Respiratory System

air flows from an area of high pressure to an area of low pressure

inhalation + exhalation

relationship between gas pressure and volume

• diaphragm contracts and moves inferiorly 
• rib cage moves superiorly
• volume of thoracic increases, pressure inside lungs decreases 
• air enters lungs until pressure equilibrium

• diaphragm relaxes and moves superiorly 
• rib cage moves inferiorly 
• pressure inside lungs increases, air forced out

dome shaped

if you get a hole in your chest wall and air gets into the pleural cavity the lung will not expand

pulmonary compliance is a measure of the lungs ability to stretch and expand

it is the loss of connective tissue in lungs - decrease pulmonary compliance

rib cage cannot move as effectively

can be reduced by low levels of surfactant being produced, alveoli collapse and arthritis

f= no. breaths per min

Ve= amount of air moved per min [Litres permin]

Ve=f x Vt

• the air that doesnt reach the alveoli is called the anatomical dead space 
• no gas exchange is possible in these places

• is the amount of air reaching the alveoli 
• Va= f x (Vt-Vd)

tidal volume - 500 ml per breath at rest

• expiratory reserve volume 
• the amount of air you can voluntarily expel after you have completed a normal resp cycle 
• up to 1000ml in men , 700ml in women

• inspiratory reserve volume 
• the amount of air you can take in over and above the tidal volume, 
• 3300ml men , 1900ml women

• functional residual capacity
• the amount of air remaining in your lungs after you have completed a esp cycle 
• it is the sum of the ERV and residual volume

residual volume is the amount of air that remains in lungs even after maximal exhalation

Vt + IRV

Vt = IRV + ERV

= Vt + IRV + ERV + residual volume