Question

Why do capillaries have small lumen?

Answer 1

Capillaries :

1. The final branches of the circulatory system are the capillaries.
2. Blood capillaries have a very thin lumen for the proper exchange of nutrients and gases.
3. The lumen of the capillaries is very small because the blood flow here is too slow for the maximum exchange process.
4. The capillaries also lack thick muscular walls.