Avascularity

Avascularity, or avascularity, is the state or property of lacking blood vessels within a tissue or organ. In avascular tissues, nutrients, oxygen, and waste products are supplied and removed primarily by diffusion from nearby vascular structures rather than by direct blood flow through vessels.

Common avascular tissues include cartilage, the cornea, the lens of the eye, some layers of the epidermis, and dental enamel. Articular cartilage, for example, has no blood vessels and relies on diffusion from the synovial fluid and subchondral bone for nourishment. The cornea and lens are specialized for transparency and rely on avascularity to maintain optical clarity. The enamel layer of teeth is also avascular, with nourishment supplied during development by cells that produce the tissue.

Avascularity has important functional and clinical implications. It often limits the rate of growth and repair, since replenishing damaged cells or regenerating tissue requires diffusion rather than rapid vascular supply. Consequently, healing in avascular tissues tends to be slower and more constrained than in vascularized tissues. In pathology, loss of vascular supply can lead to ischemia and necrosis, as seen in avascular necrosis of bone. In research and medicine, promoting or inhibiting angiogenesis (the growth of new blood vessels) is a strategy in conditions ranging from wound healing to cancer, where avascular regions may influence treatment responses.

Overall, avascularity is a defining feature of certain tissues that supports specific functions while imposing limits on regeneration and susceptibility to ischemic injury.