Ear, Airways and Larynx Flashcards
what is the outer ear made of?
auricle
external acoustic meatus (EAM)
what is the function of the EAM?
collects vibrations and mediates their passage to the middle ear
what are the depressions, eminences and folds of the auricle?
Helix and lobule: Folded outer margin of the auricle
Antihelix: Parallel inner margin
Tragus and antitragus: Eminences anterior and inferior to the EAM respectively
Concha: The auricle’s hollow centre
within which bone does the middle and inner ear lie in?
petrous part of the temporal bone
from which structure does the middle ear conduct sound from to the oval window?
tympanic membrane
what are the 3 ossicles?
Malleus
Incus
Stapes
malleus muscle
Tensor tympani muscle (V3): Pulls the handle of the malleus medially. This tenses the tympanic membrane, reducing the force of vibrations in response to loud noises
stapes muscle
Stapedius (VII): Pulls the stapes posteriorly to prevent excessive oscillation
what is the function of the pharyngotympanic (Eustachian) tube connection the internal ear to the nasopharynx?
Equalises barometric pressure between the middle ear and the external environment
functions of the facial nerve?
Motor:
- Muscles of facial expression and posterior suprahyoid muscles
- Stapedius
- Parasympathetic to lacrimal gland, salivary glands, mucous membranes of nasal cavity
Sensory:
- Taste anterior 2/3 tongue
- General sensation to external auditory meatus and auricle
nerves of the facial nerve
Extracranial component of facial nerve Posterior auricular nerve* Greater petrosal nerve* Chorda-tympani Nerve to stapedius
journey of CNVIII in ear
Enters the middle ear through the internal acoustic meatus (along with VII) and then splits into the vestibular and cochlear nerves (both SSA).
branches of vestibular nerve
1) Upper branch, SSA fibres to the semi-circular canals and utricle
2) Lower branch, SSA fibres to the saccule
where are the vestibulocochlear nuclei located?
pons/medulla
VIII nuclei and branches
1) cochlear nucleus- cochlea
2) vestibular nuclei- semicircular canals and utricle (upper) + saccule (lower)
features of EAM and tympanic membrane
pars flaccida lateral process of malleus posterior malleolar fold handle of malleus umbo cone of light
what is the URT lined with?
resp epithelium
what are the two functions of respiratory epithelium?
1) removed trapped particles
2) warms and humidifies air
where does the larynx come from in the upper resp tract?
in the lower part of the tract
what are the two functions of the larynx?
1) sphincter of the lower resp tract
2) specialised for phonation in humans
how is the nose the first line of defence? [3]
- Nasal mucosa and conchae, warm and humidify inhaled air
- Hairs trap large particles
- Cilia move rubbish laden mucus to the back to be swallowed
what are the four mechanisms that prevent aspiration?
1) gag reflex
2) swallowing
3) sneezing
4) coughing
what are the sensory and motor components of the gag reflex?
sensory: soft palate and back of tongue predominantly IX
motor: pharyngeal constrictors (X)
the three phases of swallowing
1) oral (voluntary)
2) pharyngeal (reflex)
3) oesophageal
oral phase nerves
V, VII, IX, X, XII
pharyngeal phase nerves
IX, X, XII
oesophageal phase nerves
IX, X
phase 1 of swallowing process
1) Food is chewed by the muscles of mastication (V3). Bolus is held on tongue.
2) Elevation of soft palate, tensor and levator palatini (Mandibular V3 and Vagus X, respectively).
3) Bolus into oropharynx, done by the tongue (XII). Airway is still OPEN.
phase 2 of swallowing process
1) Triggered when bolus hits pharyngeal arch, tongue (XII) retracts pushing bolus into pharynx
2) Airway CLOSED – action of pharyngeal muscles (X)
3) Bolus propelled through pharynx (pharyngeal constrictors, X)
phase 3 of swallowing process
Oesophagus opened, airway closed, breath held. Bolus propelled through oesophagus
afferents and efferents of coughing
afferent: X
efferent: V3 and X
afferents and efferents of sneezing
afferent: V2 and I
efferent: X
what are the conchae?
superior, middle and inferior from 3 recesses
what are the sinuses?
frontal
sphenoidal
maxillary
ethmoidal cells
where does the sphenoidal recess drain?
sphenoethmoidal recess
where do the posterior ethmoidal cells drain?
lateral wall of the superior meatus
where do the middle ethmoidal cells drain?
what also drains here?
middle meatus
frontal sinus, anterior ethmoidal cells, maxillary sinuses
where does the lacrimal duct drain?
inferior meatus
which sinuses does the ophthalmic (V1) nerve supply?
Frontal, sphenoid + ethmoid sinuses
which sinuses does the maxillary (V2) supply?
maxillary sinus
frontal sinus innervation
Supraorbital branch of Frontal branch of V1
sphenoid sinus innervation
Post Ethmoidal branch of Nasociliary of V1
ethmoid sinus innervation
Ant and Post Ethmoidal branches of Nasociliary of V1
maxillary sinus innervation
Infraorbital branch of V2
frontal sinus
Superior to the orbit in the frontal bone
Triangular; base parallel to midline and apex 1/3 along orbit
- drains into middle meatus
- innervated by supraorbital branch of V1
- blood supply: Anterior ethmoidal artery (branch of ophthalmic artery
sphenoidal sinuses
Within the body of sphenoid
- drains into sphenoethmoidal recess
- innervated by Posterior ethmoidal branches (of the nasocillary) of V1
- blood supply: Pharyngeal arteries (maxillary artery)
maxillary sinuses
Completely fill the bodies of their respective maxillae
Largest paranasal sinus and is pyramidal
- drains into Middle of semilunar hiatus of the middle meatus
- innervated by Infraorbital and alveolar branches of V2
- blood supply: infra-orbital and superior alveolar branches of the maxillary arteries
what are the 3 parts of the ethmoid bone?
Cribriform plate
Perpendicular plate
Ethmoidal labyrinth
ethmoidal sinuses
Fill the ethmoidal labyrinth
variable individual air cells (divided into anterior, middle and posterior)
- drains into:
1) Anterior: Nasofrontal duct (15%) or ethmoidal infundibulum
2) Middle: Ethmoidal bulla (directly into the middle meatus)
3) Posterior: Superior meatus (directly)
- innervated by: Anterior and posterior ethmoidal branches (of the nasocillary) of V1 (opthalmic division of trigeminal)
- blood supply: Anterior and posterior ethmoidal (opthalmic)
summary of paranasal sinuses:
1) which ones are there?
2) where do most of them drain?
3) innervation?
frontal, sphenoidal, ethmoid air cells and maxillary
Mostly drain into the middle meatus
Except for the sphenoid sinus which drains into the sphenoethmoidal recess
Frontal, sphenoid and ethmoid: Ophthalmic division of trigeminal (V1)
Maxillary: Maxillary division of trigeminal (V2)
how can infection travel down the Eustachian tube?
to the mastoid antrum and air cells and then erode the temporal bone
infection from root of teeth
reach the maxillary sinuses due to proximity
how can pituitary tumours be accessed?
surgical route through the sphenoidal sinuses via the nose
two functions of larynx?
1) protects lower airways
2) phonation
where is the larynx located?
under the hyoid bone and above the trachea
what is the innervation to the larynx?
X entirely
vagus branches that innervate the larynx
1) Superior Laryngeal
2) Recurrent Laryngeal - sensation below vocal folds and all other muscles
superior laryngeal innervation of the larynx
Internal – sensation above vocal folds
External – one muscle, the cricothyroid
what is damage to the recurrent laryngeal associated with?
Damage to recurrent laryngeal is associated with hoarseness and deepening voice. Bilateral damage can be life-threatening.
what are the 3 unpaired cartilages of the larynx?
Cricoid
Thyroid
Epiglottis
what are the 3 paired cartilages of the larynx?
Arytenoid
Corniculate
Cuneiform
what are the 2 extrinsic membranes of the larynx?
Thyrohyoid membrane
Cricotracheal ligament
what are the 2 instrinsic membranes of the larynx?
Cricothyroid
Quadrangular
4 main muscles of the larynx
1) transverse arytenoid muscle
2) thryoarytenoid muscle
3) posterior cricoarytenoid muscle
4) lateral cricoarytenoid muscle
which is the lowest unpaired cartilage in the larynx?
cricoid (the only complete cartilaginous ring in all air passages)
thryoid angle
90-120 degrees
what does anterior movement of the thyroid result in?
what joint facilities this?
stretching of the vocal ligament
cricothryoid joint
what does the cricoid ligament connect?
cricoid to thyroid cartilages
what does the cricoid ligament form at the superior border?
vocal ligament (thickened)
what does the vocal ligament attach to?
vocal process of the arytenoid cartilage
what does the cricoarytenoid joint enable?
allows abduction and adduction of the vocal ligaments (and also vestibular, to a smaller degree)
what is the space between the vocal ligaments called?
rima glottides
how is the epiglottis attached to the thyroid?
thyroepiglottic ligament
what motion of the epiglottis carries out its function?
Retroflexes over the pharyngeal isthmus to protect it during swallowing
superior and inferior attachments of quadrangular membrane?
It is superiorly connected to epiglottis and inferiorly to the thyroid and arytenoids
what does the quadrangular membrane form at the inferior border?
vestibular ligament (thickened)
membranes and the ligament they form
cricothyroid ligament forms the vocal ligament (superior)
quadrangular membrane forms the vestibular ligament (inferior)
which nerve innervates the larynx?
what are there main branches
vagus
- superior laryngeal nerve
- recurrent laryngeal nerve
what are the branches of the superior laryngeal nerve and what do they provide?
Internal laryngeal nerve:
All sensation above the vocal folds
External laryngeal nerve:
Cricothyroid muscle only
what is the function of the recurrent laryngeal nerve?
All sensation below the vocal folds
All muscles of the larynx except cricothyroid
what is the effect of movement of the cartilages?
the movement of the thyroid and arytenoid will cause movement of the vocal ligaments and results in altered phonation
what does the movement of the arytenoid also caused alongside movement of the vocal ligament?
movement of the vestibular ligament
this provides the protective function of the airway
what will the movement of the epiglottis cover?
cover the pharyngeal isthmus
serves as protection
what innervates the cricothyroid muscle?
external laryngeal nerve (inferior to the internal)
the movement of the cricothyroid muscle?
forward and downward movement of thyroid cartilage along cricothyroid joint
(made of straight and oblique parts)
increases tension on vocal ligaments
what muscle adjusts tension on the vocal ligaments?
vocalis
movement go the posterior crico-arytenoid?
what is the purpose of this movement?
Abduction of the vocal ligaments
Increased air flow = increased volume of sound
movement of the lateral crico-arytenoid?
Adduction of the vocal ligaments
movement of the transverse arytenoid?
adduction of the arytenoid cartilages
movement of thyroid-arytenoid and oblique arytenoid muscles?
Sphincter of laryngeal inlet
Narrows the laryngeal inlet by pulling arytenoid cartilages forward while pulling the epiglottis toward the arytenoid cartilages
Contraction occurs as part of pharyngeal phase of swallowing
what is the effect of damage to the vagus before branching to the superior laryngeal nerve?
complete paralysis
what is the effect of lesion of the internal laryngeal nerve?
loss of sensation above the vocal folds
what is the effect of lesion of the external laryngeal nerve?
paralysis of the cricothyroids
what is the effect of lesion of the recurrent laryngeal nerve?
paralysis of all muscles of the larynx except cricothyroid
loss of sensation below the vocal folds
which artery does the superior laryngeal nerve travel alongside?
what is this artery a branch of?
what is an effect of a lesion of this artery?
superior thyroid artery
branch of the external carotid artery
can affect action the cricothyroid
which artery does the recurrent laryngeal nerve travel past upwards then behind?
how is this relevant in surgery?
inferior thyroid artery
the nerve is vulnerable in surgery that involves ligating the inferior thyroid artery
what can cause compression of the recurrent laryngeal?
what is the effect of this compression?
a bronchial/oesophageal tumour
mediastinal lymphadenopathy
results in hoarseness, breathlessness or both
(inferior thyroid artery supply superior oesophagus and trachea)
sneeze reflex
via afferents via maxillary division (V2)
inspiration
intrathoracic pressure increased by glottis closure, abdominal muscle contraction
soft palate depression against tongue via palatopharyngeus/palatoglossis (branch of X)
sudden abduction of the vocal folds to release the intrathoracic pressure via nose or mouth
cough reflex
via afferents via vagus branches
inspiration
intrathoracic pressure increased by glottis closure, abdominal muscle contraction
soft palate raised and tensed against posterior wall of pharynx
via Levator veli palatine (X), tensor veli palatine (V3), superior constrictor (X)
sudden abduction of the vocal folds to release the intrathoracic pressure via nose or mouth
how can the airways be managed in an emergency?
- Chin lift/ Jaw thrust
- Oropharyngeal/Nasopharygeal airway
- Endotracheal intubation
- Cricothyroidotomy (through the Cricothyroid membrane)
- Tracheostomy
where is a tracheostomy performed?
Between tracheal rings
skin –> superficial cervical fascia –> platysma –> Deep cervical fascia –> strap muscles –> pretracheal fascia –> thyroid isthmus –> stoma in 2nd , 3rd & 4th rings
6 functions of the facial nerve
1) salivation
2) lacrimation
3) facial expression
4) taste
5) mastication and swallowing
6) general sensation
also provides tension to middle ear bones (innervation to stapedius)
salivation via CNVII
VII provides GVE fibres from the superior salivary nucleus destined for submandibular and sublingual salivary glands via the SUBMANDIBULAR ganglion
lacrimation via CNVII
VII provides GVE fibres from the superior salivary nucleus destined for LACRIMAL gland via PTERYGOPALATINE ganglion.
taste via CNVII
SVA fibres from anterior two thirds of tongue to the solitary nucleus via the geniculate ganglion
mastication and swallowing via CNVII
SVE fibres to the buccinator (mastication), raising larynx during swallowing, innervates stylohyoid and posterior belly of digastric
nucleus for salivation, lacrimation, taste
superior salivatory nucleus
nucleus for stapedius and facial expression
facial nucleus
