Why do capillaries need to be thin walled?

Answer

To allow effective diffusion of nutrients and oxygen to the cells and also diffusion of waste and carbon dioxide from the cells

Explanation.

-Capillaries are small vessels that are only one cell thick; which is an adaptation that allows them to undertake their function effectively.

-The function of capillaries is to allow food and oxygen to diffuse to cells while waste is diffused from cells.

-Therefore; they need to be thin walled for these functions.

-If the capillaries did not have thin walls, the gases could not diffuse through, which would be difficult to carry out their functions.

sodium i think the chemical element of atomic number 11, a soft silver-white reactive metal of the alkali metal group.