Final answer:
The pressure in the airway
when you breathe in (inhalation) decreases below atmospheric pressure due to the expansion of the chest cavity, creating a negative gauge pressure that allows air to flow into the lungs for gas exchange.
Step-by-step explanation:
Understanding Pressure in the Airway During Inhalation:
When you breathe in, the pressure in the airway, or intra-alveolar pressure
becomes lower than the atmospheric pressure. This decreased pressure is referred to as negative gauge pressure. The drop in pressure within the alveoli of the lungs is because the diaphragm contracts and the chest cavity expands, creating a vacuum effect that allows air to flow into the lungs. This is an essential process for gas exchange as it enables oxygen to flow from the higher pressure in the inspired air
to the lower pressure in the bloodstream
. The eventual equilibrium of pressure between the lungs and the external atmosphere is driven by the difference in pressure gradients.
During normal respiration, the pressure in the airway is slightly negative relative to the atmospheric pressure, which facilitates the entry of air into the lungs. Contrary to this, during activities such as forced exhalation, the airway pressure can increase significantly above atmospheric pressure, demonstrating the dynamic changes in pressures linked with various breathing efforts.