What will happen to the food nutrients if the capillaries have thick walls?

• What are the Capillaries?

The capillaries are the smallest blood vessels in the human body, the other blood vessels being the much larger veins and arteries.

Known as micro-vessels, capillaries are typically only 1 mm long, with a diameter so small that red blood cells must travel in single file.

The capillaries in one human body could reach around the earth twice, and cover the extraordinary distance of 50,000 miles.

• What do they do?

Connecting arterioles and venules, capillaries allow the exchange of water, oxygen, carbon dioxide and other important nutrients and waste products between blood and tissue.

These include food molecules such as glucose and amino acids, as well as minerals like calcium iron and vitamins.

Capillaries hold 1.4 times the body's total blood volume and so do not remain open all at once. The dilation (opening) and constriction (closing) of capillaries is known as Vacillation and Vasoconstriction.

• Types of Capillary

Continuous Capillaries - An uninterrupted lining of endothelial cells, only allowing tiny molecules of water and ions to pass or diffuse through them.

Fenestrated Capillaries - Named after the Latin word, 'Fenestra', which  means 'Window'. Fenestrated capillaries have pores in their endothelial cells, and are covered by a diaphragm of fine fibers called fibrils, which let small amounts of protein flow through them