Exam 4 Part 1 Flashcards
Integumentary system consists of:
–Skin
–Hair
–Nails
–Sweat glands
–Sebaceous (oil) glands
Skin consists of two distinct regions:
–Epidermis: superficial region
•Consists of epithelial tissue, avascular
–Dermis: underlies epidermis
•Mostly fibrous connective tissue, vascular
Hypodermis (superficial fascia)
Not part of skin but shares some functions
Mostly adipose tissue that absorbs shock and insulates
Anchors skin to underlying structures: mostly muscles
Cells of the Epidermis
Epidermis consists mostly of keratinized stratified squamous epithelium
- Keratinocytes
- Melanocytes
- Dendritic (Langerhans) cells
- Tactile (Merkel) cells
Keratinocytes
Produce fibrous keratin (protein that gives skin its protective properties)
Most common cells of epidermis
Tightly connected by desmosomes
Millions slough off every day
Melanocytes
Produce pigment melanin - protect the nucleus from UV damage
Dendritic (Langerhans) cells
Key activators of immune system
Tactile (Merkel) cells
Sensory receptors that sense touch
Five layers of skin
- Stratum basale
- Stratum spinosum
- Stratum granulosum
- Stratum lucidum (only in thick skin)
- Stratum corneum
Stratum basale (basal layer)
–Deepest of all epidermal layers (base layer)
–Consists of a single row of stem cells
–Actively mitotic
Stratum spinosum (prickly layer)
–Cells joined by desmosomes
–Contains melanosomes and dendritic cells
Stratum granulosum (granular layer)
–Cells accumulate lamellar granules, a water-resistant glycolipid that slows water loss
–Cells above this layer die
•Too far from dermal capillaries to survive
Stratum lucidum (clear layer)
–Found only in thick skin
Stratum corneum (horny layer)
–Flat, anucleated, keratinized dead cells
–Though dead, cells still function to:
- Protect deeper cells from the environment
- Prevent water loss
- Protect from abrasion and penetration
- Act as a barrier against biological, chemical, and physical assaults
Dermis
- Strong, flexible connective tissue
- Cells include fibroblasts, macrophages, and occasionally mast cells and white blood cells
- Fibers in matrix bind body together
–Makes up the “hide” that is used to make leather
- Contains nerves, blood vessels, and lymphatic vessels
- Contains epidermal hair follicles, oil glands, and sweat glands
- Two layers
–Papillary
–Reticular
Papillary Layer
- Superficial layer of areolar connective tissue consisting of loose, interlacing collagen and elastic fibers and blood vessels
- Loose fibers allow phagocytes to patrol for microorganisms
Dermal papillae
Superficial region of dermis that sends fingerlike projections up into epidermis
Reticular Layer
- Makes up ~80% of dermal thickness
- Consists of coarse, dense fibrous connective tissue
–Many elastic fibers provide stretch-recoil properties
–Collagen fibers provide strength and resiliency
•Bind water, keeping skin hydrated
Cleavage (tension) lines
•in reticular layer are caused by many collagen fibers running parallel to skin surface
–Externally invisible
–Important to surgeons because incisions parallel to cleavage lines heal more readily
Flexure lines
•dermal folds at or near joints
–Dermis is tightly secured to deeper structures
–Skin’s inability to slide easily for joint movement causes deep creases
–Visible on hands, wrists, fingers, soles, toes
Three pigments contribute to skin color
Melanin
Carotene
Hemoglobin
Melanin
•Only pigment made in skin; made by melanocytes
–Shields DNA from sunlight
–Sun exposure stimulates melanin production (suntan)
- Two forms: reddish yellow to brownish black
- Color differences are due to amount and form of melanin
- Freckles and pigmented moles are local accumulations of melanin
Carotene
- Yellow to orange pigment
- Most obvious in palms and soles
- Accumulates in stratum corneum and hypodermis
- Can be converted to vitamin A for vision and epidermal health
Hemoglobin
•Pinkish hue of fair skin is due to lower levels of melanin
–Skin of Caucasians is more transparent, so color of hemoglobin shows through
Alterations in skin color can indicate disease
–Cyanosis
•Blue skin color: low oxygenation of hemoglobin
–Erythema (redness)
•Fever, hypertension, inflammation, allergy
–Pallor (blanching or pale color)
•Anemia, low blood pressure, fear, anger
–Jaundice (yellow cast)
•Liver disorders
–Bronzing
•Inadequate steroid hormones (example: Addison’s disease)
–Bruises (black-and-blue marks)
•Clotted blood beneath skin
Derivatives of the epidermis
–Hairs and hair follicles
–Nails
–Sweat glands
–Sebaceous (oil) glands
Hair
- Consists of dead keratinized cells
- None located on palms, soles, lips, nipples, and portions of external genitalia
- Functions:
–Warn of insects on skin
–Hair on head guards against physical trauma
–Protect from heat loss
–Shield skin from sunlight
Hairs (also called pili)
- flexible strands of dead, keratinized cells
- Produced by hair follicles
- Contains hard keratin, not like soft keratin found in skin
–Hard keratin is tougher and more durable, and cells do not flake off
•Regions:
–Shaft: area that extends above scalp, where keratinization is complete
–Root: area within scalp, where keratinization is still going on
Hair pigments are made by
•melanocytes in hair follicles
–Combinations of different melanins (yellow, rust, brown, black) create all the hair colors
•Gray/white hair results when melanin production decreases and air bubbles replace melanin in shaft
- Hair bulb: expanded area at deep end of follicle
- Hair follicle receptor (or root hair plexus): sensory nerve endings that wrap around bulb
–Hair is considered a sensory touch receptor
•Arrector pili: small band of smooth muscle attached to follicle
–Responsible for “goose bumps”
•Hair papilla
–Dermal tissue containing capillaries that supply nutrients to growing hair
Sweat glands AKA sudoriferous glands
•Two main types
–Eccrine (merocrine) sweat glands
–Apocrine sweat glands
Eccrine (Merocrine) Sweat Glands
- Most common type
- Abundant on palms, soles, and forehead
- Ducts connect to pores
- Function in thermoregulation
–Regulated by sympathetic nervous system
•Their secretion is sweat
–99% water, salts, vitamin C, antibodies, dermcidin (microbe-killing peptide), metabolic wastes
Apocrine Sweat Glands
- Confined to axillary and anogenital areas
- Secrete viscous milky or yellowish sweat that contains fatty substances and proteins
–Bacteria break down sweat, leading to body odor (bromhidrosis)
- Larger than eccrine sweat glands with ducts emptying into hair follicles
- Begin functioning at puberty
–Function unknown but may act as sexual scent gland
Modified apocrine glands
–Ceruminous glands: lining of external ear canal; secrete cerumen (earwax)
–Mammary glands: secrete milk
Functions of Skin
–Protection
–Body temperature regulation
–Cutaneous sensations
–Metabolic functions
–Blood reservoir
–Excretion of wastes
Skin Protection
–Chemical barrier
–Physical barrier
–Biological barrier
Chemical barrier
–Skin secretes many chemicals, such as:
- Sweat, which contains antimicrobial proteins
- Sebum and defensins, which kill bacteria
- Cells also secrete antimicrobial defensin
–Acid mantle: low pH of skin retards bacterial multiplication
–Melanin provides a chemical barrier against UV radiation damage
Physical barrier
–Flat, dead, keratinized cells of stratum corneum, surrounded by glycolipids, block most water and water-soluble substances
–Some chemicals have limited penetration of skin
Biological barriers
–Epidermis contains phagocytic dendritic cells
–Dermis contains macrophages
–DNA can absorb harmful UV radiation, converting it to harmless heat
Metabolic Functions
- Skin can synthesize vitamin D needed for calcium absorption in intestine
- Chemicals from keratinocytes can disarm some carcinogens
- Keratinocytes can activate some hormones
Skin Cancer
•Three major types of skin cancer
–Basal cell carcinoma
–Squamous cell carcinoma
–Melanoma
Basal cell carcinoma
–Least malignant and most common
–Stratum basale cells proliferate and slowly invade dermis and hypodermis
–Cured by surgical excision in 99% of cases
Squamous cell carcinoma
–Second most common type; can metastasize
–Involves keratinocytes of stratum spinosum
–Usually is a scaly reddened papule on scalp, ears, lower lip, or hands
–Good prognosis if treated by radiation therapy or removed surgically
Melanoma
–Cancer of melanocytes; is most dangerous type because it is highly metastatic and resistant to chemotherapy
–Treated by wide surgical excision accompanied by immunotherapy
–Key to survival is early detection: ABCD rule
- A: asymmetry; the two sides of the pigmented area do not match
- B: border irregularity; exhibits indentations
- C: color; contains several colors (black, brown, tan, sometimes red or blue)
- D: diameter; larger than 6 mm (size of pencil eraser)
Burns
•Tissue damage caused by heat, electricity, radiation, or certain chemicals
–Damage caused by denaturation of proteins, which destroys cells
- Immediate threat is dehydration and electrolyte imbalance
- To evaluate burns, the Rule of Nines is used
–Body is broken into 11 sections, with each section representing 9% of body surface (except genitals, which account for 1%)
–Used to estimate volume of fluid loss
