 Skin & Appendages (hair, nails, skin glands)

 Cutaneous membrane – skin, primary organ of integumentary system; largest body organ

 Serous membranes – line the body cavities that lack opening to the outside and covers the surfaces of organs in those cavities  Composed of simple squamous epithelium and loose connective tissue  Types  Parietal – portion that lines walls of body cavity (ex. – parietal pleura, parietal peritoneum)  Visceral – portion which covers organs (ex. – visceral pleura, visceral peritoneum)  Cells of serous membranes secrete watery serous fluid that lubricates membrane surfaces

 Mucous membranes – line cavities and tubes opening directly to the exterior  Composed of various types of epithelium & loose connective tissue  Epithelial cells of mucus membranes secrete mucus  Ex. – respiratory, digestive, urinary, & reproductive tracts.

 Synovial membrane – organs that line joint cavities  Composed of only various connective tissues  Cells secrete synovial fluid that lubricates the ends of bones at joints

 Outermost layer composed of stratified squamous epithelium that lacks blood vessels  Deepest layer, stratum germinativum, contains cells undergoing mitosis  Epidermal cells undergo keratinization as they are pushed toward the surface (cytoplasm replaced by the protein keratin – waterproofing)  The outermost layer, stratum corneum, is composed of dead epidermal cells  Production of epidermal cells = rate which they are lost at the surface  Epidermis functions to protect underlying tissues against water loss, mechanical injury, & the effect of harmful chemicals  Melanin – pigment produced by melanocytes, protects underlying cells from the effects of UV light – melanocytes transfer pigment to nearby epidermal cells

 Layer composed largely of fibrous connective tissue that binds the epidermis to underlying tissues  Also contains muscle fibers, blood vessels, & nerve fibers  dermal papillae – parallel rows of peglike projections (grooves) – fingerprints (unique, pattern never changes, only grows)  Deeper areas of dermis are filled with collagen & elastic fibers; number of Elastic fibers & fat storage decrease with age which leads to wrinkles  Dermal blood vessels supply nutrients to all skin cells & help regulate body temp.  Nervous tissue is scattered through the dermis  Some carry impulses to muscles & glands of the skin  Others are associated with various sensory receptors in the skin

 Composed of loose connective tissue & adipose tissue  Adipose tissue helps conserve body heat

 Hair Follicles  Hairs occurs in nearly all regions of the skin; some exceptions – palms, lips, nipples, penis, soles of feet  Hair growth begins from dermal papillae  Hair root lies hidden in follicles & visible part of hair is called the shaft  Arrector pili – smooth muscle that contracts to cause “goose bumps” – regulated body temperature by “trapping air”

 Secrete sebum – helps keep skin & hair soft & waterproof  Usually found attached to hair follicle but some open directly to the skin  Level of secretion increases during puberty & amount of secretions is regulated by sex hormones  Inflamed & overactive glands  acne (plugged )

 Located in nearly all regions of the skin & consist of a coiled tube  Types  Eccrine sweat glands – most numerous; produce sweat to help regulate body temperature; not connected to hair follicles  Apocrine sweat glands (scent glands)  Respond to emotional stress  Found primarily in axilla & around genitalia & usually associated with hair follicles  Secrete a thicker milky secretion  Breakdown of secretion by skin bacteria produces odor  Decrease in activity by both types of glands as a result of aging causes  less able to control body temp.  dryness in skin

Eccrine gland

 Protective covers on the ends of fingers & toes  Produced by epidermal cells that undergo keratinization

 Specialized nerve endings that make it possible for skin to act as a sense organ  Meissner’s corpuscle – capable of detecting light touch  Pacinian corpuscle – detects pressure  Other receptors respond to pain, cold, heat, crude touch, & vibration

 Heat production & loss  Heat is a byproduct of cellular respiration C 6 H 12 O 6 + 6CO 2  6H 2 O + 6CO 2 + ATP + heat  When body temp increases  increase blood flow in dermal vessels  Heat lost to the outside by radiation, conduction, convection, & evaporation  Body temp. decreases  decrease blood flow; sweat glands become inactive  Excessive heat loss  contraction of skeletal muscles  increase cellular  Respiration  produces heat

 Problems in Temperature Regulation  Humid days – sweat doesn’t evaporate  Air temp. may be greater than body temp. – no heat loss by radiation  Heat stroke – stop sweating

 First degree – sunburn – only surface layers involved, no blistering & minimal tissue damage  Second degree – involved deep epidermal & upper dermal damage, blisters, severe pain  Third degree – complete destruction of epidermal & dermal layers; often underlying muscles & bones are damaged; fluid loss, infection

Why are percentages different in the adult and child?

 Squamous cell carcinoma – slow growing malignant tumor of the epidermis, if caught quickly usually doesn’t metastasize  Basal cell carcinoma – most common type, originates in cells of the lower epidermis, much less likely to metastasize  Malignant melanoma – most serious form of skin cancer, can metastasize and lead to death  Kaposi sarcoma – rare, frequently associated with immune deficiencies

Malignant Melanoma Kaposi Sarcoma