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Human eye
Compoond ee o Antarctic krill
Anatomical terminology

Een are organs o the veesual seestem. Thay provide organisms wi veesion, the abeelity tae receive an process veesual detail, as weel as enablin several photae response functions that are independent o veesion. Een detect licht an convert it intae electro-chemical impulses in neurons. In heicher organisms, the ee is a complex optical seestem that collects licht frae the surroondin environment, regulates its intensity throu a diaphragm, focuses it throu an adjustable assemmly o lenses tae form an eemage, converts this eemage intae a set o electrical seegnals, an transmits thir signals tae the harn throu complex neural pathweys that connect the ee via the optic nerve tae the veesual cortex an ither auries o the harn. Een wi resolvin pouer hae come in ten fundamentally different forms, an 96% o ainimal species possess a complex optical seestem.[1] Eemage-resolvin een are present in molluscs, chordates an arthropods.[2]

The semplest "een", sic as thae in microorganisms, dae naething but detect whither the surroondins are licht or daurk, that is sufficient for the entrainment o circadian rhythms.[3] Frae mair complex een, retinal photosensitive ganglion cells send seegnals alang the retinohypothalamic tract tae the suprachiasmatic nuclei tae effect circadian adjuistment an tae the pretectal aurie tae control the pupillary licht reflex.


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  1. Land, M. F.; Fernald, R. D. (1992). "The evolution of eyes". Annual Review of Neuroscience. 15: 1–29. doi:10.1146/annurev.ne.15.030192.000245. PMID 1575438.
  2. Frentiu, Francesca D.; Adriana D. Briscoe (2008). "A butterfly eye's view of birds". BioEssays. 30 (11–12): 1151–62. doi:10.1002/bies.20828. PMID 18937365.
  3. "Circadian Rhythms Fact Sheet". National Institute of General Medical Sciences. Archived frae the original on 13 Mairch 2020. Retrieved 3 Juin 2015.