L3 respiratory cycle Flashcards
what happens to the air flow when the lungs are at rest
no air flow cos PA=PB
what happens to the air flow when the lungs are inspiring
PA
what happens to the air flow when the lungs are exspiring
PA>PB so air flows out down pressure graident
what happens to the lung vol in inspriation and expiration
inspiration - increases
expiration - decreases
muscles involved in inspiration
- main muscle : diaphargm contracts so pushing down and out
- scalene lifts the ribs up
- external intercostal muscles expand
muscles involved in expiration
diaphargm relaxes so pushing in and up
- internal intercostals and accessory muscles like abdominals are involved too
- passive due to the elastic recoil of the lungs
movement of elastic recoil of lungs
- collapse inwards away from the chest wall
movement of elastic recoil of chest wall
-expand outwards to the max EBQ vol
movement of elastic recoils together of lungs and chest vol
- the recoils are equal but opposite
- becomes in EQB and will be at FRC
what is pleural fluid
- fluid in the space between the pleural membranes
- couples the lung and chest wall together to reduce friction
how is interpleual pressure formed
- the recoils of the lungs and chest wall moves them away from each other
- but this causes the pressure in the interpleural space between the lungs and chest wall to pull on them back together
why is Ppl negative
the pressure of the recoils of lungs and chest walll is each 0.5 kPa so together Ppl is 1kPa but negative because it pulls the structures together
how to work Pdist
Pin - Pout so at FRC, it’s PA-Ppl
value of PA and Ppl AT FRC
PA = 0 kPa Ppl = -0.5kPa
value of Pdist
it’s PA-Ppl so 0–0.5 = 0.5kPa
- positive Pdist so inflation
