Tympanosclerosis middle ear. Whilst hearing loss is a common symptom in many diseases of the ear, for example in otosclerosis (abnormal bone growth in the ear), the white, chalky patches on the tympanic membrane are fairly characteristic of tympanosclerosis. Cholesteatoma is similar in appearance but the whiteness is behind the tympanic membrane, rather than inside. Hearing aids are a common treatment for hearing loss disorders. A more specific treatment is surgical, involving excision of the sclerotic areas and then further repair of the ossicular chain. There are several techniques, sometimes involving two surgeries; success rates are, however, variable. Damage to the
Biological membrane fatty acid composition in accordance with differing temperatures. In animal cells, membrane fluidity is modulated by the inclusion of the sterol cholesterol. This molecule is present in especially large amounts in the plasma membrane, where it constitutes approximately 20% of the lipids in the membrane by weight. Because cholesterol molecules are short and rigid, they fill the spaces between neighboring phospholipid molecules left by the kinks in their unsaturated hydrocarbon tails. In this way, cholesterol tends to stiffen the bilayer, making it more rigid and less permeable. For all cells, membrane fluidity is important for many reasons. It enables membrane