RETINA

The eye organ develops as an extension of the brain. Primitive retina cells exist even when the eye organ is still in the form of a pit in the front part of the neural tube, before the closure of the neural tube that will form the central nervous system. At this stage, the retina can be thought of as a small sphere connected to the brain by a stalk. Then, as this sphere collapses inward, the cells at the front of the sphere, the inward-facing side of the sphere, and the cells at the back of the sphere become closer. This situation can be likened to cracking a hollow clay soil with a finger. Anterior pole cells differentiate to form the sensory retina, and posterior pole cells differentiate to form the retinal pigment epithelium. The cells remaining in the front part differentiate and begin to form the layers of the sensory retina in the seventh week. Between the tenth and twelfth weeks, the inner and outer layers of the retina begin to become apparent. The development of the macula begins in the sixth month.