Respiratory Tract Flashcards
Function of respiratory tract
Filtration, Humidification and Warming of inspired air
Olfaction (and taste)
Gas transport
Speech
Protection against infection
Gas exchange
Respiratory epithelium
Lines tubular/conducting portion of respiratory system
Pseudostratified- all cells in contact with basement membrane
Ciliated columnar epithelial cells
Interspersed goblet cells (mucus-secreting)
Function of the nose
Filtration, humidification and warming of inspired air
Olfaction
Structure of the nose
- First part of nostrils= Keratinising stratifies squamous epithelium
- Further back= non-keratinising stratified squamous epithelium
- Nasal cavity = Respiratory epithelium
Loose fibrous connective tissue= Richly vascular lamina propria containing seromucinous glands (produce catarrh/snot)
seromucinous glands
Produce catarrh (snot)
Nose- olfaction
Olfactory epithelium structure
Roof of nasal cavity, extending down septum and lateral wall
Pseudostratified ciliated columnar epithelium of olfactory receptor cells with supporting sustentacular cells and basal cells
Serous glands of Bowman
Richly innervated lamina propria
Contains penetrating nerve fibres that will reach surface of epithelium
Stereocillia
Cillia on olfactory epithelium
Non-motile
Serous glands of Bowman
Secrete a watery fluid which help to wash the surface clean
What does olfactory epithelium line
Apex of roof of the nose and extending a short distance down inside of nasal septum and lateral wall of nasal cavity
Bipolar neurons
Dendrite extends to surface to become club-shaped ciliated olfactory vesicle
Stain with silver stains
Function of Nasopharynx
Gas transport
Humidification
Warming
Olfaction
Nasopharynx structure
Lined by respiratory epithelium
Nasal sinuses functions
Lower the weight of the front of the skull
Add resonance to the voice
Humid and warm inspired air
Nasal sinuses structure
Lined by respiratory epithelium
Air filled spaces within the bones of the skull and facial skeleton
4 nasal sinuses
Frontal
Ethmoid
Maxillary
Sphenoid
Larynx structure
Cartilaginous box (formed from mostly hyaline cartilage)- hold larynx open against negative pressure during inspiration
Inner aspect (apart from vocal chords) lined by respiratory epithelium
Beneath epithelium- loose fibrocollagenous stroma with seromucinous glands, lymphatics and boood vessels
Beneath fibrocollagenous stroma, perichondrium (layer of dense connective tissue) and then hyaline cartilage
Larynx function
Voice production
Epiglottis structure
Formed from elastic cartilage
Vocal chords structure
Stratified squamous epithelium overlying loose irregular fibrous tissue (Reinke’s space)
Beneath= vocal ligament (dense fibro-elastic connective tissue)
Beneath - vocalis muscle
Folds contain free upper margin of a cone of elastic tissue (conus elasticus)
Almost no lymphatics
Reinke’s space
Space occupied by loose irregular fibrous tissue in vocal chords
Trachea function
Conducts air to and from the lungs
Trachea structure
- Lined by respiratory epithelium
- Seromucinous glands in submucosa (loose fibrous connective tissue)
- Perichondrium
Trachealis muscle posteriorly- fills gap between C rings - C-shaped hyaline cartilaginous rings
- Perichondrium
- Thin loose connective tissue adventitia
Carina
Bifurcation of trachea
Series of bronchi and bronchioles
Main bronchi
Lobar bronchi
Segmental bronchi
Terminal bronchioles
Respiratory bronchioles
What do the trachea, main/lobar/segmental bronchi all contain
Smooth muscle
Partial cartilaginous rings
Respiratory epithelium
Some basal neuroendocrinecells
Seromucinous glands and goblet cells
What do bronchioles contains
Smooth muscle
Ciliated columnar epithelium
Some basal neuroendocrine cells
Few goblet cells
Clara cells
Clara cells structure
Most numerous in terminal bronchioles
Roughly cuboidal
Contain: mitochondria, sER, secretory granules
No cilia
Vesicular cytoplasm
Clara cell function
(Unclear)
Secrete a lipoprotein that helps prevent luminal collapse during exhalation
Oxidation of inhaled toxins
Produce antiproteases to neutralise the effects of inflammatory reaction
Surfactant production/elimination
Stem cells?
What is the last part of the conducting airways
Terminal bronchioles which give rise to first part of the distal respiratory tract in which gas exchange can occur
Respiratory bronchiole function
First part of distal respiratory tract
Gas exchange as well as transport
Link terminal bronchioles and alveolar ducts
Respiratory bronchiole structure
Cuboidal ciliated epithelium
Spirally-arranged smooth muscle
No cartilage
Alveoli function
Site of gas exchange
150-400 million per lung
Size of alveoli
250 um in diameter
Alveoli cell types
Type I pneumocytes
Type II pneumocytes
Type I pneumocytes structure
40% of cell population
90% of surface area
Flattened cells- squamous epithelia cells
Flattened nucleus
Few organelles
Type I pneumocytes function
Provide part of the blood:air barrier
Very thin
Type II pneumocytes structure
60% of cell population
5-10% of surface area
Rounded cells- cuboidal to columnar epithelium
Round nucleus
Rich in mitochondria, sER and spherical bodies
Alveolar macrophages structure
Contain carbon- in individuals who smoke or work and live in polluted environments
Phagocytes derived from blood monocytes
Luminal cells also present in the interstitium
Type II pneumocytes function
Produce surfactant- a protein which lowers surface tension in the lungs, making it easier to inflate the lungs
Also prevents desiccation of air sacs by forming a lipid-like insulating layer over surface of alveolus
When does surfactant production begin
28th week of intrauterine life
Alveolar macrophages function
Phagocytose particulates including dusts and bacteria
Enter lymphatics or leave via mucociliary escalator to be removed from lungs
Alveolar blood:air barrier
Type I pneumocytes
Fused basement membrane of pneumocyte and capillary
Vascular endothelial cell
200-800 nm thick
How thick is the alveolar blood:air barrier
200-800 nm
How many layers in the blood:air barrier
3= type I pneumocyte, basement membrane, asculaf endothelial cell (or 4 + surfactant)
Alveoli interstitium
Loose fibrous connective tissue
Where endothelial cells are not in direct contact with pneumocytes
Collagen and elastin fibres (produced by fibroblasts)
Macrophages
Pores of Kohn
Pores of Kohn
Holes in alveolar walls
Help to equalise pressure between adjacent alveoli and help lungs inflate evenly and easily
BUT allow infection to easily spread through lungs eg pneumonia
Visceral pleura structure
Flat mesothelial (squamous) cells
Loose fibrocollagenous connective tissue
Irregular external elastic layer
Interstitial fibrocollagenous layer
Irregular internal elastic layer
What does the alveolar interstitium contain
Blood vessels, lymphatics, collagen, elastin and some macrophages
Ciliated epithelium becomes ……… more distally
Flatter
Role of neuro-endocrine cells
monitoring the inspired air for allergens and other potentially harmful elements
Role of mucus
prevents dehydration of the epithelium and traps particulate matter that is removed from the system by the beating of the cilia
Swell bodies
A rich plexus of thin-walled arterioles and venules that lie deep to the epithelium of the nose
Help to warm and humidify inspired air
Source of many nose bleeds
Number of bony projections that extend from later walls of nose (concha)
3
How is inspired air filtered
Cilia and layer of mucus of surface of epithelium trap particulate matter
How is inspired air warmed and humidified
Relatively thin non-keratinising epithelium allows escape of water and heat
Where are the nasal sinuses located
In the bones of the skull with the same name
Where do the ethmoid and maxillary sinuses open into
The nasal cavity below the upper and middle turbinates respectively
Where do the ethmoid and maxillary sinuses open into
The nasal cavity below the upper and middle turbinates respectively
Where does the frontal sinus drain into
Roof of nasal cavity, anterior to olfactory epithelium
Where do the sphenoid sinuses drain into
Roof of nasal cavity posteriorly
Location of olfactory epithelium
Located below the cribriform plate in roof of nose
Innervation of olfactory epithelium
Unmyelinated olfactory nerves pass through holes in cribriform plate to connect to olfactory bulb of brain
Bipolar neurons whose dendritic processes reach surface of epithelium
Serous glands of olfactory epithelium function
Produce a watery secretion that acts as a solvent for odorous substances
Irrigate the surface and help refresh epithelium
Advantages of stratified squamous epithelium for vocal chords
More robust
Is accustomed to wear
Can withstand vibrations of folds
Which muscles manipulate folds of vocal chords
Vocalis muscle
Extrinsic muscle of larynx eg crico-thyroid muscle
Number of C shaped rings of hyaline cartilage in trachea
12-15
Shape of goblet cells
Wine-glass shape
MALT lymph nodule
Mucosa associated lymph tissue
Lie in underlying connective tissue of bronchi
Lymph node vs MALT
MALT= less discrete, lacks a capsule, present in a mucosa
Lymph node= discrete encapsulated collection of lymphoid tissue
Role of fibroblasts in alveoli
Produce a framework of reticulin (collagen III) and elastic tissue important in elastic recoil of lungs during exhalation
Threshold of blood:air barrier leading to impaired gas exchange
1.2um
What 5 layers of tissue does oxygen and carbon dioxide diffuse across
- Surfactant
- Alveolar cell
- Basement membrane
- Capillary endothelium
- Red cell membrane
Fate of particulate-carrying alveolar macrophages
Enter respiratory and terminal bronchioles and are expelled from lungs via muco-ciliary escalator
Fate of particulate-carrying fixed (septal) macrophages
Remain in interstitium of lungs or enter lymphatics
What occurs if particulate matter is indigestible or larger than a macrophage
Macrophages fuse together to form giant cells- may induce granuloma formation
True and false folds of the larynx
Below epiglottis, the mucosa is thrown into 2 sets of folds
Uppermost set and lowermost set
Vestibule lies between them (covered by respiratory epithelium)
Uppermost set of folds in larynx
False cords lined by respiratory epithelium (may be islands of stratified squamous epithelium)
Lowermost set of folds in larynx
True vocal cords lined by stratified squamous epithelium
Function of elastic tissue in alveolar walls
Allows alveoli to stretch and recoil during inspiration and expiration
Serves as a spring tethering bronchioles walls open, preventing bronchioles and alveolar collapse during expiration
Infantile respiratory distress syndrome
Absence of surfactant when prematurely born as cells develop late in gestation
Leads to widespread alveolar collapse
Parasympathetic Innervation of bronchioles
Contraction of smooth muscle
Luminal diameter decreases
Reduced air flow
Sympathetic Innervation of bronchiole
Relaxation of smooth muscle
Luminal diameter increases
Increased airflow
Olfactory mucosa
Pseudostratified columnar epithelium composed of olfactory receptor cells, supporting (sustentacular) cells and basal cells
Vestibule
lies between true and false folds of larynx
lined by respiratory epithelium
