DrSaBaQureshi1

lungs bronchioles bronchi trachea larynx pharynx nose human respiratory system fish gills counter current mechanism for the exchange of gase specialized structures for respiration respiration by lungs respiration by gills respiration by diffusion types of respiratory system functions of respiratory system reason why we breatth definition of breathing dr. saba qureshi breathing conducting system of heart blood flow and cardiac cycle of heart chambers of heart functions of valves of heart valves of heart functions of different layers of heart different layers of heart function of heart location of heart definition of heart heart