Summary of Section 5
- The cells of animal tissues are held together by the extracellular matrix and by cell junctions.
- The extracellular matrix in animals is composed of a hydrated mixture of glycosaminoglycans (GAGs) and proteoglycans, in which various proteins, especially fibrous proteins like collagen, are embedded. The nature of the proteins determines the properties of the matrix, which vary from tissue to tissue.
- Cells can be linked by several types of cell junctions, formed by specialised membrane proteins.
- Epithelial cells are characterised, in part, by their very close packing. They are held together by specialised junctions between adjacent cells.