MICROANATOMY

Detailed explanation-1: -Diffusion only takes place with a concentration gradient. Gases will flow from a high concentration to a low concentration. A high oxygen concentration in the alveoli and low oxygen concentration in the capillaries causes oxygen to move into the capillaries.

Detailed explanation-2: -Gas exchange is achieved by diffusion. This is a process by which particles move naturally from a region where they are in high concentration to a region where they are in lower concentration. They move down a concentration gradient: the steeper the gradient, the faster the rate of diffusion.

Detailed explanation-3: -a) There are many capillaries around every alveoli. This good blood flow maintains a steep concentration gradient between the oxygen (and carbon dioxide) in the alveoli and the blood so that the rate of diffusion is faster.

Detailed explanation-4: -Oxygen is diffusing from the air inside the alveoli within the lungs into the erythrocytes and blood plasma. Diffusion is a type of passive transport, where molecules move from high concentration to low concentration. This means that the concentration of oxygen in the air must be higher than it is in the blood.