Lec 25 Flashcards
Surfactant secreted by
alveolar type II cels
surfactant function
Lines the inside of the alveoli
2- decrease surface tension
2.1- decrease inard pressure
3- prevent alveoli from collapsing
4- alveoli easier to expand
5- equalizer– smaller bubbles have more force to collapse – surfactant equalize tendency of different size fo molecules to collapse – pump more surfactant to smaller bubble
decrease surface tension will
decrease the pressure make alveoli easier to expand
Law of Laplace
P=2T/r (p=pressure,T=tension,r=radius)
intrapleural pressure P(ip)
always negative
-4mmHg relatiove to atmosphere
intra-alveolar pressure P(alv)
Normally 0 mmHg relative to atmosphere
transpulmonary pressure
P(alv)-P(ip)
normal transpulmonary pressure
0 - (-4)=4
Pneumothorax
if air enters pleural sac
bond holding lung to chest wall is broken and lung collapse
changes during quiet breathing
1- chest expansion lower p(ip)
2- transpulmonary pressure increase
3- pressure forces lung toward chest wall increase
4- lungs expand and p(alv) decrease
5- air flows into lung (p alv=p atm)
max vol of air during normal inspiration
500 ml
2 important property lung for normal function
1- high compliance (breath in)
2- elastic recoil (breath out)
if problem with elastic recoil
broblem with breath out
should force exhale
Compliance
ability of lung to stretch
change in vol. for given change in pressure
decrease compliance diseases
restrictive pulmonary diseases
ex: fibrosis
elastance
ability to spring back after being stretched
due to presence elastin fibers
decrease in elastin content disease
emphysema
what happens when inspiratory muscle contract
1- lung vol increase
2- pressure inside lung decrease
3- air is sucked in
what happens when inspiratory muscle relax
1- lung vo. decrease
2- pressure inside lung increase
3- air is blown out
mechanical changes during inspiration
1- diaphragm contract and flatten
2- muscles of inspiration contract
3- thoracic and lung vol. increase
4- p atm > p alv
5- air flow in
mechanical changes during expiration
1- diaphragm relax and move up
2- muscles inspiration relax
3- thoracic and lung vol. decrease
4- p alv > p atm
5- air flow out
what measures pulmonary function
spirometry
tidal volume
normal inhale/exhale (500)
residual volume
minimum left (1200)
