You gotta have skin;You gotta have skin;All you really need is skin.All you really need is skin.Skin's the thing, that if you've got it Skin's the thing, that if you've got it outside,outside,It helps keep your insides in. It helps keep your insides in.

Alan Sherman (1924-1973) Alan Sherman (1924-1973)

Ch 4: Integumentary SystemCh 4: Integumentary System

Cutaneous MembraneCutaneous Membrane EpidermisEpidermis DermisDermis HypodermisHypodermis

Accessory Structures Accessory Structures Excretory glands (?)Excretory glands (?) HairHair NailsNails

Type of EpitheliumType of Epithelium

AvascularAvascular

Different layers Different layers (=strata)(=strata) 4 layers in 4 layers in

thin skinthin skin

5 layers in 5 layers in thick skinthick skin

Stratum germinativum

= stratumbasale

Innermost, single layer

Cell types:Cell types: Stem cells (basal cells)Stem cells (basal cells) MelanocytesMelanocytes Merkel cells (touch receptors in hairless skin Merkel cells (touch receptors in hairless skin

only)only)

Stem cell daughter cells (some can still divide)Stem cell daughter cells (some can still divide) Establishment of DesmosomesEstablishment of Desmosomes

The desmosomes create the “spines” as artifact pulls The desmosomes create the “spines” as artifact pulls the cells apartthe cells apart

Several cells Several cells thick thick

Stratum

spinosum

Stratum granulosum

Cells displaced from stratum spinosum Cells displaced from stratum spinosum KeratinocytesKeratinocytes

Production of keratohyalin and keratin fibersProduction of keratohyalin and keratin fibers Cells start to die. Dehydration leaves interlocked layers of Cells start to die. Dehydration leaves interlocked layers of

keratin and keratohyalinkeratin and keratohyalin

Small granules of keratin

Stratum lucidum

In “thick skin”, i.e., palms of hands and soles In “thick skin”, i.e., palms of hands and soles of feet of feet

Cells do not stain well Cells do not stain well clear (lucid) looking clear (lucid) looking

Mostly keratin

Many layers of flattened, dead cells, filled with keratinMany layers of flattened, dead cells, filled with keratin Continually sloughedContinually sloughed Water-resistant but not water proof (Water-resistant but not water proof ( insensible insensible

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

surface of eyesurface of eyeStratum

corneum

15-30 layers 15-30 layers (much thicker (much thicker in thick skin)in thick skin)

Up to 6 x thickerUp to 6 x thicker Where??Where??

Average 0.08 mmAverage 0.08 mm Most of bodyMost of body

Refers to epidermisRefers to epidermis

cc

Hemoglobin (dermal blood supply)Hemoglobin (dermal blood supply) Reddish tonesReddish tones Pale, due to?Pale, due to? Bluish (=?), due to?Bluish (=?), due to?

Melanin Melanin Produced by melanocytes of stratum basaleProduced by melanocytes of stratum basale

CaroteneCarotene Obtained from plant foodsObtained from plant foods

Depends on 3 pigments:Depends on 3 pigments:

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

Function ? UV Function ? UV protection?protection?

Albinism

Vitiligo

1. 1. Papillary layerPapillary layer Areolar (loose) Areolar (loose) c.t.c.t.

2. Reticular layer2. Reticular layer dense irregular dense irregular c.t.

Review of Connective Tissue

This is similar to Table 4.2

•Loose (areolar)•Reticular•Adipose

•Hyaline•Elastic

•Fibrocartilage

•Irregular•Regular•Elastic

•Compact•Spongy

Dermal papillae Dermal papillae project between project between epidermal ridges.epidermal ridges.

Consist ofConsist of

Loose c.t.Loose c.t.

CapillariesCapillaries

Tactile receptorsTactile receptors

M

Consist of Consist of Dense irregular c.t.Dense irregular c.t. Accessory Accessory

StructuresStructures HairHair GlandsGlands NervesNerves Blood SupplyBlood Supply

2 other names2 other names Subcutaneous Layer Subcutaneous Layer

(subcutis)(subcutis) Superficial fascia Superficial fascia

Indistinct boundary (c.t. Indistinct boundary (c.t. fibers interwoven)fibers interwoven) Loose c.t.Loose c.t.

FunctionFunction Stabilization of skin while Stabilization of skin while

allowing for independent allowing for independent movementmovement

Hair follicles and hairHair follicles and hair GlandsGlands

1. Sebaceous Glands1. Sebaceous Glands 2. Apocrine glands2. Apocrine glands 3. Eccrine sweat 3. Eccrine sweat

glandsglands

NailsNails

5 million 5 million hairs/human body. hairs/human body. (98% not on top of (98% not on top of head)head)

Three hair types Three hair types (vellus – intermediate – (vellus – intermediate – terminal)terminal)

Function ?Function ? Hair colorHair color Growth cycleGrowth cycle

Skin Glands Skin Glands

Sebum Sebum discharged mostly into hair discharged mostly into hair folliclesfollicles(lubrication & bactericidal)(lubrication & bactericidal)

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

Folliculitis; furuncle (boil); Folliculitis; furuncle (boil); acneacne

Empty into hair follicleEmpty into hair follicle Location: armpits, groin, nipplesLocation: armpits, groin, nipples Viscous, cloudy secretion Viscous, cloudy secretion good nutrient source for good nutrient source for

bacteria (odor !!)bacteria (odor !!) Secretion may contain PheromonesSecretion may contain Pheromones Secretion begins at puberty and is stimulated during Secretion begins at puberty and is stimulated during

emotional distress emotional distress (cold sweat)(cold sweat)

Merocrine secretionMerocrine secretion

Empty directly onto skin surfaceEmpty directly onto skin surface

Location: most all over body (esp. Location: most all over body (esp. abundant on palms & soles: ~ abundant on palms & soles: ~ 500/cm500/cm22))

Clear, watery secretion (99% HClear, watery secretion (99% H22O; O;

rest NaCl + some waste products)rest NaCl + some waste products)

Sensible perspiration; Sensible perspiration; Function: ?Function: ?

Other integumentary Glands:Other integumentary Glands:

Mammary glandsMammary glands: Modified apocrine : Modified apocrine sweat glandssweat glands

Ceruminous glandsCeruminous glands: Modified sweat : Modified sweat glands in earsglands in ears

1.1. Basal Cell Carcinoma (Epithelioma)Basal Cell Carcinoma (Epithelioma)1.1. Most common, not malignantMost common, not malignant

2.2. Squamous Cell CASquamous Cell CA1.1. Stratum spinosumStratum spinosum

3.3. MelanomaMelanoma

BCC

SCC

Iris MelanomaIris Melanoma Dermal Dermal MelanomaMelanoma

Skin and Aging Process