Without exposure to sunlight, vitamin D 3 must be supplied in the diet. Blistering diseases Bullous pemphigoid and pemphigous vulgaris are diseases that result from autoimmunity to adhesion molecules. The former alters adhesion to the basement membrane in the basal layer, while the latter alters cell adhesion in the spinous layer. Epidermolysis bullosa simplex and epidermolytic hyperkeratosis result from mutations in keratin genes expressed in the basal and spinous cell layers. Proliferative diseases Psoriasis is caused by increased proliferation of keratinocytes resulting in an accumulation of cells in the stratum corneum.
Warts are benign epidermal growths caused by papillomaviral infection of keratinocytes.
It contains extensive vasculature, neurons, smooth muscle, and fibroblasts. It is the principal mechanical barrier of skin. Its networks of elastic fibers function to support the epidermis and bind the skin to the deeper hypodermis. The dermis contains two layers, the papillary layer and the reticular layer . The papillary layer is a loosely woven, superficial connective tissue region that interdigitates with the epidermal ridges and the deeper reticular layer.