Gross and Microscopic Anatomy of the Upper Airway Flashcards
Upper respiratory tract
Nasal cavity, nasopharynx, oropharynx, upper laryngopharynx (larynx).
Lower respiratory tract
- Larynx
- Trachea
- Brocnchi; and
- The rest of the respirtaory tree located in the lungs
Functions of the respiratory system
- Gas exchange
- Humidifying and warming air
- Filtering air
- Voice production
- Olfaction
- Immune functions
- Minor endocrine role
- Involved in regulation of blood pH
- H20 + CO2 <–> H2CO3 <–> H+ + HCO3
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- H20 + CO2 <–> H2CO3 <–> H+ + HCO3
Conducting zone
- Nasal cavity
- Pharynx
- Larynx
- Trachea
- Bronchi
- Bronchioles
Respiratory zone
- Respiratory bronchioles, alveolar ducts and sacs, alveoli
External nose
Composed of bone and cartilage (cartilage missing on skulls).
- Openings (nostrils (nares = 1)) lead into nasal cavity.
The nasal cavity
The nasal cavity is located between the nares anteriorly and the choane posteriorly where the passage becomes the nasopharynx.
The first part of the nasal cavity is divided into a respiratory region where air is warmed and humidified and mucus captures dust particles and an olfactor region superiorly, the part of the nasal cavity involved in smell.
Lateral nasal wall
Three conchae/turbinates (superior, middle and inferior) are bony projections from the lateral wall of the nasal cavity (note the small size of the superior concha - can be hard to identify).
Space underneath concha
termed ‘meatus’.
Superior, meatus, middle meatus and inferior meatus in the nasal wall.
Function of conchae
Increase the surface area of respirtory epithelium and cause turbulent flow of inspired air, aiding warming, humidification and removal of dust particles.
Bones of lateral nasal wall
Middle and superior concha are processes of the ethmoid bone and the inferior nasal concha is a separate bone. Other bones of the lateral wall include the; nasla, macilla, lacrimal, ethmoid, palatine and sphenoid.
Roof, floor of nasal cavity
The nasal cavity is separated superiorly form the brain by frontal, ethmoid, sphenoid bones and inferiorly it is separated fromt he oral cavity by the hard palate (maxilla and palatine bones).
Choanae
Posteriorly, the nasal cavity is continuous with nasopharynx at teh choanae.
Nasal septum
Separates the nasal cavity at the midline, bone include the vomer and perpendicular plate of ethmoid. Note that the anterior part of the nasal septum is cartilaginous.
Histology of the vestibule of the nasal cavity.
Lined with stratified squamous epithelium (keratinised –> non-keratinised) and also contains thick hairs for filtering large particles.
Histology of the respiratory region of the nasal cavity
Thick mucosa (epithelium + underlying CT) for warming and humidifying inspired air. Mucus captures particles and cilia move mucus posteriorly into nasopharynx where it is usually swallowed.
Epithelium is pseudostratified columnar, ciliated with goblet cells and the underlying CT (lamino propria) has abundant blood vessels and seromucous glands (not always obvious).
Types of glands in the nasal cavity
Mucous glands (and goblet cells) secrete mucus to trap small inhaled particles.
Serous glands secrete watery secretion to help humidify inspired air, large, thin-walled venules warm inspired air.
What is the lamina propria of the nasal cavity continuous with?
Periosteum or perichondrium.
What cell types of present in respiratory epithelium?
- Ciliated columnar cells
- Goblet cells
- Small granule cells (Kulchitsky cells): enteroendocrine cells
- Basal cells: divide and differentiate into other cell types
- Brush cells: may transduce general sensation or chemosensory.
Olfactory region of nasal cavity.
About 10cm2
Superior part of the nasal cavity
Composed of pseudostratified, ciliated columnar epithelium with olfactor receptor neurons.
How do you differentiate between olfactory and respiratory epithelium in the nasal cavity?
NO goblet cells and the nuclei appear more organised in olfactor epithelium compared to respiratory epithelium.
Cells of olfactory epithelium
- Olfactor cells: bipolar neurons
- Supporting (sustentacular) cells: provide mechanical and metabolic support for olfactor cells, nuclei located more apically.
- Basal cells: stem cells tor eplace olfactor and supporting cells, nuclei are located more basally.
- Brush cells: general sensory cells (other than olfaction)
Bowman’s glands
Olfactor glands.
Branched tubuloalveolar seorus glands. Secretions function to continue trap then wash away adorants.
Olfactory receptor neurons
Bipolar neurons (1 dendrite, 1 axon) with a dendrit knob bearing (probably) non-motile cilia (up to 200um long). Odorant receptors are located on the cilia.
Unlike most nerve cells, olfactor neurons are replaced throughout life (lifespan 1-2 months) from basal cells located in the basal region of the olfactory epithelium.
What is the pathway of the olfactor cell axons and nerves?
Axons travel from the olfactory cell body to the olfactory nerve (CNI) then to the CNS. Olfactor nerved pass through cribiform plate of ethmoid bone, synapse in olfactor bulb (part of CNS)
Paranasal air sinuses
Outgrowths of nasal cavity, expand into surrounding skull bones during childhood.
- Frontal
- Sphenoid
- Maxillary
- Ethmoid ‘air cells’
Paranasal air sinus histology
Lined by repiratory mucosa (fewer glands and goblet cells and usually thinner compared to the rest of the nasal cavity).
Sphenoid sinus
Opens into sphenoethmoidal recess posterior to superior concha.