Tissue Architecture Flashcards
Tissue Level Function
-muscle movement
Cellular Level Functions
– Cell morphology/shape
– Motility
– Cell adhesion
– Division
Subcellular Level Functions
– Organization – Tensile strength – Chromosome segregation – Cell polarity – Vesicular movement
Cytoskeletal filaments are ___ and ___.
dynamic and adaptable
Cytoskeletal filaments
- intermediate filaments
- microtubules
- microfilaments
Intermediate Filaments
• Great tensile strength
– Enable cells to withstand mechanical stresses
• Found in cytoplasm of most animal cells
– Form a network throughout cytoplasm
– Surround the nucleus and extend to periphery
• Often anchored to plasma membrane at cell- cell junctions
• Form mesh-like structure called nuclear lamina
– Underlies and strengthens nuclear envelope
• Rope-like properties give high tensile strength
• Often further stabilized by accessory proteins
– Cross-link filaments into bundles
– Link to microtubules, actin filaments, and cell-junctions
Microtubules
• Crucial organization role in all eukaryotic cells
• Long and stiff hollow tubes
• Rapid assembly and disassembly
• Extend from centrosome to cell periphery
– Create “tracks” to transport vesicles, organelles and other cell components
• Form mitotic spindle for chromosome segregation
• Part of cilia and flagella
Microfilaments
• Actin filaments (F-actin) – Twisted polymer of G-actin (globular) – Structural polarity • Present in all cell types • Many are unstable – Association with other proteins can form stable structures • Essential for cell movements – Locomotion, phagocytosis, cell division, contraction, etc • Many proteins bind to and modify actin properties – Stabilize – Strengthen – Cross-link – Organize
ECM and Basal Lamina
• Components produced intracellularly and secreted and aggregate
– Composed of interlocking fibrous proteins and proteoglycans
• Matrix which interacts with cells/tissues via transmembrane proteins
– Anchors/clusters cells into tissues with distinct function
• Composition and properties controlled and vary by tissue type, location etc.
– Strength in tendons, strength and rigidity in teeth and bones, cushioning in cartilage
Collagen
• Main structural protein in ECM/connective tissue and basal laminae
– 28 distinct types of collagen
• Trimeric proteins – Homotrimers
– Heterotrimers
– Form collagenous triple helix
• Associate as fibers, sheets or transmembrane structures
• Nutrient deficiencies and genetic conditions in clinical conditions
Ehlers-Danlos Syndrome
• Caused by a mutation in collagen or collagen synthesis genes
– Fibrous Proteins: COL1A1, COL1A2, COL3A1, COL5A1, COL5A2, and TNXB
– Enzymes: ADAMTS2, PLOD1, B4GALT7, DSE, and D4ST1/CHST14
• Mutations alter the structure, production, or processing of collagen or proteins that interact with collagen
• Weakens connective tissue in the skin, bones, blood vessels, and organs
Cell Connections and Junctions
• Cell junctions link cells to neighboring cells,
• Focal contacts link cells to extracellular matrix, or basil lamina
• Roles in migration, immune system function, wound healing, tissue architecture
• Also involved in intracellular signaling pathways
– Cell death/survival, secretion, etc…
Cell Adhesion Molecules (CAMs)
• 3 major domains
– Extracellular (binding to adjacent cell/matrix proteins
– Transmembrane (links CAM to membrane)
– Cytoplasmic (bind to cytoskeleton via linker proteins)
Catherine Superfamily
• Ca2+ dependent adhesion molecule – Important in formation of junctions between cells (epithelial “sheets”) • Desmosomes and adherens junctions – Homophilic interactions (extracelluar) – Interacts with cytoskeleton (actin) • E-cadherin – Epithelial cadherin • N-cadherin – Neural cadherin • VE-cadherin – Vascular-endothelial cadherin • LI-cadherin – Liver-intestine cadherin
EMT and Cadherin Switching
• Cadherins can serve as biomarkers for invasive, metastatic tumors
• EMT
– Epithelia to Mesenchymal Transition
Less invasive
– In transitional bladder cancer
– in E-cadherin and in N- cadherin
– Increased invasiveness of the tumor cells
– Increased metastatic potential
