3.1.9 Terminally differentiated cells have a short lifetime. 3.1.10 Transit cells migrate towards the epthelium surface. Terminally differentiated cells are anucleate, keratin-filled squames that are continuously shed from the epithelium surface. For the epithelium to remain a constant thickness, the rates of cell production and cell loss must balance. Some cells are completely surrounded by ECM .
Epithelial cells make contact with only one surface.
3.2.2 Epithelial cells are separated from adjacent connective tissue by a specialised matrix called the basement membrane. Many epithelial cells are polarised, with apical surfaces specialised for absorption or secretion and a basal surface attached to the basement membrane. Cell surface receptors, integrins , consist of a combination of so-called a and b subunits. 3.2.13 a 3 b 1 binds to collagen I, fibronectin and laminin. 3.2.14 a 6 b 4 binds to laminin.