Cell Adhesion and the ECM Flashcards
What is the difference between the functional units of connective and epithelial tissue ?
In connective tissue, the cells make the functional components (ECM)
In epithelia, the cells are the functional components
What are the main components of the ECM ?
Fibrillar proteins + hydrated gel of glycosaminoglycans (i.e. proteoglycans)
What are examples of fibrillar proteins ? Which cell produces these ?
Collagen, elastin, fibronectin, laminin.
Fibroblasts
Which cell produces the GAGs ?
Fibroblaststs
What are GAGs ?
Charged polysaccharide sugar chains
What is the function of fibroblasts ?
Synthesizing collagen, elastin, proteoglycans
Microscopically, how does the synthesis of fibrillar proteins look?
Extensions of the fibroblasts are involved in secreting collagen filaments
What are the steps to collagen formation ?
Procollagen synthesized in RERE —-> assembled to form x3 helix —>released via secretory pathway through Golgi —> Procollagen then exoyctosed of the fibroblast and trimmed to form tropocollagen, and enzyme-catalysed cross-linked to make a fibril —> fibrils then organised into fibres
How is vitamin C relevant to the collagen synthesis ?
Vitamin C is very important for procollagen synthesis in the RER
What is a distinctive microscopic feature of fibroblasts ?
Presence of abundant RER (seen by purple stained ribosomes thanks to heamatoxylin)
How does transport of such large units occur from the RER ?
Through specialised large vesicles build in a parallel pathway.
What is the relationship between fibroblasts and tendons ?
Fibroblasts are oriented along the tendon direction (tendon is oriented collagen fibres in the same direction)
What are the structural features of Elastin ?
- Quite hydrophobic so naturally coils up
- Linked by cross-likns
Which cells produce Elastin ?
Fibroblasts, smooth muscle cells, chondroblasts
Given an example of a GAG.
Chondroitin Sulfate
What are the functions of proteoglycans ?
Provide
- Matrix support/cushioning/hydration (since GAGs highly charged)
- Glue-like function
- Links between proteins of ECM and ECM and cell surface
What are the main components of a proteoglycan aggregate ?
GAGs, core proteins, link proteins
How is the ECM linked to the cytoskeleton ?
Collagen/proteoglycans bind fibronectin which links to Integrin (transmembrane protein) which bind via Adaptor proteins to cytoskeleton (actin or other)
Which protein links the ECM components and the integrin ?
Fibronectin
What are the functions of myofibroblasts ?
- Fibroblast-like: secrete collagen (hence important in tissue healing and tissue fibrosis)
- Smooth-muscle-like (actin, myosin, desmin)
How do myofibroblasts differentiate from fibroblasts ?
They differentiate under mechanical tension.
They are then able to proliferate
What is the distinctive property of myofibroblasts ?
They are able to contract to reduce size of damaged area. They do that through focal adhesions and smooth muscle actin.
What do mast cells contain ? How do they appear in microscopy?
Granules containing hearing and histamine.
They appear filled with purple granules (purple due to matacromasia, due to negative charge of heparin)
What is the characteristic microscopic feature of plasma cells ?
Eccentric nucleus and large cytoplasm (bluish due to ribosomes).