BIO 202 chapter 6

integumentary system

hair, nails, cutaneous glands

stratum basale

most vulnerable organ

skin

skin

largest and heaviest organ

epidermis

stratified squamous epithelium

dermis

deeper connective tissue layer

hypodermis

adipose tissue layer below the skin

dermatology

scientific study and medical treatment of integumentary system

stratum lucidum

stratum granulosum

stratum spinosum

resistance to trauma and infection

keratin, dermic and defense's, acid mantle

thin skin

hair follicles, sebaceous glands, and sweat glands

skin barrier functions

water, UV radiation, harmful chemicals

vitamin D synthesis

skin carries out first step-- liver and kidneys complete rest

sensation

skin extensive sense organ; receptors for temp, touch, pain, and more

thermoregulation

thermoreceptors, vasoconstriction/ vasodilation, perspiration

stratum corneum

nonverbal communication

facial expression; important in social acceptance and self image

thick skin

sweat glands, but no hair follicles or sebaceous (oil) glands
palms of hands and soles of feet

keratinized stratified squamous epithelium

includes dead cells at skin surface packed with keratin proteins

avascular

lacks blood vessels
Depends on the diffusion of nutrients from underlying connective tissue

five epidermal cell types

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

stem cells

undifferentiated cells that give rise to keratinocytes

keratinocytes

great majority of epidermal cells, synthesize keratin

melanocytes

synthesize melanin that shields DNA from UV radiation

tactile cells

light touch receptor cells associated with dermal nerve fibers

dendritic cells

macrophages originating in bone marrow that guard against pathogens

4 events in stratum granulosum

1. Keratohyalin granules release filaggrin—a protein that binds keratin into tough bundles
2. Cells produce tough envelope proteins beneath their membranes
3. Membrane-coating vesicles release lipid mixture that spreads out over cell surface and waterproofs it
4. Keratinocytes’ organelles degenerate and the cells die

epidermal water barrier

water retention is fostered by tight junctions between skin cells and the waterproofing that occurs in the stratum granulosum

papillary layer

thin zone of areolar tissue in and near the dermal papilla
rich in small blood vessels

reticular layer

thicker layer of dense, irregular connective tissue
stretch marks (striae)

hypodermis

contains more areolar and adipose tissue
pads body and binds skin to underlying tissues
common site of drug injection due to many blood vessels

melanin

Most significant factor in skin color
Produced by melanocytes, accumulates in keratinocytes

eumelanin

brownish black

pheomelanin

reddish yellow (sulfur containing)

hemoglobin

pigment in red blood cells; adds reddish to pink hue in skin

carotene

Yellow pigment acquired from egg yolks and yellow/orange
vegetables; Concentrates in stratum corneum and subcutaneous fat

UV light harmful effects

causes skin cancer, breaks down folic acid

UV light benefits

stimulates vitamin D synthesis

cyanosis

blueness due to oxygen deficiency (Grandmas fingers turn blue)

erythema

redness due to increased blood flow to skin

pallor

paleness due to decreased blood flow to skin

jaundice

yellowing due to bilirubin in blood (can be caused by liver)

hematoma

bruising; clotted blood under skin

friction ridges

Markings on the fingertips that leave oily fingerprints (unique pattern, remains unchanged throughout life)

flexion lines (creases)

Lines on the flexor surfaces of the digits, palms, wrists, elbows

Hemangiomas

(birthmarks) Patches of discolored skin caused by benign tumors of dermal capillaries

accessory organs

Hair, nails, and cutaneous glands

Pliable soft keratin

makes up stratum corneum

compact hard keratin

makes up hair and nails

Pilus/ Pili

aka hair follicle

3 hair zones

bulb, root, shaft

bulb

swelling at the base where hair originates in
dermis or hypodermis

root

remainder of the hair in the follicle

shaft

portion of hair above the skin surface

dermal papilla

Bud of vascular connective tissue encased by bulb
Only source of nutrition for hair

hair matrix

Region of mitotically active cells immediately above
papilla
Hair’s growth center

3 layers of hair

medulla, cortex, cuticle

medulla

Core of loosely arranged cells and air spaces

cortex

Constitutes bulk of the hair
Consists of several layers of elongated keratinized cells

cuticle

Composed of multiple layers of very thin, scaly cells that overlap each other
Free edges directed upward

follicle

diagonal tube that extends into the dermis and possibly
hypodermis, contains the hair root and has two principal layers

epithelial root shaft

Extension of the epidermis lying adjacent to hair root
Widens at deep end into bulge—source of stem cells for
follicle growth

connective tissue root sheath

Derived from dermis but a bit denser
Surrounds epithelial root sheath

hair receptors

sensory nerve fibers entwining follicles

piloerector muscles

(erector pili) smooth muscle attaching follicle to dermis

black and brown hair

eumelanin

red hair

pheomelanin

blond hair

intermediate amount of pheomelanin and very little eumelanin

gray and white hair

hair have little or no melanin

nail plate

hard part of nail

free edge

overhangs the fingertip

nail body

visible attached part of nail

nail root

extends proximally under overlying skin

apocrine sweat glands

groin, anal region, axilla, areola of nipple beard area of men
Produce sweat that is milky and contains fatty acids

bromhidrosis

Disagreeable body odor produced by bacterial action on sweat from apocrine glands

merocrine sweat glands

Simple tubular glands; Watery perspiration that helps cool the body
MOST NUMEROUS SKIN GLAND

myoepithelial cells

Found in both apocrine and eccrine glands
Contract in response to stimulation by sympathetic nervous system and squeeze perspiration up the duct

acid mantle

inhibits bacterial growth

diaphoresis

Sweating with wetness of the skin
• 1 L sweat per hour may be lost during exercise

cutaneous transpiration

Water loss from skin not due to sweating
• Water diffuses between the keratinocytes and evaporates from the skin surface

sebaceous glands

flask-shaped and have short ducts opening into hair follicles
holocrine secretion style

sebum

oily secretion of sebaceous glands

ceruminous glands

secrete a combination of both sebum and dead epithelial cells to form cerumen

mammary glands

Produce milk

mammary ridges

(milk lines) Two rows of mammary glands in most mammals

basal cell carcinoma

Most common skin cancer
Least dangerous because it seldom metastasizes
forms in stratum basale

Squamous Cell Carcinoma

Arises from keratinocytes of stratum spinosum
Tends to metastasize to lymph nodes and may become lethal

Melanoma

arises from melanocytes
less than 5% of skin cancers

burns

leading cause of accidental deaths

burn deaths

Fluid loss, Infection, Toxic effects of eschar (burned, dead tissue)

debridement

removal of eschar

first degree burn

Only involves the epidermis
• Redness, slight edema, and pain
• Heals within days

second degree burn

(partial-thickness burn) Involves part of dermis, May appear red, tan, or white; blistered and painful, Two weeks to several months to heal and may leave scars

third degree burn

(full-thickness burn) Involves all of dermis and often some deeper tissues, Often requires skin grafts, Needs fluid replacement, infection control, supplemental nutrition

autograph

tissue from another location on the same person’s body

split-skin graft

involves taking epidermis and part of the dermis from undamaged area such as the thigh or buttocks

isograft

tissue from identical twin

homograft

(allograft) tissue from unrelated person