Transcript Chapter 5 - HCC Learning Web

Chapter 5
Integumentary System
5-1
Integumentary System
• Consists of:
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Skin
Hair
Nails
Glands
Integument means “covering”
• Functions
– Protection
– Sensation (sensory
receptors detect heat, cold,
touch, pressure,pain)
– Temperature regulation
– Vitamin D production
– Excretion
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Hypodermis
• Skin rests on this, but
not a part
• Attaches skin to
underlying muscle;
supplies it with blood
vessels, nerves
• Consists of loose
connective tissue and fat
• Types of cells
– Fibroblasts
– Adipose cells
– Macrophages
• Also called:
Thickens markedly when one gains weight
– Subcutaneous tissue
– Superficial fascia
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Skin
2 Major Layers
• Dermis
– Strong, flexible
connective tissue layer
attached to hypodermis
– Structural strength
– Two layers
• Reticular: Cleavage
lines
• Papillary: Blood
vessels, Fingerprints
• Epidermis
– Layer of thick,
keratinized stratified
squamous epithelium
that rests on dermis
– 4 Cell types
– 5 Layers or strata
– Avascular
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Dermis and Epidermis
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Epidermal Cells
• Cell types
– Keratinocytes: Produce keratin for strength and
permeability
– Melanocytes: Contribute to skin color
– Langerhans’ cells: Part of the immune system
– Merkel’s cells: Detect light touch and light pressure
• Desquamate: Older cells at surface slough off
• Keratinization:
– Cells move from deeper layers to surface, change shape and
become filled with keratin
– Produces outer layer that resists abrasion and forms permeability
layer
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Epidermal Strata
• 5 Strata, from deepest to most superficial:
• Stratum Basale
– Deepest portion of epidermis; single layer of cuboidal
or columnar cells representing the youngest
keratinocytes
– High mitotic activity
– Melanocytes (10-25% of cells in this layer) produce
melanin
• Stratum Spinosum
– Limited mitosis
– Keratin fibers and lamellar bodies accumulate
– Together with stratum basale, often called stratum
germinativum
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Epidermal Strata (cont’d)
• Stratum Granulosum
– Keratohyalin granules accumulate in cell
– Lamellar bodies release lipids; cells die
• Stratum Lucidum
– Thin, clear zone; appears translucent
– Consists of several layers of dead cells
– Only present in a few areas of body
• Stratum Corneum
– Most superficial; consists of cornified cells
– 25 or more layers of dead squamous cells
(dandruff, flaky dry skin)
Millions of dead keratinocytes rub off daily, giving us totally new
epidermis every 25-45 days
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Epidermal Layers and Keratinization
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Melanin Transfer from Melanocyte to Keratinocytes
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Thick and Thin Skin
• Refers to epidermis only; not total skin thickness
(which is measured by a thickness in the dermis)
• Thick skin
– Has all 5 epithelial strata
– Stratum corneum has many layers of dead cells
– Found in areas subject to pressure or friction
• Palms of hands, fingertips, soles of feet
• Thin skin
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More flexible than thick skin
Stratum lucidum absent; other 4 strata are thinner
Covers rest of body
Where hair is found
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Skin Color
• Determined by 3 factors:
– Pigments
• Melanin: Provides for protection against UV light
• Albinism: Deficiency or absence of pigment
• Carotene: Yellow pigment from carrots, corn
– Blood circulating through the skin
• Imparts reddish hue and increases during blushing,
anger, inflammation, fever, hypertension, allergy
• Cyanosis: Blue color caused by decrease in blood
oxygen content
– Thickness of Stratum Corneum
Freckles, pigmented moles: local accumulations of melanin
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5-13
Accessory Skin Structures
• Hair
– Found everywhere on human skin except palms, soles,
lips, nipples, parts of external genitalia, and distal
segments of fingers and toes
– Lanugo, terminal hairs, vellus hairs
• Glands
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Sebaceous or oil glands
Sudoriferous or sweat glands
Ceruminous glands or earwax glands
Mammary glands
• Nails
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Hair Structure
• Composed of shaft
and root
– Shaft protrudes
above skin surface
– Root located below
surface and base
forms the hair bulb
• Has 3 concentric
layers of dead
keratinized
epithelium
– Medulla: Central axis
– Cortex: Forms bulk
of hair
– Cuticle: Forms hair
surface
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5-16
Hair Growth, Color, and Muscles
• Hair Growth
– Cycles
• Growth stage and resting stage
– Growth stage-hair is formed by cells of the matrix
differentiating, become keratinized and die; hair grows
longer as cells add to base of hair root
– Resting stage-then new cycle begins; new hair replaces
old hair
• Hair growth varies depending on location (average
0.3mm/day)
– Eyelashes grow for 30 days, rest for 105; scalp hair grows
for 3 years, rests for 1-2 years
– Permanent hair loss
• Pattern baldness most common
• Hair follicles lost; remaining produce vellus hair
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Hair Growth, Color, and Muscles (cont’d)
• Hair Color
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Caused by varying amounts and types of melanin
Blonde hair: little black-brown melanin
Black hair: most melanin
Brown hair: intermediate amounts of melanin
Red hair: varying amounts of red melanin
Gray or white hair: with age, melanin decreases
• Muscles
– Arrector pili:
• Smooth muscle cells associated with each hair follicle
• Muscle contraction causes hair to “stand on end”; the raised
hair follicles are called “goose bumps”
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Oil and Sweat Glands
• Sebaceous glands
– Holocrine glands located in
dermis
– Produce sebum
– Oils hair and skin surface
• Sudoriferous glands
– Merocrine sweat glands
• Most common
• Open directly onto skin
through pores
• Numerous in palms and
soles
– Apocrine sweat glands
• Open into hair follicle
• Found in axillae, genitalia,
around anus
• Cause body odor
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OTHER GLANDS
• Ceruminous glands:
• modified merocrine sweat glands in the ear canal
• produce cerumen (earwax)
• cerumen+ hairs protect eardrum; prevent dirt and small
insects from entering ears
• Mammary glands:
• modified apocrine sweat glands in breast
• part of female reproductive system
• milk production
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Nails
• Anatomy
– Nail is stratum corneum
with hard keratin
– Nail root proximally
– Nail body distally
– Eponychium or cuticle
– Nail matrix: produces
the nail
• Growth
– Grow continuously
(unlike hair) at an
average rate of 0.51.2mm per day)
– Grow from base, like
hair
The distal end of primate digits have nails
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Summary of Integumentary System Functions
1. Stratified squamous epithelium of skin protects against abrasion
2. Prevents entry of microorganisms and other harmful
substances into the body. Contains components of
the immune system that protects against microbes
3. Melanin absorbs ultraviolet light and protects underlying
structures
4. Hair protection: heat insulator; protection against ultraviolet light and
abrasion; eyebrows keep sweat out of the eyes; eyelashes protect eyes
from foreign objects; nose and ear hairs prevent entry of dust and
other materials.
5. Nails protect the ends of digits.
6. Prevents water loss-lipids prevent diffusion of lipids
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Sensation
•Sensory receptors in all layers detect pain, heat and cold
•Epidermis and dermal papillae: touch receptors
•Dermis, deeper tissues: pain, heat, cold, touch, pressure
receptors
•Hair follicles (but not hair): well innervated; sensory receptors
near base of hair follicles sense hair movement
Temperature Regulation
•Maintain homeostasis
• To cool off: blood vessels in dermis dilate (vasodilate); more
blood flows close to surface; heat given off as perspiration
• To retain heat: blood vessels in dermis constrict
(vasoconstriction); reduces surface blood flow and heat loss
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Vitamin D Production
• Functions as a hormone
•stimulates uptake of calcium(Ca) and phosphate(P) from small
intestines
•promotes their release from bones
•reduces Ca loss from kidneys; resulting in increased blood Ca/P
Ca/P needed for normal bone metabolism
Ca needed for normal nerve and muscle function
Vitamin D synthesis begins in the skin in response to
ultraviolet light;
• precursor molecule 7-dehydrocholesterol;
• converted to cholecalciferol by UV light: released into the blood
• modified in liver and kidneys to active vitamin D (calcitriol)
•Can also be ingested and absorbed by intestines: liver, egg yolks, dairy products,
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fortified milk, vitamin pills
Excretion
•Removal of waste products from the body
•Perspiration (sweat):
water+ salts+ small amounts of waste products
(urea, uric acid, ammonia)
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Aging Effects
•Skin more easily damaged; slower repair
•Epidermis thins; decrease of collagen in dermis
•Skin becomes drier
•Sebaceous gland activity decreases
•Skin sags and wrinkles
•Loss of fat from hypodermis; decrease in elastic fibers in
dermis
•Functioning melanocytes decrease, but
increase on hands and face as age spots
•Sunlight ages skin more rapidly
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The Rule of Nines
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Surface area estimations
Burns
Classifications
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Partial thickness burns
– First-degree: epidermis only;
red, painful and edema(swelling);
sunburn, brief exposure to hot
objects; heal in a week; no scar
tissue
– Second-degree: epidermis
and dermis; red, pain, edema and
blisters; heal in 2 weeks;
deep dermis-several months to
heal; scar tissue may appear
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Full thickness burns
– Third-degree: epidermis and
dermis destroyed; no pain;
varying colors; loss of functions
of the integumentary system
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Skin Grafts
– Split skin
– Artificial skin
– Cadavers or pigs
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Clinical Disorders of the Skin
• Bacterial Infections
– Acne, impetigo
• Viral Infections
– Chicken pox, German measles, cold sores, warts
• Fungal Infections
– Ringworm, athlete’s foot, jock itch
• Cancer
– Basal cell carcinoma (most common; least malignant)
– Squamous cell carcinoma (may metastasize)
– Malignant melanoma (will metastasize-starts from
mole; spreads to other body sites)
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