pigment epithelium

the single layer of pigmented cells that abuts the tips of the photoreceptors in the retina. The pigment in the cells reduces light scatter by absorbing photons that elude the photopigments in the photoreceptors. The pigment epithelium is also critical for the health of the photoreceptors because it phagocytoses (engulfs) discarded disks of membrane that are continually shed by the photoreceptors. Also called retinal pigment epithelium (RPE).

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Psychology term of the day

November 17th 2024

REM sleep

rapid-eye-movement sleep: the stage of sleep, formerly called desynchronized sleep, in which most dreaming tends to occur during which electroencephalograms show activity that resembles wakefulness (hence, it is also known as paradoxical sleep) except for inhibition of most skeletal and cranial muscles. This stage has two phases—tonic and phasic—and it is largely during the phasic period that muscle twitches and bursts of rapid eye movements occur. REM sleep accounts for one quarter to one fifth of total sleep time. Compare NREM sleep.