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Schedule
9/17- Tissue Practicum, Tissue Drawings Due9/18- Integ Notes; Lab activity (End 1st 6 wks)
9/21- Finish Integ Notes, Finish Lab 9/22- Integ. Lab Due, Disease & Disorder Lecture9/23- Case Studies Whatya have? Whatya have?9/24- Review for Test9/25- Tissue/Integumentary Test (coloring
due)
9/28- Intro to Bones, Bones Lab9/29- Intro to Bones (contd), Bones Lab9/30-10/1-10/2- Vocab 4 & 5 Quiz
The Skin
•Waterproof, stretchable, washable, repairs small rips, cuts and burns
•The skin and the associated organs of sweat and oil glands, hairs, and nails make up the Integumentary system
Fun Facts
• Consists of Skin, Hair, Nails, and Glands
• Avg. makes up about 9-11 lbs. or 7% of your weight
• Regenerates every 25-45 days
Structure• Epidermis: Stratified squamous
epithelium that is keratinized• Dermis: Dense fibrous connective tissue• A burn or friction causes a separation of
the layers : blister• Hypodermis or superficial facia:
subcutaneous tissue; adipose tissue: anchors skin to underlying organs. Shock absorber, insulator
Skin Anatomy AKA Cutaneous Membrane consists of:
epidermis (epithelial) dermis (fibrous) subcutaneous layer (fat) hypodermis
Epidermis• (keratinocytes & melanocytes); avascular; “tissue layer above
skin”; stratified squamous epithelium; BARRIER LAYERFive layers:• Stratum corneum: “horny” layer; dead stratified squamous; look
rough; keratin present (water-repellent protein); can become thick from irritation (callus)
• Stratum lucidum: “clear” layer; dead cells• Stratum granulosum: “granular” layer; thin; cells dying; begin
keratinization (cells move up)• Stratum spinosum: “spiny” layer; protein synthesis with RNA to
generate keratin; living cells• Stratum basale: “base” layer; AKA stratum germinativum; rapid
mitosis; youngest cells; melanin (pigment protects from UV light);
NOTE:
• Thick skin- covers palms, fingertips, soles of feet
• Thin skin – covers rest of body– missing stratum lucidum and sometimes stratum
granulosum
Cells of the Epidermis
• Keratinocytes, melanocytes, Merkel cells and Langerhan’s cells
• Majority of the cells are keratinocytes– Produce keratin, a fibrous protein: protective– Connected by desmosomes and arise in the
stratum basale layer until they rich the outer surface where the dominate the cells content. Here they are dead, scale-like structures
– We shed our skin every 25-45 days
Epidermis• Stratum basale:deepest
layer; contains the only epidermal layer that receive adequate nourishment via diffusion from the dermis
• Cells constantly undergoing mitosis: stratum germinativum
Dermis: True Skin
Contains sensory receptors for pain, pressure, touch, and temperature; vascular; forms basement membrane
• Papillary Layer- thin; projections of collagen and elastin into basement membrane; areolar tissue; elastic fibers ex. fingerprints
• Reticular Layer- “skin network”; thick; dense fibrous connective tissue; elastic fibers (stretchable); arrector pili muscles (attach to hair follicle & contract when cold); stretch marks (tears of elastic fibers)
Papillary Layer
Thin superficial areolar connective tissue with collagen and elastin fibers
Superior surface appears as peg like projections called dermal papillae that indent the epidermis
House Meissner’s corpuscles (touch receptors); pain receptors and capillary loops
Reticular Layer
80 % of the dermal thickness is dense irregular tissue
Contains blood vessels, sweat and oil glands
Deep pressure receptors (Pacinian corpuscles)
Phagocytes: prevent bacteria from penetrating to deeper body layers
II. SKIN COLOR• GENETICS is the key factor• Quantity of melanin
– (yellow to reddish- brown to black)– protects skin from UV radiation
• In melanocytes, use enzyme tyrosinase to convert tyrosine into dark brown melanin pigment, albinos lack DNA code to make tyrosinase
• sunlight increases melanin production by affecting release of hormones
• freckles or moles are accumulations of melanin• other pigments such as carotene or hemoglobin
contribute to skin color
SKIN ColorThree pigments :
1.The amount and kind of melanin (yellow, reddish brown or black)2.The amount of carotene deposited in the stratum corneum and subcutaneous tissue3. The amount of oxygen bound to hemoglobin
SKIN ColorFreckles and pigmented moles are large accumulations of melanin
Melanoctyes are stimulated when the skin is exposed to sunlight
Prolonged exposure causes substantial melanin buildup which helps protect the DNA of viable skin cells from UV radiation by absorbing the light and dissipating the energy as heat
Hair: aka pilicovers all of humans
EXCEPT palms of hands, soles of feet, lips, nipples some genitalia
1. Hair follicle- shaft, root, medulla (inner), cortex (outer), cuticle (cover)
2. Growth- 4 in./year or 2 mm/week; male-pattern
baldness- genetic, sex-influenced, hormones (testosterone)
Nails• Consists of:
– free edge– Body– Root– Cuticle– Lunula– keratin
• growth- 0.5 mm/week• fingernails faster than
toe nails – blood flow?
Skin Glands1. Sweat Glands- AKA sudoriferous;
found in palms, feet, forehead (perspiration/ sweat – 99% water) or found in axillary and anogenital regions – milky color
2. Sebaceous Glands- in dermis; secrete sebum oil for hair and skin; 2/hair; antifungal; antibacterial
3. Ceruminous Glands- cerumen or earwax; can block ear from insects
Sebaceous (Oil) Glands• Found all over except on the soles and palms• Holocrine glands; ducts usually empty into a hair follicle• Sebum: mixture of oily substances and fragmented cells;
acts as a lubricant that keeps skin soft and prevents the hair from becoming brittle; contains chemicals that kill bacteria
Sweat (Sudoriferous) Glands• Two types: eccrine and apocrine
1. Eccrine/merocrine glands: sweat: clear secretion primarily water, salts
2. Apocrine: axillary and genital areas; Secretion contains fatty acids and proteins, as well as the eccrine substances; can appear milky-white or yellow
Skin PhysiologyA. Protection: from microorganisms, chemicals, physical injury,
dehydration, UV lightB. Sensation: receptors C. Excretion: sweat contains uric acid, ammonia, urea, salt,
waterD. Metabolism: Vitamin D production by absorbing UV lightE. Immunity: T cells, Langerhans cells, and macrophages found
in the skin to fight microorganismsF. Temperature Regulation: varies from 37.6oC to 36.2oC; heat
produced comes from metabolism in muscles and glands; heat is lost if blood vessels widen (vasodilation); heat is saved if blood vessels constrict (vasoconstriction); regulated by hypothalamus