Respiratory Organs:• Sponges,Coelenterates,

Flatworms,etc – No respiratory organs

Earth worms – Moist Skin

Insects – Tracheal tubes

Fishes,Aquatic artropodes,Molluscs – Gills

Reptiles,Birds,Mammals - Lungs

Amphibians - Lungs and Skin

Human Respiratory System

Steps in Respiration

Mechanism of Breathing

Mechanism of Breathing

Respiratory Volumes

IRV

ERV

RV

IC

EC

FRC

VC

TLC

Partial Pressure (in mm Hg)

Exchange of Gases

Alveolus