Circulation & Gas Exchange
- The circulatory system consists of a network of blood vessels connected to the heart and lungs
- The heart pumps deoxygenated blood to the lungs where gas exchange surfaces take up oxygen
- Oxygen diffuses into the blood from the alveoli
- Alveoli are specialised structures that have a large surface area to volume ratio and thin walls to maximise gas exchange
- Carbon dioxide (waste gas) diffuses from the blood into the lungs (to be exhaled) via the alveoli
- Oxygen diffuses into the blood from the alveoli
- Oxygenated blood then returns to the heart which pumps it out in arteries around the body towards organs
- Arteries narrow to capillaries as they pass through the organ
- A network of small capillaries allows for gas exchange with organ tissues
- Capillaries widen to veins as they move away from the organ to carry deoxygenated blood back towards the heart
The alveolus is the gas exchange surface in humans
A network of small capillaries allows for efficient gas exchange in organ tissues