Читать книгу Introduction to the Human Cell - Danton PhD O'Day - Страница 21

The following diagram shows that cells can adhere via various mechanisms (Figure 3.2). Many of these cell adhesions mediate other cellular functions, as we will see throughout this volume. The image that is shown is based on the organization of junctional adhesion complexes that are seen in the human gut.

Figure 3.2. The localization and components of cell adhesion junctions in intestinal epithelial cells.

Cells adhere to each other via:

•Junctional adhesion mechanisms (tight junctions, adherens junctions, desmosomes, gap junctions)

•Cell adhesion molecules (next chapter)

Cells adhere to the substratum, basal lamina or extracellular matrix via:

•Hemidesmosomes

•Focal contacts (detailed in later chapters)

•Integrins (detailed in later chapters)

•Integral membrane proteoglycans (summarized in a later chapter)

As shown in the following figure, groups of junctions including tight and adherens junctions and desmosomes make up junctional adhesion complexes as seen in epithelial and cardiac tissues (Figure 3.3). These junctional adhesion complexes provide strong binding between these cells that are often subjected to great stresses. They also mediate intercellular communication and play a critical role in cell polarity. Links to the cytoskeleton (actin, keratin) are also present. The following transmission electron microscope photo shows the junctional adhesion complex present in the apical region of the intestinal mucosa (Figure 3.3).

Figure 3.3. An ultrastructural image of the localization of cell adhesion junctions in intestinal epithelial cells.