Expansion
Cells, fibres and ground substance
Expansion
Cells
- Fibroblasts: the principal resident cell, producing fibres and ground substance
- Macrophages: phagocytosis and antigen presentation
- Mast cells: histamine and heparin; degranulate in type I hypersensitivity
- Plasma cells: antibody
- Adipocytes
- Transient leucocytes
Fibres
- Collagen (type I): tensile strength. The most abundant protein in the body
- Elastic: elastin core with fibrillin microfibrils. Recoil. Abundant in aorta, lung and skin
- Reticular (type III): fine branching network forming the scaffold of liver, spleen, lymph node and bone marrow; demonstrated by silver stain
Ground substance: glycosaminoglycans, proteoglycans and glycoproteins, holding water and resisting compression.
Types by arrangement
- Loose (areolar): general packing, beneath epithelia
- Dense regular: tendon and ligament, parallel fibres for unidirectional strength
- Dense irregular: dermis and capsules, multidirectional strength
Marfan syndrome is a fibrillin-1 defect, so elastic tissue fails: aortic root dilatation, lens dislocation and joint hypermobility all follow.