Integumentary System Ch. 5 Part 1

Integumentary System Anatomy Epidermal layer Dermal layer Physiology Regulate body temperature Protects connective tissues Sensations – touch, temperature, pressure, pain Excretion – water, salts, heat Immunity Blood reservoir – many tiny blood vessels Makes vitamin D

Cross Section of Skin

Skin has 2 layers Epidermis– outer, thinner portion composed of epithelium Dermis – inner, thick part composed of connective tissue

Epidermis Keratinized stratified squamous epithelium cells Keratinocytes – produce protein keratin – Keratin – fibrous protein for waterproofing and insulation Melanocytes – produce melanin – Melanin – pigment for skin color and absorbs UV light

Epidermis – deep to superficial layers Thin skin – most of the body – Stratum basal (stratum germinativum) – Stratum spinosum – Stratum granulosum – Stratum corneum (thin layer) Thick skin – palms, soles of feet Stratum basale (stratum germinativum Stratum spinosum Stratum granulosum Stratum lucidum Stratum corneum (thick layer

Stratum Germinativum (basale) Basal (base) cell layer (germinal) undergoes continuous mitotic division Produces all the other layers Made up of stem cells – Simple cuboidal or columnar

Stratum spinosum When prepared, shrink to have thorn-like projections Have melanocytes and Langerhans cells – Help with skin immunity to microbes

Stratum granulosum Cell apoptosis occurs here Contains lamellar granules – provide waterproof sealant to skin Transition between alive layers and dead layers of skin

Stratum lucidum Consists of flattened, dead, clear keratinocytes

Stratum corneum Keratinization – accumulation of keratin by moving through epidermal layers Dead cells are sloughed off (shed) and replaced by newly dead cells from deeper layers Made up of dead stratified squamous cells Callus – abnormal thickening of stratum corneum

Dermis Composed of connective tissue Blood vessels, nerves, glands, hair follicles 2 regions – Papillary – Reticular

Papillary region Consists of areolar C.T with elastic fibers Dermal papillae – projections into the dermis create ridges: fingerprints Contain tactile receptors – corpuscles of touch – Nerves sensitive to touch Pacinian corpuscles – sensitive to pressure Free nerve endings – sensitive to temperature

Reticular region Made of connective tissue, mainly collagen and elastic fibers Also contains – Adipose tissue – Hair follicles – Nerves – Oil glands – Sweat glands

Skin color Genetically determined Melanin – brown-black pigment, number the same in all races; production of melanin differs Carotene – yellow-orange pigment Hemoglobin – reddish/pinkish tint in Caucasians