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Anatomy
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The Integumentary System
Chapter 5
Chapter 5 Outline
Epidermis, dermis, hypodermis- structure/function
Skin color
Sunlight & vitamin D3
Hair
Glands
Nails- structure
Integumentary System
Largest system of the body
16% of body weight
1.5 to 2 m2 in area
1st line of defense
Made up of 2 parts
Cutaneous membrane
Accessory structures
Cutaneous Membrane
Cutaneous membrane has 2 components
Epidermis (outer)
Superficial epithelium (epithelial tissues)
Dermis (inner)
Connective tissues
Accessory Structures
Originate in the dermis
Extend through the epidermis to skin surface
Hair
Nails
Multicellular exocrine glands
Introduction to the Integumentary System
Connected to other systems
Cardiovascular system
Blood vessels in the dermis
Nervous system
Sensory receptors for pain, touch, temperature
Integumentary System
Subcutaneous layer (superficial fascia or
hypodermis)
Loose connective tissue
Below the dermis
Location of
hypodermic injections
Components of the Integumentary System
Functions of Skin
Protects underlying tissues and organs
Excretes salts, water, and organic wastes (glands)
Maintains body temperature (insulation &
evaporation)
Synthesizes vitamin D3
Stores lipids
Detects touch, pressure, pain, and temperature
Basic Organization of the Epidermis
Avascular stratified squamous epithelium
Nutrients, oxygen diffuse from capillaries in dermis
Mechanical & pathogen protection
Cells of the Epidermis
Keratinocytes
Contain large amounts of keratin
Most abundant cells in epidermis
Basic Organization of the Epidermis
Thin SkinCovers most of body
4 layers of keratinocytes Thick Skin
Covers palms & soles
5 layers of keratinocytes
Structure of Thick Epidermis
.
1
2
3
4
5
Stratum Germinativum
Germinative layer
Many germinative cells (basal cells)
Attached to basal lamina by hemidesmosomes
Forms strong bond between epidermis & dermis
Forms epidermal ridges (fingerprints)
Dermal papillae (tiny mounds)
Increase area of basal lamina
Strengthen attachment between epidermis &
dermis
Epidermal Ridges of Thick Skin
Stratum Spinosum
Spiny layer
Produced by division of stratum germinativum
8 -10 layers of keratinocytes bound by desmosomes
Cells shrink until cytoskeletons stick out (spiny)
Continue to divide, increasing thickness of
epithelium
Stratum Granulosum
Grainy layer, 3-5 layers keratinocytes
Stops dividing, starts producing
Keratin- tough, fibrous protein makes up hair, nails
Keratohyalin- forms dense granules promote cross-
linking of keratin fibers
Stratum Lucidum
Clear layer
Found only in thick skin
Covers stratum granulosum
Stratum Corneum
Exposed surface of skin
15 - 30 layers keratinized cells
Water resistant
Shed & replaced every 2 weeks
Stratum Corneum
Keratinization- formation of layer of dead,
protective cells filled with keratin
Occurs on all exposed skin surfaces except eyes
15–30 days for cell to move from stratum
germinativum to stratum corneum
Each of the following is a function of the
integumentary system, except
A. Protection of underlying tissue
B. Excretion of salts & wastes
C. Synthesis of vitamin C
D. Maintenance of body temperature
Perspiration
Insensible perspiration
Interstitial fluid lost by evaporation through the
stratum corneum, pint/day
Sensible perspiration
Water excreted by sweat glands
Dehydration- damage to stratum corneum (burns,
blisters) increase rate insensible perspiration
Burns- reduce water barrier, dangerous fluid loss
Immersion in hypertonic solution (seawater- water flows
out of cells, osmosis)
Skin Color
Skin color is influenced by 2 pigments
Carotene: orange-yellow pigment
Found in orange vegetables
Accumulates in epidermal cells & fatty tissues of dermis
Can be converted to vitamin A
Melanin: yellow-brown or black pigment
Produced by melanocytes in stratum germinativum
Stored in transport vesicles (melanosomes)
Transferred to keratinocytes
Melanocytes
Manufacture melanin from tyrosine and
package it in intracellular vesicles-
melanosomes
Melanocytes- Pigment Transfer
Melanosome are transferred to keratinocytes- color temporary
Melansome will fuse with lysosome and be broken down
Skin Pigmentation
Pale skin- transfer occurs in
stratum germinativum &
spinosum, superficial layers lose
pigmentation
Dark skin- transfer occurs in
stratum granulosum as well,
darker pigmentation
Skin Pigmentation
Skin pigmentation differences generally
not number of melanocytes, different
levels of synthesis of melanin
Freckles
Rates of melanin production different by your own
melanocytes
Face, shoulders
Liver spots- senile lentigos
Function of Melanocytes
Melanin protects skin from sun damage
UV radiation causes DNA mutations & burns-
lead to cancer & wrinkles
Dermal Circulation
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
Illness and Skin Color
Jaundice- buildup of bile produced by liver, yellow
color
Addison disease- disease of pituitary gland,
produce ACTH, skin darkening
Vitiligo- loss of melanocytes, loss of color
Vitamin D3
Epidermal cells produce
cholecalciferol (vitamin D3)
in the presence of UV
radiation
Liver & kidneys convert
vitamin D3 into calcitriol
Aid absorption of calcium
& phosphorus
Insufficient vitamin D3 can
cause ricketsBending of weak
bones under weight
of body
Dermis
Located between epidermis & subcutaneous
layer
Anchors epidermal accessory structures (hair
follicles, sweat glands)
Has 2 components:
Outer papillary layer
Deep reticular layer
Dermis- Papillary Layer
Areolar tissue- contains smaller capillaries, lymphatics, sensory neurons
Dermal papillae projecting between epidermal ridges
Dermis- Reticular Layer
Dense irregular connective tissue- contains larger blood vessels, lymph vessels, nerve fibers
Contains collagen and elastic fibers
Contains connective tissue proper
Dermatitis
Inflammation of papillary layer
Caused by infection, radiation, mechanical
irritation, or chemicals (poison ivy)
Characterized by itch or pain
Dermal Strength and Elasticity
Presence of 2 fibers:
Collagen fibers: very strong, resist stretching but
bend easily- provide flexibility
Elastic fibers: permit stretching & then recoil to
original length- limit flexibility of collagen fibers to
prevent damage to tissue
Skin turgor- properties of flexibility & resilience
Affected by water content
Skin Damage
Sagging and wrinkles (reduced skin elasticity) caused:
Dehydration
Age
Hormonal changes
UV exposure
Stretch Marks
Thickened tissue resulting from excessive stretching of
skin due to pregnancy, weight gain
Lines of Cleavage of the Skin
Collagen & elastic fibers in the dermis
Arranged in parallel bundles
Resist force in a specific direction
Establish important patterns
Parallel cut remains shut, heals well
Cut across (right angle) pulls open & scars
Dermal Circulation
Network of arteries
along reticular
layer
Capillary network
from small
arteries in
papillary layer
Capillary return deep to papillary plexus
Hypodermis
Subcutaneous layer
Lies below the integument
Stabilizes the skin
Allows separate movement
Made of elastic areolar & adipose tissues
Connected to reticular layer of integument by
connective tissue fibers
Has few capillaries and no vital organs
Site of subcutaneous injections using hypodermic
needles
The 2 major components of the dermis
are the
A. Papillary layer and reticular layer
B. Superficial fascia & cutaneous
membrane
C. Epidermis and hypodermis
D. Stratum germinativum & stratum
corneum
Integumentary Accessory Structures
Hair, hair follicles, sebaceous glands,
sweat glands, nails
Derived from embryonic epidermis
Located in dermis
Project through the skin surface
Hair
The human body is covered with hair, except
Palms
Soles
Lips
Functions of Hair
Protects and insulates
Guards openings against particles and insects
Sensitive to very light touch
Hair Follicle
Located deep in dermis
Produces nonliving hairs
Is wrapped in a dense
connective tissue sheath
Base is surrounded by
sensory nerves- root hair
plexus
Accessory Structures of Hair
Arrector pili
Involuntary smooth muscle
Causes hairs to stand up
Produces “goose bumps”
Sebaceous glands
Lubricate the hair
Control bacteria
Hair Follicles
[INSERT FIG. 5.10c]
Exocrine Glands in Skin
Sebaceous glands (oil glands)
Holocrine glands (rupture of secretory cell)
– Secrete sebum- oily lipid secretion, lubricates & protects
epidermis (inhibits bacterial growth)
Sebaceous follicles
Discharge directly onto skin surface
– Face, back, chest, nipples, external genitalia
Sweat glands (sudoriferous)
Two types: apocrine and merocrine (eccrine) glands
Watery secretions
Sweat Glands
Apocrine Sweat Glands- actually merocrine secretion
Found in armpits, around nipples, groin
Secrete products into hair follicles
Begin secreting at puberty
Produce sticky, cloudy secretions, break down & cause odors
Merocrine Sweat Glands
Widely distributed on body surface, especially palms & soles
More numerous than apocrine sweat glands
Discharge directly onto skin surface
Sensible perspiration
Functions: cool skin, excretes water & electrolytes, flushes
microbes & harmful chemicals from skin
Sweat Glands
.
Aprocrine
sweat
gland
Merocrine
sweat
gland
Other Integumentary Glands
Mammary glands
Produce milk
Ceruminous glands
Produce cerumen
(earwax)
Protect the eardrum
Nails
Protect fingers and toes
Made of dead cells packed with keratin
Metabolic disorders can change nail structure
Yellow- chronic respiratory disorder, thyroid disorder, AIDS
Concave- blood disorder
Structure of a Nail
Nail body- visible portion of the nail, covers nail bed
Lunula- pale crescent at base of nail
Sides of nails lie in lateral nail grooves
Surrounded by lateral nail folds
Important Concepts Ch 5
Know functions, structure, cell types of:
Cutaneous membrane
Epidermis- epithelial tissue
– Thin/thick skin, stratums
Dermis- connective tissue
– Outer papillary layer & deep reticular layer
Subcutaneous layer (superficial fascia or hypodermis)
Loose connective tissue below dermis
Skin color production
Cholecalciferol (Vitamin D3) production
Dermal Strength and Elasticity- fibers, damage, lines of
cleavage, circulation
Accessory structures- functions, structure