Breathing and Exchange of Gases

Respiratory Organs

Different animals use different organs for breathing based on their habitats and organization, such as skin and moist cuticle in earthworms, trachea in insects, gills in aquatic animals, and lungs in terrestrial vertebrates.

Mechanism of Breathing

Breathing involves two main phases: inspiration (inhalation), where air enters the lungs due to the contraction of the diaphragm and external intercostal muscles increasing thoracic volume, and expiration (exhalation), where air is expelled.

Exchange of Gases

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

Transport of Gases

Oxygen is primarily transported bound to hemoglobin in red blood cells 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 maintained by the respiratory rhythm center in the medulla oblongata, with the pneumotaxic center in the pons modulating the rate of breathing based on body demands.