Biology – 3.1 Diffusion | e-Consult

Diffusion of gases is crucial for gas exchange in terrestrial animals because it allows oxygen to move from areas of high concentration (the lungs or air sacs) to areas of low concentration (the blood) and carbon dioxide to move in the opposite direction. This process is essential for providing the body with oxygen for cellular respiration and removing carbon dioxide, a waste product.

Ventilation is the process of moving air into and out of the lungs. This creates a continuous supply of fresh air with a high concentration of oxygen. The movement of the diaphragm and rib muscles facilitates ventilation, ensuring a constant gradient of oxygen concentration across the respiratory surfaces.

The structure of the respiratory system is specifically adapted to enhance gas exchange via diffusion. For example, in mammals, the lungs contain millions of tiny air sacs called alveoli. These alveoli have very thin walls, facilitating rapid diffusion of gases. The large surface area provided by the alveoli maximizes the area available for gas exchange. The capillaries surrounding the alveoli also have thin walls, further reducing the diffusion distance. The partial pressure gradients of oxygen and carbon dioxide drive the diffusion process.

Without efficient gas exchange via diffusion, the body would not receive enough oxygen to sustain metabolic processes, leading to cellular damage and ultimately death. Therefore, the coordinated action of ventilation and the structural features of the respiratory system are vital for survival.