AP BIOLOGY

Detailed explanation-1: -Inspiration can occur if the pressure within the lungs (intrapulmonary pressure ) is less than the atmospheric pressure, i.e., there is a negative pressure in the lungs with respect to atmospheric pressure. Similarly, expiration takes place when the intrapulmonary pressure is higher than the atmospheric pressure.

Detailed explanation-2: -Gases tend to flow from areas of high pressure to areas of low pressure. When the pressure in the lungs decreases due to the increase in volume, lung pressure becomes lower than atmospheric pressure, which causes atmospheric air containing oxygen to flow into the lungs.

Detailed explanation-3: -This increase in volume leads to a decrease in intra-alveolar pressure, creating a pressure lower than atmospheric pressure. As a result, a pressure gradient is created that drives air into the lungs.

Detailed explanation-4: -Explanation: During inspiration, the lungs expand as the diaphragm contracts and internal intercostal muscles relax. As the volume of the thoracic cavity increases, its pressure decreases.

Detailed explanation-5: -Air flows because of pressure differences between the atmosphere and the gases inside the lungs. Air, like other gases, flows from a region with higher pressure to a region with lower pressure. Muscular breathing movements and recoil of elastic tissues create the changes in pressure that result in ventilation.