Respiratory Physiology II Flashcards
what causes the change in presssure that result in ventilation (2)?
what is the pressure like
a) @ the beginnning of the resp. tract?
b) @alveolus?
what happens when
a) Patm = Pa?
b) Pa c) Pa> Patm?
change in presssure that results in ventilation:
- elastic recoil
- muscular breathing movements
a) Pressure at beginnning of the resp. tract: atmospheric pressure (Patm)
b) alveolus pressure = Alveolar Pressure (Pa)
a) Patm = Pa = no airflow
b) Paairflows into lungs
c) Pa> Patm = airflows out of lungs
what is boyles law? how is applicable to lungs and gas flow?
boyles law: if the volume of a gas is made to increase, the pressure exerted by the gas decreases
SO - when alveolar expand during inhalation, pressure inside decreases and the gas flows into the alveoli from conducting airways
how does lowering diaphragm cause quiet inhalation?
lowering the diaphragm reduces pressure around the lungs and generates inspiration
under normal conditions:
- chest wall pulls which direction?
- lung pulls which direction?
what is intrapleural pressure? explain it at end of expiration
under normal conditions:
- **chest wall pulls outwards
- lung pulls inwards**
these balance each other
intrapleural pressure (Ppl)
- the chest wall and lungs are locked together by the **intrapleural fluid in the intrapleural space
-
at the end of exipration getopposing forces:
a) lungs:elasticityis causing them tocollapse** - *b)** chest wall: elasticity is causing to spring outwards
- generates a pressure = PPl
what is intrapleural pressure usually like with respect to the atmosphere and the air pressure in the alveoli?
ntrapleural pressure usually negative with respect to the atmosphere and the air pressure in the alveoli
what are the changes that occur in intrapulmonary (pressure in lungs) and intrapleural pressure during inspiratio and expiration?
during each breath, get about 500ml of air in/out of lungs
inspiration:
intrapulmonary pressure: becomes more negative / decreases (lung volume increases)
intrapleural pressure: becomes more negative / decreases
expiration:
intrapulmonary pressure: becomes more positive / increase (lung volume decrease)
intrapleural pressure: returns to inital value as chest wall recoils
what happens to intrapleural pressure PPl if pleural cavity becomes ruptured?
whats name of this
- air can enter the pleural cavity, where it may exceed the atmopsheric pressure and the pressure surrounding the lungs will increase - lungs collapse
- called pneumothorax
how do you calculate compliance in respiratory physiology?
compliance = change in volume / change in pressure
where (during inhalation / exhalation) is compliance smaller?
at any given pressure, lung vol during inhalation is bigger or small c.f exhalation?
what is airway closure?
- compliance smaller at high expanding pressure (full inhalation - the curve becomes flatter)
- at any given pressure, lung vol during inhalation is less c.f exhalation (harder to inflate the lung than deflate lung) = called (phenomenon called hysteresis)
- airway closure: where small airways close, trapping gas in alveoli. means that the lung walways has some air in it
which diseases cause reduced compliance (3)?
where do you see increased compliance (2)?
- *reduced compliance:**
- pulmonary fibrosis
- collapse of lungs
- increase in pulmnary venous pressure
- *increased compliance:**
- age
- emphysmea
explain how emphysema’s effect on lung compliance (2)
desctruction of the alveoli: elastic fibres and collagen lost
- causes impaired elastic recoil
- lung is more easily distended and compliance increases
- (same amount of pressure causes easier inflation)
label correctly using:
a) fibrosis
b) emphysema
c) normal
what else can affect compliance?
diseases that effect the structure of the thorax
but lung compliance more usually affected
the elastic properties of the lungs are generated by which two main components?
- *elastic fibres and collagen**
- elastic fibres stretch
surface tension forces
explain what the surface tension in alveoli is?
surface tension in alveoli:
- *- on inner surface,** the water surface is surface is trying to contract
- results in alveoli trying to collapse
- net effect to generate an elastic contractile force throughout the entire lungs - surface tension elastic force
what is leplaces law ?
how is it applicable to alveoli?
how do lungs compensate with problem of pressure differences arising from having alveoli of different sizes?
P = 2T/r
where P = pressure within bubble, T = surface tension & r = radius
- means that the smaller the bubble, the greater the internal presure is required to keep it inflated
lungs compensate with problem of pressure differences arising from having alveoli of different sizes:
- *- have surfactant** (mix of lipds & proteins)
- *-** lowers the surface tension of smaller alveoli and thus reduces the surface tension elastic forces of the smaller alveoli
what is role of surfactant in alveoli and what is a major (50%) component?
what is it secreted by? where does assembly occur?
surfactant
role: greatly reduces the surface tension and therefore the surface tension elastic forces
structure: 50% phospholipid - dipalmitoylphosphatidylcholine (DPPtdCho)
secreted by: type II alveolar epithelial cells.
assembly: lamellar body
what are laminar and turbulent airway flows?
how is poiseuilles law relevent to airway flow and flow resistance?
laminar flow: movement is orderly and streamline
turbulent flow: movement of air is chaotic
(most cases flow can be considered laminar)
- *Poiseuille’s Law:**
- flow is dependent on radius of tube, so small changes in diameter of radius of airways can cause to big changes in flow
