imsk derm skin

3 main layers of normal canine skin

epidermis, dermis, subcutis

skin keeps out

microbes, chemicals, toxins, physical impacts

skin keeps in

water, electrolytes, macromolecules

skin is a messenger that can

reflect internal disease processes and communicate w/other individuals

epidermis

composed of keratinocytes that are born to die

keratinization

is a highly orchestrated, genetically programmed process resulting in structural and metabolic changes

complete cell turnover in a healthy dog is

22 dogs

proliferation

is reproduction

desmosomes are

hands

hemidesmosomes

anchors connect intracellular keratin filament types

synthesis of lipid-containing lamellar bodies

cholesterol, ceramides, free fatty acids and enzymes

progressive flattening of cells, keratin filaments get progressively packed into

large, insoluble polymers w/the help of filaggrin

insoluble polymers

formation of the cornified envelope

filaggrin

keratohyaline granules

the cornified envelopes are firmly connected via

corneodesmosomes and tight junctions

extrusion of lipid-containing lamellar bodies

lipids fills intercorneocyte space

keratinocytes are

terminally differentiated and coated by lipids, separated by proteases and are constantly shed

main physiological fxns of the epidermis

protection and enveloping

3 steps of the protection fxn of the epidermis

formation of the cornified envelope, production of antimicrobial substances during this process, permanent shedding of corneocytes

1st internal impact of the epidermis

malnutrition/lack of essential fatty acids

2nd internal impact of the epidermis

epidermal lipid deficiency

3rd internal impact of the epidermis

scaling, poor barrier fxn

external impacts of the epidermis

excessive washing, chemicals, dry/wet env which weakens epidermal barrier, increased scaling, increased transepidermal water loss

epidermal pigmentation

are melanocytes

melanocytes reside among

basal keratinocytes

melanocytes possess

long dendrites that transfer of melanosomes to keratinocytes (pigmentation and UV light protection)

langerhans cells reside among

basal keratinocytes or suprabasilar

langerhans specialize in

antigen processing and antigen presentation, also immunosurveillance

merkel cells reside in

the basal layer and fxn as mechanoreceptors

free epidermal nerve endings stem

from nerves in the dermis

additional fxns of the epidermis

vitamin D production, contribution to temperature regulation via TEWL

TEWL

transepidermal water loss

main physiologic fxns of the dermis

absorbs stress from movement, maintains skin shape, water storage

dermis is made up of

fibers (mainly collagen) and polymers (proteoglycans, hyaluranan)

collagen resists

pull'/tensile forces

proteoglycans, hyaluranan

resist push/compression forces

additional physiologic fxns of the dermis

immunologic surveillance, thermoregulation/cooling via radiation & blood vessels & sweat glands

thermoregulation/heat preservation via

vasoconstriction, erection of hair

cutaneous sensation

thermoreceptors, specialized mechanoreceptors pain/nociceptors, itchi-specific nerve pathways that can be triggered by a variety of pathways

main physiologic fxns of the subcutis

energy reserve, thermoinsulation, protective padding, steroid metabolism, estrogen production