Download The Integumentary System

The Integumentary System
The Integumentary System
Integument = skin
 System includes: skin as well as hair and
nails
 3 regions:
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 Epidermis
(epithelial tissue)
 Dermis (connective tissue)
 Hypodermis
Functions of skin
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Prevents unnecessary water loss (dehydration)
Protection (chemical and physical barrier)
 Cushions
and insulates and is waterproof
 Protects from chemicals, heat, cold, bacteria, viruses
 Screens UV
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Regulates body temp
Synthesizes vitamin D with UV
Blood Reservoir
Secretion/Excretion
Epidermis
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*Keratinized stratified squamous epithelium
Four basic layers (from top to bottom): We have a
totally “new” epidermis every 25-45 days
 Stratum corneum (Horny layer) “cornu”
Greek for horn
 Top
layer and fully keratinized
 20-30 layers thick
 Protect skin from abrasion and penetration
 Glycolipids provide waterproofing
 40 lbs of dandruff shed in a lifetime
 Too far from blood vessels for diffusion so cells
die
Stratum granulosum (Granular layer)
 3-5 cell layers thick
 Stratum spinosum (Prickly Layer)
 Prickly layer (Keratinocytes shrink but desmosomes hold
in place)
 Stratum basale/germinativum (Base germinating layer)
 Deepest layer of the epidermis
 Single layer thick
 Contain melanocytes (special spider shaped cells)
 *Stratum lucidum (Clear layer)
 Only a few layers thick; found only in hairless thick skin,
that is,
 Palms of hands
 Soles of feet
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Epithelium: layers (on left) and cell types (on right)
Dermis
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*Rich supply of nerves and blood vessels
Strong, flexible connective tissue: your “hide”
 Strong flexible envelope of connective tissue
 Dermal Papillae from upper dermis form ridges
in the epidermis for grip (Fingerprints/footprints)
 Reticular layer of lower dermis (deepest skin
layer) of thickness made up of dense irregular
connective tissue
 Pigments
which affect skin color
 Melanin
(melan is Greek for black) (ONLY PIGMENT
PRODUCED IN THE SKIN – varies in color from yellow
to reddish brown to black)
 Carotene (Yellow/orange pigment found in plants which
accumulates in the thick epidermis)
 Hemoglobin (Red from the red blood cells)
 Cyanosis – bluish hue to the skin due to heart failure or
respiratory distress
 Erythema – reddish hue to the skin due to blushing, fever,
hypertension, polycythemia
 Pallor or blanching – pale skin hue due to emotional stress
(fear, anger), anemia, or hypotension
 Jaundice – yellow hue to the skin due to liver disorder
 Hematoma – (Bruises) blood leaks out of capillaries due to
trauma and clots under the skin
Dermal structures
1. Sudoriferous (sweat) glands (2.5 million per person) 2 types:
 Eccrine – Most abundant sweat gland covers; found all over the body
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sweat is secreted by exocytosis into pores which empty onto the skin (possible
to lose up to 7 L per day)
 99% water, remaining solutes are sodium chloride, vitamin C, ammonia, urea,
uric acid, and lactic acid (which attracts mosquitoes)
 Sweat is acidic; which inhibits the growth of bacteria
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Appocrine - Located in the axillary and genital areas
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Larger than eccrine glands.
Secreted/Empty into hair follicles beginning at puberty
Contains true sweat, lipids, and proteins and appears as a milky or yellowish
color
odorless upon secretion, but bacteria decompose molecules forming body odor
Increase of secretions during pain, stress, or sex but physiological function is
unknown (believed to be sexual scent glands as menstruation affects output)
Modified apocrine glands: Ceruminous – secrete earwax; Mammary – secrete
milk
2. Sebaceous glands: AKA: oil glands
 Located
all over body except palms and soles
 Secrete sebum which lubricates and softens hair and
skin, prevents water loss, and has bactericidal
properties
 Whitehead - occurs when duct is blocked by
accumulated sebum and staphylococcus infection
begins
 Blackhead – when whitehead oxidizes and dries out
3. Hair (and Hair Follicles)
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Body hair – served early humans by providing insulation
The bulk of the hair shaft is dead material and almost entirely
protein
Hair color due to melanin (blonde to black hair) gray hair is a
result of lack of melanin or the replacement of melanin with air
bubbles in the hair shaft
Hair appearance due to shaft shape (Flat shaft = curly hair, oval
shaft = wavy hair, round shaft = straight hair)
Hormones account for the development of hair
Average hair growth is 2 mm per week
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*Hair follicle
Extend from epidermis into the dermis
 Arrector pili (small bands of smooth muscle cells)
cause “Goose bumps” upon contraction
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 Trap air close to skin for warmth
 Make us appear larger to predators
4. Nails
Corresponds to the hoof or claw of other animals
 Nail matrix is responsible for growth of new nail
 Nails look pink due to blood supply in underlying
dermis, with the exception to this being the white
crescent shaped area called the lunula
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*Dermis layers
*Dermal papillae
*
*
Epidermis and dermis of (a) thick skin (5 layers) and
(b) thin skin (4 layers)
Hair and hair follicles: complex
Derived from epidermis and dermis
Everywhere but palms, soles, nipples, parts of genitalia
*“arrector pili” is smooth muscle
*
Hair bulb:
epithelial cells
surrounding
papilla
Hair papilla
is connective
tissue________________
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Functions of hair
– less in man than other mammals
 Sense light touch of the skin
 Protection - scalp
 Warmth
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Parts
 Root
imbedded in skin
 Shaft projecting above skin surface
Make up of hair – hard keratin
 Three concentric layers
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 Medulla
(core)
 Cortex (surrounds medulla)
 Cuticle (single layers, overlapping)
Nails
keratin
 Corresponds to hooves and claws
 Grows from nail matrix
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The dermis is the receptive
site for the pigment of tattoos
Lunula vs. No/few lunula
Hypodermis
 Hypodermis
(Gk) = below the skin
 “Subcutaneous” (Latin) = below the skin; AKA:
“superficial fascia”
 Fatty tissue which stores fat and anchors skin
(areolar tissue and adipose cells)
 Different patterns of accumulation
(male/female)
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Pathophysiology: homeostatic imbalances of skin
 Skin Cancer
 Benign (Non-spreading) vs. malignant (spread into other
tissue)
 One in five Americans now develops skin cancer at some
point in his or her life
 Basal cell carcinoma – most common and least malignant
 Shiny lesions in the stratum basale which grow into the
dermis
 Full cure is the rule in 99% of cases after surgery
 Squamous cell carcinoma
 Cells of the stratum spinosum form a lesion which
appears a papule (small, rounded elevation)
 Lesion usually forms on scalp, ears, dorsum of hands,
and lower lip
 Grows rapidly and can metastasize if not removed
 If caught early and removed, chance of cure is good
 Melanoma
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(5% of skin cancers)
Cancer of the melanocytes
Most dangerous of the skin cancers
Usually appears as a spreading brown to black patch
Metastasizes rapidly to lymph and blood
Chance for survival is about 50% (early detection helps)
ABCDE rule to detect:
 Asymmetry – two sides don’t match
 Border irregularity – not smooth and have indentations
 Color – more than one color
 Diameter – larger than 6 mm in diameter
 Elevation – elevated above skin surface
Skin Cancer
Sqaumous cell carcinoma
Basal cell carcinoma
Melanoma
 Burns
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1st degree – only epidermis is damaged e.g. sunburn
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2nd degree – epidermis and upper region of dermis damaged
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Heal in 2-3 days
Blisters form (Fluid collects between dermis and epidermis)
Heal in 3-4 weeks
Critical if over 25% of body has 2nd degree burns
3rd degree – epidermis and all of dermis is damaged (entire
thickness of skin = full-thickness burns)
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Burn area appears blanched (gray-white) or blackened
Nerve endings are destroyed, so burned area is not painful
Skin grafting necessary to cover exposed tissues
Fluid loss can be catastrophic (dehydration & electrolyte imbalance
lead to renal failure and shock)
Infection can be rampant
Critical if more than 10% of the body is affected or if the face, hands,
or feet have 3rd degree burns
Burns
First-degree
(epidermis only; redness)
Second-degree
(epidermis and dermis,
with blistering)
Third-degree
(full thickness, destroying
epidermis, dermis, often part
of hypodermis)
Estimate by “rule of 9’s”
Critical burns
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Over 10% of the
body has thirddegree burns
25 % of the body
has seconddegree burns
Third-degree
burns on face,
hands, or feet