Chapter 6 Skin and the Integumentary System Composed of several tissues Maintains homeostasis Protective covering Retards water loss Regulates body temperature Houses sensory receptors Contains immune system cells Synthesizes chemicals Excretes small amounts of waste 1 Skin Cells help produce Vitamin D needed for normal bone and tooth development some cells (keratinocytes) produce substances that simulate development of some WBCs 2 Layers of Skin Epidermis Dermis Subcutaneous layer beneath dermis not part of skin 3 1
Subcutaneous Layer also called the hypodermis composed of loose connective tissue and adipose tissue insulates major blood vessels of the skin found here 4 Epidermis lacks blood vessels keratinized-dead cells filled with keratin to make skin water-proof thickest on palms and soles (0.8-1.4mm) contains melanocytes which make melanin rests on basement membrane stratified squamous 5 Epidermis Layers of Epidermis stratum corneum top layer stratum lucidum Thick skin only stratum granulosum Cells stop dividing Begin making keratin stratum spinosum stratum basale Epidermal ridges 6 2
Dermis on average 1.0-2.0mm thick contains dermal papillae ridges that form fingerprints binds epidermis to underlying tissues irregular dense connective tissue contains muscle cells, glands, hair follicles, blood vessels, specialized sensory receptors, nerve cell processes 7 Hair Follicles made up of epidermal cells tube-like depression extends into dermis hair root-part of hair embedded in the skin hair papilla-projections of connective tissue at bottom of follicle hair shaft-part of hair that extends from skin surface dead epidermal cells melanin-pigment that gives hair its color arrector pili muscle-smooth muscle attached to hair follicle 8 Causes goose bumps 9 3
Nails protective coverings nail plate- cover the nail bed nail bed-skin under the nail plate lunula-thick area of the nail free edge-part that you trim eponychium or cuticle-covers the nail root (growing part) 10 Sebaceous Glands usually associated with hair follicles holocrine glands secrete sebum absent on palms and soles 11 Sweat Glands sudoriferous glands widespread in skin originates in deeper dermis or hypodermis eccrine glands-regulate temperature apocrine glands-associated with body order ceruminous glands-produce cerum (ear wax) mammary glands-produce milk 12 4
Regulation of Body Temperature 13 Problems in Temperature Regulation Hyperthermia abnormally high body temperature Hypothermia abnormally low body temperature 14 Skin Color Genetic Factors varying amounts of melanin varying size of melanin granules albinos lack melanin Environmental Factors sunlight UV light from sunlamps X rays darkens melanin Physiological Factors dilation of dermal blood vessels constriction of dermal blood vessels accumulation of carotene jaundice-yellow color due to liver problems Types of melanin Eumelanin-brownish-black Pheomelanin-reddish-yellow 15 5
Healing of Cuts 16 Healing of Burns First degree burn superficial partial-thickness Second degree burn deep partial-thickness Third degree burn full-thickness Require a skin graft autograft-take skin from on part of the body and replace the damaged skin homograft-take skin from a donor to replace the damaged skin various skin substitutes 17 Rule of Nines Used to estimate the extent of burns to determine the amount of fluid to replace 18 6
Life Span Changes Skin becomes scaly Age spots appear Epidermis thins Dermis becomes reduced Loss of fat Wrinkling Sagging Sebaceous glands secrete less oil Melanin production slows Hair thins Number of hair follicles decrease Nail growth becomes impaired Sensory receptors decline Body temperature unable to be controlled Diminished ability to activate Vitamin D 19 20 Clinical Application Acne Vulgaris most common skin disorder sebum and epithelial cells clog glands produces whitheads and blackheads (comedones) anaerobic bacteria trigger inflamation (pimple) largely hormonally induced androgens stimulate sebum prodiction treatments include antibiotics, topical creams, birth control pills 21 7
Clinical Application Xerosis Excessively dry skin Vitiligo Lose melanocytes Dermatitis Inflammation of the skin, normally involving the papillary layer 22 Clinical Application Skin cancer Most common type of cancer Basal cell carcinoma - orignates in stratum germinatvium; most common skin cancer Squamous cell carcinoma Malignant melanomas - most deadly form of skin cancer ABCD Asymmetry Boarder Color 23 Diameter 8