Cholesteatoma either by metaplasia of the middle ear mucosa or by traumatic implantation of ear canal or tympanic membrane skin. In addition, cholesteatoma inadvertently left by a surgeon usually regrows as an epidermal cyst. Some authors have also suggested hereditary factors. More commonly, keratin accumulates in a pouch of tympanic membrane which extends into the middle ear space. This abnormal folding or 'retraction' of the tympanic membrane arises in one of the following ways: Cholesteatoma may also arise as a result of metaplasia of the middle ear mucosa or implantation following trauma. Cholesteatoma is diagnosed by a doctor by physical examination
Cell membrane cells to hold them together to form tissues. Fungi, bacteria, most archaea, and plants also have a cell wall, which provides a mechanical support to the cell and precludes the passage of larger molecules. The cell membrane is selectively permeable and able to regulate what enters and exits the cell, thus facilitating the transport of materials needed for survival. The movement of substances across the membrane can be either "passive", occurring without the input of cellular energy, or "active", requiring the cell to expend energy in transporting it. The membrane also maintains the cell potential. The cell membrane thus works