HEENT 02: Throat, Nose, Sinus, Middle Ear Flashcards
Describe the structure of the nose and nasal cavity.
- 3 conchae (turbinates) or curved bone shelves to slow air flow
- covered with mucosal epithelium, separated by meatuses (spaces)
- warms and humidifies air entering body
- nose hairs filter out large particles (> 30 mm)
Describe the structure of nasal mucosa layer.
- attached to periosteum (bone) or perichondrium (cartilage) by highly vascularized connective tissue
- blood supply from ethmoidal (internal carotid), sphenopalatine, greater palatine, labial and nasal arteries (external carotid)
Describe the parasympathetic mucosal innervation.
- from pterygopalatine ganglion
- stimulation causes non-cholinergic vasodilation, increases mucus production
Describe the sympathetic mucosal innervation.
- from superior cervical ganglion
- stimulation causes constriction of mucosal vessels (tone)
- nasal congestion occurs upon withdrawal of sympathetic input
Describe the sensory innervation of the nasal mucosa.
- nasopalatine (V2) and nasociliary (V1) branches of trigeminal nerve
- mediate pain, pruritis, response to inhaled irritants
- olfactory nerve innervates for sense of smell
What are the 3 types of cells of the ciliary epithelium?
- ciliated columnar epithelial cells
- goblet cells
- basal cells
What do ciliated columnar epithelial cells do?
cilia move in mucous blanket to promote removal of particulate matter to nasopharynx where it is swallowed
What do goblet cells do?
secrete glycoproteins (mucin)
What do basal cells do?
attach mucous epithelium submucosal tissues
What is mucous composed of?
- 95% water
- glycoproteins, electrolytes, enzymes, anti-enzymes, antioxidants, antibacterial agents, lipids, and cellular mediators derived from submucosal glands and plasma extravasation (antibodies, etc.)
- pH 5.5-6.5
What is the submucosal (sero-mucous) gland?
- mucous excretion is increased by activation of parasympathetic nervous system
- M2 and M3 receptors
- sensory nerve endings in epithelium detect inhaled irritants
- neurogenic release of substance P and neurokinin A neuropeptides can increase mucous production through activation of NK1 receptor (also vasodilatory)
What do M2 receptors do?
mediate increased mucous production
What do M3 receptors do?
inhibit mucous production (by inhibition of acetylcholine release)
What type of receptors do olfactory neurons contain?
one type of GPCR – activated by particular odorant
What is allergic rhinitis?
inflammation of nasal mucosa
What are the symptoms of allergic rhinitis?
itching, sneezing, nasal discharge, nasal blockage
Describe the pathogenesis of allergic rhinitis.
- IgE-mediated through environmental factors in genetically predisposed individuals
- allergens reacting with IgE on surface of nasal mucosal mast cells and basophils cause degranulation and release of histamine and inflammatory mediators
What does histamine do in allergic rhinitis?
acts on nasal mucosa to cause nasal blockage, sneezing, pruritis, and rhinorrhea
- H1 receptor activation mediates allergen-induced symptoms
- H3 receptor activation contributes to nasal stuffiness by inhibition of release of noradrenaline by sympathetic efferent fibers
What is pruritus and sneezing (reflex) mediated by?
activation of trigeminal nerves
What is rhinorrhea due to?
increased vascular permeability (plasma exudate) and increased glandular secretions (containing lactoferrin and lysozymes) mediated by increased parasympathetic tone
How does inflammation affect nasal passages?
slows mucuciliary clearance, increases blood flow and vascular permeability, and decreases diameter of nasal passages
Describe the structure of paransal sinuses.
- paired, air filled, cavities near nasal cavity
- lined with ciliated, pseudostratified columnar epithelium that is continuous with nose
- frontal, maxillary, and anterior ethmoid sinuses drain to middle meatus
- posterior ethmoid and sphenoid sinuses drain to superior meatus
What do the paransal sinuses do? (3)
- produce mucous
- lighten skull
- aid in sound transmission
What is sinusitis (rhinosinusitis)?
inflammation of mucosal epithelium of nose and sinuses
What is acute rhinosinusitis?
< 4 weeks
- viral: rhinovirus (more common)
- bacterial: S. pneumoniae, H. influenzae, M. catarrhalis (more rare)
- nasal obstruction and discharge, changes in smell, facial pain/pressure, pain worsens with bending and can radiate to teeth
- results in edema, obstruction, and decreased mucociliary activity
What is chronic rhinosinusitis?
> 12 weeks
- differentiated by presence of nasal polyps – outgrowths of edematous inflammatory tissue that have grown into middle meatus
- cough and fatigue common
- moderate to severe pain is not common
Describe the structure of the nasopharynx.
- connects nasal passage to larynx
- lined with mucosal epithelium
- drains sinuses, lymph, and auditory tubes
- pharyngeal tonsil: mucosal epithelium has M cells that transmit antigens to lymphoid
- soft palate: closes nasal passage during swallowing
Describe the structure of the oropharynx.
connects mouth to esophagus
Describe the structure of the nasopharynx.
- epiglottis closes larynx during swallowing to prevent aspiration
- common passageway for food and air
What is pharyngitis?
inflammation of the pharynx (sore throat)
- often secondary to infection – rhinovirus, streptococcus, candida
- pharyngeal erythema and swelling, tonsillar exudate, edematous uvula
What pathogens cause pharyngitis?
- children (5-15): Streptococcus pyogenes
- group A hemolytic streptococcal pharyngitis
pharyngeal erythema and swelling, tonsillar exudate, edematous uvula
untreated: lasts 10 days, and infectious for 7 days
What happens if pharyngitis is not treated?
lasts 10 days, and infectious for 7 days
Describe the structure and function of the external ear (auricle or pinna).
- lies at outer end of short tube called external acoustic meatus
- collects sound waves and funnels them through to external acoustic meatus to tympanic membrane
Describe the structure and function of the tympanic membrane (eardrum).
- circular structure at internal end of external acoustic meatus
- energy of sound wave is converted into vibration of tympanic membrane
What is the function of the middle ear?
transmit and amplify vibrations from tympanic membrane to inner ear
What are the 3 ossicles of the middle ear?
- malleus: attached to internal surface of tympanic membrane
- incus: connects malleus with stapes
- stapes: attaches to vestibular (oval or cochlear) window, stapedius muscle prevents excess movement of stapes and controls amplitude of sound waves from external environment to middle ea
Describe the connection between the middle ear and auditory tube.
- middle ear is filled with air
- auditory tube is normally closed – opens during yawning or swallowing to allow equalization of pressure in middle ear (may hear soft pop sound at high altitude)
Why is acute otitis media common in children?
short auditory (eustachian) tube
- increases risk of infected secretions reaching middle ear
- daycare is risk factor
What are the signs and symptoms of acute otitis media?
- results in bulging of tympanic membrane
- may be associated with localized pain, headache, fever, nausea, vomiting
What pathogens cause acute otitis media?
S. pneumoniae, H. influenzae, M catarrhalis
- occurs frequently after viral upper respiratory infection
What is mastoiditis?
spread of acute otitis media infection to mastoid bone
- can occur without AOM treatment
What are the 2 functional organs of the inner ear (vestibule)?
- cochlea: coiled tube divided into 3 chambers that transduces sound for hearing
- vestibular apparatus: semicircular canals (sense rotation), otolith organs (sense gravity and linear movement)
What detects sound and motion in the inner ear?
hair cells
What is drug-induced ototoxicity?
damaging effect of medication on auditory or vestibular organs resulting in hearing loss and/or balance problems
What drugs can induce ototoxicity?
aminoglycosides – tobramycin, gentamicin
- some agents affect vestibular apparatus and some affect cochlea
- risk increases with total drug exposure
What is vestibulotoxicity?
typically manifests with ataxia, dysequilibrium and oscillopsia (visual blurring with head movement)
- can be detected by Dynamic Illegible E test:
What is chocleotoxicity?
- may be detected by loss of response to high frequency sound
- aminoglycosides are irreversible ototoxins that cause hair cell dysfunction and death – possibly by promoting oxygen radical formation
- affect outer hair cells of cochlea more than inner hair cells
- innermost hair cells or apex of vestibular organs are affected before peripheral hair cells
