6: ECM, Histopathology (Tissues) Flashcards
Extracellular matrix (ECM)
Everything that surrounds cell
Not mobile
Cell deposit proteins and carbohydrates around themselves
Communicates with nearby cells via surface receptors
Helps keep structural support of tissue
Helps cells function and influences what they do
Connective tissue is composed of (2)
ECM
Component cells
4 components of ECM
Collagen - fibril forming, non-fibril forming
Multiadhesive glycoprotiens - laminins, fibronectins
Elastic fibres - elastin, fibrillin
proteoglycans
4 connective tissues in ECM
Bone
Cartilage
Tendon
Vitreous humour
Collagen
Fibrous
28 types
Multiple genes
Most abundant protein
Fibre layering affects strength
Collagen structure
Triple helix
three a chains
gly-x-y
stiff helix
glycine - H side chain =pack together
Composure of collagen fibre
One alpha chain –> 3 alpha chains–> collagen fibril –>collagen fibre
Collagen synthesis
1)one alpha chain
2) hydroxylation (add OH) - Vit C is a cofactor{scurvy}, glycosylation (add carbohydrate chain) x3
3) Become triple helix, bonds form between chains
[4) IF not secreted: keep non collagenous domains- unless fibrillar collagens]
4) IF secreted: cleavage of non collagenous domains
5) Fibrils form, crosslinking occurs
Basement membranes
Non fibrillar collagens - type IV
flexible / bendy
join together laterally & head to tail
rotary shadowing = self assembly
form a sheet
Where are basement membranes found
Flexible ECM around tubes/under epithelium
Essential to kidney for GBM
Diabetic nephropathy
thick/too much ECM in membrane, Filtrate unable to enter nephron
results in renal failure
Alport syndrome
Collagen IV disorder
GBM becomes split and laminated
Elastic tissues are required in
Arteries/vessels
in skin
lungs
Elastic fibres
In absence of stretching force = elastin proteins in compact conformation
When subject to stretching force - elastin proteins elongate, but remain attached by cross links
Elastic fibres consist of
elastin core
microfibrils (fibrillin)
Marfans syndrome
Fibrillin disorder- affects elastin production, loss of elastic tissue
Tall, slender people-tissues collapse, e.g eye lens dislocate, aneurisms burst, vessels not elastic due to lack of elastin
Two types of glycoproteins
Laminins
Fibronectins
Laminins
3 different chains
large proteins
cross shaped
bind to many other ECM components
Fibronectins
In fluids
soluble and insoluble
U shaped
Interact with other ECM components
Fibronectins are involved in
Involved in embryogenesis, tissue repair and clotting
Laminin infection causes
muscular dystrophy
epidermolysis bullosa
Proteoglycans
core protein + GAG chain
Often negative
depending on repeating unit there are 4 categories of GAGs
GAG chains are
two amino sugars joined together = disaccharide unit
types of GAGs
Hyaluronan - vitreous humour and synovial fluid
Chondroitin sulphate and Dermatan sulphate
Heparan sulphate
Keratan sulphate
- dependant on varying repeating unit
Too much ECM can lead to
Fibrotic disorders
- liver fibrosis - cirrhosis
- kidney fibrosis - diabetic nephropathy
- lung fibrosis - idiopathic pulmonary fibrosis (IPF)
To little/loss of ECM can lead to
Lack of support
e.g osteoarthritis
Taking a biopsy
remove tissue - scalpel, needle
preserve with formalin - to keep integrity
put in wax
cut into tiny sections
mount on a glass slide for microscopy
What is histopathology used for
Cancer diagnosis
observing if treatment works
What stain is used to see leucocytes in a biopsy
H&E stain (Hematoxylin and eosin)
- makes nuclei and cytoplasmic granules visible