A&P Chapter 5

surface area of the skin

1.8 m^2

covers the entire surface of the body

skin

skin is comprised of what types of tissue

ALL 4 types:
- epithelial
- muscular
- nervous
- connective

other names for the integumentary system

- cutaneous membrane
or
- the integrument

name the 2 regions of the skin:

1. epidermis
2. dermis

attaches the skin to underlying tissue

hypodermis (or subcutaneous tissue)

- outer, thinner region
- lacks blood vessels & has tightly packed cells
- made of stratified squamous epithelium
- 5 layers (strata) ~ deep to superficial

epidermis

what are the 5 layers (strata) of the epidermis?

1. stratum basale
2. stratum spinosum
3. stratum granulosm
4. stratum lucidum
5. stratum corneum

- just superficial to dermis
- constantly dividing; new cells are pushed to the surface, then die & are sloughed off

stratum basale

Cells:
most numerous; produce keratin

keratinocytes

a waterproofing protein

keratin

Cells:
macrophages, a type of white blood cell that phagocytize microbes & then travel to lymphatic system to stimulate the immune system

langerhans cells

Cells:
produce melanin; skin color & protection from UV radiation

melanocytes

Sensory Nerves:
pain & temperature sensations

free nerve endings

Sensory Nerves:
touch sensations

tactile cells (Merkel cells)

- cells can still divide by mitosis
- spiny appearance due to keratin fibers

stratum spinosum

- flattened cells
- contain a lot of keratin & dark-staining pigment granules
- cells are tightly sealed together to form an effective barrier

stratum granulosum

- just deep to stratum corneum
- found only in thick skin (palms of the hand, soles of feet, & elbows)
- provides protection from constant friction

stratum lucidum

- tough, uppermost layer of epidermis
- cells are keratinized (hardened) and dead
- keratin prevents water loss & water gain
- serves as a mechanical barrier against microbes

stratum corneum

- thicker than epidermis
- dense, irregular connective tissue
- numerous sensory nerve fibers

dermis

- fingerlike projections that project into & anchor the epidermis
- they cause ridges in the overlying epidermis which result in fingerprints

dermal papillae

_________ fibers prevent skin from being torn (location: dermis)

collagenous

__________ fibers stretch to allow movement of muscles & joints (location: dermis)

elastic

____________ of dermis supplies oxygen & nutrients to cells of dermis causes temporary changes to skin color (location: dermis)

vascularization

- subcutaneous layers located below the dermis
- composed of loose connective tissue

hypodermis

_________ tissue provides energy storage, insulation, & protective padding (location: hypodermis)

adipose

characterized by excessive body & facial hair in women due to increased production of male sex hormone, treated with injections to kill the hair roots

hirsutism

hair loss

alopecia

male pattern baldness, inherited

androgenic alopecia

sudden onset of patchy hair loss

alopecia areata

- formed from epidermal cells
- located in dermis

hair follicles

portion of hair within follicle

hair root

portion of hair that continues beyond the skin

hair shaft

smooth muscle attached to hair follicle, when contracted it causes the hair to stand up, this causes "goose bumps

arrector pili muscle

formed from specialized epithelial cells

nails

base of the nail

nail root

visible portion of the nail

nail body

fold of skin that hides the root

cuticle

area of rapidly dividing cells, whitish color

lunula (moon)

groups of specialized cells that produce & secrete substances into ducts

glands

Glands:
- present in all regions of the skin; some become more active under stress
- can be as many as 90 glands per square centimeter on the leg & 400 glands per square centimeter on the palms & soles

sweat (sudoriferous) glands

Glands:
- open into hair follicles in anal regions, groin, & armpits
-begin to secrete at puberty
- mammary glands are modified apocrine glands that produce milk only after childbirth

apocrine glands

Glands:
- open onto surface of skin
- active when body heats up; helps lower body temperature
- sweat (perspiration) is mostly water, but also excretes wastes

eccrine sweat glands

Glands:
- modified sweat glands that produce cerumen (earwax)

ceruminous glands

Glands:
- most are associated with a hair follicle
- secrete an oily substance called sebum

sebaceous galnds

inflammation of the sebaceous glands

acne vulgaris

fungal infection often involving skin of the toes & soles

athlete's foot

bacterial infection common in young children, results in pustules that crust over

impetigo

yeast infection mainly in moist areas

candidiasis

inflammation of the skin bc of sensitivity to various chemicals (soaps, detergents)

eczema

caused by a dry scalp producing flaking & itching

dandruff

allergic reaction causing reddish, elevated, & often itchy patches

urticaria (hives)

- classified as either melanoma or nonmelanoma
- begins with mutation of the skin cell DNA

skin cancer

(melanoma/nonmelanoma) cancers - less likely to metastasize

nonmelanoma

2 types of nonmelanoma cancers

1) basal cell carcinoma
2) squamous cell carcinoma

- most common type of skin cancer
- UV radiation causes epidermal basal cells to form a tumor, while suppressing the immune system's ability to detect the tumor

basal cell carcinoma

- 5x less common than basal cell carcinoma
- begins the superficial cells of the epidermis
- more likely to spread than basal cell carcinoma
- about 1% of cases result in death
- triggered by excessive UV exposure

squamous cell carcinoma

(melanoma/nonmelanoma) - most likely to be malignant

melanoma

- starts in the melanocytes
- has the appearance of an unusual mole, or a spilled ink spot
- most common in fair-skinned people
- mole may be elevated above the skin surface, and the skin around it turns gray, white, or red
- increases with the number of

melanoma

5 ways to avoid skin cancer:

1) use broad-spectrum sunscreens of at least SPF15
2) wear protective clothing to cover skin
3) wear a wide brimmed hat
4) wear UV sunglasses
5) stay out of the sun between 10 am & 3 pm
* avoid tanning machines

4 ways wrinkles form:

1) loose epidermis
2) fewer fibers
3) less padding in hypodermis
4)UV damage

6 functions of the skin:

1) help prevent bacterial invasion
2) regulation of water loss & gain
3) assists the urinary system
4) vitamin D production
5) gathers sensory information
6) helps regulate body temperature

(sensible/insensible)
can be felt as water evaporates from the body

sensible

(sensible/insensible)
occurs without one's awareness as water evaporates from the bldy

insensible

body temperature above normal

hyperthermia

examples of hyperthermia:

- heat exhaustion: high body temperature, low blood pressure, profuse sweating, loss of salts
- heat stroke: elevated temperatures, no sweating

body temperature below normal

hypothermia

examples of hypothermia:

- uncontrollable shivering, incoherent speech, lack of coordination
leads to slow pulse, unconsciousness, shallow breathing, & death