MICROANATOMY

Detailed explanation-1: -When the lungs inhale, the diaphragm contracts and pulls downward. At the same time, the muscles between the ribs contract and pull upward. This increases the size of the thoracic cavity and decreases the pressure inside.

Detailed explanation-2: -The diaphragm also relaxes and moves higher into the thoracic cavity. This increases the pressure within the thoracic cavity relative to the environment, and air rushes out of the lungs.

Detailed explanation-3: -The primary inspiratory muscles are the diaphragm and external intercostals.

Detailed explanation-4: -Although it fluctuates during inspiration and expiration, intrapleural pressure remains approximately –4 mm Hg throughout the breathing cycle. Competing forces within the thorax cause the formation of the negative intrapleural pressure.

Detailed explanation-5: -The pleural cavity always maintains a negative pressure. During inspiration, its volume expands, and the intrapleural pressure drops.