What physical principle primarily drives air into the lungs during inhalation in mammals?

During mammalian inhalation, the primary physical principle at work is negative pressure mechanics. This process involves the diaphragm and intercostal muscles contracting, which increases the volume of the thoracic cavity. As the volume increases, the pressure within the lungs decreases relative to atmospheric pressure.

According to Boyle's law, when the volume of a gas increases, its pressure decreases. Consequently, when the lung volume expands, the pressure inside the lungs becomes lower than that of the outside atmosphere. This pressure gradient causes air to flow into the lungs from the surrounding environment, moving from an area of higher pressure to one of lower pressure. This inhalation mechanism is efficient and pivotal for respiration in mammals, allowing them to oxygenate their blood.

Negative pressure mechanics is a fundamental concept in respiratory physiology, distinguishing mammalian breathing from other methods that might rely on mechanisms such as positive pressure, which is not characteristic of standard mammalian inhalation.