Why does a cornea heal and cartilage wears out, when neither has a blood supply?

Why does a cornea heal and cartilage wears out, when neither has a blood supply? © Getty Images

The outer layer of the cornea is called the epithelium. It is made up of cells that are constantly turned over, as the outermost cells are shed into the tear film. Corneal abrasions usually affect this layer. The entire epithelium is turned over in approximately 7-10 days, and this process is accelerated during wound healing.

Historically, cartilage was thought to ‘wear and tear’ as we age, leading to osteoarthritis. But we now know that it’s a disease of the entire joint, including bone, cartilage, ligaments, fat and the tissues lining the joint. Beyond simple wear and tear, osteoarthritis can cause the cartilage to degrade, change bone shape and cause inflammation – all of which are difficult to reverse.

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Asked by: Mark R Slack, via email

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