How it works
This animal eye anatomy quiz asks for one part at a time on two eyes, a cat's and then a bird's. Each eye is drawn twice: from the front, and cut through from front to back.
Read the full guide
The cat: three bands at the back
In the cut eye, three bands lie one behind another at the back. The innermost is the retina and the outermost the sclera. The tapetum lucidum is the band between them, drawn in the upper half only. The third eyelid is on the other drawing: the fold in the inner corner of the eye seen from the front.
The bird: three parts of its own
The pecten is the pleated strip that reaches in from the back of the cut eye. The scleral ring is the pair of blocks at the front, where the cornea meets the eyeball. The nictitating membrane is the thin sheet drawn half across the eye seen from the front.
- Cornea, lens, retina and optic nerve are asked on both eyes, and they sit in the same places on each.
Questions and answers
Which animals are on the animal eye anatomy quiz?
Two: a cat and a bird. The bird stands for birds in general and is drawn after the eye of a domestic fowl. No dog, eagle or shark eye is drawn.
Do humans have a tapetum lucidum?
No. Humans lack one, so it is on no diagram of the human eye. Many other vertebrates have it: carnivores such as cats and dogs, and cows, sheep, goats and horses.
Do birds blink?
Not with the upper and lower lids. A bird's eyelids are not used in blinking: the nictitating membrane sweeps sideways across the eye and keeps it moist. On the cat the quiz calls the same part the third eyelid.
What does the scleral ring do in a bird's eye?
It holds the eye rigid. The ring is made of twelve to eighteen overlapping plates, most often fourteen, and fishes and many reptiles have one too.