What Is the Retina?

The retina is the inner layer of the eyeball wall, and is divided into a blind retina and a visual part. The blind part includes the retinal iris part and the retinal ciliary body part, each of which is attached to the inner surface of the iris and the ciliary body and is a component part of the iris and the ciliary body.

The retina is the inner layer of the eyeball wall, and is divided into a blind retina and a visual part. The blind part includes the retinal iris part and the retinal ciliary body part, each of which is attached to the inner surface of the iris and the ciliary body and is a component part of the iris and the ciliary body.

Chinese name

Retina

Foreign name

retina

Make up

Pigment epithelium and retinal sensory layer

Features

Nutritional photoreceptor cells, regeneration and repair

Location

Attach to the back wall of the eyeball

Disease

Retinitis pigmentosa, macular degeneration, etc.

Retina Overview

The retinal vision is often referred to as the retina, which is a soft and transparent film that is closely attached to the inner surface of the choroid and has the effect of feeling light stimulation. The thickness of the retina varies, usually 0.4mm, the edge of the optic disc is the thickest, about 0.5mm, and the fovea is the thinnest, which is 0.1mm, and the jagged edge is 0.15mm. The retina is mainly composed of pigment epithelial cells, optic cells, bipolar cells, ganglion cells, horizontal cells, amacrine cells, reticulum cells, and Muller cells. These cells and their processes are arranged in an orderly manner, so that the retina can be divided into 10 layers from the outside to the inside. Pigment epithelium: consists of a single layer of pigment epithelial cells; rod cone: consists of rod cells and cones' exocytosis; outer membrane: formed by the extruded ends of Muller cells Nuclear layer: composed of cell bodies of rod cells and cone cells; outer reticulum layer: composed of inner processes of rod cells and cone cells and dendrites of bipolar cells; inner core layer: composed of bipolar cells, Cell bodies of horizontal cells, amacrine cells and Muller cells; Intrasacral reticulum: composed of axons of bipolar cells and adenoids and dendritic cells of ganglion cells; sacral cell layer: composed of somatic cells of ganglion cells The sacral nerve fiber layer: consists of axons of ganglion cells; the sacral inner limiting membrane: formed by the end of the inner process of Müller cells.

Local retina anatomy

Pigment epithelium: It is a layer of short hexagonal prismatic cells, with a height of 8-10 m and a width of 12-18 m. Many 5-7 m long protrusions protrude from the top of the cell. During embryogenesis, the base of the epithelium and the choroid are tightly connected, but the top is not tightly connected with the optic cells, so retinal detachment is prone to occur here. Observed by electron microscope, there are tight junctions, intermediate junctions and gap junctions between the cells, and there are inner membrane folds and mitochondria at the base, so it is speculated that the pigment epithelium has transporting ions and barrier functions. The nucleus is round and located at the base of the cell. The top cytoplasm contains many oval or round melanin particles and lamellar debris. The endoplasmic reticulum of the slippery surface is well developed and is distributed between pigment particles and remnants. There are Golgi complexes, lysosomes, rough endoplasmic reticulum and lipid droplets. These structures reflect the multiple functions of pigment epithelium: pigment particles are produced by the rough endoplasmic reticulum and transported to the top of the cytoplasm via the Golgi complex. It is known that when amphibians and fish are exposed to strong light, the pigment particles move into the protrusions; when it is dark, the pigment particles return to the cytoplasm, which indicates that the pigment epithelium has the effect of absorbing light and protecting the visual cells from strong light. Lipid droplets can accumulate and store vitamin A, and participate in the synthesis of rhodopsin by optic cells through the esterification and transport of the endoplasmic reticulum of the slippery surface; can engulf the outer membrane discs of rod cells and lysosomes Enzymatic hydrolysis digestion and formation of residues; secretion of proteoglycans, binding and maintaining the positional relationship between rod, cone and pigment epithelium, thereby ensuring the renewal of rhodopsin and the transfer of nutrients.

Optic cells: also known as photoreceptor cells, divided into rod cells and cone cells. There are about 120 million rod cells in the human retina, which are sensitive to weak light stimulation; there are 6.5 to 7 million cone cells, which are sensitive to strong light and color. The two types of cells are arranged in parallel, and cone cells are mainly concentrated in the fovea; rod cells gradually increase from the fovea to the periphery. To the vicinity of the jagged edge, the visual cells disappeared.