Chapter 5 Flashcards
Skin (2 regions)
Epidermis- superficial region
Dermis- underlies epidermis
Hypodermis
Not part of skin
Mostly adipose tissue
Anchors skin to underlying structures
Muscles
Epidermis
Keratinized stratified squamous epithelium
4 or 5 layers
4 cell types
5 Layers of Epidermis
Deep to Superficial Stratum Basale Stratum Spinosum Stratum Granulosum Stratum Lucidum Stratum Corneum
4 Cell Types of Epidermis
Keratinocytes
Melanocytes
Dendritic (Langerhans) Cells
Tactile (Merkel) cells
Keratinocytes
Produce fibrous protein keratin
No long living, stratified squamous cells
Location; mostly in epidermis
Connected by desmosomes
Melanocytes
10-25% of cells in deepest epidermis
Produce pigment melanin
Dendritic (Langerhans) Cells
Macrophages- involved in the immune system
Tactile (Merkel) Cells
Sensory touch receptors
Layers of Epidermis: Stratum Basale (Basal Layer)
Deepest epidermal layer Firmly attached to dermis Single row of stem cells -Actively mitotic -Produces two daughter cells --One cell journeys from basal layer to surface
Layers of Epidermis: Stratum Spinosum (Prickly Layer)
Several layers thick
Cells contain web-like system of filaments attached to desmosomes
Abundant dendritic cells
Layers of Epidermis: Stratum Granulosum (Granular Layer)
Thin- 4 to 6 cell layers Cell appearance changes -Cell flatten -Nuclei and organelles disintegrate -Keratinization begins
Layers of Epidermis: Stratum Lucidum (Clear Layer)
Only in thick skin
Thin, Translucent band superficial to the stratum granulosum
A few rows of flat, dead keratinocytes
Layers of Epidermis: Stratum Corneum (Horny Layer)
20-30 rows of dead, flat, anucleate keratinized membranous sacs 3/4 of epidermal thickness Cells Functions: -Protection of deep layers -Protection from physical factors -Barrier
Cell Differentiation in Epidermis
Cells change from stratum basale to stratum corneum
Accomplished by specialized form of apoptosis (flake off)
Dermis
Strong, flexible connective tissue Many cells Fibers in matrix bind together Contents: -Nerve fibers -Blood and lymphatic vessels -Epidermal hair follicles -Oil and sweat glands Two layers -Papillary -Reticular
Papillary Layer
Areolar connective tissue with collagen and elastic fibers and blood vessels
Dermal Papillae
Dermal Papillae
Superficial peglike projections into the epidermis Contents: -Capillary loops -Meissner's corpuscles (Touch receptors) -Free nerve endings (Pain receptors) Function: -Enhance Gripping -Contributes to sense of touch -Contributes to sense of pain -Fingerprints
Other Skin Markings
Striae
Blister
Striae
Slivery-White Scars
stretch marks
Extreme stretching causes dermal tears
Blister
From acute, short term trauma
Fluid-filled pocket that separates epidermal and dermal layers
Skin Color
Three pigments contribute to skin color
- Melanin- only pigment made in skin
- Carotene
- Hemoglobin
Melanin
Two forms -Reddish-yellow to Brownish-black Color is due to amount Produced in melanocytes -Same relative number in all people Freckles and pigmented moles -Local accumulations of melanin Sun exposure stimulates melanin production
Carotene
Yellow to orange pigment
-most obvious in palms and soles
Can be converted to vitamin A for vision and epidermal health
Yellowish-tinge of some Asians- carotene and melanin variations
Hemoglobin
Pinkish hue of fair skin
Skin Color in Diagnosis Cyanosis
Blueish
Low oxygen
Skin Color in Diagnosis Erythema
Redness
Fever, Hypertension, Inflammation
Skin Color in Diagnosis Pallor
Blanching
Anemia, Low blood pressure, fear, anger
Skin Color in Diagnosis Jaundice
Yellowish
Liver disorder
Skin Color in Diagnosis Bruises
Clotted blood beneath skin
Appendages of the Skin
Derivatives of the Epidermis
Hair and Hair Follicles
Nails
Sweat Glands
Sebaceous (oil) glands
Hair
Dead keratinized cells of hard keratin -More durable than soft keratin of skin Functions include: -Warn insects on skin -Physical Trauma -Heat loss -Sunlight Hair pigments -Melanin gives it color -Gray/white is decreased melanin production, increased air bubbles in shaft
Hair Follicles
Extend form epidermal surface to dermis Two layered wall- part dermis, part epidermis Hair bulb -Expanded deep end -Hair follicle -Sensory nerve endings- touch receptors -Hair matrix
Arrector Pili
Smooth muscle attached to hair follicle
Responsible for “goosebumps”
Types and Growth of Hair
Vellus Hair
-Pale, fine body hair of children and adult females
Terminal Hair
-Coarse, long hair of eyebrows, scalp
-At puberty
Nutrition and hormones affect hair growth
Follicles cycle between active and regressive phases
Average 2.25mm growth per week
Lose 90 scalp hairs daily
Hair Thinning and Baldness
Alopecia
-Hair thinning in both sexes after age of 40
True Baldness
-Genetically determined and sex-influenced condition
-Male pattern baldness caused by follicular response to DHT (dihydrotestosterone)
Nails
Scalelike modifications of epidermis
Protective cover for distal, dorsal surface of fingers and toes
Contain hard keratin
Sweat Glands
All skin surfaces except nipples and parts of external genitalia
Two main types
-Eccrine
-Apocrine
Contain myoepithelial cells
-Contract upon nervous system stimulation to force sweat into ducts
Eccrine Sweat Glands
Most numerous Abundant on palms, soles, and forehead Ducts connect to pores Function in thermoregulation -Regulated by sympathetic nervous system Secrete Sweat
Apocrine Sweat Glands
Confined to axillary and anogenital areas
Secretes sweat + fatty substance + proteins
-Viscous; milky or yellowish
-Odorless until bacterial interactions (body odor)
Duct empty into hair follicles
Begin functioning at puberty
Sebaceous (Oil) Glands
Widely distributed -not in thick skin of palms and soles Secrete into hair follicles Inactive until puberty -Stimulated by hormones (especially androgens) Secrete oily secretion -Bactericidal -Softens hair and skin
Functions of Integumentary System
Protection Body Temperature Regulation Cutaneous Sensation Metabolic Functions Blood Reservoir Excretion
Protection 3 Barriers
Chemical
Physical
Biological
Protection (Chemical)
Skin secretions
-Low pH retards bacterial multiplication
Melanin
-Defense against UV radiation damage
Protection (Physical)
Flat, dead cells of stratum corneum surrounded by lipids
Keratin and glycolipids block most water
Limited penetration of skin
Protection (Biological)
Dendritic cells of epidermis
-present foreign antigens to white blood cells
Macrophages of dermis
-present foreign antigens to white blood cells
DNA
-absorption of UV radiation
-Radiation converted to heat
Body Temperature Regulation
If body temperature rises
-Dilation of dermal vessels
-Increased sweat gland activity cool the body
Cold external environment
-Dermal blood vessels constrict
-Skin temperature drops to slow passive heat loss
Cutaneous Sensations
Sensory receptors (part of nervous system) detect temperature, touch, and pain
Metabolic Functions
Synthesis of vitamin D (precursor and collagenase)
Converts carcinogens and some hormones
Blood Reservoir
Up to 5% of body’s blood volume
Excretion
Nitrogenous wastes and salt in sweat
Skin Cancer
Most skin tumors are benign and do not metastasize
Risk Factors:
-Overexposure to UV radiation
-Frequent irritation of skin
3 Major Types of Skin Cancer
Basal Cell Carcinoma
Squamous Cell Carcinoma
Melanoma
Basal Cell Carcinoma
Common -Most common Skin Layers -Stratum Basale Cells proliferate and invade dermis and hypodermis Malignancy -Least malignant Prognosis -Surgical excision -99% of cases are cured
Squamous Cell Carcinoma
Common -Second most common Skin layers -Keratinocytes of stratum spinosum Appearance -Scaly red on scalp, ears, lower llip, and hands Malignancy -Yes, typically metastasize Prognosis -Good -Treated by radiation therapy or removed surgically
Melanoma
Cancer of melanocytes
Common
-Most dangerous
Malignancy
-Highly metastatic and resistant to chemotherapy
Prognosis
-Treated by wide surgical excision accompanied by immunotherapy
Key to survival is early detection- ABCD rule
ABCD Rule
A: Asymmetry; two sides of the pigmented area do not match
B: Boarder Irregularity; exhibits indentations
C: Color; contains several (black, brown, tan, sometimes red or blue
D: Diameter; larger than 6mm (size of pencil eraser)
Burns
Tissue damage caused by heat, electricity, radiation, certain chemicals -denatures proteins and kills cells Immediate Threat -Dehydration and electrolyte imbalance To evaluate burns -Rule of nines -Used to estimate volume of fluid loss
Burns Classified by Severity
Partial-Thickness Burns
-First Degree- epidermal damage only; redness, swelling, pain
-Second Degree- epidermal and upper dermal damage; blisters appear, pain
Full-Thickness Burn
-Third Degree- entire thickness of skin involved, cherry red or blackened, not painful (nerve endings destroyed), skin grafting usually necessary
Severity and Treatment of Burns
Critical if: - 25% of body has Second Degree Burns - 10% of body has Third Degree Burns -Face, hands, or feet bear third degree burns Treatment includes: -Debridement (removal) of burned skin -Antibiotics -Temporary covering -Skin Grafts
Developmental Aspects
Aging Skin
-Epidermal replacement slows, skin becomes thin, dry, and itchy
-Subcutaneous fat and elasticity decrease, leading to cold intolerance and wrinkles
-Increased risk of cancer due to decreased numbers of melanocytes and dendritic cells
-Hair thinning
Ways to prevent/Delay
-UV protection, good nutrition, lots of fluids, good hygiene
