Anatomy: Nasal Cavities and Paranasal Sinuses Flashcards
crista galli
median ridge of the bone that projects from the cribiform plate of the ethmoid bone
what forms the roof of the nasal cavities
cribiform plate and crista galli (and anterior cranial fossa)
what forms the lateral wall of the nasal cavities
superior and middle conchae, ethmoidal air cells, orbital plate of ethmoid (+inferior conchae)
what forms the septum of the nasal cavity
perpendicular plate of ethmoid and vomer
anterior cranial fossa
depression in the floor of the cranial base which houses the projecting frontal lobes of the brain.
Le Fort I, II and III
which Le Fort fractures risk spread of infection from nasal cavity and paransal sinuses into the anterior cranial fossa
II and III - can disrupt the cribriform plate of the ethmoid bone
which Le FOrt fractures can result in fluid in the antra (maxillary sinuses)
I and II
vomer
perpendicular plate of ethmoid
palatine bone
medial wall of RIGHT nasal cavity (right side of the nasal septum)
pterygoid plates of sphenoid bone
LATERAL WALL OF RIGHT NASAL CAVITY
regions of nasal cavity
mucosa of nasal cavities
- keratinised stratified squamous epithelium
- Schneiderian epithelium (respiratory)
- olfactory mucosa
describe the course of CNI
originates in the nasal cavity at the olfactory mucosa - fila olfactoria (bundles of olfactory axons)
then enters the cranial cavity through the cribriform plate (ethmoid bone - roof of nasal cavity)
then enters olfactory bulb (in olfactory groove on anterior cranial fossa)
2nd order nerves now pass posteriorly in the olfactory tract, which ends in the temporal bone
olfactory tract
notice V1 and V2 innervation
describe the innervation
V1 - anterosuperiorly via nasociliary nerve
V2 - posteroinferiorly via nasopalatine nerve
where does the ophthalmic artery branch from
internal carotid artery
where do the facial and maxillary arteries branch from
external carotid artery
which arteries branch from the internal carotid artery to supply the nose
ophthalmic artery - anterior and posterior ethmoidal artery
descend into nasal cavity through cribriform plate
which arteries branch from maxillary artery to supply the nasal cavity
(external carotid artery)
sphenopalatine and greater palatine arteries
which arteries branch from the facial artery to supply the nasal cavity
lateral nasal branch of facial or septal branch of superior labial artery
superior labial artery
which area in the nose is a common site for epistaxis
there is a greater concentration of anastomosing arteries in the anterior third of the nose, in particular, on the nasal septum - Kiesselbach’s (Little’s) area
cause can be local or systemic
describe the nasal conchae
conchae are curved shelves of bone, they project into the nasal cavity creating 4 pathways for air to flow - meatuses
what is the function of nasal conchae
increase the surface area of the nasal cavity - increase the amount of inspired air
make flow of air slow and turbulent so that it can be humidified
where does the spheno-ethmoidal recess lie
superiorly and posteriorly to the superior concha
what is the inferior nasal concha supplied by
CNV2
inserting a nasogastric tube
where does the eustachian (auditory/pharyngotympanic) tube open into
lateral wall of nasopharynx
how can correct placement of a nasogastic tube be confirmed
X ray
- NG tube must remain in midline
- tip must be visible below diaphragm - 10cm beyond GOJ (to ensure that it is in the stomach)
what is the function of the nasal cavities
patent conduit for air to be transported to the nasopharynx
filters air of particulate material - vibrissae
humidifies air - via glands
warms inspired air in the nasal passage - via blood
sense of smell as air passes over the olfactory epithelium
vibrissae
hairs inside nostrils to stop large particles from entering the nasal passages
paranasal sinuses
maxillary sinuses = antra
what is the inner surface of the paranasal sinuses lined by
respiratory mucous secreting mucosa
where do the paranasal sinuses drain to
Sinuses are formed by the nasal cavity eroding into surrounding bone – as sinuses are all outgrowths of nasal cavity they all drain back into it
Ostia found on roof and lateral walls of nasal cavity
describe the drainage of the paranasal sinuses
frontal, maxillary and anterior ethmoidal open out onto middle meatus
the sphenoid sinus opens into the posterior roof (sphenoethmoidal recess)
ethmoidal cells drain into superior and middle meatuses
drainage of nasolacrimal gland
lacrimal gland produces tears which empty into the nasolacrimal duct, drains into the inferior meatus of nasal cavity
sinusitis
As paranasal sinuses are continuous with the nasal cavity, URT can spread to sinuses
Results in pain and swelling of the mucosa
Sinuses can become filled with infected mucous
pansinusitis
>1 sinus inflamed
where can pain from sinusitis be referred to
the maxillary nerve supplies the nasal cavity (maxillary sinus) and maxillary teeth - therefore, inflammation can present with toothache
why is the maxillary sinus predisposed to inflammation
because the maxillary sinus ostia is located superiorly in the medial wall of the sinus rather than the floor, so the maxillary sinus mucous has to drain against gravity
oroantral fistula
Oro-antral fistula is an abnormal communication between the maxillary sinus and oral cavity
how is a persistent oro-antral fistula managed
surgically closed
what is the clinical significance of an oroantral fistula
a dental abscess can spread via the roots of the upper teeth into the antrum and cause a sinus infection
what duct may be injured in a Le Fort I fracture
nasolacrimal duct
which structures pass through the jugular foramen
IJV, IX, X, XI
what is this bone
- describe its defining features
atlas (C1)
- no vertebral body or spinous process
what is this bone
axis (C2)
- odontoid process (dens)
inferior concha
sphenoethmoidal recess
what drains here
inferior meatus - nasolacrimal duct drains here
