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