Which function is not performed by capillaries?

Capillaries play a critical role in the circulatory system primarily by facilitating the exchange of substances between the blood and surrounding tissues. Their structure, featuring thin walls that allow for easy diffusion, makes them ideal for transporting nutrients and removing waste products from cells.

While capillaries are essential for transporting nutrients and waste removal, they do not carry oxygen-rich blood in the way that larger blood vessels do. Instead, oxygen-rich blood is typically found in arteries, which carry oxygen from the heart to the body's tissues. Capillaries then serve as the sites where oxygen is exchanged for carbon dioxide at the tissue level. Therefore, the statement about carrying oxygen-rich blood is accurate for arteries, highlighting that capillaries are not involved in this function within the circulatory system.

When considering the other functions, it’s clear that capillaries connect arteries and veins, perform nutrient transport, and facilitate waste removal effectively; thus, they do not align with the function of carrying oxygen-rich blood.