3 - Connective Tissues Flashcards
Three embryological germ layers
Ectoderm, endoderm,
mesoderm
Germ layers from which epithelium develops from
All germ layers
Germ layers that connective tissue develops from
Mesenchymal stem cells from mesoderm
Common layout of connective tissue
Few cells to a large mass of extracellular matrix which consists of fibres embedded in ground substance containing tissue fluid: extracellular fluid
Dominant component that determines type of connective tissue
Extracellular matrix
Cell that produces most fibres in the body (EG: collagen, elastin)
Fibroblasts
Molecular makeup of collagen
3x alpha polypeptide chains that form a helix.
Type I collagen
Connective tissue proper, bone, tendon, ligament
Type II collagen
Hyaline cartilage, intervertebral disc
Type III collagen
Reticular collagen.
Forms framework in certain tissues (EG: liver, bone marrow)
Type IV collagen
Forms basement membrane
Type VII collagen
Anchoring fibrils that link to basement membranes
How are type III collagen fibres stained?
Not with H&E.
With silver stains
Shape of elastin fibres
Branching fibres or sheets
Where is elastin most commonly found?
Lung, skin, aorta
Ground substance
Viscous, clear substance.
Glycosaminoglycans bound to core protein (forms proteoglycan).
Negative charge attracts Na+, which attracts water.
Examples of glycosylated proteins that can be found in ground substance
Fibronectin, fibrillin, laminin
ECM
Fibres + ground substance
Resident cells
– Fibroblasts, myofibroblasts – Macrophages – Mast cells – Mesenchymal stem cells – Adipocytes – Cells of specific CT: adipocytes, osteoblasts, chondroblasts, haematopoietic cells
Wandering cells
Lymphocytes, eosinophils, plasma cells, basophils
Example of dense connective tissue
Tendon
Why doesn’t ground substance stain in H&E?
Water is removed from it during slide preparation
Composition of cartilage 1) 2) 3) 4)
1) Predominance of proteoglycan ground substance 2) Collagen type II 3) Connective tissue cells are chondrocytes 4) Main type of cartilage is hyaline which is avascular
Composition of bone
1)
2)
1) Predominantly collagenous (type 1) matrix called osteoid which becomes mineralised
2) Connective tissue cells are osteoblasts and osteocytes
Basement membrane
Interface between support tissues and parenchymal cells e.g. epithelia
Mainly produced by the cells being supported EG epithelia
Basement membrane composition 1) 2) 3) 4)
Composed of extracellular matrix:
1) Predominantly collagen IV
2) Heparan sulphate
3) Structural glycoproteins: laminins, fibronectin.
4) Collagen VII attaches basement membrane to underlying connective tissue
Laminins and fibronectin are involved in linking integrins of epithelial cells to extracellular matrix
Example of basement membrane
Basal lamina around muscles
Basement membrane functions
– Structural support
– Control of epithelial growth
– Links epithelium to underlying tissue
– Selective barrier to nutrients
