Chapter 5: Integument - Exam 1

Skin Functions

protection, temperature regulation, sensation, matabolic functions, blood reservoir, and excretion/waste elimination

Chemical Protection

sweat and oily secretions kill bacteria

malanin prevents damage caused by UV light

Physical Protection

skin prevents entrance of bacteria by being dry and acidic

Biological Protection

dendritic cells patrol dermis to stop anything that passes through

macrophages destory large sized invaders

Insensible Perspiration

unnoticeable sweat loss during the day

used for making smaller temperature adjusments

Sensible Perspiration

noticeable sweat loss that occurs when excess heat needs to be lost by the body

helps maintain internal body temp and make large temperature adjusments

Skin Temperature Regulation

when colder = blood vessels constrict

when warmer = blood vessels widen

this blood is redirected to deeper body parts like visceral organs = maintains internal body temp and temp of visceral organs

Exteroceptors

cutaneous sensory receptors for the skin

respond to stimuli arising outside the body

can be nociceptors (pain sensation), thermoreceptos (temperature), or mechanoreceptors (mechanical stimuli like pressure)

Skin Metabolic Functions

involved in vitamin D production = necessary for calcium to be absored by the digestive tract and for bone health

Skin Blood Reservoir

5% of the total blood volume can be found in the skin

can be moved by the central nervous system to conserve temperature

Skin Excretion

sweat allows for some elimination of certain nitrogenous wastes (urea, ammonia, uric acid)

Epidermis

unvascularized outermost portion of the skin

a new one is grown every 25-45 days

Dermis

vascularized portion

makes up most of the skin by mass, the hide of the body

made up of strong and flexible connective tissue

has lots of fibroblasts and macrophages with a semifluid matrix

lots of fibers

two layers: papillary and reticular dermis

Hypodermis

lies deep to the dermis, but is not a true structure of the skin

composed mostly of adipose tissue

functions: storage of energy sources, protecton and shock absorption for internal organs, insulation to prevent heat loss, and anchor that holds skin to muscle tissue

Keratinocytes

produce keratin proteins

linked by desmosomes (with some tight junctions)

produce mitotically in response to epidermal growth factor = reproduce from the bottum up

callus formation in certain areas with lots of friction like heels of runners and fingers of guitar players

function: gives epidermis its protective qualities (tough and dry)

Melanocytes

contain melanosomes that contain melanin

Melanosomes

produce melanin pigment thats transferred to keratinocytes

melanin migrates to the sunny side of the keratinocyte = protection from the sun which only shines on the top of the cell

Dendritic Langerhan Cell

move to the epidermis from bone marrow

presenting cells help activate the immune system by screening cells until they find the pathogen, bind to it, and show it to the nearest WBC

Tactile Merkel Cells

present in epidermal-dermal junction

associated with nerve endings - sensory receptor function

help us percieve light touch and vibration

Layers of Epidermis

1. stratum basale

2. stratum spinosum

3. stratum granulosum

4. stratum lucidum

5. stratum corneum

Stratum Basale

base layer - innermost layer

simple layer of stem cells attached to the dermis

rapid division of cells is seen here = maintains skin thickeness and function

composed mostly of keratinocytes with 10-15% melanocytes

Stratum Spinosum

spiny stratified layer

cells contain pre-keratin protein = thick bundles of filaments that resist tension

dendritic cells are most abundant here

Stratum Granulosum

granular layer where keratinization begins

accumulation of two granule types in cells of this layer: keratohyaline and lammelar granules

cells here are especially tough and water resistant

Keratohyaline

type of granule in stratum granulosum

helps with the formation of keratin in upper layers of epidermis

Lammelar Granules

type of granule in stratum granulosum

contains water resistant glycolipid = important for waterproofing cells and preventing water loss through the skin

Stratum Lucidum

clear layer

cells at this layer are not living, has no melanin

diffusion of nutrients and water does not reach this layer so cells are dead

only found in thick skin like the top of the back and the front of the thighs

Stratum Corneum

horny outermost layer

cells here are not living, has no melanin

makes up most of the epidermal thickness

glycolipids between cells help to waterproof this layer

keratin inside cells protect from friction and abrasion

Papillary Dermis

thin areolar connective tissue

fibers are so thin defensive cells can wander freely here

has projections called dermal papillae

Dermal Papillae

projections on dermis that can have pain receptors and tactile corpuscles

projections indent the overlying epidermis that form friction ridges

genetically determined feature, aka: fingerprints

Reticular Dermis

lies deep to papillary dermis

composed of dense irregular connective tissue

forms cleavage lines in skin

forms flexure lines at or near joints

Cleavage Lines

in reticular dermis

not visible externally

lines formed by alternating dense and less dense regions of fibers

useful to suergons who cut parallel to these lines

Flexure Lines

in reticular dermis

dermis is tightly anchored at these lines - doesn’t move easily

dermis is forced to fold forming creases that are externally visible

ex: found over joins like fingers, palms, elbow, wrist, knee, ankle, and feet

Skin Color

determined by melanin, carotene, and hemoglobin

Melanin

polymer that comes in two forms: reddish yellow or brownish black

synthesized by protein tyrosinase

skin pigments depends on amount produced by melanocytes

How does Skin get Darker?

exposure to sun damages DNA in cells

repair signal sent by DNA makes melanin

keratinocytes release chemical to activate melanocytes

Carotene

yellow orange pigment

accumulates in stratum corneum and adipose tissue

can be used by body to produce vitamin A = used for vision and epidermal health

Hemoglobin

pinkish red pigment

oxygenated pigment = color comes from blood supply to dermis

Skin Color Imbalances

jaundice = liver failure with yellow skin

albinism/melanism = genetic cause with extremely light or dark skin

cyanosis = hemoglobin deprived of blood flow causing pale skin

argyria = silver causing blue skin

Hair Pili

grow from follicles in the skin

has 2 regions: root (in skin) and shaft (out of skin)

has 3 layers: medulla, cortex, and cuticle

function: sensory structures and nerves and protection on scalp, eyes, and nose

consist of dead, hard keratinized cells

Medulla

found in skin hair

central core composed of large cells and air space

absent in fine hairs of the body

Cortex

found in skin hair

several layers of flattened cells

Cuticle

outermost layer that is most heavily keratinized

cells in layer are stacked like roof shingles to prevent hair from sticking together (matted hair)

Hair Follicle

results from fold extending from epidermal surface into dermis

has 3 layers: peripheral sheath, glassy membrane, and root sheath

Peripheral Sheath

layer of hair follicle

outermost layer composed of dermis

Glassy Membrane

layer of hair follicle

basement membrane joining the peripheral sheath to the root sheath

Root Sheath

layer of hair follicle

innermost layer derived from the epidermis

Root Hair Plexus

found at the base of the hair follicle (hair bulb)

contains nerve endings that help detect wind direction and allow us to feel stimuli on body

Dermal Papilla

provide capillaries to hair follicles

Arrector Pili

smooth muscle cells attached to the hair follicle

contraction pulls hair follicle upright = goosebumps

Hair Shape

dependent on the hair follicle shape at the skin surface

round = straight hair

oval = wavy/slightly curly hair

flattened = very curly/coiled hair

Hair Color

depends on melanin deposition to cortex of hair

heavy deposition = darker hair

red hair is caused by pheomelanin

grey/white hair is caused by melanin decreasing with age and cortex filling with air

Hair Matrix

composed of rapidly dividing cells from hair bulb of the hair follicle

new cells push old cells up and out

most growth is cyclical = growth phase, resting phase, and shedding phase

hair stages are staggered (not all in the same one)

Vellus Hair

thin/fine hairs

ex: infant and women have more on arm and face

Terminal Hair

thick coarse hairs

typically darker in color

ex: males have more

Hair Thinning

happens typically at older ages when hair loss exceeds hair growth

Baldness

usually influenced by sex chromosomes and genetics (males more likely)

hair follicles respond to androgen hormones differently with time - hair becomes vellus and shed easier

Nails

found on the distal portion of fingers and toes

contain hard keratin

composed of root, nail plate, and free edge

matrix is responsible for growth

function: protective covering for distal portion of fingers and toes, helps dexterity

Sweat Glands

has myoepithelial cells

specialized cells that will contract when stimulated

secretory cells pull materials needed to produce sweat from the blood (mostly water with salts and wastes)

two types: eccrine and apocrine

exercise: starts at head and moves down

nerves/lying: upper lip and palms of hand

Eccrine Sweat Glands

especially abundant on palms, soles of feet, and forehead

more numerous type of sweat gland

simple tubular glands that open directly to skin surface on pores

function: body temperature regulation

Apocrine Sweat Glands

located in axillary and anogenital areas

empty into hair follicles, then release to skin

same sweat components as other gland, but has more fatty substances and proteins

function: not sure, but similar to sexual scent glands in mammals

ex: ceruminous glands (ear wax) and mammory glands

Sebaceous Glands

secretes sebum (oily substance)

function: lubricant for skin/hair, slows water loss from epidermal surface, kills bacteria

Sebum

oil substance that largely lipid based with cellular components

released by emptying into hair follicle first

Skin Cancer

skin exposed to excess UV light can cause this

most common type of cancer

3 major forms: basal cell, squamous cell, and melanoma

Basal Cell Carcinoma

most common form, least malignant

slow growing, metastasis is rare

cells in stratum basale proliferate = UV related

found mostly on face, often colorless with rolled edges

Squamous Cell Carcinoma

second most common

fast growing, will usually metastasize if left untreated = UV related

cancer of keratinocytes of stratum spinosum

appears as scaly, red lesion found mostly on head (not face), and hands

Melanoma

lowest amount of cases but most deadly

metastasized quickly and can be chemo resistant

cancer of melanocytes, can occur spontaneous

1/3 cases come from preexisting moles = not related to UV radiation

early detection is key = ABCDE rule

ABCDE Rule

used to assess possible melanoma moles

asymmetry, border, color, diameter, and evolving

1st Degree Burn

painful, reddened skin, inflammation

no scarring or fibrosis involved in healing

ex: sunburn

2nd Degree Burn

pain, redness, fluid filled pouches (blisters)

takes longer to heal, no scarring or fibrosis

ex: sunburn, mild heat exposure, sometimes radiation

3rd Degree Burn

full thickness burns

treatment: usually IV fluids, skin grafts, and heavy antibiotic use

fibrosis occurs during healing

feel no pain because nerves are burnt off

ex: extreme heat, severe chemical or radiation exposure