What is gaseous exchange, and describe the mechanism of inspiration at rest

Gaseous exchange is the process by which one gas is exchanged for another, and occurs via diffusion between air in alveoli and the blood capillaries surrounding them. Inspiration is the process by which air is sucked into the lungs. To initiate inspiration, the diaphragm contracts and flattens, and the intercostal muscles contract, pulling the ribcage upwards and outwards. This process causes the volume within the thoracic cavity to increase, decreasing the pressure within. This drop in pressure causes air to be pulled into the lungs from an area of high pressure, which is the atmosphere, to low pressure, being within the thoracic cavity.