Stratum Granulosum 3 to 5 layers Flat keratinocytes Produces lipid-filled vesicles that waterproof the skin forms a barrier between surface cells and deeper layers cuts off surface strata from nutrient supply, so top layers are dead 10
Stratum Lucidum Thin translucent zone seen only in thick skin Keratinocytes Cells have no nucleus or organelles 11 Stratum Corneum
Up to 30 layers of dead, scaly, keratinized cells surface cells flake off (exfoliate) forms dust 12 Life History of Keratinocytes
Produced by stem cells in stratum basale New cells push others toward surface Cells filled with keratin Cells die and exfoliate 13 Dermis
Thickness = 0.6mm to 3mm Composition Dermal papillae - extensions of the dermis into the epidermis collagen, elastic and reticular fibers,
fibroblasts forming the ridges of the fingerprints 2 Layers papillary layer - top reticular layer - bottom 14 Hypodermis
Hemoglobin = red pigment of red blood cells Carotene = yellow pigment concentrates in stratum corneum and fat Melanin = yellow, brown, and black hues pigment synthesis stimulated by UV radiation 16 Abnormal Skin Colors 1
Cyanosis = blueness from deficiency of oxygen in the blood (cold weather) Erythema = redness due to dilated cutaneous vessels (anger, sunburn, embarrassment) Jaundice = yellowing of skin and sclera due to excess of bilirubin in blood (liver disease) 17
Skin Markings Hemangiomas (birthmarks) Freckles and moles = group of melanocytes
freckles are flat; moles are elevated Friction ridges leave oily fingerprints on touched surfaces discolored skin caused by benign tumors of dermal blood capillaries (strawberry birthmarks disappear in childhood -- port wine birthmarks last for life) unique pattern formed during fetal development
Flexion creases form after birth by repeated closing of the hand Flexion lines form in wrist and elbow areas 26 Characteristics of Human Hair Hair (composed of hard keratin) Hair found almost everywhere
differences between sexes or individuals is difference in texture and color of hair 3 different body hair types lanugo -- fine, unpigmented fetal hair vellus -- fine, unpigmented hair of children and women terminal hair -- coarse, long, pigmented hair of scalp 27 Structure of Hair and
Follicle Hair is filament of keratinized cells shaft = above skin; root = within follicle Follicle is oblique tube within the skin bulb is where hair originates vascular tissue (papilla) in bulb provides nutrients
Texture and shape of hair straight hair = round; wavy = oval Hair color = pigment in cells of cortex 28 Hair Color and Texture, Brunette
Eumelanin pigment colors brown and black hair. 29 Hair Color and Texture, Blonde Blond hair contain pheomelanin pigment, but little eumelanin. 30 Hair Color and Texture, Red
Red hair contains little eumelanin but lots of pheomelanin. 31 Hair Color and Texture, Gray and White White hair = air in medulla and lack of pigment in cortex. Gray hair is a mixture of white and pigmented hairs. 32 Structure of Hair Follicle
goose bumps 33 Hair Growth and Loss Hair cycle = 3 repeating cycles anagen is growth stage (90% of scalp follicles)
catagen is shrinking follicle (lasts 2-3 weeks) telogen is resting stage (lasts 1-3 months) Thinning or baldness = alopecia Pattern baldness = genetic and hormonal lasts 6-8 years in young adult
sex-influenced trait(dominant in males, recessive in females); expressed only with high testosterone levels Hirsutism = excessive hair growth hormone imbalance (ovary or adrenal cortex problem) 34 Functions of Hair Body hair (too thin to provide warmth)
Scalp hair heat retention and sunburn cover Beard, pubic and axillary hair indicate sexual maturity and help distribute sexual scents
Guard hairs and eyelashes alert us to parasites crawling on skin prevent foreign objects from getting into nostrils, ear canals or eyes Expression of emotions with eyebrows 35 Fingernail Structure
36 Nails Derivative of stratum corneum densely packed cells filled with hard keratin
Flat nails allow for fleshy, sensitive fingertips Growth rate is 1 mm per week new cells added by mitosis nail plate is visible part of nail medical diagnosis of iron deficiency = concave nails 37 Sweat (Sudoriferous)
Glands Purpose = cool us down 500 ml of insensible perspiration/day sweating with visible wetness = diaphoresis 2 types of sweat glands: Eccrine all over body
Apocrine glands mainly axillary regions produce sweat containing fatty acids found only near hair follicles and respond to stress and sex bromhidrosis is body odor produced by bacterial 38 action on fatty acids Oil (Sebaceous) Glands
Sebaceous- oily secretion called sebum that contains broken-down cells lanolin in skin creams is sheep sebum opens into hair follicle 39 Ceruminous Glands
Found only in external ear canal Their secretion combines with sebum to produce earwax waterproof keeps eardrum flexible bitterness repel mites and other pests 40 Mammary Glands
Develops in female breasts at puberty (male glands do not develop) Function: produce milk after pregnancy Additional nipples (polythelia) 41 Skin Cancer Induced by UV rays of the sun basal cell carcinoma (least dangerous)
arises from stratum basale and invades dermis With surgery 99% survival rate squamous cell carcinoma arises from keratinocytes in stratum spinosum metastasis to the lymph nodes can be lethal malignant melanoma (most deadly)
arises from melanocytes of a preexisting mole 42 Figure 6.11a 43 Figure 6.11b 44 Figure 6.11c
45 ABCD Rule by American Cancer Society A: A symmetry-the 2 sides of the pigmented spot or mole do not match
B: Border irregularity-borders of the lesion are not smooth, but exhibit indentations C: Color- the pigmented spot contains several colors D: Diameter-spot larger than 6 mm (E: Elevation) 46 Burns Hot water, sunlight, radiation, electric shock
or acids and bases Death from fluid loss and infection Degrees of burns 1st-degree = only the epidermis (red, painful and edema) 2nd-degree = epidermis and part of dermis (blistered) 3rd-degree = epidermis, dermis and more is
destroyed epidermis regenerates from hair follicles and sweat glands often requires grafts or fibrosis and disfigurement may occur Treatment IV nutrition and fluid replacement, remove dead tissue, and infection control 47
51 UVA, UVB and Sunscreens UVA and UVB are improperly called tanning rays and burning rays Both thought to initiate skin cancer As sale of sunscreens has risen so has skin cancer those who use have higher incidence of basal cell chemical in sunscreen damage DNA and
generate harmful free radicals PABA, zinc oxide and titanium dioxide Dear 16 year old Me https://www.youtube.com/watch?v=_4jgUcxMez52 M Skin Grafts and Artificial Skin Third-degree burns require skin grafts
Graft options autograft -- tissue from patient isograft -- tissue from identical twin cultured keratinocyte patches Temporary grafts (immune system) homograft (allograft) -- from unrelated person heterograft (xenograft) -- from another species amnion from afterbirth artificial skin from silicone and collagen
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