chapter 5: skin

A&P 1 - dr tenneson

what are 4 ways the skin impacts body temperature?

what are 4 ways the skin impacts body temperature?

sweat & vasodilation (cool down), adipose & hair (insulate)

how does the skin protect the body?

mechanical injury, infection, UV, dehydration

what does the skin excrete?

heat, water, salt

how much blood does the skin hold? explain why we get pale

8-10% of total blood volume. we get pale when cut because body constricts bv’s & pull blood from skin

what are 6 skin functions?

1. body temp

2. protection

3. sensation

4. excretion

5. blood reservoir

6. immunity

the skin is a large organ composed of all ___ tissue types

4

the superficial epidermis consists of which tissue?

epithelial tissue

the deeper dermis consists of which tissue?

connective tissue

which layer is not technically a part of the skin?

deep subcutaneous layer/hypodermis

the deep subcutaneous layer is made of what 2 tissues?

areolar & adipose

what is thermoregulation?

• what type of feedback is it?

• what are the affectors, control center, & effectors?

body temp homeostasis. negative. skin thermoreceptors (sense temp). hypothalamus. sweat glands & bv’s

name the 5 layers of the epidermis in order from top to bottom

1. stratum corneum

2. stratum lucidum

3. stratum granulosum

4. stratum spinosum

5. stratum basale

the epidermis contains stratified squamous epithelium. it is avascular. it has 4 types of cells & HOW MANY distinct strat (layers) of cells?

4-5

describe keratinocytes

produce the protein keratin. protect skin from heat, microbes, chemicals, lamellar granules (release waterproof sealant)

describe melanocytes

produce melanin → skin color & absorb damaging UV

describe langerhans cells

derived from bone marrow. immune response

describe merkel cells

sensation of touch

_____ keratinocytes are found on the very top layer of skin. they are inactive & mostly keratin.

dead

the very top layer of skin is called the _____ surface

apical

cells transform as they move up through the skin layers over what period of time?

1 month

describe the stratum corneum

many layers. dead cells shed continuously. lipids make it water repellant

describe the stratum lucidum

dead cells. high wear areas only (finger tips, palms, soles)

describe the stratum granulosum

flat dying cells. secrete lipids → waterproof

describe the stratum spinosum

most melanin here

describe the stratum basale

new cells - mitosis. basement layer

define calluses

constant exposure to friction causing corneum layer to abnormally thicken

describe psoriasis

chronic skin disorder. rapid division/movement of keratinocytes. cells shed in 7-10 days as flaky silvery scales

why would there be a need for a skin graft?

injury penetrates through epidermis & gets to stratum basale → skin can’t heal from the bottom up → takes long time to heal

what’s an autograft?

cover would with healthy skin from self

what’s an isograft?

skin graft from twin

what is autologous skin?

transplantation of patient’s skin after growing in culture

where is the dermis located?

below epidermis

what is the dermis?

• what is it composed of?

• what does it contain?

connective tissue layer made of collagen fibers, elastic fibers, fibroblasts, macrophages, & fat cells. contains hair follicles, glands, nerves, & bv’s

what are the 2 major regions of the dermis? (where are each located relative to each other?)

papillary region (superficial) & reticular region (deep)

what part of the dermis produces fingerprints?

dramatic lifts → epidermal ridges

what are stretch marks called? how do they occur? what are they made of?

striae. dermal tears from extreme stretching. dermis not growing fast enough. collagen heals the dermal tears, so they’re scars.

describe dermatoglyphs

fingerprints left by sweat glands open on ridges. increase grip

why don’t twins have identical fingerprints?

chance differences in tissues during development due to environment

what are the 2 types of sweat? which has to do with fingerprints?

liquid sweat & oil sweat. oil

what are lines of cleavage?

• how do they impact surgeons & patients?

indicate the predominant direction of the underlying collagen fibers. incisions made parallel to them make a much smaller scar than those made perpendicular to the lines

what is thin skin & where is it found?

covers all parts of body except palms, digits, soles. lacks epidermal ridges. has less sensory receptors.

what is thick skin & where is it found?

covers palms, digits, soles. has thick epidermal ridges. lacks hair follicles & arrector pili muscles. has more sebaceous glands & sweat glands than thin skin

what are tattoos

injection of permanent dye into dermis

what colors does melanin range from?

yellow to black

melanin is an ____ pigment

epidermal

what are ethnic differences of melanin

same number of melanocytes. variances in amount of melanin production (how active they are)

melanin requires tyrosine. what happens when there is a lack of tyrosine?

albinism or vitiligo

what 4 areas is melanin most common?

extremities, genitals, nipples, face (extremeties & face likely because ancestors needed extra protection from being in the sun alot)

clusters of melanin cause what 2 things?

freckles & age spots

what are freckles called? define them.

ephilides. localized accumulation of melanin in keratinocytes at sun exposed areas. common in fair skinned/red headed people)

what are age spots called? define them.

solar lentigines. localised proliferation of melanocytes. middle age/sun damage. larger & more defined than freckles. don’t disappear in the winter

what is the name for chicken skin? what causes it?

keratosis pilaris. harmless skin condition. buildup of keratin blocks follicles. small, hard bumps. disappear with age

explain skin color inheritance

polygenic inheritance (many genes affect skin color). more activated genes = darker skin)

what color do carotene pigments cause?

where are they located?

which vitamin is a precursor?

what causes excessively this color of skin?

yellow → orange. dermis. vitamin A. carrots are absorbed but don’t break down, so orange pigment goes to skin, causing orange skin

what colors do hemoglobin pigments cause?

what is the reason for each color?

where is it found?

red (oxygenated), pink (deeper, oxygenated), purple (deoxygenated). [amount of O2]. dermis

what is jaundice?

yellowish color of skin & whites of eyes. buildup of yellow bilirubin in blood from liver disease

what is cyanosis

bluish color to nail beds & skin. hemoglobin depleted of oxygen looks purple-blue

what is erythema?

redness of skin due to enlargement of capillaries during inflammation, infection, allergy, or burns

what are 6 epidermal derivatives

1. hair

2. sudoriferous glands (sweat)

3. sebaceous glands (oil)

4. ceruminous glands (wax)

5. nails

6. dermatoglyphs

describe hair shaft

project above skin. dead keratinized cells

what do round & oval hair shafts indicate?

round = straight. oval = curly

where is the hair root located?

below skin

where is the hair medulla?

innermost layer

where is the hair cortex?

middle layer, pigment

where is the hair cuticle layer?

outer layer, keratinized cells

where is the hair follicle?

surrounds root

what are the 2 types of sheaths are involves with hair follicles?

external root sheath & internal root sheath

where is the hair bulb located?

base of follicle

what is hair papilla?

areolar connective tissue; matrix (germinal layer = hair growth)

what are arrector pili?

• what is their purpose?

smooth muscle; elevates hair for insulation & minimizes air flow

what is the purpose of hair root plexus?

touch

what are the 6 layers of the hair root & follicle

medulla, cortex, cuticle, internal root sheath, external root sheath, dermal root sheath

what is terminal hair of the scalp?

longer & thicker than vellus hair. always associated with sebaceous gland to keep hairs flexible

what are the 2 basic kinds of hair? give examples of each

1. vellus: arms, legs

2. terminal: scalp, eyelashes, eyebrows, androgen-sensitive areas

what factors impact the growth of scalp hair?

illness, diet, surgery, hormones, chemo

at what length does hair usually stop growing? why?

2-3 feet. theory is that force of gravity is detected by matrix cells

what are the 3 functions of scalp hair?

cushion, from injury, uv protection, insulation

what 2 things cause male pattern baldness?

DHT (type of testosterone) & genetics

what is lanugo

fine, nonpigmented hair covering fetus

what is vellus

short, fine hair replacing lanugo. sense of touch

what is gooseflesh

raises hair to prevent heat loss

what does nasal hair do

filters & protects airways/lungs

what is the purpose of axillary hair & pubic hair?

possibly to enhance pheromone release
- (pheromones: chemicals released from 1 individual that effects other individual)

• not well understood

• associated with oily sweat glands

• sex hormones here

• hairs release pheromones

define hirsutism

increased number of hairs in androgen sensitive areas on females

hirsutism occurs because of high androgen levels. where do these high levels come from?

adrenal glands

what is hypertrichosis

increased hair growth in non-androgen sensitive areas

what are 2 types of hair removal? what is the difference between them?

1. electrolysis: permanent

2. laser therapy: temporary

mechanical hair removal [does/doesn’t?] cause hair to grow more rapidly, but sometimes thicker diameter

doesn’t

what are the 4 types of skin glands?

1. sebaceous (oil)

2. sudiferous (sweat)

3. ceruminous (wax)

4. mammary (milk)

which type of gland connects to hair follicles to keep hair shafts flexible?

sebaceous

where are sebaceous glands NOT located?

palms & soles

what is sebum

skin oil

sebum

• contains cholesterol, proteins, fats, salts

• moistens hair

• _____ & softens skin

• inhibits growth of what 2 things?

• waterproofs

• bacteria & fungi

where do blackheads get their color from?

melanin

acne

• cystic can lead to scarring

• bacterial inflammation of _____

• secretions are stimulated by _____ at puberty

• glands

• androgens

how does acne occur?

bacteria → inflammation → duct closes → infection can’t get released → builds up

what are 2 types of sudoriferous glands?

eccrine & apocrine

what other type of gland is histologically similar to sudoriferous glands?

mammary

where are eccrine glands located?

most areas of skin - hands, feet, forehead

does this refer to eccrine or apocrine sweat glands?

• ducts terminate at pores at the surface of the epidermis

eccrine