The only part of the human body that does not receive a blood supply is the cornea of the eye. Instead of blood vessels, it obtains oxygen directly from the air and nutrients through diffusion from the tear fluid on the outside and the aqueous humor inside the eye. This lack of blood vessels is essential to maintain the cornea's transparency, which is critical for vision. The cornea is also known as the fastest healing tissue in the body, with most abrasions healing within 24-36 hours
. Other body parts such as hair, nails, tooth enamel, and the outer layers of the skin also lack blood vessels, but the cornea is unique in having living cells that are not directly served by blood vessels
