Biology - Gas Exchange and Lungs

Function of lungs:
- Facilitate the process of cellular respiration by providing oxygen to the bloodstream.
- Remove carbon dioxide from the body.

Inhalation Process:
- Air enters through the mouth or nose.
- Travels down the trachea (windpipe).
- Divides into two bronchi, which branch into smaller bronchioles.
- Finally, reaches the alveoli, the sites of gas exchange.

Alveolus Structure:
- Composed of a single layer of very thin cells (similar to blood capillaries).
- Short diffusion pathway increases the rate of gas exchange.
Surface Area:
- Adults possess hundreds of millions of alveoli, significantly increasing surface area.
- If spread out, they could cover half a tennis court.
Moist Walls:
- Walls are moist, allowing gases to dissolve and enhancing diffusion rates.

Oxygen Diffusion:
- Oxygen concentration in alveoli is high compared to deoxygenated blood returning to the lungs (illustrated as blue blood).
- Oxygen diffuses from the alveoli into the blood due to a favorable concentration gradient.
Carbon Dioxide Diffusion:
- Carbon dioxide concentration is higher in the blood than in the alveoli, enabling easy diffusion into the alveoli to be expelled during exhalation.
- Carbon dioxide is primarily dissolved in blood plasma rather than being carried by red blood cells.

The entire process is ongoing:
- Deoxygenated blood consistently entering the capillaries.
- Oxygenated blood continuously leaving post gas exchange.

Breathing rate can be calculated as:
- Breathing Rate = Number of Breaths / Time (in minutes).
- Example: 42 breaths in 3 minutes yields a rate of 14 breaths per minute.