Structure and function of the skin

The functions of the skin include:1 Physical protection2 Protection against UV light3 Protection against microbiological invasion4 Prevention of fluid loss5 Regulation of body temperature6 Sensation7 Immunological surveillance.The epidermis• The epidermis is composed of stratified squamous epithelium.
• It is derived from ectoderm.
• Epidermal cells undergo keratinization in which their cytoplasm is replaced with
keratin as the cell dies and becomes more superficial.The epidermis is composed of the following five layers, from deep tosuperficial.1 Stratum germinativum• This is also known as the basal layer.
• The cells within this layer have cytoplasmic projections, which firmly link them
to the underlying basal lamina.• This is the only actively proliferating layer of skin.
• The stratum germinativum contains melanocytes.
2 Stratum spinosum• The stratum spinosum is also known as the prickle cell layer.
• This layer contains large keratinocytes which produce keratin.
• The cells within this layer are joined to each other by tonofibrils (prickles).
3 Stratum granulosum• The stratum granulosum contains mature keratinocytes, which possess cytoplasmic
granules of keratohyalin.• This layer is called the stratum granulosum because of these granules.
• The stratum granulosum is the predominant site of protein synthesis.
4 Stratum lucidum• This is a clear layer.
• The stratum lucidum is only present in the thick skin of the palms and feet.
5 Stratum corneum• The stratum corneum contains non-viable keratinized cells.
• The thick cells of this layer protect against trauma.
• The stratum corneum:
• Insulates against fluid loss
• Protects against bacterial invasion.
• Sebum produced by the sebaceous glands of the stratum corneum is bactericidal
to both streptococci and staphylococci.read more...