Chapter 16 Study Questions (Pt. 3) Flashcards
what does ENaC stand for?
epithelial Na channels
what is the role of ENaCs, and why do they do it?
ROLE: move Na+ out of airway lumen and into epithelial cell to limit the NaCl osmotic pressure (and therefore water) created by CFTR in the lumen
WHY: limit amount of water going into the lung airway lumen
where are ENaC channels located?
apical membranes
describe the composition of ENaC channels
3 SUBUNITS
Beta-protein subunit forms the ion channel
alpha and gamma subunits form a gate to regulate access to the ion channel opening
what causes CF?
defective or total loss of CFTR channels
why does defective or total loss of CFTR channels cause CF?
- if no CFTRs, Cl- are not drawn into the airway lumen = Na+ is not attracted = Na+ flows out of the lumen through ENaCs, reversing the osmotic pressure and water is pulled out of the airway lumen
then, airway mucus gets dehydrated and becomes to viscous for cilia to be able to sweep out trapped particulates including bacteria
CF patients lose the interplay between what two things?
- CFTR channels and 2. ENaC channels
name two CF mutations. which leads to minimal function and which leads to no function?
- G551D -> minimal
- F508 -> most common, no function
what is the function of the pleural sac?
create less pressure above the lungs than you’d find in the alveoli
why is the function of the pleural sac important?
moving air in and out of our lungs requires a pressure gradient. maintaining Palv lower than Psac creates that pressure gradient
what is transpulmonary pressure?
Palv - Psac
how do you increase transpulmonary pressure?
- increase Palv
- decrease Psac
what is the advantage of increasing transpulmonary pressure?
less pressure when trying to inflate. drives ventilation -> gradient -> air movement.
why does a puncture in the pleural sac that causes the intrapleural pressure to equilibrate with atmospheric pressure cause a lung to collapse?
Patm enters on a gradient
Palv decreases
therefore, Palv < Psac = P atm
when Palv < Psac , Palv cannot inflate and it collapses. trying to blow up a balloon while you’re squeezing it.
how does a gas create pressure?
no form; constrained by container.
force of collisions causes pressure.
what does Boyle’s law say about lung volume and alveolar pressure?
pressure and volume are inversely related!
what is the role of: extracellular matrix proteins, collagen, fibrin, fibronectin, and elastin
when lung tissue is damaged, it is replaced with connective tissue. as the amount of connective tissue increases, so does the distance between alveolus and vasculature (where gas exchange occurs), rendering our breathing less effective because our gas exchange is less effective
why would collagen and fibronectin accumulate in place of alveoli?
WBC destroys alveoli during inflammation or infection
damage tissue -> replace with collagen and lose function
