Cytoskeleton and Cellular Junctions Review

Cytoskeleton review: Includes microtubules, microfilaments, and intermediate filaments.
Cytoskeleton function: Provides structure, scaffolding for organelle attachment, and enables cellular movement.

Structure: Hollow tubes made of proteins.
Function: Serve as attachment points for organelles, allowing them to move along the microtubules.
Location: Radially extend from the nucleus.

Composition: Made of actin protein.
Function: Crucial for cell movement, especially in muscle cells during contraction and relaxation.
Location: Positioned just below the plasma cell membrane.
Mechanism: Generate forces to aid cell movement.

Function: Offer strength to cells, preventing them from tearing under various forces.
Structure: Protein fibers wound together like a rope to resist pulling forces.

General Expectation: Typically, one nucleus per cell.
Exceptions:
- Mature red blood cells: Lack a nucleus.
- Skeletal muscles: Contain multiple nuclei.

Functions:
- Enable cell communication.
- Maintain cell attachment.
- Create barriers within tissues.
Types: Tight junctions, desmosomes, and gap junctions.

Structure: Proteins spanning plasma membranes of adjacent cells, forming a seal.
Function: Prevent fluid seepage between cells; create a tight connection, much like sewing fabric together.
Example: Digestive system lining, where preventing seepage between cells is important.

Function: Create strong connections between cells, especially in tissues experiencing significant forces, such as muscle cells.
Components:
- Linker proteins: Located in the intercellular space, creating a strong connection similar to interdigitating fingers.
- Plaques: Thicken the plasma membrane to strengthen the connection; intermediate filaments attach to these.
- Intermediate filaments: Strengthen the connection by attaching to plaques.
Clinical Relevance: Disrupted desmosome formation leads to arrhythmogenic right ventricular dysplasia (ARVD).
- ARVD: A condition affecting linker protein formation, leading to weakened connections between cardiac muscle cells.
- Impact: Heart muscle cells can be pulled apart over time due to weakened linker proteins.
- Risk: Can result in cardiac arrest, especially in young athletes.

Structure: Proteins forming cylinders between adjacent cells.
Function: Allow molecules to move quickly from one cell to another, facilitating cell coordination.