1. External Respiration: This takes place in the lungs.
* Inhaling: Air is drawn into the lungs through the nose and mouth, passing through the trachea (windpipe) and bronchi into tiny air sacs called alveoli.
* Gas Exchange: Oxygen from the inhaled air diffuses across the thin walls of the alveoli and into the tiny blood vessels called capillaries surrounding them. Simultaneously, carbon dioxide from the blood diffuses into the alveoli to be exhaled.
2. Internal Respiration: This takes place in the cells of the body.
* Oxygen Transport: Oxygen carried by the blood is delivered to individual cells throughout the body.
* Cellular Respiration: Cells use oxygen to break down glucose (sugar) for energy. This process releases carbon dioxide as a waste product.
* Carbon Dioxide Transport: Carbon dioxide from the cells travels back to the lungs via the blood to be exhaled.
So, while the lungs are the primary site of external respiration, respiration itself is a continuous process that occurs throughout the body at the cellular level.
