Choroid
The choroid, also known as choroid or choroid, is the largest portion of the central eyeball ( tunica media of the eyeball ). It forms the middle layer between the white sclera ( sclera ) and retina ( retina) in the posterior half of the eyeball.
Layer
The choroid consists of several layers:
- Lamina supra choir ( i) oidea
- Lamina vasculosa
- Tapetum lucidum
- Lamina choir ( i) oidocapillaris ( choriocapillaris )
- Lamina basalis.
The lamina supra choir ( i) oidea is the outermost layer and consists of elastic connective tissue and pigmented connective tissue cells.
The lamina vasculosa is the location for the sclera, ie vascular outer layer and contains the larger arteries and veins. They are embedded in connective tissue, which is also highly pigmented.
The tapetum lucidum is not present in all mammals, in human, pig and rabbits, for example, is missing. In most mammals, however, a poor district pigment is formed in the back of the eye. This consists either of flattened cells (eg predators ), some with crystal inclusions overlays (eg dogs) or specially arranged connective tissue fibers (eg, horses, ruminants). This cause diffraction and reflection of light and act as a residual light amplifiers, as they direct the light back on the photoreceptors of the retina. Therefore, the tapetum lucidum is especially active at dusk species of importance. It also causes the characteristic flash of the eye is irradiated animals in the dark.
The lamina choir ( i) oidocapillaris or choriocapillaris is the deep disposed toward the retinal vascular layer. It consists of a fine capillary which ensures the diet of the outer layers of the retina.
The lamina basalis ( Synonyms: Complexus basalis Lamina vitra or Bruch's membrane) located directly on the pigment layer of the retina and provides the connection to this.