Chapter 10 Cell and Tissue Architecture PDF

Chapter 10 Cell and Tissue Architecture  Tissues and Organs Tissue - group of cells working together to perform a specific function. Organ – group of tissues working together to perform a specific function Shape of cells and organs reflects function. Cy...

Chapter 10 Cell and Tissue Architecture  Tissues and Organs Tissue - group of cells working together to perform a specific function. Organ – group of tissues working together to perform a specific function Shape of cells and organs reflects function. Cytoskeleton, cell junctions, and extracellular matrix all contribute to shape of cells, integrity of tissues/organs, and function of tissues and organs as integral units in the body.  Epidermis – Water Resistant, Protective Barrier formed by Multiple Layers of Cells Dermis supports epidermis physically and supplies nutrients Epithelial Cells – 1-Multiple layers of Cells that Covers Outside of Body and Lines Organs Melanocytes give skin color Keratinocytes that protect underlying tissue. Basal lamina supports the epithelial cells. Dermis – Large amount of Extracellular Matrix that Makes Connective Tissue Cell type present in dermis is the fibroblast Produces extracellular matrix and is important in repairing skin damage Cytoskeleton – Provides Internal Structural Support and Enables Movement of Substances in Cell Long chains of protein subunits joined together Microtubules - α and β Tubulin Subunits Arranged in Tube-Like Structure Largest diameter cytoskeletal protein Microtubules radiate out from the centrosome, helping maintain shape Many organelles are tethered to microtubules.  Microfilaments – Thinnest, Branching Cytoskeletal Structure that Reinforce and Organize Proteins in Membrane  Epithelial Cells and Microfilaments 1. Transport of materials in cells 2. Shortening of muscle cells during contraction. 3. Separation of cells at end of animal cell division.  Microtubules and Microfilaments - Dynamic Growth occurs more quickly at plus ends. Microtubules positioned with ‘minus’ ends near centrosome and ‘plus’ ends projecting toward the cell membrane. Important for cell division (rapid cycles of shortening followed by slower growth) Dynamic Instability Motor Proteins Help Move things in Cell Body Vesicles can move on a microtubule track. Ex. – vesicles move on tracks from Golgi to cell membrane Kinesin moves cargo toward the plus end. Dynein moves cargo toward the minus end. Microtubule Examples: Cilia and Flagella Intermediate Filaments – Mechanical Strength! Different proteins depending on the cell type. Epithelial cells – mostly keratins, some vimentin Fibroblasts— vimentins Neurons— neurofilaments Nucleus—laminins Intermediate Filament Defects: Epidermolysis Bullosa Major Functions of Cytoskeletal Elements Cell Adhesion: Sponge Cell Adhesion: Amphibian Embryo Cadherins – Transmembrane Adhesion Proteins that Bind Adjacent Cells Structural continuity between two cells. Integrins – Contacts to the Extracellular Space Cytoplasmic domain interacts with ECM Association is important for structural integrity of tissues under physical stress. Cell Junctions – Connect Cells to Other Cells or Basal Lamina (supported by cytoskeleton) 5 Cell Junctions: 1. Adherens junctions 2. Desmosomes 3. Hemidesmosomes 4. Tight junctions 5. Gap junctions Adherens Junctions – Band that Goes Around Cell and Attaches to Band of Actin Desmosomes – Points that Hold Adjacent Cells Together Hemidesmosomes – Anchors to Basal Lamina Tight Junctions – Create Barrier that Keeps Substances in or Out  Gap Junctions and Plasmodesmata Plasmodesmata—Plant Cell Plasmodesmata are connections between two plant cells that cross the cell wall and membrane. Gap junctions – 2 cells communicate through joined rings of integral membrane proteins. Plasmodesmata - communication channels that can cross the cell wall of plant cells because the cell membranes of the plants are continuous.  Interactions in Junctions, Adhesion Molecules, and Cytoskeletal Elements Extracellular Matrix – Insoluble Mesh of Proteins and Polysaccharides Plant Extracellular Matrix  Collagen – Most Abundant in ECM and Most Abundant Animal Protein on Planet Basal Lamina – Support for Epithelial Tissues Collagen here provides flexibility to tissue and scaffolding for other proteins.  Cancer Metastasis – Tumor Cells Escape Tumor and Move to New Site All blood vessels have a basal lamina, so for metastasis to occur, a tumor cell must cross the basal lamina of a blood vessel 2x.  Specific Integrin has been found on Metastatic Cells but not Normal, healthy Cells When these integrins are blocked, metastatic cells are unable to cross the basal lamina and move into the bloodstream. ECM Influence on Cell Shape – Stiffness and Planes  Composition of ECM and Cell Shape Having appropriate proteins in ECM is key as protein type has a direct effect on cell shape. When laminins are added to cell growth cultures, neurons exhibit their appropriate shape. ECM Influences Gene Expression Joan Caron – looked at role of different proteins and expression of albumin by hepatocytes Hepatocytes grown with type I collagen did not express albumin. Hepatocytes grown in a mixture of ECM proteins AND type I collagen showed increased albumin expression. How Do We Know? Caron’s Experiments Also grew hepatocytes with isolated single proteins and combos of proteins from ECM Showed that ECM protein laminin influences the expression of albumin in hepatocytes.