Tympanic membrane retraction caused by erosion of the ossicles (hearing bones). Discharge from the ear often indicates that the retraction pocket has developed into a cholesteatoma. Three factors must occur for the tympanic membrane to become retracted: When gas pressure within the middle ear is less than atmospheric pressure, the eardrum can become sucked into the middle ear space. This is caused by inadequate opening of the Eustachian tube and absorption of air from the middle ear space. People with a patulous Eustachian tube may also cause negative middle ear pressure by repeatedly sniffing to try to keep their Eustachian tube closed. The
Common name not always English. For example, "Dikkop" is the centuries-old South African vernacular name for their two local species: "Burhinus capensis" is the Cape dikkop (or "gewone dikkop", not to mention the presumably much older Zulu name "umBangaqhwa"); "Burhinus vermiculatus" is the "water dikkop". The thick joints in question are not even, in fact, the birds’ knees, but the intertarsal joints—in lay terms the ankles. Furthermore, not all species in the genus have “thick knees”, so the thickness of the "knees" of some species is not of clearly descriptive significance. The family Burhinidae has members that have various common names even