All galleries » Special senses » Eye » Item 1 of 6

Posterior sclera, choroidea, retina

« Previous

sclera (fibrous layer)
sclera (cartilage layer)
choroidea
pigment cell layer of the retina
layer of rods and cones
external nuclear layer
external plexiform layer
internal nuclear layer
internal plexiform layer
ganglion cell layer
nerve fiber layer

Transverse section through the wall of the posterior segment of the eye of a pigeon (HE)

The wall of the eye is composed of three layers: the tunica externa/ tunica fibrosa (cornea and sclera), the tunica media (uvea) and the tunica interna (retina).

The tunica fibrosa can be divided in the anterior cornea and posterior sclera and is responsible for maintaining the shape of the eye.

The uvea consists of the choroid, the ciliary body and the iris. A tapetum cellulosum is only present in some nocturnal species as the nightjar (Caprimulgus spp).

The retina of birds is composed of 10 layers, as in mammals. In contrast to mammals, the avian retina is avascular.