Vascular pigmented layer

The vascular pigmented layer (Latin: tunica vasculosa bulbi), also known as the uvea or uveal tract, is the middle layer of the eyeball. It has a lot of blood vessels, melanocytes, and smooth muscle cells.

The vascular pigmented layer consists of three parts: the choroid, ciliary body, and iris.

The choroid is the posterior, the biggest part lying between the sclera and retina. The choroid is rich in blood vessels and melanocytes. The choroid provides the blood supply to the outer layers of the retina.

The ciliary body is the thick part located in front of the choroid. The ciliary body is made of blood vessels, connective tissue, and smooth muscles. The thick frontal part of the ciliary body is called corona ciliaris, but the dorsal thinner part - orbiculus ciliaris. Orbiculus ciliaris has around 70 projections called processus ciliares. These projections are responsible for producing aqueous humor. The ciliary muscles allow the accommodation of the eye and provide the vitreous body with glycosaminoglycans.

The iris is found in front of the ciliary body and located in a frontal plane. Also, this part consists of the blood vessels, melanocytes responsible for the iris color, and smooth muscle, but it is covered by the retina from the inside. The iris has an opening anteriorly - the pupil. The iris is responsible for controlling the size of the pupil.