Chapter 6

dermatology

scientific study and medical treatment of the integumentary system

functions of skin

resistance to trauma and infection, other barrier functions, vitamin D synthesis, sensation, thermoregulation, nonverbal communication

keratin in skin

-Presents a physical barrier to most microorganisms
-Is resistant to weak acids and bases, bacterial enzymes, and toxins

melanin

produced by melanocytes, accumulates in keratinocytes, different skin color (can't have more melanocytes, just more melanin produced)

epidermis

outermost layer of skin; includes dead skin cells, packed with keratin, lacks blood vessels

five epidermal cell types

stem cells, keratinocytes, melanocytes, tactile cells, dendritic cells

stem cells

do mitosis, give rise to keratinocytes, found in stratum basale

keratinocytes

majority of epidermal cells, synthesize keratin

Melanocytes

produce melanin in the stratum basale (branches distribute melanin to keratinocytes)

Tactile (Merkel) cells

sensory touch receptors in basal layer

Dendritic cells

macrophages that help activate immune system; found in stratum spinosum and granulosum (living part of epidermis)

layers of epidermis

stratum corneum
stratum lucidum
stratum granulosum
stratum spinosum
stratum basale

stratum basale

the deepest layer of the epidermis; single layer of stem cells and keratinocytes, few melanocytes and tactile cells

stratum spinosum

Several layers of keratinocytes unified by desmosomes and tight junctions

stratum granulosum

a layer of the epidermis that marks the transition between the deeper, metabolically active strata and the dead cells of the more superficial strata

stratum lucidum

Clear, transparent layer of the epidermis; only in thick skin

stratum corneum

outermost layer of the epidermis; 20-30 layers of dead keratinized cells (resists abrasion and water loss)

thick skin

Covers the palms of the hands and soles of the feet
lacks hair folecules and sebacous glands
Stratum Lucidum

thin skin

Covers most of the body
Hair folecules, sebacous glands, and sweat glans

life history of keratinocytes

-Produced by stem cells in stratum basale
-New cells push others toward surface
-cells grow flat and fill with vesicles
-Cells filled with keratin
*forms water barrier
-Cells die and exfoliate

layers of dermis

papillary and reticular

papillary layer

thin, superficial layer of the dermis, made of loose areolar connective tissue
anchors epidermis
rich in blood vessels
contains tactile (meissner) corpuscles (touch) and free never endings (pain and tem)

reticular layer

Deeper layer of the dermis
dense irregular connective tissue
oil glands, sweat glands, and hair
stretch marks (torn collagen fibers)
lamellar (pacinian) corpuscles (pressure)

fingerprints

Dermal papillae push up and elevate the overlying epidermis (create epidermal ridges). Increase friction

Hypodermis (subcutaneous layer)

Deep to the dermis; not technically part of the skin; made of adipose tissue; helps insulate and energy, lots of blood vessels

cutaneous membrane

skin

skin color

melanin - dark
carotene - red/pink
hemoglobin - yellow (concentrates in corneum)

skin color disorders

cyanosis - blue, oxyegen deficient
erythema - red, increase blood flow
pallor - pale, reduced blood flow
albinism - lack of melanin
jaundice - yellow, bilirubin in blood
hematoma - brusing, clotted blood under skin

hair

compressed, keratinized cells that arise from hair follicles

3 zones of hair

bulb - end of root; matrix cells (mitosis)
root - bellow surfaces
shaft - above surface

3 layers in cross-section of hair

medulla (core)
cortex (middle layer)
cuticle (outer layer)

hair receptors

sensory nerve fibers entwining follicles; detect hair movement

Piloerector muscle (arrector pili)

smooth muscle attaching follicle to dermis
Contracts to make hair stand on end (goose bumps)

functions of hair

protection, light touch, heat retention, and excretion

anatomy of fingernail

composed of thin dead cells packed with hard keratin, stratum corneum

sudoriferous (sweat) glands

merocrine (eccrine) and apocrine

merocrine (eccrine) sweat glands

Most numerous skin glands
ducts open to surface of skin
regulates body temp

apocrine sweat glands

found in axillary, beard, and anogenital areas
ducts lead to hair foliciles
responce to stress
MEROCRINE SECRETION

Sebaceous glands

most open into a hair folicile
helocrine secretion
produce sebum
keeps skin from dyring out
inhibits growth of bacteria

ceruminous glands

modified sweat glands, located in external ear canal, secretes cerumen (earwax)

mammary glands

Milk-producing glands; Apocrine secretion

skin cancers carcinomas

basal cell, squamous cell, and melanoma

basal cell carcinoma

Most common and least severe type of skin cancer; often characterized by light or pearly nodules, seldom mastasizes

squamous cell carcinoma

arises from keratinocytes of stratum spinosum, chance of recovery, tends to mestasize, scaly and redened

Melanoma

The most serious form of skin cancer, less tna 5%, greatest risk factor is family history

melanoma characteristics

ABCDE

• Asymmetrical

• Borders irregular

• Color dark and variation

• Diameter is large (> 6MM)

• Evolving

burns

tissue damage and cell death caused by heat, electricity, UV radiation, or chemicals

debridement

removal of eschar (burned/dead skin)

first degree burn

only epidermis is damaged; skin is red and swollen (sunburm)

second degree burn

A partial-thickness burn involving the epidermis and the dermis.; red, white, tan, blistered and painful

third degree burn

A full-thickness burns that involve the epidermis, dermis, and varying levels of the subcutaneous and underlying structures; requires skin grafts and fluid replacement