Download Anat2_02_Integumentary

Integumentary System
Dr. Michael P. Gillespie
Integumentary System
 The skin (cutaneous membrane) covers the
external surface of the body.
 It is the largest organ of the body in terms of
both surface area and weight.
Functions of the Integumentary
System
 Thermoregulation
 Reservoir for blood
 Protection from external environment
 Cutaneous sensations
 Excretion and absorption
 Vitamin D synthesis
Structure of the Skin
 Two main parts
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Epidermis – epithelial tissue
Dermis – connective tissue
 Subcutaneous layer (hypodermis) – not part
of the skin – areolar and adipose tissue

Contains nerve endings called lamellated
(Pacinian) corpuscles
Epidermis
 Keratinized squamous epithelium
 4 types of cells
 5 basic layers of the epidermis
Cell Types in Epidermis
 Keratinocytes (90%)
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Keratino = hornlike; cytes = cells
Keratin –protects from heat, microbes, and chemicals
 Melanocytes (8%)
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Melano = black
Produce pigment melanin – absorbs UV light
 Langerhans cells
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Arise from red bone marrow – migrate to epidermis
Immune response
 Merkel cells
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Tactile (Merkel) disc
Layers of Epidermis
 Stratum Basale
 Stratum Spinosum
 Stratum Granulosum
 Stratum Lucidum
 Stratum Corneum
Stratum Basale
 Deepest layer
 Single row of columnar or cuboidal
keratinocytes
 Keratin protects the deep layers from injury
 Stem cells
 Also known as the stratum germinativum
(germ = sprout)
Stratum Spinosum
 Spinos = thornlike
 8 – 10 layers of many sided keratinocytes
close together
 Provides strength and flexibility to the skin
Stratum Granulosum
 Middle of the epidermis
 Granulos – little grains
 3-5 layers of flattened keratinocytes
 Undergoing apoptosis (cell death)
 Lamellar Granules – release a lipid-rich
secretion
Stratum Lucidum
 Lucid = clear
 Present only in the thick skin of the
fingertips, palms, and soles
 3-5 layers of flattened clear, dead
keratinocytes
Stratum Corneum
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Corne = horn or horny
25 – 30 layers of flattened dead keratinocytes
Shed and replaced by cells from deeper strata
Mostly keratin
Between the cells are lipids from lamellar granules
– creates water repellent barrier
 Protects deep layers from injury
 Friction creates a callus – abnormal thickening
Growth of Epidermis
 Newly formed cells are pushed to the surface
 Accumulate more keratin (keratinization)
 Undergo apoptosis
 Keratinized cells slough off
 4 weeks
Psoriasis
 Common skin disorder
 Keratinocytes divide more quickly than normal and
shed prematurely (7-10 days)
 Immature keratinocytes make abnormal keratin
 Forms flaky, silvery scales
 Knees, elbows, and scalp (dandruff)
 Tx. Topical ointments, UV phototherapy
(decreases cell division)
Dermis
 Deeper layer
 Mainly connective tissue
 Collagen and elastic tissue
 Fibroblasts, macrophages, and adipocytes
Dermis Continued…
 Papillary region – dermal papillae (papillae =
nipples) – indent the epidermis – capillary
loops
 Corpuscles of touch (Meissner corpuscles)
 Free nerve endings – warmth, coolness, pain,
tickling, and itching
Dermis continued…
 Reticular region (reticul = netlike) – deeper part of
dermis
 Dense irregular CT
 Adipose cells, hair follicles, nerves, sebaceous (oil)
glands, sudoriferous (sweat) glands
 Striae – streaks – stretch marks
 Epidermal ridges – grip / friction – palms, fingers,
soles, toes
Types of Skin
 Thin skin – covers all surfaces of the body
except for the palms, palmar surfaces of the
digits, and soles.

Lacks a stratum lucidum
 Thick skin – covers the palms, palmar
surfaces of the fingers, and soles
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Distinct stratum lucidum
Accessory Structure of the Skin
 Hair
 Skin glands
 Nails
Hair
 Hair or pili – present on most surfaces except the
palms, palmar surfaces of fingers, soles, and plantar
surfaces of feet
 Shaft – superficial portion – projects from skin
 Root – deeper portion – penetrates the dermis and
sometimes into the subcutaneous layer
 Arrector pili – muscle which pulls on hair shaft
causing it to raise – emotional stress (cold or fright)
Conditions
 Hirsutism = excessive body hair due to
excessive androgens – tumor of the adrenal
glands, testes, or ovaries
 Androgenic alopecia – male-pattern baldness
Skin Glands
 Sebaceous Glands (greasy) – oil glands - typically
connected to hair follicles
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Secrete sebum – coats hair and keeps it from becoming
dry and brittle – keeps skin soft and pliable
 Sudoriferous Glands – sweat glands
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Eccrine – throughout skin
Apocrine – skin of axilla, groin, areolae and bearded
regions
 Ceruminous Glands – cer = wax – external ear
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Cerumen = earwax – creates sticky body to impede
entrance of foreign substances
Nails
 Tightly packed, hard, keratinized epidermal
cells
 Nail body, free edge and nail root
 Lunula
 Hyponychium – beneath free edge
 Eponychium (cuticle) adheres to the lateral
margin of the nail wall.
Epidermal Wound Healing
 Cells enlarge and migrate across the wound
 Contact inhibition – when migrating cells
touch one another they stop due a this
cellular response
Deep Wound Healing
 The injury extends to the dermis and subcutaneous
layer
 Inflammatory phase
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Blood clot forms
Inflammation eliminates wastes and microbes
 Migratory phase
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Damaged blood vessels begin to regrow
 Proliferative phase
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Extensive growth of epithelial cells
Deposition of fibroblasts
 Maturation phase
Contributions of the
Integumentary System
 The Integumentary System contributes to the
functioning of all other body systems.
 Refer to the table on page 155.
Skin Disorders
 Skin Cancer
 Burns
 Pressure Ulcers
Skin Cancer
 Almost exclusively caused by excessive
exposure to the sun.
 Basal cell carcinomas
 Squamous cell carcinomas
 Malignant Melanomas
Basal Cell Carcinoma
Squamous Cell Carcinoma
Detection of Malignant
Melanoma
 A Asymmetry
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MM lack symmetry
 B Border
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MM have notched, indented, scalloped, or indistinct
borders
 C Color
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MM have uneven coloration, may contain several colors
 D Diameter
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MM are typically greater than 6mm (0.25 in.)
 E Elevation
Normal Nevus & Malignant
Melanoma
Risk Factors for Malignant
Melanoma
 1. Skin type
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Light skinned individuals who burn, but don’t tan
 2. Skin exposure
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Sunny areas, high altitude (UV light), outdoor occupation
 3. Family Hx.
 4. Age
 5. Immunological status
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Immunosuppressed individuals have a higher risk of skin
cancer
Burns
 Tissue damage caused by
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Excessive heat
Electricity
Radioactivity
Corrosive chemicals
 Destroy some of the skin’s contributions to
homeostasis
Grading of Burns
 First-degree burn
 Second-degree burn (partial thickness)
 Third-degree burn (full thickness)
Systemic Effects of Burns
 1. Large loss of water, plasma, and plasma
proteins (causes shock)
 2. Bacterial infection
 3. Reduced circulation of blood
 4. Decreased production of urine
 5. Diminished immune response
Severity of Burns
 Determined by the depth of the burn and the extent
of the area involved.
 According to the American Burn Association a
major burn includes:
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Third-degree burns over 10%
Second-degree burns over 25%
Third-degree burns over face, hands, feet, or perineum
 When the burn area exceeds 70%, more than half of
the victims die
Determining the Extent of a
Burn
 Rule of nines – a quick method for
estimating the surface area affected by burns
 Lund-Browder method – a more accurate
method for assessing the extent of burns
Skin Color
 Melanin – causes skin color from pale yellow to
black
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Melanocytes produce melanin
Freckles and liver spots are accumulations of melanin
 Carotene – yellow-orange pigment
 Hemoglobin – imparts a red color
 Albinism – inability to produce melanin - missing
from the hair, eyes, and skin
 Vitiligo – loss of melanocytes from patches of skin
Skin Color Clues
 Cyanotic – blue - hemoglobin is depleted of
oxygen
 Jaundice – yellow – buildup of the yellow
pigment bilirubin in the blood – usually
indicates liver disease
 Erythema – red – engorgement of capillaries
in the skin – skin injury, heat, infection,
inflammation, allergies
Carotonemia
Cyanosis
Jaundice
Vitiligo
Scabies