Guide 05 / six systems
Respiratory system
A carefully folded exchange surface that brings oxygen in and moves carbon dioxide out with every breath.
The job
Ventilates the lungs and exchanges gases across the alveoli to support cellular respiration.
Orient yourself
Separate ventilation from exchange. Ventilation moves air through the airways. Gas exchange happens at the alveoli, where a very thin barrier places air next to pulmonary capillaries.
Trace a pathway
Follow air from nose or mouth through the pharynx, larynx, trachea, bronchi, and smaller bronchioles until it reaches the alveoli. The diaphragm creates the pressure changes that draw air in and push it out.
Make the connection
- The cardiovascular system carries oxygen away from the alveoli and returns carbon dioxide.
- The muscular system supplies the diaphragm and accessory muscles of breathing.
- The nervous system adjusts breathing rate in response to carbon dioxide and other signals.
Close the page
Can you explain it without looking?
Active recall turns recognition into understanding. Answer these prompts in your own words, then return to the guide only for the part you could not reconstruct.
Where does gas exchange actually occur?
What changes inside the thorax during inhalation?
Why are alveoli so numerous and thin-walled?