Introduction to the Integumentary System The integument is the largest system of the body 16% of...
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Transcript of Introduction to the Integumentary System The integument is the largest system of the body 16% of...
Introduction to the Integumentary System
The integument is the largest system of
the body
16% of body weight
1.5 to 2 m2 in area
The integument is made up of two parts
______________________ membrane (skin)
Accessory structures (hair, nails, exocrine glands)
Introduction to the Integumentary System
Fig 5–1
Introduction to the Integumentary System
Origin
Ectoderm
Cells that respond to FGF2 turn into nervous tissue. Cells
that don’t turn into skin
Connections
Cardiovascular system
Blood vessels in the papillary layer of the dermis
Nervous system
Sensory receptors for pain, touch, and temperature
Introduction to the Integumentary System
Functions of Skin
Protects underlying tissues and organs (U.V., invaders)
Excretes salts, water, and organic wastes (glands)
Maintains body temperature (insulation and evaporation)
Synthesizes vitamin D3
Stores lipids
Detects touch, pressure, pain, and temperature
Epidermis
The most abundant cells of the epidermis are ____________.
Contain large amounts of keratin
Epidermis is avascular stratified squamous epithelium
Nutrients and oxygen diffuse from capillaries in the dermis
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
Lacks hair and sebaceous glands
Epidermis
Fig 5-3
The S. coreum would be thinner in thin skin. The S. lucidum is found only in thick skin.
Epidermis
Stratum Germinativum (Stratum Basale) 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 ____________________(e.g., fingerprints)
Dermal papillae (tiny mounds) Increase the area of basal lamina
Strengthen attachment between epidermis and dermis
Epidermis
Fig 5-4
Fig. 5-2
Dermal papilla: Tiny mounds that (1) increase the area of the basal lamina and (2) strengthen the attachment between the epidermis and the dermis
Epidermis
Specialized Cells of Stratum Germinativum
______________________(1% of cells in the skin)
Found in hairless skin (sensory function)
Respond to touch (trigger nervous system)
______________________ (3% of cells in the skin)
Contain the pigment melanin
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 (______________) cells, active in
immune response
Epidermis
Stratum Granulosum
The “grainy layer”
Cells stop dividing, produce protein fibers, dehydrate,
and die
Keratin:
– a tough, fibrous protein
– makes up hair and nails
Keratohyalin :
– dense granules
– cross-link keratin fibers
Epidermis
Stratum Lucidum
The “clear layer”
Found only in thick skin
Covers stratum granulosum
Epidermis
Stratum Corneum
The “horn layer”
Exposed surface of skin
15 to 30 layers of keratinized cells
Water resistant
Shed and replaced every 2 weeks
Epidermis
Keratinization
The formation of a layer of dead, protective
cells filled with keratin
Occurs on all exposed skin surfaces except
eyes
Skin life cycle
It takes 15–30 days for a cell to move from
stratum germinativum to stratum corneum
Dandruff is caused by excessive shedding of cells from the outer layer of skin in the scalp. Thus
dandruff is composed of cells from which epidermal layer?
1. Stratum germinativum2. Stratum spinosum3. Stratum corneum4. Stratum granulosum
Skin Color Skin color is influenced by
Two pigments ______________________:
– orange-yellow pigment– found in orange vegetables– accumulates in epidermal cells and fatty tissues of the
dermis– can be converted to vitamin A
______________________:– yellow-brown or black pigment– produced by melanocytes from tyrosine in the stratum
germinativum– stored in transport vesicles (melanosomes)– transferred to keratinocytes
Blood circulation (red blood cells)
Skin Color
Fig 5-5
(contains melanin)
(in melanosome)
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
Production of cholecalciferol (Vit. D3) within epidermal cells
Stimulates secretion of melanocyte stimulating hormone from
keratinocytes (this gives you a tan)
Skin color depends on melanin production (bigger
melanosomes), ____________ number of melanocytes
Skin Color
Localized differences in rates of melanin production by melanocytes: Freckles:
Small pigmented areas with irregular borders on relatively pale skin.
Most abundant on surfaces with greater exposure to the sun (e.g., face).
Lentigos: Similar to freckles, but have regular borders and contain
abnormal melanocytes.
Senile lentigos (liver spots/age spots): Variable pigmented areas on sun-exposed skin in older
individuals with pale skin.
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 (i.e., yellow pigment accumulates in
body fluids)
Addison disease A disease of the pituitary gland Skin darkening (i.e., secretion of large qunatities of
ACTH, a hormone structurally similar to MSH)
Vitiligo (1% of population) Loss of melanocytes (attacked by lymphocytes) Loss of color
Skin Cancer
Basal cell carcinoma = most common. Squamous cell carcinomas = restricted to areas
of sun-exposed skin.
Malignant melanomas = metastasize through the lymphatic system. A = Asymmetry B = Border C = Color D = Diameter
Why does the skin of a fair-skinned person appear red during exercise in hot weather?
1. Sunlight stimulates erythrocyte production in skin.
2. Blood is diverted to the superficial dermis to eliminate heat.
3. Sunlight bleaches fair skin, allowing blood to be seen.
4. Heat stimulates cutaneous blood vessels, causing leaks.
Vitamin D3
Vitamin D3
Epidermal cells in s. spinosum and s. basale 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
Essential for bone maintenance and growth
Insufficient vitamin D3
Can cause __________________ in children and osteomalacia in adults.
Vitamin D3
Fig 5-7
In some cultures, women must be covered completely, except for their eyes, when they go
outside. Explain why these women exhibit a high incidence of problems with their bones.
1. UV light prevents calcium deposition in bones.
2. Melanin production is necessary for bone growth.
3. Cloth prevents oxygen from diffusing into skin and bones.
4. UV light is necessary to produce the hormone cholecalciferol (vitamin D3).
Epidermal Growth Factor (EGF)
Is a powerful peptide growth factor
Is produced by glands (salivary and duodenum)
Is used in laboratories to grow skin grafts
Functions of EGF Promotes division of germinative cells
Accelerates keratin production
Stimulates epidermal repair
Stimulates glandular secretion
The Dermis
The Dermis
Is located between epidermis and
subcutaneous layer
Anchors epidermal accessory structures (hair
follicles, sweat glands)
Has two components Outer papillary layer
Deep reticular layer
The Dermis
The Papillary Layer Consists of areolar tissue Contains smaller capillaries, lymphatics, and sensory
neurons Has dermal papillae projecting between epidermal
ridges
The Reticular Layer Consists of dense irregular connective tissue Contains larger blood vessels, lymph vessels, and
nerve fibers Contains collagen and elastic fibers Contains connective tissue proper
The Dermis
Dermatitis
An inflammation of the papillary layer
Caused by infection, radiation, mechanical
irritation, or chemicals (e.g., poison ivy)
Characterized by itch or pain (due to
abundance of sensory receptors in skin.
The Dermis
Dermal Strength and Elasticity Presence of two types of fibers
Collagen fibers:– very strong, resist stretching but bend easily
– provide flexibility
Elastic fibers:– permit stretching and then recoil to original length
– limit the flexibility of collagen fibers to prevent damage to tissue
Properties of flexibility and resilience
Skin turgor:
Skin Damage (dermal level) Sagging and wrinkles (reduced skin elasticity)
are caused by: Dehydration (loss of skin turgor) Age Hormonal changes UV exposure
Stretch Marks (Thickened tissue resulting from excessive stretching of skin due to): Pregnancy Weight gain/loss Note: Tetinoin (Retin-A), a derivative of Vit. A,
increases blood flow to dermis and stimulates dermal repair leading to a decrease in wrinkles.
The Dermis
Lines of Cleavage
Collagen and elastic fibers in the
dermis Are arranged in parallel bundles
Resist force in a specific direction
Lines of cleavage establish important
patterns A parallel cut remains shut, heals well
A cut across (right angle) pulls open and
scars
Fig 5.8
The Hypodermis
The __________________ layer or hypodermis Lies below the integument
Is connected to the reticular layer of integument by connective tissue fibers
Is made of elastic areolar and adipose tissues
(Subcutaneous fat deposits can be reduced by lipoplasty)
Has few capillaries and no vital organs (only the superficial region or reticular layer of the dermis has large arteries and veins.
Is the site of subcutaneous injections using hypodermic needles
Hair
Hair, hair follicles, sebaceous glands,
sweat glands, and nails
Are integumentary accessory structures
Appendages of the skin that represent
specializations of keratinocytes that extend from
the connective tissue to the skin
Are derived from embryonic epidermis
Are located in dermis
Project through the skin surface
Hair
The Hair Follicle
Is located deep in dermis
Produces nonliving hairs
Is wrapped in a dense
connective tissue sheath
Base is surrounded by
sensory nerves (root hair
plexus)
Hair
Hair Shaft Structure
Medulla
The central core
Cortex
The middle layer
Cuticle
The surface layer
Cross-Section Through a Hair Follicle
Fig 5.10
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
Hair
Accessory Structures of Hair
_______________________
Involuntary smooth muscle
Causes hairs to stand up
Produces “goose bumps”
________________________
Lubricate the hair
Control bacteria
Fig 5.10
Hair Hair Color:
Produced by melanocytes at the hair papilla
Determined by genes
Alopecia Areata:
Ability to produce hair is gone (2% of population)
Due to immune system attack on the hair follicles
Male Pattern Baldness:
Hair growth is inhibited by testosterone receptor alterations (50% of
men over 50)
Rogaine can stimulate production of growth factors that stimulate
weakened hair follicles to create larger amounts of hair
Which two events are possible results of the contraction of the arrector pili muscle?
1. Goose bumps/release of sebum
2. Sweating/contraction of underlying muscles
3. Goose bumps/localized increase in blood flow
4. Localized pallor/release of sebum
Sebaceous Glands and Sweat Glands Exocrine Glands in Skin
Sebaceous glands (oil glands)
Simple branched alveolar glands are associated with
hair follicles
Holocrine glands
Secrete sebum (lipids and other stuff that lubricate and
protect the epidermis while inhibiting bacteria)
Sweat glands
Two types: apocrine glands and merocrine (eccrine)
glands
Watery secretions
Clinical Correlations
Folliculitis: Local inflammation of hair follicle as a result of a
bacterial infection.
Furuncle or “boil”: Abscess from blockage of a gland’s duct.
Acne: Due to increased concentration of sex hormones
during puberty.
Seborrheic dermatitis: Inflammation around abnormally active sebaceous
glands Sebaceous glands and sweat glands
Sebaceous Glands and Sweat Glands
____________________ sweat glands
Found in armpits (axillae), around nipples, and groin
Secrete products into hair follicles
Produce sticky, cloudy secretions
Break down and cause odors
Surrounded by myoepithelial cells
Squeeze apocrine gland secretions onto skin surface
In response to hormonal or nervous signal
Sebaceous Glands and Sweat Glands
__________________ (Eccrine) sweat glands Widely distributed on body surface Especially on palms and soles Coiled, tubular glands Discharge directly onto skin surface Sensible perspiration (water is excreted by sweat glands) Water, salts, and organic compounds Functions of merocrine sweat gland activity
Cools skin Excretes water and electrolytes Flushes microorganisms and harmful chemicals from skin
Other Integumentary Glands
Mammary glands: Anatomically related to apocrine sweat glands Sexual and pituitary hormones control their
development and secretion Produce milk
Ceruminous glands: Modified sweat glands in external ear Produce cerumen (earwax) Protect the eardrum
Control of Glandular Secretions
Control of Glands Autonomic nervous system
Controls sebaceous and apocrine sweat glands Works simultaneously over entire body
Merocrine sweat glands Are controlled independently Sweating occurs locally
Thermoregulation Is the main function of sensible perspiration Works with cardiovascular system Regulates body temperature
What are the functions of sebaceous secretions?
1. Inhibits the growth of bacteria
2. Lubricates and conditions the surrounding skin
3. Lubricates and protects the keratin of the hair shaft
4. All of the above
Nails
Nails protect fingers and toes
Made of dead cells packed with keratin
Metabolic disorder can change nail structure,
shape or appearance
Fig 5-13
Nails
Fig 5-13
(Cuticle)
Nails
Yellow nails: Chronic resp. disorders, thyroid gland disorders, or
AIDS
Blue-purple nails: Hypoxemia (e.g., congenital heart defect) Cynaosis
Pitted and distorted nails: Psoriasis
Concave (spoon) nails: Blood disorder (e.g., iron deficiency anemia)
Clubbing of nails: Hypoxemia (e.g., COPD, emphysema)
Repair of the Integument
Bleeding occurs
Mast cells trigger inflammatory response
A blood clot or 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
Fig 5-14
1. Blood clot and scab formation
Repair of the Integument
Fig 5-14
2. Cellular migration
Repair of the Integument
Fig 5-14
3. Epidermis covers granulation tissue
Repair of the Integument
Fig 5-14
4. Epidermis covers scar tissue
Repair of the Integument
Fig 5-15
Fibroblasts produce scar tissueInflammation decreases, clot disintegratesFibroblasts strengthen scar tissueA raised keloid may form
Rule of Nines
Method for estimating the percentage of surface area affected by burns.
Importance of the Integumentary System
Importance of the Integumentary System
Importance of the Integumentary System
Importance of the Integumentary System