respiration

bulk flow

moves solutes and water or gas together using pressure

diffusion

moves solutes/gases across membranes because of concentration differences

what kind of pressure is pressure from muscles

negative

pressure from the heart

positive

inhale1 for birds

ari comes into the beak and backk to the posterior air sacs

exhale 1 for birds

air goes from posterior air sack to lungs

inhale 2 for birds

air goes from lungs to anterior air sacs

exhale 2

air goes out

inhale 1 and 2

happen concurrently

exhale 2 and 4

happen concurrently

during inhalation 1

• some air also goes into the lungs. also true for exhalation

• there is a steady supply of fresh air across the parabronchi