pulmonary ventilation + boyle's law

respiration - function

O2 in and CO2 out

responds to respiratory demands of the body

external respiration

transfer of O2 and CO2

transfer between environment and blood

responds to respiratory demands of body

internal respiration

exchange of O2 and CO2

transfer of O2 from blood into tissues

release of CO2 from cells into blood

Boyle’s law

volume and pressure have an inversely proportional relationship

* volume increases, pressure decreases
* volume decreases, pressure increases

pressure changes - at rest

not inspiring or expiring

atmospheric pressure (760mmHg) = alveolar pressure (760mmHg)

intrapleural pressure = 756mmHg

pressure changes - inhalation

muscles contract to increase area inside lungs

* according to Boyle’s law pressure inside lungs decreases

atmospheric pressure (760mmHg) > alveolar pressure (758mmHg)

intrapleural pressure = 754mmHg

pressure changes - exhalation

muscles relax to decrease space

* according to Boyle’s law pressure inside lungs increases

alveolar pressure (762mmHg) > atmospheric pressure (760mmHg)

intrapleural pressure = 756mmHg

inspiration - process

active process

contraction of muscle

expiration - process

passive process

elastic recoil of fibres in alveolar walls

role of pleura in ventilation

frictionless movement

intra-pleural pressure

* water molecules stick together in groups
* molecules of parietal and visceral membrane attract to keep lungs attached to ribcage for movement