Breathing and Exchange of Gases

Respiratory Organs

Different animals use different organs for respiration based on their habitats and levels of organization, such as skin and lungs in amphibians, gills in fishes, and the human respiratory system featuring lungs and conducting pathways.

Mechanism of Breathing

Breathing involves inspiration (air enters lungs when thoracic volume increases and pressure decreases) and expiration (air leaves lungs when thoracic volume decreases and pressure increases), aided by the diaphragm and intercostal muscles.

Exchange of Gases

Gas exchange occurs across the respiratory membrane between alveoli and pulmonary capillaries primarily by simple diffusion, driven by partial pressure gradients of oxygen and carbon dioxide.

Transport of Gases

Oxygen is primarily transported bound to hemoglobin as oxyhemoglobin, while carbon dioxide is transported as bicarbonate ions, dissolved in plasma, and bound to hemoglobin as carbaminohemoglobin.

Regulation of Respiration

Respiratory rhythm is primarily regulated by the respiratory rhythm center in the medulla oblongata, with a pneumotaxic center in the pons moderating its functions and chemoreceptors sensing blood CO2 and H+ levels.