects SLN and RLN
- bilateral vagal denervations produces flaccid, midpositioned cords, resulting in aphonia
superior laryngeal artery (SLA)
- blood supply to supraglottic laryngeal structures
- carotid –> superior thyroid artery –> SLA
inferior laryngeal artery (ILA)
- blood supply to infraglottic laryngeal structures
- subclavian –> inferior thyroid artery –> ILA
venous drainage
superior/inferior thyroid veins to SVC
