pigmentary epithelium, pigmented epithelium. that made of cells containing granules of pigment. posterior epithelium. the single layer of epithelial cells on the back of the cornea, between stroma and aqueous humour; the corneal endothelium.retinal pigment epithelium. see retina.sense epithelium, sensory epithelium. see neuroepithelium (1).he single layer of epithelial cells on the back of the cornea, between stroma and aqueous humour; the corneal endothelium. retinal pigment epithelium. see retina. sense epithelium, sensory epithelium. see neuroepithelium (1).
Since at least the mid-19th century, doctors have known that silver or silver compounds can cause some areas of the skin and other body tissues to turn grey or blue-grey. Argyria occurs in people who ingest or inhale
There are various types of skin darkening. One type is hyperpigmentation that occurs when certain skin cells release more pigment (dark color). Darkening of the skin due to  blueness  is called cyanosis (see also blue skin) or purple skin. Darkening may sometimes occur from redness or bruising.