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[...]... (PAS) stain, because of its abundance of neutral mucopolysaccharides Electron microscopy (Fig 2.9) shows that the lamina densa (rich in type IV collagen) is separated from the basal cells by an electron-lucent area, the lamina lucida The plasma membrane of basal cells has hemidesmosomes (containing bullous pemphigoid antigens, collagen XVII and α6 β4 integrin) The lamina lucida contains the adhesive macromolecules,... activation C Complement fixation Complement activation Neutrophil influx C3b Membrane attack complex Opsonin C5a chemotactic factor Neutrophil III Damage to basement membrane zone, leading to subepidermal blister ( ) C Cell or membrane damage Cell or membrane damage or phagocytosis Fig 2.15 Bullous pemphigoid; a humoral cytotoxic (type II) reaction against a basement membrane zone antigen FUNCTION AND... cells, which express immunoreactivity for various neuropeptides Fig 2.8 Langerhans cell (electron micrograph), with characteristic granule (inset) FUNCTION AND STRUCTURE OF SKIN Epidermal appendages The skin appendages are derived from epithelial germs during embryogenesis and, except for the nails, lie in the dermis They include hair, nails and sweat and sebaceous glands They are described, along with... and reacts to external ones Usually, it adapts easily and returns to a normal state, but sometimes it fails to do so and a skin disorder appears Some of the internal and external factors that are important causes of skin disease are shown in Fig 1.1 Often several will be operating at the same time; just as often, no obvious cause for a skin abnormality can be foundaand here lies much of the difficulty... keratinocytes, aided by entactin, promote adhesion between the basal cells above the lamina lucida and type IV collagen, the main constituent of the lamina densa, below it The laminins act as a glue, helping to hold the epidermis onto the dermis Bullous pemphigoid antigens (of molecular weights 230 and 180 kDa) are synthesized by basal cells and are found in close association with the hemidesmosomes... fine collagen fibres, seen in fetal skin and around the blood vessels and appendages of adult skin Elastic fibres account for about 2% of the dry weight of adult dermis They have two distinct protein components: an amorphous elastin core and a surrounding ‘elastic tissue microfibrillar component’ Elastin (molecular weight 72 kDa) is made up of polypeptides (rich in glycine, desmosine and valine) linked... also responsible for ‘goose pimples’ (bumps) from cold, nipple erection, and the raising of the scrotum by the dartos muscle Striated fibres (e.g the platysma) and some of the muscles of facial expression, are also found in the dermis Blood vessels Although the skin consumes little oxygen, its abundant blood supply regulates body temperature The blood vessels lie in two main horizontal layers (Fig 2.10)... into the epidermis Some of these are associated with Merkel cells (p 14) Free nerve endings detect the potentially damaging stimuli of heat 18 CHAPTER 2 LEARNING POINTS 1 More diseases are now being classified by abnormalities of function and structure rather than by their appearance 2 Today’s patients are inquisitive and knowledgeable If you understand the structure and function of the skin, your explanations... these mediators, histamine (from the granules) and leukotrienes (from the cell membrane) induce vasodilatation, and endothelial cells retract allowing transudation into the extravascular space The vasodilatation causes a pink colour, and the transudation causes swelling Urticaria and angioedema (p 94) are examples of immediate hypersensitivity reactions occurring in the skin Antigen may be delivered... Treatment Temperature control Cannot sweat when too hot: cannot vasoconstrict when too cold Hence temperature swings dangerously up and down Controlled environmental temperature Barrier function Raw skin surfaces lose much fluid and electrolytes Heavy protein loss Bacterial pathogens multiply on damaged skin Monitor and replace High protein diet Antibiotic Bathing/wet compresses Cutaneous blood flow Shunt