External respiration is the process where gas exchange occurs between the environment and the lungs, helping us take in oxygen and expel carbon dioxide. It consists of two main steps:
- Inspiration (Inhalation): We breathe in air through our nose, and it travels down the trachea (windpipe) to the lungs, which fill with oxygen needed for the body's functions.
- Expiration (exhalation): Oxygen from inhaled air enters the bloodstream and is delivered to organs and tissues. The blood then carries carbon dioxide (a waste product) back to the lungs, where it is expelled during exhalation.
2. Internal Respiration
Internal respiration is the gas exchange that happens inside our body, between the blood and the tissues.
- Once oxygen has travelled through the blood to various parts of the body, it exits the blood and enters the tissue fluid surrounding the cells.
- The cells use this oxygen for various functions.
- At the same time, carbon dioxide (a waste product produced by cells) moves from the tissue fluid into the blood.
- The blood then carries this carbon dioxide back to the lungs, where it will be expelled during exhalation.
3. Cellular Respiration
Cellular respiration is the process by which our cells convert nutrients like glucose into energy, using oxygen and releasing waste products like carbon dioxide and water.
- Cells break down dissolved nutrients like glucose gradually, using oxygen from breathing to release energy.
- As glucose is oxidised (combined with oxygen), it releases energy in the form of ATP (adenosine triphosphate). ATP is like a small battery that provides energy to cells.
- During this process, waste products like carbon dioxide and water vapour are also created.
- The carbon dioxide is then transported to the lungs to be exhaled, and water vapour is either used by the body or expelled.
Cellular respiration can be summarised by the following equation:
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy (38 ATP)
