3 - Extracellular Matrix and Connective Tissue Flashcards
What are fixed cells? What are some examples?
Relatively stable populations of long-lived (weeks, months) cells that develop from mesenchyme.
Fibroblasts, which form from ECM, and adipocytes, which store lipids.
What are free/wandering cells?
Changing populations of specific defense cells (WBCs) that are short-lived (days) and enter the connective tissue from the blood vessels.
Macrophages, eosinophils, monocytes, lymphocytes, plasma cells, and mast cells.
What is extracellular matrix?
Hydrated gel-like substance with fibers embedded in it.
Dominant component of connective tissue.
Complex of non-living macromolecules manufactured by the cells of the tissue; exported by them in to the extracellular space.
What are five normal functions of connective tissue?
- Mechanical support/anchoring to organs
- Exchange of metabolites
- Storage of energy reserves (- lipids in fat cells
- Protection against infection - phagocytosis by macrophages
- Repair following injury - fibroblast secretion in wound healing
What is the ground substance of ECM made of? What are the fibers made of?
A mixture of GAGs and proteoglycans that resist compression.
Fibers: collagen and elastic for tensile strength
What types of tissue has high amount of extracellular matrix? Low?
High - connective tissue
Low - nervous tissue
What are adhesion glycoproteins in the ECM and what is their function?
Laminin and fibronectin, link the cell to the ECM by binding to integrins in the cell membrane.
What are glycosaminoglycans (GAGs)? What is their function in the ECM?
Long, inflexible polysaccharide chains made of repeating disaccharides.
Highly negative.
Amino sugar is usually sulfated and has carboxyl projecting from it.
Helps make a porous hydrated gel that absorbs compressive loads.
What are the four types of GAGs?
Which is prominent in loose supporting connective tissue?
- Hyaluronate
- Chondroitin sulfate and dermatan sulfate
- Heparan sulfate and heparin
- Keratan sulfate
Hyaluronate predominant in loose connective tissue.
What differentiates hyaluronic acid from other GAGs? When is it produced in large quantities?
It is not sulfated, single disaccharide unit consisting of long chains,
It doesn’t form covalent links to other proteins.
Large quantities during wound healing.
How do sulfated GAG chains interact with other proteins?
Covalently link with core protein in golgi to form proteoglycans with a bottlebrush appearance.
What are aggregan proteoglycans?
Proteins that bind to a hyaluronate backbone by link proteins to make cartilage and connective tissue.
What is the structure of collagen? How is it made?
Triple helix composed of three a-helix chains; usually repeat Gly-X-Y where X and Y can be any amino acid.
Made and secreted by fibroblasts.
- Secreted as procollagen and cleaved by peptidases
- Tropocollagen selassembles .
Where is type 1 collagen polymerized to? III? IV? VII?
Type 1: fibril
Type III: reticular fibers
Type IV: Sheetlike network (basal lamina)
Type VII: anchoring fibrils
What is osetogenesis imperfecta?
Defect in type 1 collagen, yielding easily fractured bones.
“Brittle bone”
What is chondrodysplasia?
Defect in type II collagen resulting in cartilage join deformities.
Usually results in dwarfism b/c growth plate does not make new bone cells.
What is Ehlers-Danlos Syndrome?
Type III collagen mutation resulting in weak skin, fragile blood vessels, and hypermobile joints.
Minor injuries may result in gaping wounds, sprains, and dislocations.
What are elastic fibers made of? How are they made?
Made of elastin and fibrillin proteins, elastin linked by lysines.
Elastin made by fibroblasts in the ECM: elastin core covered by sheath of microfibrils made of fibrillin.
What is marfan syndrome?
Mutations in fibrillin gene resulting in weakening of connective tissues rish in elastic fibers.
Weakened tissues stretch, distort, and can tear. Aneurisms/ruptured vessels common.
What is the structure of fibronectin?
A large glycoprotein heterodimer containing collagen, heparin and integrin separated by flexible hinge proteins.
What is the structure of laminin? What is this the major component of?
Large glycoprotein made of three large polypeptide chains formong a cross pattern of one long and three short chains held by disulfide bonds.
Basement membrane (basal lamina).
Where is the basement membrane found?
Under all epithelial cell sheets, separating epithelia from connective tissue.
MAde of type IV collagen, perlecan heparan sulfate, laminin, and entactin.
Collagen fibrils tether it to connective tissue.
What are the three function of the basement membrane?
- Molecular filter
- Selective barrier to cells such as fibroblasts and endothelial cells
- Scaffolding for regeneration
What are fibroblasts? What are they associated with? What do they look like?
Most abundant cells of connective tissue.
Synthesis of almost all ECM in connective tissue and is associated with collagen bundles.
Cytoplasm contains golgi and abundant RER for making collagen.
