Integumentary System Comprises the Skin and Its Appendages

The Integumentary system consists of the skin and its accesory structures and the subcutaneous tissue. The two major layers of the skin are the outer epidermis and the inner dermis.

Epidermis- made of stratified squamous epithelium; cells called keratinocytes.

1. Stratum Germanitivum- the inner most layer where mitosis takes place; new cells produce keratin and die as they are pushed to the surface.
2. Stratum Corneum- the outermost layers of dead cells; keratin prevents loss and entry of water and resists entry of pathogens and chemicals.
3. Langerhans Cells- phagocytize foreign material and stimulate an immune response by lymphocytes.
4. Melanocytes in the lower epidermis, produce melanin. UV rays stimulate melanin production; melanin prevents further exposure to the stratum germanitivum to UV rays by darkening the skin.
Dermis- made of irregular fibrous tissue; collagen provides strength, and elastin provides elasticity, capillaries in the papillary layer nourish the stratum germanitivum.
1. Hair Follicles-mitosis takes place in the hair root; new cells produce keratin,die, and become the hair shaft. Hair of the scalp provides insulation from cold for the head; eyelashes keep dust out eyes; nostril hairs keep dust out of the nasal cavities.
2. Nail Follicles- at the ends of the fingers and the toes; mitosis takes place in the nail root; the nail itself if dead, keratinized cells. Nails protect the ends of the fingers and the toes enable the fingers to pick up small objects.
3. Receptors- detect changes in the skin: touch, pressure, heat, cold, and pain; provide information about the external enviroment that indicates appropriate responses; sensitivity of the skin depends on the number of receptors present.
4. Sebaceous Glands- secrete sebum into hair follicles or to the skin surface; sebum prevents the drying of skin and hair.
5. Ceruminous Glands- secrete cerumen in the ear canals; prevents drying of the eardrum.