Integumentary System

Cutaneous Membrane Accessory Structures

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Integumentary System

Made up of all 4 tissue types . . . .??

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Two Major SubdivisionsTwo Major Subdivisions

• Cutaneous Membrane– Epidermis– Dermis– Hypodermis

• Accessory Structures – Excretory glands (?)– ?– ?

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EpidermisEpidermis• Type of Epithelium?

• _vascular

• Different layers (=strata)– 4 layers in

thin skin

– 5 layers in thick skin

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Stratum germinativum

= stratumbasale

Innermost, single layer

Stratum GerminativumCell types:• Stem cells (basal cells)• Melanocytes• Merkel cells (touch receptors in hairless skin only)

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Stratum spinosumSeveral cells

thick

Stratum Spinosum• Stem cell daughter cells (some can still divide)• Melanocytes & Langerhans cells• Establishment of Desmosomes

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Stratum granulosum

Stratum Granulosum• Cells displaced from stratum spinosum Keratinocytes• Production of keratohyalin and keratin fibers• Cells start to die. Dehydration leaves interlocked layers of

keratin, keratohyalin & PL membranes

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Stratum lucidum

Stratum Lucidum• In palms of hands and soles of feet • Cells do not stain well clear (lucid) looking

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Stratum Corneum

• Many layers of flattened, dead cells, filled with keratin• Continually shed in sheaths• Water-resistant but not water proof ( insensible

perspiration)• Relatively dry - advantage?• Keratinization occurs everywhere except for anterior

surface of eye

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15-30 layers (much thicker in thick skin)

Thin vs. Thick Skin

• Up to 6 x thicker• Where??

• Average 0.08 mm• Rest of body

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Refers to epidermis

Contour of skin surface follows pattern of epidermal ridges. Advantage ??

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Unique fingerprints

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Skin Color depends on 3 pigmentsHemoglobin (dermal blood supply)

– Reddish tones– Pale, due to?– Bluish (=?), due to?

Melanin – Produced by melanocytes of stratum basale

Carotene Obtained from plant foods

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Number of melanocytes same in all people, production levels differ !

Melanocytes

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Function ?

DermisDermis

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Papillary layer loose c.t.

Reticular layer dense irregular c.t.

Papillary LayerPapillary Layer

• Dermal papillae project between epidermal ridges.

Consist of

• Loose c.t. = _____

• Capillaries

• Tactile receptorswww.freelivedoctor.com

M

Reticular LayerReticular LayerConsist of

• ______________ c.t.

• + ??

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Pacinian corpuscule(deep pressure)

HypodermisHypodermis

• 2 other names ?2 other names ?

• Indistinct boundary (c.t. fibers interwoven)

Made up of– Loose c.t. + lots of . . .

Function– Stabilization of skin while

allowing for independent movement

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Accessory Structures: Hair Follicles & Hair

• 5 mio hair/hu body. (98% not on top of head)

• Three hair types (vellus – intermediate – terminal)

• Function ?

• Hair color

• Growth cycle

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Skin Glands: 1) Sebaceous GlandsSkin Glands: 1) Sebaceous GlandsHolocrineSebum discharged into hair follicles

(lubrication & bactericidal)excessive shampooing leads to dry & brittle hair

Sebaceous follicles, = Large sebaceous glands, discharge directly to epidermis

Where ?Folliculitis; furuncle (boil); acne

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2) 2) Apocrine Sweat GlandsSweat Glands• Have merocrine secretion!!

• Empty into hair follicle

• Location: armpits, groin, nipples

• Viscous, cloudy secretion good nutrient source for bacteria (odor !!)

• Secretion may contain Pheromones

• Secretion begins at puberty and is stimulated during emotional distress (cold sweat)

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3) Merocrine Sweat Glands3) Merocrine Sweat Glands

• Empty directly onto skin surface

• Location: most all over body (esp. abundant on palms & soles: ~ 500/cm2)

• Clear, watery secretion (99% H2O; rest NaCl + some waste products)

• Sensible perspiration; Function: ?

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For purpose of completion:

Other integumentary Glands:

• Mammary glands: Modified apocrine sweat glands

• Ceruminous glands: modified sweat glands in __________

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Nails not covered.Skin and Aging Process

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