The Human Eye (Edexcel GCSE Biology)

• The eye is a highly specialised sense organ containing receptor cells that allow us to detect the stimulus of light
• The retina of the eye contains two types of receptor cells:
  • Receptor cells that are sensitive to light, known as rods, and receptor cells that can detect colour, known as cones

The eye

Functions of the Parts of the Eye Table

• Other structures of the eye include:
  • conjunctiva - a clear membrane that covers the white of the eye and the inside of the eyelids; it lubricates the eye and provides protection from external irritants
  • The ciliary muscle - a ring of muscle that contracts and relaxes to change the shape of the lens
  • The suspensory ligaments - ligaments that connect the ciliary muscle to the lens
  • The sclera - the strong outer wall of the eyeball that helps to keep the eye in shape and provides a place of attachment for the muscles that move the eye
  • The fovea - a region of the retina with the highest density of cones (colour detecting cells) where the eye sees particularly good detail
  • The aqueous humour - the watery liquid between the cornea and the lens
  • The vitreous humour - the jelly-like liquid filling the eyeball
  • The choroid - a pigmented layer of tissue lining the inside of the sclera that prevents the reflection of light rays inside the eyeball
  • The blind spot - the point at which the optic nerve leaves the eye, where there are no receptor cells