The cornea is the only part of the human body that has no blood supply. It gets oxygen directly from the air.
This is because the cornea is transparent, and blood vessels would block light from passing through. Instead, the cornea receives its nutrients and oxygen from the tears that bathe it and from the air.
The cornea is also the fastest healing tissue in the human body, which is why most corneal abrasions will heal within 24-36 hours.
While other areas of the body, like hair, nails, tooth enamel, and the outer skin layers, also don't have blood vessels, these tissues are not entirely devoid of blood supply.
