Lecture 5 - Integumentary System

'cutaneal' and ‘dermal’

pertain to the skin

main components of the Integumentary System

Skin, oil and sweat glands, hair, sensory receptors, and nails.

primary functions of the Integumentary System

Covering and protection, regulation of body temperature, reception of sensory information, synthesis of vitamin D, and elimination of some waste.

three layers of the skin

Epidermis, dermis, and subcutaneous layer.

epidermis

outer layer made of epithelial tissue

dermis

connective tissue layer composed of collagen and elastic fibers. have two regions

tissues found in subcutaneous layer

Adipose and areolar connective tissue.

outermost layer of the epidermis

Stratum corneum

keratinocytes

make up 90% of the epidermis and produce keratin

take about 4 weeks to reach surface of skin unless removed by abrasion or burns

time for keratinocytes to reach surface of skin

Approximately 4 weeks unless removed by abrasion or burns.

melanocytes

make up 8% of epidermis, produce melanin

function of Langerhan cells

contribute to immune defense

function of Merkel cells

function as touch receptors

Papillary Region

upper 20% of dermis, made out of areolar tissue

dermal papillae

Finger-like projections that anchor the epidermis to the dermis.

Reticular Region

composed of dense irregular connective tissue, provides structure containing interlacing collagen and elastic fibers packed with oil glands, sweat glands and hair follicles

Stretch Marks

occur due to dermal tears from stretching, showing limits in elasticity of dermis

Thin skin

covers most of the body characterized by thinner epidermis (0.1 to 0.15mm)

lacks stratum lucidum (2nd epidermal layer)

thick skin

found ONLY on the palms of hands and soles of feet

characterized by thicker epidermis (0.6 to 4.5mm) & distinct layers

lacks hair follicles and sebaceous glands

adapts to high friction areas

melanin

produced in epidermis by melanocytes

melanocytes convert tyrosine to melanin

UV sunlight increases melanin production

same # in everyone with different amount of pigment produced

carotene

found in dermis

yellow-orange pigment (precursor of vitamin A)

found in stratum corneum (1st epidermal layer) and dermis

Hemoglobin

red, oxygen carrying pigment in blood cells

if other pigments absent, pinkness is evident since epidermis is translucent

freckles/liver spots clinical observation

melanocytes in a patch

albinism clinical observation

inherited lack of tyrosine (no pigment)

vitiligo clinical observation

autoimmune loss of melanocytes in areas of the skin produces white patches

hair structure

consists of a visible shaft and a root (below surface) surrounded by follicle

3 layers of hair shaft

medulla, cortex and cuticle

with cross sectional shapes varying by hair type

follicle surrounds root

external & internal root sheath

goosebumps (arrector pilli)

arrector pilli contracts in response to cold or fear causing hair to stand up

hair root plexes

network of nerve endings that detects hair movement, contributing to the sense of touch

function of hair

prevents hair loss, decreases sun burn, protects eye through eyelashes

hair color

determined by the type and amount of melanin produced by melanocytes in the hair bulb

dark hair

contains true melanin

blonde and red hair

has melanin mixed with iron and sulfur, affecting their hue

graying hair

results from a decline in melanin production

white hair

contains air bubbles in medullary shaft

4 specialized exocrine glands found in dermis

Sebaceous glands (sweat), sudoriferous glands (sweat), ceruminous glands (wax), and mammary glands (milk)

sebaceous glands

secretory portion in the dermis

most open onto hair shafts

secretes sebum to keep hair and skin soft, and pliable

inhibits bacterial and fungal growth

acne

Bacterial inflammation of sebaceous glands, often stimulated by hormones at puberty.

eccrine glands (sweat)

most common sweat glands found in most areas of skin

secretory portion in dermis with duct to surface

regulate body temperature through perspiration

apocrine glands (sweat)

sweat glands located in the armpit and pubic region with duct that open onto hair follicle

secretions are more viscous

ceruminous glands

secrete a waxy secretion called cerumen in the ear canal that helps form a barrier against foreign bodies

cerumen contains secretions of oil and wax glands, as well as dead epithelial cells

impacted cerumen may reduce hearing

nails

tightly packed, keratinized cells

nail body is pink due to underlying capillaries

lunula (nail bottom) appears white due to thickened stratum basale (deepest epidermal layer) in that area

cuticle is stratum corneum (1st epidermal layer)

nail matrix

region is deep to the nail root and is where nail growth is

growth is 1mm per week, faster in summer and on most used hand

skin function (thermoregulation)

release of sweat onto the skin (perspiration and its evaporation lowers body temperature)

adjusting flow of blood to the body surface (in moderate exercise more blood brought to surface helps lower temperature, in extreme exercise blood is shunted to muscles and body temperature rises

shivering and constriction of surface vessels (raises internal body temperature as needed)

skin function (skin as a barrier)

Acts as a physical, chemical, and biological barrier

tight cell junctions prevent bacterial invasion

lipids released retard evaporation

pigment protects somewhat against UV light

Langerhan cells alert immune system

skin function (excretion and absorption)

only a minor role is played by the skin (400mL of water evaporates from the skin daily with small amounts of salt, co2, ammonia and urea being excreted)

lipid-soluble substances can be absorbed through the skin such as vitamins A, D, E, K, oxygen, and chemicals like acetone, dry - cleaning fluid, lead, mercury, & the poisons in poison ivy and oak trees

cutaneous skin sensations (6 sensations)

sensations that arise from the skin

include touch, temperature, pressure, vibration, tickling and some pain

skin function (synthesis of Vitamin D)

Sunlight activates a precursor to vitamin D, which is transformed into calcitriol by enzymes in the liver and kidneys

vitamin D is necessary for absorption of calcium from food in the gastrointestinal tract

three major types of skin cancer

Basal cell carcinoma, squamous cell carcinoma, and melanoma.

basal cell carcinoma

least malignant and most common skin cancer

stratum basale (innermost layer) cells proliferate and slowly invade dermis and hypodermis

cured by surgical excision in 99% of cases

squamous cell carcinoma

2nd most common type; can metastasize

involves keratinocytes of stratum spinousm (4th epidermal layer)

usually is a scaly reddened papule on scalp, ears, lower lip or hands

good prognosis if treated by radiation or surgically removed

melanoma

cancer of melanocytes (MOST DANGEROUS)

highly mestastic and resistant to chemotherapy

treated by wide surgical excision accompanied by immunotherapy

ABCD rule for melanoma

A: asymmetry - 2 sides of pigmented area do not match

B: border irregularity - exhibits indentations

C: color variation (black, brown, tan), sometimes red or blue)

D: diameter - larger than 6 mm (size of pencil eraser)

E: evolving - changing in shape, size, color, elevation etc

immediate threat for burns

Dehydration and electrolyte imbalance leading to renal shutdown and circulatory shock.

rule of nines

used to estimate the volume of fluid loss by dividing the body into sections representing 9% of body surface area

all areas of the body except for genitals (having 1%) carrying 9% body surface area

first degree burn

Epidermal damage only with localized redness, edema, and pain

partial - thickness burn

second - degree burn

Epidermal and upper dermal damage, with blisters present

partial - thickness burn

third - degree burn

Involves the entire thickness of skin, with skin color turning gray-white, cherry red, or blackened.

no edema and no pain felt due to loss of nerve endings

skin grafting is usually necessary

full - thickness burn

critical conditions for burns

>25% of body has second-degree burns

>10% has third-degree burns

if face, hands, or feet are affected.

treatment for burns

debridement (removal) of burned skin

antibiotics

temporary covering

skin grafts