ENT Flashcards
(429 cards)
Function of the nasal cavity
= most superior part of the respiratory tract
- Warms and humidifies inspired air.
- Removes and traps pathogens and particulate matter from the inspired air.
- Responsible for sense of smell.
- Drains and clears the paranasal sinuses and lacrimal ducts.
Respiratory vs Olfactory regions of nasal cavity
Respiratory region = lined by a ciliated pseudostratified epithelium, interspersed with mucus-secreting goblet cells.
Olfactory region = located at the apex of the nasal cavity. It is lined by olfactory cells with olfactory receptors.
What are the nasal conchae?
= curved shelves of bone projecting out of the lateral walls of the nasal cavity.
They project into the nasal cavity, creating four pathways for the air to flow
What are the four pathways of air flow created by the nasal conchae?
- Inferior meatus – between the inferior concha and floor of the nasal cavity.
- Middle meatus – between the inferior and middle concha.
- Superior meatus – between the middle and superior concha.
- Spheno-ethmoidal recess – superiorly and posteriorly to the superior concha.
What is the aim of the nasal conchae creating different paths of air flow?
to increase the surface area of the nasal cavity
to disrupt the flow of air to make it turbulent (so that it spends longer in the nasal cavity).
What structures drain into the nasal cavity?
Paranasal sinuses - frontal, maxillary, ethmoidal, sphenoid
Nasolacrimal Duct
Auditory (Eustachian) tube
Cribriform Plate
Sphenopalatine foramen
Incisive canal
What is the purpose of the Auditory (Eustachian) tube opening into the nasal cavity?
Connects the middle ear to the nasopharynx (opens onto the lateral wall of the nasal cavity)
It allows the middle ear to equalise with the atmospheric air pressure.
What is a problem that can occur due to the Auditory (Eustachian) tube opening into the nasal cavity?
Provides means for infection to spread from the upper respiratory tract to the ear.
Incisive Canal of nasal cavity
Pathway between the nasal cavity and incisive fossa of the oral cavity.
Transmits the nasopalatine nerve and greater palatine artery.
Sphenopalatine foramen of nasal cavity
Located at the level of the superior meatus
Sphenopalatine artery, nasopalatine and superior nasal nerves pass through
Cribriform plate of nasal cavity
part of the ethmoid bone
forms a portion of the roof of the nasal cavity
contains very small perforations, allowing fibres of the olfactory nerve to enter and exit.
Arterial Supply of nasal cavity
Internal carotid branches:
- Anterior ethmoidal artery
- Posterior ethmoidal artery
External carotid branches:
- Sphenopalatine artery
- Greater palatine artery
- Superior labial artery
- Lateral nasal arteries
These arteries form anastomoses with each other, especially in the anterior portion of the nose.
Little’s / Kiesselbach’s area
An area in the anterior portion of the nose, where there are lots of anastomoses of arteries
common site for nosebleeds (~90% from this area)
Venous drainage of the nose
The veins of the nose tend to follow the arteries.
They drain into the pterygoid plexus, facial vein or cavernous sinus.
How can the innervation of the nose be divided?
Special = the ability of the nose to smell
General = sensory innervation
Special sensory innervation of the nose
OLFACTORY NERVE
The olfactory bulb lies on the superior surface of the cribriform plate
Branches of the olfactory nerve run through the cribriform plate to provide special sensory innervation to the nose.
General sensory innervation of the nose
Innervation to the septum and lateral walls is delivered by the nasopalatine nerve (branch of maxillary nerve) and the nasociliary nerve (branch of the ophthalmic nerve).
Innervation to the external skin of the nose is supplied by the trigeminal nerve.
Parts of the external ear
Auricle
External Acoustic Meatus
Tympanic Membrane
Auricle
Functions to capture and direct sound waves towards the external acoustic meatus.
A mostly cartilaginous structure:
=> Helix, anti-helix, concha, tragus, antitragus
External acoustic meatus
A sigmoid-shaped tube
=> Initially superoanterior, then superoposterior, then inferoanterior.
Extends from the deep part of the concha to the tympanic membrane.
External 1/3 formed by cartilage
Internal 2/3 formed by the temporal bone.
Tympanic Membrane
Connective tissue structure; covered with skin on the outside and a mucous membrane on the inside
Connected to the surrounding temporal bone by a fibrocartilaginous ring
On the inner surface, the handle of malleus attaches to the tympanic membrane, at the umbo
Vasculature of external ear
Supplied by branches of the external carotid artery:
- Posterior auricular artery
- Superficial temporal artery
- Occipital artery
- Maxillary artery (deep auricular branch) – supplies the deep aspect of the external acoustic meatus and tympanic membrane only.
Venous drainage is via veins following the arteries listed above
Sensory innervation of external ear
Greater auricular nerve (branch of the cervical plexus) – innervates the skin of the auricle
Lesser occipital nerve (branch of the cervical plexus) – innervates the skin of the auricle
Auriculotemporal nerve (branch of the mandibular nerve) – innervates the skin of the auricle and external auditory meatus.
Branches of the facial and vagus nerves – innervates the deeper aspect of the auricle and external auditory meatus
Why can some individuals complain of an involuntary cough when cleaning their ears?
due to stimulation of the auricular branch of the vagus nerve (the vagus nerve is also responsible for the cough reflex).