19-Extracellular Matrix Flashcards
What is the role of the extracellular matrix?
Holds the cells in place by the tissue by connections with the extracellular matrix
How is collagen secreted?
Secreted from fibroblasts
What is the ECM?
The ECM is the “material” (CT) in between cells that gives each tissue its structure and strength
How does collagen provide tensile strength?
Three collagen molecules twist around each other. (triple helices) these then combine to form collagen fibrils which combine to form collagen fibres
What bonding is involved in collagen molecules?
Covalent cross links - intramolecular and intermolecular
What is the role of vitamin C in collagen biosynthesis?
Vitamin C is required as a co factor for the addition of OH groups to stabilise the collagen triple helices under physiological conditions
What is procollagen?
Collagen that is not yet fully processed
What are the consequences of vitamin C deficiency?
Scurvy
How do integrin molecules link the ECM to the cytoskeleton?
Cells attach poorly to collagen so an adaptor molecule - fibronectin bind to the cells via integrins
Integrins attach to the actin cytoskeleton and this give the cell tensile strength
What are integrins?
Transmembrane receptors
What are the different types of cell-cell junctions?
Leak -proof seal - tight junctions
Cell-cell binding- adherens junctions and desomomes
Cell-basal lamina binding-hemidesmosomes
Cell-cell transport- gap junction
Give some examples of epithelial sheets
skin- stratified
Lung
mammary gland
What are the functions of the epithelial cells?
Barrier
Secretion of hormones, milk
Nutrient absorption
Retinal function hearing
What are the two faces of the epithelial sheets?
Apical and basal surfaces
What is the apical side exposed to?
Air/fluid such as GIT
Where is the basal side?
At the bottom of the cell and is attached to the basal lamina
What is the basal lamina?
A specialised ECM made up of type IV collagen and laminin
What is the role of laminin?
Connects the basal lamina to integrins in the epithelial cells to keep them anchored
What are tight junctions made from?
Proteins called claudins and occludins - form the seal/barrier that prevent leakage
What is the role of tight junctions?
Maintain correct composition of the extracellular medium in the gut and contribute to epithelial cell polarity
What is the role of desomomes in the ECM?
Link the keratin intermediate filaments from one cell to another
What is the role of hemidesmomes is the ECM?
Anchor the keratin filaments to the basal lamina
