Transcript Ch 6 integumentary system notes

Integumentary System
Integumentary System
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7% of total body weight
Components:
1. Cutaneous Membrane
a. Epidermis
b. Dermis
c. Subcutaneous layer
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2. Accessory structures
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Hair
Nails
Glands
Sensory receptors
Functions
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1. protection, cushion, insulate
2. excretion of salts, water, wastes
3. maintenance of temp.
4. synthesis of Vitamin D3
5. storage of nutrients
6. detection of touch, pressure, pain,
and temperature
Epidermis
• Stratified squamous Epithelium
– 4-5 layers thick
– .08-.5 mm thick
Stratum Germinativum
(Basale)
• Innermost layer (deepest)
• 3-5 cells thick
• Contains Merkel cells- sensory for
touch
• Contains melanocytes (pigment
cells) 10-25%
• Cells reproduce in this layer
(mitosis)
Stratum Spinosum (spiny
layer)
• 8-10 cells thick
• Contains Langerhans cells which
defend against microorganisms and
some skin cancers
• Mitosis occurs, but less than in
Basale layer
Stratum Granulosum
(grainy)
• 3-5 cells in thickness
• Most cells stop dividing in this layer
• Produce keratohyalin to start the
hardening/waterproofing of cells
(keratinization)
Stratum Lucidum
• ONLY in THICK
skin (palms &
soles)
• 3-5 cells in
thickness
• Flattened cells
with eleidin
Stratum Corneum
• Outermost layer
• Cell membrane thicken; less
permeable
• Cells die, dehydrate, and keratinize
• Keratinization make skin water
resistant, less permeable
• Average person sheds 40 lbs (18kg)
in a lifetime
Skin Color
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Due to pigments and blood supply
1. Pigments
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b)
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Carotene- orange/yellow
Can be converted into Vitamin A
Obtained from plant foods (carrot/tomato)
Melanin- brown, yellow/brown, or black
Produced by melanocytes
Protects cells from UV rays
UV exposure = melanocyte activity =
color (tan)
– ≈ 1000 melanocytes/ mm²
Skin Color
c) Circulation
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blood in dermis
gives skin a reddish
tint due to the
hemoglobin
Hematoma = bruise
Poor 02 = bluish tint
(cyanosis)
Decubitis Ulcers
(bed sores) are
caused by lack of
blood supply to an
area
Vitamin D
• UV exposure causes epidermal cells
to produce Vitamin D, a vital
hormone, which ensures proper
bone growth and development
• Vitamin D enables calcium
absorption
Dermis
• Binds epidermis to underlying tissue
• Contains blood vessels, neurons,
hair follicles, sweat glands,
fibroblast, macrophages, and white
blood cells
• Strong flexible connective tissue
• 2 layers
Dermis
• 1. Papillary layer ( superficial 20%
of Dermis)
– Loose connective tissue (areolar)
– Contains dermal papillae
• Fingerlike pegs form fingerprints,
palmprints, footprints
Dermis
• 2. Reticular layer (80% of Dermis)
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Dense c.t./collagen and elastic fibers
collagen fibers give tensile strength/resilience
Elastic fibers provide stretch/recoil properties
Separations or less-dense regions between
the collagen bundles form the lines of
cleavage or tension lines of the skin—
important to surgeons
– Flexure lines-deep creases where dermis
attaches tightly to underlying structures
– Site of tatoos
Subcutaneous layer
(hypodermis) (superficial fascia)
• Deep to the skin
• Loose c.t. (areolar) and adipose
• Stabilize the position of the skin/anchors
to underlying structures (mostly muscle),
but allows slide
• Contains blood vessels
• No organs
• Insulator
• Thickens with weight gain
– ♀ Breast/Thighs
– ♂ anterior abdomen “beer belly”
Hair
• Present on all skin
surfaces except palms,
soles, lips , some
external reproductive
organs
• Develops from hair
follicle (epidermal
cells)
• Sense things that
lightly touch our skin,
protect scalp, shield
eyes, filter air we
breathe
Hair
• Grows 2-6 yrs, rests
2 months, then falls
out
• Cells divide at the
base and push others
up which keratinize
(hard) and die
• Root: embedded
• Shaft: above skin
surface
• Three layers:
• medulla
• Cortex
• cuticle
hair
• Color is determined by
two types of melanin and
amount
• Arrector pili muscle
(smooth) is attached to
each follicle; when
contracts = hair is on end
• Vellus- fine “peach fuzz”
(women/children)
• Terminal – long, dark,
typical (scalp/puberty)
• Average growth of 2mm
per/week
nails
• Composed of keratinized stratified
squamous epithelium
• Free edge, body, root
• Cell division occurs in nail root
(matrix) under cuticle; extends out in
half moon shape (lunula)
• As it develops, slides forward over a
layer of epithelium (nail bed)
Glands
• A. Sebaceous
– Usually around
hair follicles
– Produce oily
secretion (sebum)
– Keeps hair and
nails smooth and
soft
– Stimulated by
hormones,
especially
androgens
Sweat
• 99% water, some salts, and traces
of metabolic wastes
• Normally produce 500ml per day
and up to 12 L on hot days and
during vigorous exercise
glands
• B. Sudoriferous
(sweat)
– Originate deep in
dermis or
subcutaneous layer
– Ball shaped coil with
tube leading to
surface
Sudoriferous (sweat)
– Some sweat
glands (eccrine)
respond to high
body temperature
and are scattered
all over the body
– Most abundant on
palms, soles,
forehead, back,
neck
– Watery
Sudoriferous (sweat)
– Some sweat
glands (apocrine)
respond to stress
and are located in
the axillary and
groin regions;
functional after
puberty
– Thick, sticky,
odorous
There are two types of sweat
glands that are modified:
• 1. Ceruminous glands are in the
external ear canal and secrete
cerumen (ear wax)
• 2. Mammary glands which are in the
breasts and secrete milk
Regulation of Body temp.
• Excessive heat production
– Blood vessels in dermis dialate
– Eccrine glands activated-sweat heat
lost
– Respiration may increase; heat lost
thru exhalation
– Heart may beat faster; more blood
moves into the skin
• Excessive heat loss
– Blood vessels in dermis constrict;
decreases blood flow to skin;
conserves heat
– Sweat glands inactive
– Nerves may stimulate muscles to
contract rhythmically – shiver;
generates heat.
burns
• A burn is tissue damage inflicted by
heat, electricity, radiation, extreme
friction, or certain harmful chemicals
• The immediate threat to life from
serious burns is a catastrophic loss
of body fluids
• Fluid seeps from the burned
surfaces
• The body quickly loses water and
salts
• Dehydration leads to fatal circulatory
shock
• After the initial crisis has passed,
infection becomes the main threat.
• Burns are classified by their severity
(depth) as first, second, or third
degree burns
First degree burns
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Only the epidermis is damaged
Redness, swelling, and pain
Heal in a few days
Ex. sunburn
Second degree burns
• Injury to the epidermis and the upper
part of the dermis
• Redness, swelling, blisters, and pain
• Skin regenerates in 3-4 weeks w/
little or no scarring
Third degree burns
• Consume the entire thickness of the
skin
• White, red, or blackened
• The skin might eventually
regenerate, but it is impossible to
wait for this because of fluid loss and
infection
• Skin from other parts of the patients
body must be grafted
• Burns are considered critical if any
of the following conditions exist:
• 1. Over 10% of the body has thirddegree burns
• 2. 25% of the body has seconddegree burns
• 3. There are third degree burns on
the face, hands, or feet.
Rule of nines
• Body surface
divided into 11
regions, each
accounting for 9%
(or a multiple of
9%) of total body
area
Skin cancer
• Skin cancer is the most common
type of cancer, w/ about 1 million
new cases appearing each year in
the U.S.
• Most important risk factor:
overexposure to the UV rays in
sunlight
Basal cell carcinoma
• Least malignant
• Most common
• Cells of the stratum basale proliferate—
invade the dermis and hypodermis
causing tissue erosions
• Dome shaped, shiny nodules
• Develop a central ulcer and a “pearly”
beaded edge
• Grows slowly, metastasis seldom occurs
Squamous Cell
Carcinoma
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Keratinocytes of the stratum spinosum
Scaly, irregular, reddened papule
Grows rapidly
Will metastasize if not removed
If treated early, chance of complete cure
is good.
• Radiation therapy, surgery, or skin
creams w/ anticancer drugs
Melanoma
• Cancer of melanocytes
• Most dangerous, 1 of every 20 skin
cancers
• Melanoma can originate wherever there
is pigment, often from existing moles
• Appears as an expanding dark patch
• Metastasize rapidly
• Key—early detection
• Resistant to chemo and current
immunotherapy treatment, vaccines being
tested.
ABCD (E) rule
• A: asymmetry: the two halves of the spot
or mole don’t match
• B: Border irregularity: the borders have
indentions and notches
• C: Color: the pigment contains several
colors, blacks, browns, tans, blues, reds
• D: Diameter: larger than 6 mm (pencil
eraser)
• E: Elevation: above the skin surface