The upper portion of the spiral ligament contains numerous capillary loops and small blood vessels, and is termed the stria vascularis. It produces endolymph for the scala media, one of the three fluid-filled compartments of the cochlea. The stria is a somewhat stratified epithelium containing primarily three cell types (marginal, intermediate, and basal cells) and intraepithelial capillaries. The marginal cells are involved primarily in K+ transport and line the endolymphatic space of the scala media. The intermediate pigment-containing cells are scattered among capillaries. The basal cells separate stria vascularis from the underlying spiral ligament. The stria vascularis also contains pericyte, melanocyte, and endothelial cells. It is the only epithelial tissue that is not avascular(i.e. completely lacking blood and lymphatic vessels).
This article incorporates text from a public domain edition of Gray's Anatomy.
Avascular necrosis (also osteonecrosis, bone infarction, aseptic necrosis, ischemic bone necrosis, and AVN) is a disease where there is cellular death (necrosis) of bone components due to interruption of the blood supply. Without blood, the bone tissue dies and the bone collapses. If avascular necrosis involves the bones of a joint, it often leads to destruction of the joint articular surfaces. (see Osteochondritis dissecans).
There are many theories about what causes avascular necrosis. Proposed risk factors include, chemotherapy, alcoholism, excessive steroid use, post trauma, caisson disease (decompression sickness), vascular compression, hypertension, vasculitis, arterial embolism and thrombosis, damage from radiation, bisphosphonates (particularly the mandible), sickle cell anaemia, and Gaucher's Disease,. In some cases it is idiopathic (no cause is found). Rheumatoid arthritis and lupus are also common causes of AVN. Prolonged, repeated exposure to high pressures (as experienced by commercial and military divers) has been linked to AVN, though the relationship is not well-understood.