Respiratory System

Coordinates the diaphragm and external intercostal muscles to contract and flatten during inhalation, expanding thoracic cavity volume and dropping intrapulmonary pressure below atmospheric pressure so air flows in. Reverses the process on exhalation as the diaphragm relaxes and elastic recoil pushes air back out. Performs this cycle roughly 12-20 times per minute, entirely without conscious instruction, thanks to signals from the medulla oblongata and pons.

Manages diffusion of oxygen from inhaled air across the thin alveolar-capillary blood, while simultaneously pulling carbon dioxide out of the blood and into the alveoli to be exhaled. Relies on a steep concentration gradient and an extremely short diffusion distance ( about one cell thick) to move gases efficiently with every single breath.

Partners with the chemical buffering systems of the blood to keep pH stable within a narrow range (about 7.35-7.45). Adjusts breathing rate and depth in response to rising or falling CO2 levels - since CO2 forms carbonic acid in the blood, blowing off more CO2 raises pH, and retaining CO2 lowers it. Acts as fast-response backup to the kidneys, which handle slower, longer-term pH corrections.