Skin Flashcards by sophie rosen

what is the largest organ in the body?

the skin, ~15-20% of body mass

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4 main functions of skin

protection
sensation
thermoregulation
metabolic function

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protection

from UV, mechanical, chemical, & thermal insult

Prevents dehydration; provides physical barrier to microorganisms

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sensation

largest sense organ of body; contains receptors for touch, pressure, pain, & temperature

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thermoregulation

nsulation via hair & SQ fat; heat loss facilitated by sweat glands & dermal capillary network

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metabolic functions

energy stored in SQ fat(1’ as triglycerides); Vit D synthesized in skin via hv
Maintains homeostasis; excretory function (sweating); immune defense

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3 lays of the skin

epidermis
dermis
hypodermis (=subcutis)

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what does epidermis consist of

keratinized, stratified squamous epithelium

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cells of the epidermis are called

keratinocytes

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thickness of the epidermis

from <1 mm to >5 mm; dubbed “thin skin” or “thick skin,” respectively

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“Thick skin” has thick, highly — layer

keratinized

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thick skin is restricted to (2)

volar (soles) & palmar (palms) surfaces

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thick skin lacks

hair (glabrous)

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Most of body covered in —, with thin keratinized epidermis

“thin skin”

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Epidermis lacks blood vessels—do not penetrate

basement membrane

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Epidermis supplied & nourished by blood vessels in

underlying (subjacent) dermis

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dermis is composed of

dense, irregular, collagenous connective tissue (Type I collagen), interspersed with elastic fibers

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Progressive damage to elastic fibers results in

“aging”, loss of skin tone

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dermis is highly vascular, contains many

sensory receptors

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what are the two layers of the dermis?

papillary layer

deep reticular layer

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Papillary layer relatively thin and interdigitates with

epidermis

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Corrugations increases surface area for —, prevent (2)

attachment, prevent shear & mechanical abrasion

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Epidermal ridges (rete ridges)

epidermal projections into dermis

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Dermal ridges(dermal papillae)

dermal projections into epidermis

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Large dermal ridges in thick skin called

fingerprints (= dermatoglyphs); unique to individual

dermal ridges form basis of study of

dermatoglyphics

reticular layer compared to papillary layer

Deep reticular layerof dermis thicker & less cell than papillary layer

dermis contains (3)

hair follicles, sweat & sebaceous glands

dermis interdigitates with underlying

hypodermis(= subcutis)

Thick collagen bundles & elastin fibers in reticular layer form lines of tension,

Langer’s lines

Skin incisions --- to Langer’s lines heal with less scarring

parallel

hypodermis is located

below dermis

hypodermis

layer of loose, irregular connective tissue & adipose tissue (= subcutis= superficial fascia= panniculus adiposus)

vascular plexus consist of (3)

Superficial subpapillary plexus, deep cutaneous plexus, & deeper subcutaneous plexus

Subpapillary plexus located at junction of

papillary & reticular layers

Cutaneous plexus located at junction of

reticular layer & hypodermis

Subcutaneous plexus located deep within

hypodermis

largest of the three layers of the vascular plexi

subcutaneous plexus

vascular plexi is used in --- in (2)

Used in thermoregulation—in fingertips & ears

vascular plexus is associated with

AV shunts containing glomus bodies

glomus bodies

Thickened regions of smooth Mm in wall of arterioles, surrounded by connective tissue capsule

vascular plexi bypasses capillary bed, to re-route blood from

arterial to venous circulation

Skin is continuously (2)

grown & replaced

skin takes ~25-50 days for cells to travel from deep germinal layer, mature, & be sloughed from

superficial epidermis

psoriasis

absence of a granular layer and abnormal keratohyaline & tonofibrils

In psoriasis, keratinocyte maturation only takes ~

1 wk

Stratum basale=

stratum germinativum

stratum basale is the --- layer

basal

Mitotic layer of cuboidal germinal cells bound to basement membrane by

hemidesmosomes

Attach to underlying dermis via (2)

anchoring filaments & microfibrils

Stratum spinosum

“prickle cell layer” | cells look spiny

thickest layer of epidermis in thin skin

Stratum spinosum

Polyhedral cells with

prominent intercellular bridges (desmosomes), numerous cytoplasmic processes & lateral folding of cell membrane

Predominant cell product, cytokeratin, forms tonofilaments, aggregate into

larger tonofibrils, anchor onto desmosomes

Stratum granulosum—--- cell layer

granular

Characterized by cells containing basophilic

keratohyaline granules

non-membrane bound, electron dense granules

Keratinization of cells represents interaction between

keratohyaline granules & tonofibrils

Keratinization initiated by release of lysosomal enzymes results in

rupture of keratohyaline granules & polymerization of their contents

Forms a matrix for tonofibrils of cytokeratin results in

amorphous mass of mature keratin

Release of lysosomes also results in

death of the cell

As keratinocytes mature, they

die & lose nuclei

Cells of granular layer contain membrane-bound, lamellar structures called

keratinosomes

keratinosomes contain ---, provide waterproofing coat for skin cells

glycolipids

Cells of granular layer mature to form waterproof layer of keratinized cells, with --- coating on surface of epidermis

glycolipid

Stratum lucidum is present only in

thick skin

Stratum lucidum

Homogenous, compact layer of enucleate cells between stratum granulosum & stratum corneum

Stratum corneum—(cornified layer)

most superficial layer; thickest layer of epidermis in thick skin

stratum corner contains

flattened, enucleate, dead cell remnants, called squames

Composed 1’ of soft keratin—acts as hydrophobic barrier, prevents

desiccation

desquamation

Continuously exfoliated

In females, exfoliated cervical epithelial cells routinely examined in --- ---, to detect cervical cancer

Pap smear

common skin tumors (3)

* Squamous cell carcinoma * Basal cell carcinoma * Melanoma

squamous cell carcinoma and basal cell carcinoma are derived from

epithelial cells

melanoma is derived from

maloncytes

squamous cell carcinoma, basal cell carcinoma, and melanoma are all aggressive cancers with tendency to

metastasize

First intention healing—from a

clean (surgical), approximated incision

Incision immediately fills with

blood & clots

Within 3—24 hrs,

neutrophils infiltrate clot (acute phase)

Epithelial cells of stratum basale begin mitosis results in

epithelial closure (reapproximation) within 24—48 hrs

Day 3-7—neutrophils begin to be replaced by

macrophages (transition from acute to subacute phase)

3 processes: neovascularization, fibroplasia (fibroblasts elaborate collagen), & re-epithelialization (epithelial proliferation) results in

production of granulation tissue

~ Day 5—incision filled with

granulation tissue

Week 2—continued fibroplasia & collagen accumulation results in

mature granulation tissue

progressive decrease in

inflammation

Presence of inflammatory cells & inflammatory cell products results in

itching while healing

Month 2—connective tissue scar, without inflammation, covered by

intact epithelium

With Vit C deficiency, collagen breaks down; old scars can

re-open & bleed

Keloid

excess fibroplasia

Keloid results in

raised, thickened connective tissue scar

Second intention healing—occurs with more extensive loss of tissue, where wound edges do not

approximate (e.g., infarct, ulcer, abscess)

Following initial clot formation, epithelial cells of --- --- migrate from edges of wound at ~ 0.5 mm/day

stratum basale

Takes ~3 weeks to fill a 1 cm wide

cut

In haired skin, migration of cells from external root sheath of hair follicles augments

re-epithelialization

Simultaneous proliferation/ maturation of keratinocytes behind migrating front slowly restores multilayered,

stratified epidermis

Takes ~ 25 days for cells to mature from stratum basale to stratum corneum, results in

keratinization

Keratinazation of new cells results in

desquamation & lifting of scab from periphery after ~ 3 wks

wound repair is followed by wound contraction due to

myofibroblasts

In full thickness abrasion, or third degree burns, re-epithelialization limited by

size of wound; grafting generally necessary

1st degree—involves

only epidermis

2nd degree—involves

both epidermis & dermis

3rd degree— involves

all three layers, epidermis, dermis & hypodermis

Skin Flashcards

(102 cards)