structure and function of the airways Flashcards
what does the trachea divide into
2 main bronchi
what do the 2 bronchi divide into
2 more bronchi
what is the process of bifurcation called
dichotomous branching
what provides mechanical stability in the trachea
C shaped hyaline rings
how is the cartilage structured around the bronchi
actual rings of cartilage
where does gas exchange occur
alveolar ducts
what is the name of bronchioles that have no cartilage
terminal bronchioles
where are alveolar ducts found
respiratory bronchioles
describe type 1 cells
very thin, flat delicate barrier (facilitates gas exchange)
covers 95% of the surface
describe type 2 cells
replicate to replace type 1 cells greater in number than type 1 cells but only cover 5% of surface secrete surfactant (reduces surface tension) antiproteases
what is xenobiotic metabolism
metabolise obnoxious chemicals that may enter airways
a basic function of the respiratory airways is to act as conduit pipes to…
conduct O2 to the alveoli
conduct CO2 out of the lung
gas exchange
basic functions of the respiratory airways is facilitated by…
mechanical stability (cartilage)
control of calibre (smooth muscle)
protection and cleansing
what is the pharynx
a common passageway for foods, liquids and air
what does the conchae do
highly vascular
contributes to warming and humidification of intra nasally inhaled air
what do nasal hairs do
filters out large particles
where are the submucosal glands
embedded in airways smooth muscle
what happens when smooth muscle contracts
it narrows down airway and maybe presses against gland to squeeze out mucus
where does the produced mucus go
into the airway lumen
what do ciliated cells do
move/beat/waft mucus to the back of the throat to swallow
what other cells also produce mucus
goblet cells
what are some lining cells types
ciliated
intermediate
brush
basal
what are some contractile cells types
smooth muscle (airway, vasculature)
what are some secretory cells types
goblet (epithelium)
mucous
serous (glands)
what are some connective tissue cell types
fibroblasts interstitial cell (elastin, collagen, cartilage)
what are some neuroendocrine cell types
nerves
ganglia
neuroendocrine cells
neuroepithelial bodies
what are some vascular cell types
endothelial pericyte plasma cell (and smooth muscle)
what are some immune cell types
mast cell dendritic cell lymphocyte eosinophil macrophage neutrophil
what do mucin granules contain
mucin in a highly condensed form
what happens to mucin granules upon a stimulus
upon a stimulus > mucin granules move towards the apical surface (top surface of the cell) > fuse with apical surface and release mucus onto airway surface
what do mucous cells secrete
mucus :))))
what do serous cells secrete
antibacterial enzymes (eg. lysozme)
what do glands secrete
water and salts (eg. Na+ and Cl-)
what do cilia contain (structure)
apical “hooks” - engage with mucus
axoneme - microtubules
cell membrane
“anchoring” proteins (intracellular)
an efficient structure which moves cilia, axonemes slide over each other pushing cilium from one side to the other
what rhythm is the way cilia beats
metachronal
describe the way cilia beats
different fields of cilia
one field beats on the forward stroke and then the recovery stroke
when the first field is on the recovery stroke, the second field is on the forward stroke etc and that way it is able to beat
what are the functions of airway epithelium
secretions of mucins, water and electrolytes, components of mucus (+plasma, mediators)
movement of mucus by cilia - mucociliary clearance
physical barrier
production of regulatory and inflammatory mediators
what are some examples of regulatory and inflammatory mediators
- nitric oxide (NO - via nitric oxide synthase NOS)
- carbon monoxide (CO - via heme oxygenase HO)
- arachidonic acid metabolites (eg prostaglandins via COX)
- chemokines (eg GM-CSF)
- proteases
how to test for NOS
brown staining?
produces NO - contributes to ciliary beats
what does airway smooth muscle contribute to
structure, tone and secretion
how does airway smooth muscle contribute to tone
airway calibre - contraction and relaxation
how does airway smooth muscle contribute to secretion
mediators
cytokines
chemokines
bacterial products and cytokines act on smooth muscle > producing more NO/prostaglandins/cytokines/chemokines/adhesion molecules > recruitment of other inflammatory cells into airways
how does airway smooth muscle contribute to structure
hypertrophy
proliferation
what kind of systemic circulation exists in airway vasculature
tracheo-bronchial circulation
how much of cardiac output does the tracheo-bronchial circulation take
1-5% but high perfusion
how much blood flow to airway mucosa is there?
100-150 mL/min/100g of tissue
among highest to any tissue
what do bronchial arteries arise from
sites on aorta, intercostal arteries and others
what does blood return to tracheal circulation by
systemic veins
where does blood return from bronchial circulation to both sides of the heart by
bronchial and pulmonary veins
what lies underneath the epithelium surface
subepithelium microvascular network
plexus of arteries, capillaries and veins supplying epithelium and submucosa with nutrients and oxygen
what are some theoretical functions of the tracheo-bronchial circulation
- good gas exchange (directly between airway tissues and blood)
- contributes to warming of inspired air
- contributes to humidification of inspired air
- clears inflammatory mediators
- clears inhaled drugs (good or bad depending on drug)
- supplies airway tissue and lumen with inflammatory cells
- supplies airway tissue and lumen with proteinaceous plasma (plasma exudation - leakage of plasma)
what are controls of airway function
nerves
regulatory and inflammatory mediators
proteinases/proteases
reactive gas species
examples of nerves involved in control of airway function
parasympathetic (cholinergic)
sympathetic - adrenergic
sensory
examples of regulatory and inflammatory mediators involved in control of airway function
histamine
arachidonic acid metabolites (eg prostaglandins, leukotrienes)
cytokines
chemokines
examples of proteinases/proteases involved in control of airway function
neutrophil elastase
example of reactive gas species involved in control of airway function
O2- and NO
can the airway contract and relax
yes
what does adrenaline do to the airway
relaxes the airway - opens up airway
what does the neural pathway do to the airway
also opens up the airways - NO gas produced > caused airway to relax and open
do we have a sympathetic system to open up our airways
no
can cells produce more than one mediator and can they do more than one thing
yes
what are some respiratory diseases
asthma COPD CF - all of which are common conditions airway inflammation, obstruction and remodelling
