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