Integument System
Chapter 5
Functional Organization of Integument
Integument
System
Cutaneous
Membrane
Epidermis
Accesory
Structures
Hair
Follicles
Dermis
Papillary
Layer
Reticular
Layer
Exocrine
Glands
Nails
The Skin as an Organ
• Largest of the body
• All 4 epithelial tissue types represented
• Ranges in thickness
– Thick (palms, fingertips, soles of feet)
– Thin (rest of body)
• 2 layers
– Epidermis is stratified squamous
• 4/5 layers and 4 cell types
– Dermis is dense irregular CT
• Multiple cell types and accessory structures; 2 layers
• Hypodermis not true integument
• Connective tissue and fat cells
Epidermal Layers
• Stratum basale
– Single row, many nuclei
– Attached to basal lamina
• Stratum spinosum
– Thick layers of ‘spiny’ keratinocytes
• Stratum granulosum
– Thin, 3-5 layers
– Keratincoytes fill w/ keratin
– Cells ‘toughen’ and die
• Stratum lucidum
– Thin, translucent layer
– Only in thick skin
– Few, dead, densely packed keratinocytes
• Stratum corneum
– 20-30 cells thick
– 14 days for cells to reach and remain up to 14
Epidermal Cells
• Merkel cells
– Touch sensitive cells
– Epidermal/dermal border
• Langerhans cells
– Phagocytic cells
– Assist immune system response
– Formed in bone marrow
Epidermal Cells (cont.)
• Keratinocytes
–
–
–
–
Produce keratin
Joined by desmosomes
Formed deep
Dead at surface
• Accelerated on feet/hands
• Calluses from constant friction
• Melanocyte
– Produce melanin
– Formed deep
– Keratinocytes take up
• Skin color due to activity not number
• Tans signal DNA damage, fades as
keratinocytes destroy
Skin Coloration
• Melanin is black, yellow-brown, or brown
– Made by skin and stimulated by sun
– Freckles and moles are accumulations
• Carotene is yellow to orange pigments
– Accumulates in st. corneum and fatty tissue in skin
– Most obvious where stratum corneum is thickest
• Hemoglobin is crimson colored respiratory
pigment
– Reduced blood supply turns skin white
– Poorly oxygenated blood appears blue = cyanosis
• Response to extreme cold or from respiratory disorders
Skin Color Disruptions
• Leathery skin – clumping of elastin fibers from excessive
sun (cancer too)
• Redness – embarrassment, fever, inflammation or allergy
• Pallor/blanching – emotional distress, anemia, low BP
• Jaundice – liver disease, bile pigment deposition
• Bronzing – hypofunctioning of adrenal cortex, Addison’s
• Hematomas – black n blue bruises, escaped blood clots in
tissue
Dermis
• Flexible and strong CT
– Nerve fibers, blood vessels, and lymphatic vessels
• Tearing causes striae or strech marks
• Blisters when epi- and dermis separate by
fluid-filled pocket
• 2 layers
– Papillary layer
– Reticular layer
Dermal Layers
Papillary layer (20%)
• Areolar CT
• Ridged surface projections =
dermal papillae/epidermal
ridges
– On feet and palms
– Increase friction, enhance
grip, and fingerprints (sweat
gland)
• Contain light pain and touch
receptors (Meissner’s
corpuscle)
Reticular layer (80%)
• Dense irregular CT
• Accessory structures
• Collagen fibers and adipose
– Holds water = hydration
• Cleavage lines
– Orientation related to skin
stresses
– Parallel cuts remain closed =
faster healing
– Right angles pulled open with
recoil
• Flexure lines (elbow)
ACCESSORIES OF THE SKIN
Sudoriferous (Sweat) Glands
• Almost everywhere
• Innervation contracts causing secretion
• Eccrine sweat glands
– Palms, soles, forehead
– Hypotonic blood filtrate released by exocytosis
• Body cooling
• Emotional
– Gland in dermis, duct into surface pore
• Apocrine* sweat glands
– Axillary and anogenital regions
– Secretions into hair follicle ducts
– Similar to eccrine secretion
• Starts at puberty = body odor when mixed
w/ bacteria
• Ceruminous
– Cerumen (earwax)
• Mammary glands
Sebaceous (Oil) Gland
• Almost everywhere, but palms and soles
• Holocrine glands (describe secretion mode)
• Secreted onto hair follicle or into a pore
– Softens hair and prevents water loss = brittle
– Lubricates skin
– Antibacterial function
• Disorders
– Whitehead, blackhead, acne
– ‘Cradle cap’
– Dandruff , seborrheic dermatitis
http://z.about.com/d/dermatology/1/0/p/6/Comedone_papule.jpg
Hair
• Other mammals = warmth
• Humans = protection, sensation, filters
– Few areas lack (palms, soles, lips)
• ‘Hair’ (shaft and root) are dead, keratinized
cells
– Ribbonlike = kinky, oval = wavy, round = straight
– Matrix with 3 layers: medulla, cortex, cuticle
• Follicle into dermis  expands to bulb
– Receptors surround
– Papilla w/ capillaries = nutrients
• Arrector pili muscle
• Hair pigment from melanocytes
Nails
• Modified hard keratinized
epidermis
– Protect, grasp, and itch
• Richly vascularized
• Free edge, nail body (stratum corneum), nail
bed (stratum spinosum), and root (lunula)
• Nail folds (lateral and proximal) extend =
eponychium (cuticle)
• Hyponychium (quick)
Burns
• Loss of fluids  renal shut down,
denatured proteins
– IV of fluids immediately
– Extra caloric intake
• Rule of nines
– 11 areas at 9% body (genitals 1%)
– Estimate
• Sepsis
– Protective role decreased after 24 hours
– Immune system done 1 -2 days after
• Classifying
– 1st degree: epidermal damage; redness and swelling (sunburn)
– 2nd degree: epidermis and upper dermis; blisters form (cooking)
– 3rd degree: epidermis and dermis; gray-white/blackened, nerve destruction
• Skin grafting
Integument Functions
• Protection
– Barrier to microorganisms, abrasions, and water loss
• Thermoregulation
– Vasoconstriction or –dilation of blood vessels,
– Goose bumps or sweat
– Fat and hair
• Sensation
– Nerve endings to detect external stimuli throughout
– Meissner’s corpuscles, Merkel discs, Pacinian corpuscles, hair follicle
receptors, and free nerve endings
• Metabolic roles
– Vitamin D from cholesterol
– Proteins to deter wrinkles
• Excretion
– Removes wastes from body (sweat)