Histology of the Eye PDF

# Histology of the eye ## By Dr. Ahmed Morsi Assistant Professor of Histology & Cell Biology ## At the end of the lecture, students will be able to 1. Enlist the 2 structural components of the retina 2. Explain the structure & function of the pigmented retina 3. Explain the structure & function of...

# Histology of the eye ## By Dr. Ahmed Morsi Assistant Professor of Histology & Cell Biology ## At the end of the lecture, students will be able to 1. Enlist the 2 structural components of the retina 2. Explain the structure & function of the pigmented retina 3. Explain the structure & function of the neural retina 4. Contrast between rods & cones 5. Enumerate the layers of the retina 6. Enlist the cells of the retina ## Retina - A diagram of the eye is shown with different parts labeled. - The diagram focuses on the retina, showcasing a cross-section of several layers. - The outer layer of the retina includes the receptor area, which features "rods" and "cones." - The middle layer includes "bipolar cells" and "ganglion cells." - The inner layer is the inner nuclear layer. - The image also shows retinal pigment epithelium (RPE). ## The retina has an inverted structure and is composed of 2 parts: - **Retinal pigmented (non-neural) epithelium (single layer)** - **Neural retina (9 layers)** ## a) Retina Pigmented Epithelium - **Cubical-shaped cells** - **Abundant smooth ER (SER) specialized for retinal (vitamin A) isomerization** - **Absorbs scattered light** - **Blood-retina barrier** - **Retinal regeneration (isomerize all-trans-retinal released from photoreceptors and produce 11-cis-retinal)** - **Phagocytosis** - **Remove free radicals** ## b) Neural Retina - **Possesses 3 major layers of nuclei and their interconnected neurons exhibiting nine distinct layers** - **Outer nuclear layer (ONL) contains cell bodies of photoreceptors (the rod and cone cells).** - **Inner nuclear layer (INL) contains the nuclei of various neurons, notably the bipolar cells, amacrine cells, and horizontal cells.** - **Ganglionic layer (GL) has neurons (ganglion cells) with much longer axons. These axons make up the nerve fiber layer (NFL) and converge to form the optic nerve** ## Cells of the retina - **Pigmented cubical cells** - **Photoreceptor cells (rods & cones)** - **Bipolar cells** - **Retinal ganglion cells** - **Glial cells: Müller stem cells, amacrine cells, horizontal cells, and astrocytes.** ## Rods & Cones - A diagram showing the structure of a rod and cone cell. - The rod cell has an outer segment, cilium, inner segment, and mitochondria. - The cone cell has an external plexiform layer, and synapses with bipolar cells. ### Rods & Cones Table | Feature | Rods | Cones | |---|---|---| | Site | Allover the retina | Concentrated in the fovea | | Number | 120 millions | 6 millions | | Types | - | 3 types | | Pigment | Rhodopsin | Iodopsin | | Function | Dim light | High intensity light & colors | | Outer seg. | Rod shaped | Conical | ## Layers of the retina - A diagram showing the different layers of the retina is shown. - The different layers are labeled. - The structure of the retina is described. - The outermost layer consists of pigmented cells. - The innermost layer consists of the nerve fiber layer. - Each layer features different types of neural cells. - It points out the light entering and the neural outflow. ## Clinical application-Retinal detachment - A medical emergency in which the neural retinal is separated form the pigmented epithelium. - **Mechanism: vitreous leakage through a retinal hole.** - **If urgently treated, permanent vision loss occurs.** ## Retinal detachment - An eye model showing the retinal detachment. - The detachment occurs due to a retinal hole. - There is a space between the retinal layer and pigment epithelium. ## Reference - Junqueira’s Basic Histology: Text and atlas, 13th Edition, 2013. Anthony L. Mescher ## Thank you - An image is shown of a pen with a black body and gold nib writing "Thank you" in cursive. - The pen is shown in an upward perspective.