Chapter 6: Integumentary system

dermatology

scientific study of the skin

the integumentary system

skin, hair, nails, and associated glands

integument

the skin. largest and heaviest organ

the skin composes ___ % of body weight

8%

epidermis

stratified squamous epithelium, top layer of the skin

dermis

deeper connective tissue layer of the skin

hypodermis

connective tissue layer (subcutaneous fat) beneath the dermis. not technically part of the skin

normal skin thickness ranges from __ and __

0.5 to 6 mm

skin thickness is based on relative thickness of the…

epidermis (stratum corneum)

thick skin

epidermis is 0.5 mm thick, and stratum corneum is thickest layer. covers palms, soles, fingers, and toes. Sweat glands but no hair follicles or oil glands

thin skin

covers the rest of the body. epidermis is 0.1mm thick and the stratum spinosum is the thickest layer usually

functions of the skin

1. resistance to trauma and infection

2. barrier functions (uv radiation, example)

3. vitamin d synthesis

4. sensation

5. thermoregulation

6. non-verbal communication

keratin

tough protein in epidermal cells. gives physical protection

dermicidin and defensins

antimicrobial peptides. helps skin resist infection

acid mantle

acidic film that protects against pathogens

vitamin D is used for…

bone development and maintenance

features of the epidermis

• keratinized squamous epithelium

• avascular

• sparse nerve endings (most sensations due to nerve endings in the dermis)

keratinocytes

synthesize keratin. makes up majority of epidermal cells

stem cells of epidermis

undifferentiated cells that give rise to keratinocytes

found in the stratum basale (deepest layer)

melanocytes

synthesize melanin

branching process of melanocytes

branches spread among keratinocytes to distribute melanin via melanosomes

tactile cells

touch receptors associated with dermal nerve fibers

tactile disc

tactile cell and associated nerve fiber

dendritic cells

phagocytic immune cells found in stratum spinosum and stratum granulosum

5 cells of the epidermis

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

list the layers of epidermis from deep to superficial

stratum basale ➡ stratum spinosum ➡ stratum granulosum ➡ stratum lucidum ➡ stratum corneum

stratum basale

contains single layer of stem cells and keratinocytes on the basement membrane. Also contains melanocytes and tactile cells.

stratum spinosum

several layers of keratinocytes joined by desmosomes and tight junctions. also contains dendritic cells

stratum granulosum

three to five lanes of flat keratinocytes. contains keratohyalin granules

keratohylain granules

dark staining cells

stratum lucidum

thin layer only found in thick skin. keratinocytes packed with protein eleidin. cells have no nucleus or other organelles.

stratum corneum

up to 30 layers of dead keratinized cells

resists abrasion, penetration, and water loss

explain the history of the keratinocyte

• produced in the stratum basale

• mitosis stops when cells travel away from the dermis

• new keratinocytes push old ones to the surface

• keratinocytes flatten over time and produce lamellar granules

• in 30 to 40 days the keratinocyte reaches the skin surface and exfoliates

calluses/corns

thick accumulations of dead keratinocytes on hands or feet

epidermal water barrier formation

formation occurs in the stratum granulosum

• keratinocytes release filaggrin

• cells produce tough envelope proteins beneath their membranes

• membrane-coating vesicles release lipid mixture that spread out. over cell surface and waterproofs it

• keratinocyte organelles degenerate and the cells die leaving waterproof face enclosing keratin bundles

epidermal water barrier

important for water retention and prevents dehydration.does not prevent absorption at the stratum corneum. tight junctions between keratinocytes and formed in stratum granulosum.

characteristics of the dermis

• 0.2 mm to 4 mm thick

• contains mainly collagen but also elastic and reticular

• vascular

• contains nerve endings

• hair follicles and nail roots are connected to the dermis

dermal papillae

upward, finger-like extensions of dermis

epidermal ridges

downward waves of epidermis

two zones of the dermis

papillary layer and reticular layer

papillary layer

thin areolar tissue in and near dermal papillae

allows mobility of leukocytes and other defense cells

rich in small blood vessels

reticular layer

deeper and thicker layer

contains dense irregular connective tissue

striae

collagen fiber tearing in reticular layer

blister

serous fluid seep out of vessels, separating the epidermis from dermis

hypodermis characteristics

structure: more areolar and adipose tissue

function: pads the body and binds skin to the underlying tissue

subcutaneous fat

subcutaneous tissue that is comprised of predominately adipose tissue. function is energy reservoir and thermal insulation. thicker in women and thinner in elderly and infants

autograft

tissue from another location of same body

allograft

tissue form an unrelated person

eumelanin

dark melanin

Brown and black eumelanin

responsible for tan, brown, and black skin 

Pheomelanin:

lighter, reddish brown

other factors that affect skin color

• dermal blood vessels and white collagen

• carotene

• UV radiation

what causes variation in skin color?

same number of melanocytes but melanin is produced and accumulated differently

dark skin

greater amount of melanin produced by melanocytes

slower breakdown of melanin

melanin granules spread out in keratinocytes

Melanized cells seen throughout the epidermis

light skin

melanin clumped near keratinocytes nucleus

little melanin seen beyond stratum basale

cyanosis

blue skin due to oxygen deficiency

erythema

redness due to increased blood flow

albinism

genetic lack of melanin

pallor

pale due to decreased blood flow

jaundice

yellowing of skin due to high levels of bilirubin, maybe from poor liver function

hematoma

bruise (mass of clotted blood showing through the skin)

eccrine glands

sweat glands, dense on palms, soles, and forehead

sebaceous glands

produce oily sebum

ceruminous glands

apocrine glands found in external ear canal

apocrine glands

found in groin, anal region, areola, beard area

type of sweat gland

doesn’t use. apocrine method usually