Final answer:
The outer part of the retina receives its blood supply directly from the choroid, a vascular layer nourishing the photoreceptors responsible for converting light into neural signals. The ciliary body and optic disc are also essential structures in the eye for focusing light and transmitting visual information, respectively.
Step-by-step explanation:
The part of the retina that receives its blood supply directly from the choroid is primarily the outer retina. The choroid, which is a highly vascular tissue in the wall of the eye, nourishes the outer layers of the retina where photoreceptor cells, such as rods and cones, are found. These photoreceptors are responsible for converting light into neural signals that the brain can interpret as visual images. The retinal blood vessels primarily supply the inner retina; however, the outer retina is dependent on the choroidal circulation. The retina's foveal region, responsible for sharp central vision, also lacks blood vessels, allowing for unobstructed light perception.
The ciliary body, which is a smooth muscle structure located on the interior surface of the iris, plays a key role in adjusting the shape of the lens through zonule fibers, thereby focusing light onto the retina. The optic disc, also known as the blind spot, is where retinal ganglion cell (RGC) axons exit the eye and where blood vessels of the inner retina pass, but no photoreceptors are present in this area. This anatomy facilitates the initial processing of visual stimuli by allowing light to reach the photoreceptor cells with minimal interference before being converted into electrical signals.