Week 6 Lecture 1 Chapter 5
The Integumentary System
• Skin and its
accessory
structures
–
–
–
–
–
–
structure
function
growth and repair
development
aging
disorders
General Anatomy
• A large organ
composed of all 4
tissue types
• 22 square feet
• 1-2 mm thick
• Weight 10 lbs.
• The skin protects us against environmental hazards. It’s
the FIRST LINE OF DEFENSE
• The skin helps regulate body temperature.
• The skin is always being attacked by microorganisms
• Skin makes up about 16% of the total body weight.
• Tanning – ancient Rome women lightened their skin
with lead based cosmetics. At the time of Shakespeare
before industrial revolution un-tanned skin = high status
• Europe 18/19th century fair skin with freckles was
attractive while tan skin = manual labor like a farmer
• 20th century- indoor work increased. Tan skin = leisure
class. 1920 Coco Channel accidentally got tan on
French Riviera. She ignited a fad.
Introduction to the Integumentary
System
• Connections
– Cardiovascular system
• Blood vessels in the dermis
– Nervous system
• Sensory receptors for pain, touch, and temperature
Skin Functions
• Protection of underlying tissues and organs against
impact, abrasion, fluid loss and chemical attacks.
• Excretion of salts, water, wastes. 500 ml a day=1 pint
• Temperature- via adipocytes which insulate to keep
warmer, or evaporative ( sweating ) for cooling.
• Synthesis of D3 ( cholcalciferol )Sunlight hits the skin,
and the subcutaneous cholesterol stimulates D3 which
will go to the liver where it will make some intermediary
products which will go to the kidney which in turn will
make Calcitriol. This will increase the absorption of
calcium and phosphorous from the GI tract and increase
the deposition to he bones.
• Stores lipids in adipocytes
• Detects touch, pressure, pain, temperature, and relays
to the neural system.
Overview
• 2 Major layers of skin
– epidermis is epithelial
tissue only
– dermis is layer of
connective tissue,
nerve & muscle
• Subcutaneous tissue
(subQ or hypodermis)
is layer of adipose &
areolar tissue
– subQ = subcutaneous
injection
– intradermal = within
the skin layer
Overview of Epidermis
• Stratified squamous
epithelium
• Mechanical protection
• Keeps micro-organisms
outside
• Contains no blood vessels
• 4 types of cells
• 5 distinct strata (layers) of
cells
Cell types of the Epidermis
• Keratinocytes--90%
– produce keratin
• Melanocytes-----8 %
– produces melanin pigment
– melanin transferred to other
cells with long cell
processes
• Langerhan cells
– from bone marrow
– provide immunity
• Merkel cells
– in deepest layer
– form touch receptor with
sensory neuron
Epidermis
• Thin Skin
– Covers most of the body
– Has four layers of keratinocytes
• Thick Skin
– Covers the palms of the hands and soles of the feet
– Has five layers of keratinocytes
Layers (Strata) of the Epidermis
• Strata means
LAYER
• Stratum corneum
• Stratum lucidum
• Stratum granulosum
• Stratum spinosum
• Stratum basale
Epidermis
• Stratum Germinativum-basale ( basal cell carcinoma )
– The “germinative layer”
• Has many germinative (stem) cells or basal cells
• Is attached to basal lamina by hemidesmosomes
• Forms a strong bond between epidermis and dermis
– Forms epidermal ridges (e.g., fingerprints)
– Dermal papillae (tiny mounds)
• Increase the area of basal lamina
• Strengthen attachment between epidermis and dermis
Epidermis
Figure 5–4 The Epidermal Ridges of Thick Skin.
Epidermis
• Specialized Cells of Stratum Germinativum
– Merkel cells
• Found in hairless skin
• Respond to touch (trigger nervous system)
– Melanocytes
• Contain the pigment melanin – or not with albinism
• Scattered throughout stratum germinativum
Epidermis
• Stratum Spinosum
– The “spiny layer”
• Produced by division of stratum germinativum
• Eight to ten layers of keratinocytes bound by desmosomes
• Cells shrink until cytoskeletons stick out (spiny)
– Continue to divide, increasing thickness of epithelium
– Contain dendritic (Langerhans) cells, active in
immune response
Stratum Granulosum
• 3 - 5 layers keratinocytes
• Show nuclear
degeneration
• Contain dark-staining
keratohyalin granules
• Contain lamellar granules
that release lipid that
repels water
• Highest level where living
cells are found.
Epidermis
• Cells of Stratum Granulosum
– Produce protein fibers
– Dehydrate and die
– Create tightly interlocked layer of keratin
surrounded by keratohyalin
Stratum Lucidum
• Seen in thick skin on
palms & soles of
feet
• Three to five layers of
clear, flat, dead cells
• Contains keratin
Stratum Corneum
• Exposed layer
• 25 to 30 layers of flat dead
cells filled with keratin and
surrounded by lipids
• Continuously shed – takes
about 15-30 days for cells to
go from the basal layer to
corneum
• Barrier to light, heat, water,
chemicals & bacteria
• Coats surface with lipid
secretions form sebaceous
glands
• Friction stimulates callus
formation
• The skin is water resistant not water proof.
So we lose about 500 ml or 1 pint of water
a day. This is called insensible
perspiration.
• Ocean water is hypertonic. Water leaves
the body which results in dehydration. In
pool water (hypotonic) the water crosses
the epithelium and can increase the size of
cells 4 x the size. This is seen in the soles
and palms.
Keratinization & Epidermal Growth
• Stem cells divide to produce keratinocytes
• As keratinocytes are pushed up towards
the surface, they fill with keratin
• 4 week journey unless outer layers removed
in abrasion. Dead cells can remain an
additional 2 weeks before shedding.
• Hormone EGF (epidermal growth factor) can
speed up process
• Psoriasis = chronic skin disorder
– cells shed in 7 to 10 days as flaky silvery scales
– abnormal keratin produced
Skin Grafts
• New skin can not regenerate if stratum
basale and its stem cells are destroyed
• Skin graft is covering of wound with piece
of healthy skin
– autograft from self
– isograft from twin
– autologous skin
• transplantation of patients skin grown in culture
Dermis
• Connective tissue layer composed of collagen &
elastic fibers, fibroblasts, macrophages & fat cells
• Contains hair follicles, glands, nerves & blood
vessels
• Major regions of dermis
– papillary region -superficial
– reticular region –deeper
– Tattoo ink is held here
– Phagocytes digest the ink
Papillary Region
•
•
•
•
Top 20% of dermis- Superficial layer
Composed of loose CT & elastic fibers
Finger like projections called dermal papillae
Functions
– anchors epidermis to dermis
– contains capillaries that feed epidermis
– contains Meissner’s corpuscles (touch) &
free nerve endings (pain and temperature)
– It’s where dermatitis takes place.
Reticular Region
• Dense irregular connective tissue
• Contains interlacing collagen and elastic
fibers
• Packed with oil glands, sweat gland
ducts, fat & hair follicles
• Provides strength, extensibility &
elasticity to skin
–stretch marks are dermal tears from
extreme stretching
Skin Color Pigments (1)
• Melanin produced in epidermis by melanocytes
– same number of melanocytes in everyone, but
differing amounts of pigment produced
– results vary from yellow to tan to black color
– melanocytes convert tyrosine to melanin
• UV in sunlight increases melanin
production
• Clinical observations
– freckles or liver spots = melanocytes in a patch
– albinism = inherited lack of tyrosinase; no
pigment
– vitiligo = autoimmune loss of melanocytes in
areas of the skin produces white patches
Skin Color Pigments (2)
• Carotene in dermis
– yellow-orange pigment (precursor of vitamin A)
– Found in carrots and squash
– Found in stratum corneum & dermis
• Hemoglobin
– red, oxygen-carrying pigment in blood cells
– if other pigments are not present, epidermis is
translucent so pinkness will be evident
– When scared someone looks white as a ghost b/c blood went from
skin > muscles
– Skin gets flushed and red when body temp increases b/c
superficial blood vessels dilate so skin acts as a radiator to lose
heat.
– Scarlet fever – Strep attacks RBC- the hemoglobin
leaks into the interstitial cells.
Skin Color as Diagnostic Clue
• Jaundice
– yellowish color to skin and whites of eyes
– buildup of yellow bilirubin in blood from liver
disease
• Cyanotic
– bluish color to nail beds and skin
– hemoglobin depleted of oxygen looks purpleblue
• Erythema
– redness of skin due to enlargement of capillaries
in dermis
– during inflammation, infection, allergy or
burns
Skin Color
Figure 5–5b Melanocytes.
Skin Color
• Function of Melanocytes
– Melanin protects skin from sun damage
– Ultraviolet (UV) radiation
• Causes DNA mutations and burns that lead to cancer and
wrinkles
– Skin color depends on melanin production, not
number of melanocytes
Skin Color
• Capillaries and Skin Color
– Oxygenated red blood contributes to skin
color
• Blood vessels dilate from heat, skin reddens
• Blood flow decreases, skin pales
– Cyanosis
• Bluish skin tint
• Caused by severe reduction in blood flow or
oxygenation
Skin Color
• Illness and Skin Color
– Jaundice
• Buildup of bile produced by liver
• Yellow color
– Addison disease
• A disease of the pituitary gland
• Skin darkening
– Vitiligo
• Loss of melanocytes
• Loss of color
Vitamin D3
• Vitamin D3
– Epidermal cells produce cholecalciferol
(vitamin D3)
• In the presence of UV radiation
– Liver and kidneys convert vitamin D3 into
calcitriol
• To aid absorption of calcium and phosphorus
– Insufficient vitamin D3
• Can cause rickets
Vitamin D3
Figure 5–7 Rickets.
Skin Color
Figure 5–6 Skin Cancers.
Hair
• The human body is covered with hair, except
– Palms
– Soles
– Lips
– Portions of external genitalia
• Functions of Hair
– Protects and insulates
– Guards openings against particles and insects
– Is sensitive to very light touch
Accessory Structures of
Skin
• Epidermal derivatives
• Cells sink inward during
development to form:
–
–
–
–
hair
oil glands
sweat glands
nails
Structure of Hair
• Shaft -- visible
• Root -- below the
surface
• Follicle surrounds root
– base of follicle is bulb
• blood vessels
• germinal cell layer
Hair Related Structures
• Arrector pili
– smooth muscle in
dermis contracts
with cold or fear.
– forms goosebumps
as hair is pulled
vertically
• Hair root plexus
– detect hair
movement
Hair
A Single Hair Follicle
Figure 5–10 Hair Follicles and Hairs.
Functions of Hair
• Prevents heat loss
• Decreases sunburn
• Eyelashes help
protect eyes
• Touch receptors (hair
root plexus) senses
light touch
• Healthy loss is 50 a
day.
Glands of the Skin
• Specialized exocrine glands found in
dermis
• Sebaceous (oil) glands
• Sudiferous (sweat) glands
• Ceruminous (wax) glands
• Mammary (milk) glands
Sebaceous (oil) glands- Holocrine gland
• Secretory portion in the dermis
• Most open onto hair shafts
• Sebum
– combination of cholesterol, proteins, fats &
salts
– keeps hair and skin soft & pliable
– inhibits growth of bacteria & fungi(ringworm).
The sebaceous glands forces lipids into the
hair follicle and onto the skin creating a seal.
• Acne- ( can be a sign of EPA deficiency )
– Bacterial inflammation of glands
– secretions stimulated by hormones at puberty
Sudoriferous (sweat) glands
• Merocrine (sweat) glands
– most areas of skin
– secretory portion in dermis with duct to surface
– regulate body temperature with perspiration
• Apocrine old name. it’s now called
Merocrine (sweat) glands
– armpit and pubic region
– secretory portion in dermis with duct that opens onto
hair follicle
– secretions more viscous – the sweat produced is a
nutrient for bacteria which intensifies the odor.
Ceruminous glands
• Modified sweat glands produce waxy
secretion in ear canal
• Cerumin contains secretions of oil and wax
glands
• Helps form barrier for entrance of foreign
bodies
• Impacted cerumen may reduce hearing
• Mammary Glands produce milk – found in
both sexes, but rudimentary until puberty. With
estrogen they develop, with testosterone
they are inhibited.
Nails
• Nails protect fingers and toes
– Made of dead cells packed with keratin
– Metabolic disorders can change nail structure
• Nail production
– Occurs in a deep epidermal fold near the
bone called the nail root
Structure of Nails
• Tightly packed keratinized cells
• Nail body
– visible portion pink due to
underlying capillaries
– free edge appears white
• Nail root
– buried under skin layers
– lunula is white due to thickened
stratum basale
• Eponychium (cuticle)
– stratum corneum layer
– Nail matrix deep to the nail
root is the region from which
the nail growth occurs
Nail Growth
• Nail matrix below nail root produces growth
• Cells transformed into tightly packed keratinized cells
• 1 mm per week
Clubbing of the Finger Nails: Symptom of
Advanced Lung Cancer
• It takes about 8 months for a nail to grow out.
• White spots are called Leukonychia.- Caused by trauma,
fungus, decreased zinc, decreased protein, alcoholism,
allergy to nail products.
• Brittle nails- Decreased Iron and Biotin, thyroid and/or
kidney disease
• Clubbed nails- hypoxia, lung cancer, heart or liver disease
• Spooning- Iron deficiency anemia, systemic fungal
infections, B12 deficiency
• Beaus Lines – Transverse depression- Acute sever illness,
diabetes, chemotherapy, decreased calcium
• Splinter hemorrhages – Red/brown linear streaks, bacterial
endocarditis, trichinosis( parasite-raw food )
• Paronchyia – inflammation of nail root, manicuring, biting,
bacteria, yeast, fungi
Excretion and Absorption
• 500 mL of water evaporates from it daily
• Small amounts salt, CO2, ammonia and
urea are excreted
• Lipid soluble substances can be
absorbed through the skin
– vitamins A, D, E and K, Oxygen and CO2
– acetone and dry-cleaning fluid, lead,
mercury, arsenic, poisons in poison ivy and
oak
Transdermal Drug Administration
• Method by which drugs in a patch enter the
body
• Drug absorption most rapid in areas where
skin is thin (scrotum, face and scalp)
• Examples
– nitroglycerin (prevention of chest pain from
coronary artery disease)
– scopolamine ( motion sickness)
– estradiol (estrogen replacement therapy)
– nicotine (stop smoking alternative)
• In 2002 23,800 pre-mature deaths in U.S
form cancer due to decreased UVB
exposure which decreases the VIT D.
• Other research says 50-63,000 die a year
from decreased Vit. D. this is higher than
8800 deaths from Melanoma or squamous
cell carcinoma.
• 1 in 5 kids ( 80 % hispanics 90 %
afroamericans)
Burns
• 1st Degree – Sunburn – Skin redness erythema =
inflammation of the epidermis.
• 2nd Degree – Entire Epidermis and some dermisBlister, pain, swelling. The accessory structures usually
not effected.
• 3rd Degree – Destroys BOTH epidermis and dermis.
Swelling but less pain b/c sensory nerves are
destroyed with blood vessels.
• If burns cover more than 20 % of the body then it’s
life threatening b/c Increased :fluid loss, evaporating
cooling, bacteria on moist skin. This will lead to wide
spread infection called SEPSIS. This is leading
cause of death in burn victims.
• If burns are on 80 % of the body 50/50 % of living.
• Rules of 9 for body parts and % of burn
Arms 9/9
= 18%
Legs 18/18 = 36%
Trunk 18/18 = 36%
Head 9
= 9%
Genitals
= 1%
______________________
100 %
UVA UVB Rays
• UVAPenetrate the dermis
Produces oxygen free radicals that disrupt collagen
and elastic fibers. This is reason for severe
wrinkling.
Permeate blood vessels and destroys Folic Acid.
UVB
These rays reach the keratinocytes and convert
cholesterol into pre-vit D, which the kidney will later
make into vit D.
The melanin produced protects against DNA damage and
folate breakdown.
Repair of the Integument
• Bleeding occurs
• Mast cells trigger inflammatory response
• A scab stabilizes and protects the area
• Germinative cells migrate around the wound
• Macrophages clean the area
• Fibroblasts and endothelial cells move in,
producing granulation tissue
Repair of the Integument
Figure 5–14 Repair of Injury to the Integument.
Repair of the Integument
Figure 5–14 Repair of Injury to the Integument.
Repair of the Integument
• Fibroblasts produce scar tissue
– Inflammation decreases, clot disintegrates
– Fibroblasts strengthen scar tissue
– A raised keloid may form
Repair of the Integument
Figure 5–15 A Keloid.
Importance of the Integumentary System
Figure 5–16 The Integumentary System in Perspective.
Importance of the Integumentary System
Figure 5–16 The Integumentary System in Perspective.
Importance of the Integumentary System
Figure 5–16 The Integumentary System in Perspective.
Importance of the Integumentary System
Figure 5–16 The Integumentary System in Perspective.