255. Structure/Function of Skin

Question 1

Major functions of skin

Answer 1

1. Barrier: resist mechanical stress, limit water loss from inside, block entry from outside, UV shield
2. Repair: wound healing
3. Immunologic: temper and alert the immune system
4. Sensation: pain, itch, pressure
5. Thermoregulation: insulation, absorption
6. Appearance: quality of life

Question 2

three main layers of skin, what they look like on histology, appendages of skin

Answer 2

Epidermis: avascular, keratinizing stratified squamous epithelium, small fraction of total skin volume
Basement Membrane
Dermis: c.t. and stroma, bulk of skin volume, vascular

Appendages: hair, sebaceous glands, sweat glands, nails

Question 3

Four distinct layers of epidermis and their fx

Answer 3

1. Basal layer: stem cells to allow epidermis to regenerate, 1 cell layer thick of columnar cells, keratinocyte proliferation/anchorage to BM
2. Spinous Layer: keratinocyte adhesion, several layers of round cells with spaces between
3. Granular Layer: keratinocyte differentiation, keratin protofilaments, ~3 layers of cells with granules
4. Cornified Layer: keratinocyte death, water-tight barrier that sloughs off during desquamation

Question 4

Non-keratinocyte cells in epidermis

Answer 4

1. Langerhans Cell: extends to corneum layer, dendritic APC
2. Melanocytes: in basal layer, pigment producing cells
3. Merkel Cells: only basal layer, cross talk between skin & nervous system

Question 5

Keratin: type of protein? where? function?

Answer 5

Intermediate filaments, major protein in keratinocytes, structure and support of skin

Question 6

Epidermolysis Bullosa Simplex

genetics, sx

Answer 6

Defects in Keratin 5/14 (in basal layer)

Blistering within suprabasilar cells of epidermis

Question 7

Bullous Pemphigoid

pathogenesis

Answer 7

Auto-Ab’s against hemidesmosome - connects basal cells to BM

Causes tense bullae between basal layer and BM

Question 8

Pemphigus Vulgaris

pathogenesis

Answer 8

Auto-Ab’s against desmosome - connect keratinocytes in epidermis to eachother
Causes nontense fragile blisters and erosions

Question 9

Which layer of skin makes up the bulk of skin volume?

Answer 9

DERMIS

Question 10

What imparts tensile strength to skin? How much of skin is composed of it in dry weight?

Answer 10

Interstitial collagen!

75% collagen in dry skin