lecture 11 and 12: respiratory system Flashcards
what causes pressure changes in the lungs
changes in thorax vol (pressure dif between atmosphere and lungs)
how do the lungs expand if there are no lung muscles
skeletal muscles of the thoracic wall/cavity are used
what lines the lungs
visceral pleura
what lines the inner surface of the thoracic cavity and rib cage
parietal pleura
what is the pleural cavity (intrapleural space) filled with
fluid to reduce friction created by lung movement during in/exhalation
what type of process in inhalation
active
whats the main inspiratory muscle and what does it do
diaphragm
-contracts and is drawn downwards and becomes flat (phrenic nerve innervation)
what do external intercostals do during inspiration
contract raising ribcage up and out
what does the chest cavity do during inspiration
expand and lungs pulled outwards- thoracic vol increases
what does elevation of the ribs cause
sternum moves up and out- increases front to back dimension of thoracic cavity
what happens to alveolar pressure during inspiration
drops below atmospheric pressure- air flows into lungs until alverolar pressure=atmospheric pressure
what kind of process is exhalation
passive
what does the diaphragm do during expiration
relaxes and moves upwards (decreased vertical size of chest)
what do EIM do during expiration
relax and moves in and down (decrease chest diameter)
what happens to chest cavity during expiration
vol reduced and pressure increases
what happens to expiratory muscles during forced active expiration
contract to further reduce volume of thoracic cavity and thus lungs
what happens to abdominal muscles during forced active expiration
contract forcing diaphragm further into thoracic cavity
whats only active during forced active expiration and what do they do
IIM and they contract pulling ribs down and in
what forms the bottom of the thoracic cavity
diaphragm
why do lungs recoil on expiration
elastic fibres in alveolar wall stretch and shorten
what happens to water molecules on the alveolar surface
they have a strong attractive force for one another= surface tension which promotes collapse of smaller alveoli and an irregular rate of shrinking
how to minimise effects of surface tension on pulmonary ventilation
surfactant
what is surfactant secreted by
type 2 alveolar epithelial cells
how do surfactants work
detergent like substance that lowers surface tension and increases lung compliance (more controlled recoil)
