CONTENTS 



The differentiation of epidermal cells 

 Hard and soft keratins 

 The specialized appendages 



Localized epidermal thickenings 

 Scales 

 Horns 



The digital tips : claws, nails, hoofs 

 Feathers 

 Hairs 



The phylogeny of hair 

 Other possibly keratinized structures 

 III Differentiation and Protein Synthesis 

 The cytology of keratinizing cells 



The basal layer cells 



Cell contacts during differentiation 

 The dermoepidermal junction 

 The development of basal membranes and their role in the 

 formation of epithelia 

 The differentiated layers and the variety of cell products 

 The epidermis 



Tonofibrils . . 



Keratohyalin 



The hair follicle 



Intracellular differentiation in the hair bulb 



The feather follicle 



The avian secreted keratins 

 The synthesis of protein in epidermal systems 

 Cytology of cells which form protein 

 Biochemistry of protein synthesis 

 Secondary and tertiary structures 

 Synthesis in retaining systems 

 Synthesis in fibre-forming systems 

 The supermolecular organization of fibrous tissues (tertiary 

 structure) 

 Macromolecular fibrous texture 

 Fibrogenesis 



Collagen 



Fibrous insulin 

 Silk fibroin — aggregation of the molecule after unfolding 

 Organization of fibrous tissues 

 Epidermal fibrils 

 IV The Growth of Epidermal Structures 

 The epidermis as a growing organ 



