Cell Modifications: Apical, Basal, and Lateral

• Cell modification/differentiation occurs after cell division and involves structural modifications to newly formed cells
• These modifications allow the cells to perform their functions efficiently and effectively.
• The three types of cell modification are Apical, Basal, and Lateral modifications.

Apical Modification

• Apical modifications are found on the apical surface of cells.
• This surface includes the basement membrane, gap junctions, adhering junctions, and tight junctions.
• The surface can be found on the free surface of epithelial tissue.
• Examples of apical modifications include cilia, flagella, villi, microvilli, pseudopods, and the extracellular matrix.
• Cilia are short, hair-like structures that move in waves.
• Flagella are long, whip-like structures formed from microtubules.
• Villi are finger-like projections that arise from the epithelial layer in some organs, increasing surface area for faster and more efficient absorption.
• Microvilli are smaller projections that arise from the cell's surface increasing surface area and allowing for more efficient absorption.
• Pseudopods are temporary, irregular lobes formed by amoebas and some other eukaryotic cells, they bulge outward to move the cell or engulf prey.
• The Extra Cellular Matrix (ECM)is a compound secreted by the cell on its apical surface.
• The cell wall is the extracellular structure in plant cells that distinguishes them from animal cells.

Basal Modification

• Basal modifications are found on the basal surface of cells.
• They sit on the basement membrane, gap junctions, adhering junctions, and tight junctions free surface of epithelial tissue.
• Desmosomes/Hemidesmosomes are anchoring junctions on the basal surface of the cell.
• They form rivet-like links between the cytoskeleton and extracellular matrix components such as the basal lamina.
• Desmosomes are primarily composed of keratin, integrins, and cadherins.

Lateral Modification

• Lateral modifications are found on the lateral surface of cells.
• Tight junctions act as barriers regulating the movement of water and solutes between epithelial layers.
• Adhering junctions are anchoring junctions on the lateral surface of the cell.
• They fasten cells to each other's basement membrane.
• Gap junctions, also known as communicating junctions, are closable channels that connect the cytoplasm of adjoining cells.
• The presence of connexons allows for the direct exchange of chemicals between the cytoplasm of two cells.