Retinal Pigment Epithelium Quiz

The retinal pigment epithelium (RPE) is a single layer of epithelial cells that lines the back of the eye, between the photoreceptor cells and the choroid.

The apical side of the RPE faces the photoreceptor cells and is the side that absorbs light.

The basolateral side of the RPE faces the choroid and is involved in transporting nutrients and removing waste products.

The blood-retina barrier is a specialized barrier that prevents the passage of certain substances from the blood into the retina. It is formed by the tight junctions between RPE cells.

The RPE has many functions, including forming the blood-retina barrier, absorbing light, and transporting nutrients and waste products.

The RPE absorbs light that isn't absorbed by photoreceptor cells, preventing it from reflecting back into the eye. This helps to improve visual clarity.

The RPE facilitates the movement of nutrients and waste products between the blood and the retina. It does this by regulating the passage of substances through its tight junctions and by actively transporting specific molecules using specialized protein transporters.

GLUT1 and GLUT3 are examples of glucose transporters found in the RPE. These transporters help to facilitate glucose uptake from the blood into the eye.

The RPE (retinal pigment epithelium) actively regulates potassium (K+) concentration in the subretinal space to maintain proper function of photoreceptor cells.

Hyperpolarization refers to a change in the electrical potential of the RPE cell membrane, making it more negative. This occurs when potassium (K+) effluxes out of the cell, leading to a decrease in the concentration of positive charges inside the cell.

RPE cells have special channels that allow potassium (K+) ions to pass through the cell membrane. These channels open or close in response to changes in the potassium concentration in the subretinal space, regulating the flow of K+ into and out of the cell.

The concentration of potassium ions in the subretinal space, the fluid between the RPE and the photoreceptor cells, is crucial for proper photoreceptor function.

RPE cells have the ability to engulf and digest worn-out parts of photoreceptor cells, specifically the outer segments.

The process of phagocytosis involves the RPE cell extending its microvilli to engulf the outer segment, forming a phagosome. The phagosome then fuses with an endosome, and later a lysosome, breaking down the ingested material.

The process of phagocytosis of photoreceptor outer segments is regulated by a circadian rhythm and takes place primarily in the morning, often triggered by light.

Phagocytosis of photoreceptor outer segments is essential for maintaining retinal health, but if it fails, it can lead to the accumulation of debris and potential damage to the photoreceptor cells.

Retinal cells remove waste products like lactic acid through facilitated diffusion using monocarboxylate transporters (MCTs). This process ensures efficient removal of waste products from the eye.

Carbon dioxide (CO2) diffuses from retinal cells into the blood either directly or by combining with water to form carbonic acid (H2CO3).

The RPE regulates pH using a carbonic acid buffer and cotransporters for bicarbonate (HCO3-) and protons (H+).

Water moves across the RPE through aquaporins from the subretinal space to the choriocapillaris, following localized hypertonic solutions.

The sodium-potassium pump (Na+/K+-ATPase) creates an electrochemical gradient by pumping sodium out of the cell and potassium into the cell, driving water movement.

The NKCC cotransporter uses the sodium gradient to move chloride (Cl-) into the RPE cell, contributing to the movement of water.

The RPE maintains ion homeostasis in the subretinal space by transporting ions, buffering changes by providing potassium (K+) when needed and removing it when not.

In the dark, gated ion channels allow sodium (Na+) and calcium (Ca2+) to enter the outer segment of the photoreceptor, while potassium (K+) exits at the inner segment, creating a 'dark current'.