Capillaries connect arteries to veins and help in the exchange of substances across cells.
Capillaries are the smallest of blood vessels. They serve to distribute oxygenated blood from arteries to the body’s tissues and feed deoxygenated blood from the tissues back into the veins. The arteries deliver the oxygen-rich blood to the capillaries, where the actual oxygen and carbon dioxide exchange occurs.
There are three primary types of capillaries in the circulation:
- Continuous: These capillaries have no perforations and allow only small molecules to pass through. They are present in muscle, skin, fat, and nerve tissue
- Fenestrated: These capillaries have small pores that allow small molecules through and are located in the intestines, kidneys, and endocrine glands.
- Sinusoidal or discontinuous: These capillaries have large open pores and are enough to allow a blood cell through.