Breathing and Exchange of Gases

Respiratory Organs

Different animals use different organs for respiration depending on their habitats and levels of organization, such as skin and lungs in amphibians, gills in aquatic animals, and lungs in terrestrial mammals.

Mechanism of Breathing

Breathing involves inspiration (air enters) and expiration (air leaves), driven by the pressure gradients created in the thoracic cavity by the contraction and relaxation of the diaphragm and intercostal muscles.

Exchange of Gases

Gases diffuse across the respiratory membrane from regions of higher partial pressure to lower partial pressure, occurring primarily between alveoli and blood, and between blood and body tissues.

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 controlled by the respiratory rhythm center in the medulla oblongata, with a pneumotaxic center in the pons moderating its functions based on blood chemical levels.