Cell Junctions for Anatomy and Physiology - Gap, Cadherens, Adherens, Anchoring, Tight, Desmisomes..

Summary

This script explores the three main types of cell junctions in epithelial tissues: tight junctions, anchoring junctions, and gap junctions. Tight junctions create a barrier that separates apical and basal compartments, preventing substance movement between cells. Anchoring junctions, including desmosomes, hemidesmosomes, and adherens junctions, stabilize the tissue by providing strong, flexible connections between cells and the extracellular matrix. Gap junctions allow the passage of small molecules and ions, coordinating the function of adjacent cells through electrical and metabolic coupling.

Takeaways

• 😀 Tight junctions separate epithelial cells into apical and basal compartments, blocking extracellular space to create selective barriers.
• 😀 Tight junctions prevent the movement of substances through the extracellular space between adjacent cells.
• 😀 Anchoring junctions stabilize epithelial tissues and are common on the lateral and basal surfaces of cells.
• 😀 There are three types of anchoring junctions: desmosomes, hemidesmosomes, and adherens junctions.
• 😀 Desmosomes are patches of structural proteins on the inner surface of cell membranes that use cadherin molecules to connect adjacent cells.
• 😀 Hemidesmosomes are similar to desmosomes but link cells to the extracellular matrix using integrins instead of cadherins.
• 😀 Adherens junctions use either cadherins or integrins depending on their link to other cells or the matrix, and they include the contractile protein actin.
• 😀 The actin protein in adherens junctions can form isolated patches or a belt-like structure that affects the shape and folding of epithelial tissue.
• 😀 Gap junctions create intracellular passageways between adjacent cells that allow small molecules and ions to move between them.
• 😀 Gap junctions enable electrical and metabolic coupling, which coordinates the function of adjacent cells.

Q & A

What are the three basic types of cell junctions in epithelial cells?

The three basic types of cell junctions in epithelial cells are tight junctions, anchoring junctions, and gap junctions.

What is the function of tight junctions in epithelial cells?

Tight junctions separate epithelial cells into apical and basal compartments, preventing extracellular space between cells and blocking the movement of substances through this space. This helps the epithelium act as a selective barrier.

How do anchoring junctions stabilize epithelial tissues?

Anchoring junctions stabilize epithelial tissues by providing strong and flexible connections between adjacent cells, often found on the lateral and basal surfaces of the cells.

What are the three types of anchoring junctions?

The three types of anchoring junctions are desmosomes, hemidesmosomes, and adherens junctions.

What role do desmosomes play in epithelial cells?

Desmosomes provide structural support to epithelial cells by linking them together through adhesion molecules, specifically cadherins, which connect adjacent cells.

How are hemidesmosomes different from desmosomes?

Hemidesmosomes resemble half of a desmosome and link cells to the extracellular matrix, using integrins as adhesion proteins, rather than cadherins.

What is the function of adherens junctions in epithelial cells?

Adherens junctions, using cadherins or integrins, are involved in maintaining the structural integrity of epithelial tissues. They also influence the shape and folding of the tissue due to the contractile protein actin located in the cell membrane.

How does the actin protein contribute to adherens junctions?

The actin protein at adherens junctions connects isolated patches or forms a belt-like structure within the cell, influencing the shape and folding of epithelial tissue.

What is the purpose of gap junctions in epithelial cells?

Gap junctions create intracellular passageways between adjacent cells, facilitating the movement of small molecules and ions between their cytoplasm. They enable electrical and metabolic coupling of cells, which helps coordinate their function.

Why are gap junctions important for cell communication?

Gap junctions are critical for cell communication because they allow adjacent cells to exchange small molecules and ions, which is vital for coordinating cellular functions, especially in tissues that require synchronized activity.