Which group of structures is part of the vascular tunic of the eye?

The vascular tunic of the eye, also known as the uvea, comprises structures that are highly vascularized and play crucial roles in nourishing the eye as well as regulating light entry. Among these structures, the iris, ciliary body, and choroid are primary components.

The iris is responsible for controlling the amount of light that enters the eye by adjusting the size of the pupil. The ciliary body aids in focusing by altering the shape of the lens, ensuring that light rays are properly focused onto the retina. The choroid is a layer filled with blood vessels that supplies nutrients and oxygen to the outer layers of the retina while also helping absorb excess light to enhance visual clarity.

Each of the other groups mentioned lacks the defining characteristics of the vascular tunic. The cornea and sclera are part of the outer fibrous tunic, which serves primarily protective functions. The retina and optic nerve are parts of the inner neural layer, crucial for vision but not involved in the vascular supply. Lastly, the lens and vitreous body are not vascular structures; the lens is an avascular transparent structure focusing light, while the vitreous body is a gel-like substance filling the eye's interior, providing shape but without vascular connections. Thus,