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
Serous membrane edition of Anatomy & Physiology text-book by OpenStax College" Serous membrane In anatomy, serous membrane (or serosa) is a smooth tissue membrane consisting of two layers of mesothelium, which secrete serous fluid. The inner layer that covers organs (viscera) in body cavities is called the visceral membrane. A second layer of epithelial cells of the serous membrane, called the parietal layer, lines the body wall. Between the two layers is a potential space, mostly empty except for a few milliliters of lubricating serous fluid that is secreted by the two serous membranes. The Latin anatomical name is "tunica serosa". Serous