apical cortex

Definition

Target type: cellularcomponent

The region that lies just beneath the plasma membrane on the apical edge of a cell. [GOC:bf]

The apical cortex is a specialized region of the plasma membrane found at the apical, or uppermost, surface of epithelial cells. It is characterized by a unique molecular composition and structural organization, which contribute to its diverse roles in cellular function.

**Molecular Composition:**

The apical cortex is enriched in a variety of proteins, including:

* **Adhesive proteins:** These proteins, such as cadherins and integrins, mediate cell-cell and cell-matrix interactions, respectively, contributing to the integrity of epithelial tissues.
* **Transporters and channels:** These proteins facilitate the transport of molecules across the apical membrane, playing a crucial role in nutrient uptake, waste removal, and ion homeostasis.
* **Enzymes:** Apical cortex enzymes, such as hydrolases and peptidases, participate in the digestion of nutrients and the breakdown of extracellular matrix components.
* **Signaling molecules:** Receptors and signaling proteins located in the apical cortex mediate responses to external stimuli, regulating cellular behavior and tissue homeostasis.

**Structural Organization:**

The apical cortex exhibits a distinct structural organization, featuring:

* **Microvilli:** Finger-like projections extending from the apical surface, increasing the surface area for absorption and secretion.
* **Tight junctions:** Specialized cell-cell junctions that seal the space between epithelial cells, preventing the passage of molecules between cells.
* **Actin cytoskeleton:** A network of actin filaments underlying the apical membrane, providing structural support and facilitating the movement of membrane components.

**Functions:**

The apical cortex plays a crucial role in various cellular functions, including:

* **Absorption and secretion:** Apical membrane transporters and channels mediate the uptake of nutrients and the secretion of waste products.
* **Barrier function:** Tight junctions seal the space between epithelial cells, preventing the passage of molecules between cells and maintaining tissue integrity.
* **Cell-cell and cell-matrix interactions:** Adhesive proteins in the apical cortex mediate interactions between cells and with the extracellular matrix, contributing to tissue structure and function.
* **Signal transduction:** Receptors and signaling molecules in the apical cortex receive and transmit signals from the external environment, regulating cellular behavior and tissue homeostasis.

**Examples:**

The apical cortex plays a vital role in various physiological processes, including:

* **Intestinal absorption:** The apical cortex of intestinal epithelial cells mediates the absorption of nutrients, such as carbohydrates and proteins.
* **Kidney filtration:** The apical cortex of kidney epithelial cells contributes to the filtration of blood and the reabsorption of essential nutrients.
* **Lung function:** The apical cortex of lung epithelial cells forms the air-blood barrier, facilitating gas exchange.
* **Skin barrier:** The apical cortex of skin epithelial cells forms a barrier against environmental insults, protecting the body from infection and dehydration.

**Conclusion:**

The apical cortex is a highly specialized and dynamic region of the plasma membrane that plays a crucial role in a wide range of cellular and physiological functions. Its unique molecular composition and structural organization contribute to its diverse roles in nutrient uptake, waste removal, barrier function, and signal transduction, ultimately ensuring the integrity and function of epithelial tissues.'
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Proteins (3)

Compounds (179)