Epithelial cells are compactly arranged and thus to provide mechanical support and keeping the cells together desmosomes are in abundance. Tight junctions are coming found in columnar epithelium to stop leakage across a tissue.

Desmosomes abundantly occur in epithelial tissues.

Desmosomes are a type of cell surface junctions that play a crucial role in maintaining the structural integrity of epithelial tissues. These junctions are formed by the interaction of transmembrane proteins known as cadherins, which are linked to the cytoskeleton through intermediate filaments.

Function of Desmosomes:
Desmosomes provide strong adhesion between adjacent cells and help distribute mechanical stress evenly throughout the tissue. They prevent the cells from being easily separated from each other and provide resistance against shearing forces.

Structure of Desmosomes:
Desmosomes consist of two main components: the transmembrane proteins called desmogleins and desmocollins, and the intracellular plaque. The desmogleins and desmocollins interact with each other in a calcium-dependent manner, forming homophilic interactions between adjacent cells. The intracellular plaque is composed of desmoplakin, plakoglobin, and plakophilin, which connect the transmembrane proteins to the intermediate filaments.

Formation of Desmosomes:
The formation of desmosomes begins with the clustering of desmogleins and desmocollins at the cell membrane. This clustering is mediated by calcium ions, which bind to specific sites on the transmembrane proteins. Once clustered, the desmogleins and desmocollins interact with each other, forming strong adhesive bonds between adjacent cells. The intracellular plaque then connects to the cytoskeleton, anchoring the desmosomes to the cell's internal structure.

Importance in Epithelial Tissues:
Epithelial tissues line the surfaces of organs and cavities, providing a protective barrier and regulating the exchange of substances. The presence of desmosomes in epithelial tissues allows them to withstand mechanical stress, such as stretching and bending, without disrupting the integrity of the tissue. This is especially important in tissues that experience constant mechanical forces, such as the skin, heart, and gastrointestinal tract.

Summary:
Desmosomes are cell surface junctions that abundantly occur in epithelial tissues. They provide strong adhesion between adjacent cells, distribute mechanical stress evenly, and prevent the cells from being easily separated. The formation of desmosomes involves the interaction of desmogleins and desmocollins, which are connected to the cytoskeleton through the intracellular plaque. These junctions play a crucial role in maintaining the structural integrity of epithelial tissues and are essential for their proper functioning.