Week 7

Question 1

Skin/Epidermis

Answer 1

1. Largest, 16% BW, 9.5 million cells/in2
2. Protection (hydrophobic, pathogen-proof); sensation (nerve endings as mechanoreceptors); thermoregulation (dil/cons); water loss prevention

Question 2

Dermis (Lower)

Answer 2

Blood vessels

Sweat glands

Question 3

Epidermis: Basale

90+% keratinocytes, 5% melanocytes-color; 2% merkel-touch sensors

Answer 3

1. Anchorage to dermis
2. Tissue maintenance via proliferative cells from ki67 staining/differentiated cells
3. Basal layer cells –> SC + progenitors –> spinous cells –> granular cells –> corneocytes
   4.

Question 4

Basale Disease

Answer 4

1. UV under dermis + sub-dermis fat –> DNA mutation –> low TSG and high oncogene (squamous carcinoma, highly organized and structureless)
2. Inflammation and psoriasis (long; immune cells create cytokines –> no shedding + proliferation)

Question 5

Epidermis: Basale: Basement Membrane (Connect dermis and epidermis via lamina densa and lucida)

Answer 5

1. Epidermolysis bullosa simplex: AD mutation of R125P on K15 + WT K5 –> basal cell cytolysis –> blistering (8/1mil)
   > Hyperhidrosis, worse in warmth (WEBER-COCKAYNE), mild oral erosion (KOEBNER), and generalized erosion/thickened nails (DOWLING-MEARA**)
2. Junctional Epidermolysis Bullosa: decreased hemidesmosomes (laminin3/2/b defect, AR); poor keratinocyte adhesion to BM (HERLITZ- no scarring/bad teeth/anemia; NON-HERLITZ- scarring/nail atrophy/normal life span); 80+% has subs. premature termination codon.
3. Dystrophic epidermolysis bullosa: decreased anchoring fibrils; AD/AR in COL7A1 (AD- extremity blistering, scarred-healing, mild oral; AR- severe blistering+oral+scarring, corneal defects)

Question 6

Epidermis: Basale: Basement Membrane Treatment

Answer 6

Harvest Patient cells

> Retroviral transduction –> correct lamina B3 GE and delivery to keratinocytes –> transgenic skin grafting (JEB)

Question 7

Epidermis: Spinosum

6-10 layers, strength, keratin, no division; 90+% keratinocytes, 10% langerhan Immune cells

Answer 7

1. Basal cell progeny; (hemi- kera to kera); desmosomes (kera to BM; IC adhesion)
   > Normal: desmocollin and desmogleins form dimers for sticking
   > Abnormal: Auto-Ab PEMPHIGUS VULGARIS messes up IC bridge –> K1/K10 defects + cytolysis of spinous and upper layers –> thickened tissues + large gap + skin erosion + oral/palate; treatment via B-cell receptors

Question 8

Epidermis: Granulosum

3-5 layers, metabolically active strata to dead/superficial strata transition

Answer 8

1. Lamellar granules: lipid release between corneum cells
2. Keratohyalin granules (Dark-staining from filaggrin-led keratin aggregation)
3. Epidermal Differentiation Complex (1q21) and Filaggrin mutations (dry skin from ichthyosis vulgaris loss of function)

Question 9

Epidermis: Lucidum

3-4 layers of dead cells

Answer 9

1. Palms and soles only: transition between granular and corneum)

Question 10

Epidermis: Corneum

Answer 10

1. Formation: more cells in basale –> cells pushed up –> gran becomes corn (4-6 weeks)
2. Dead and hydrophobic: nuclei-less cells fuse to squamous sheets (shed)
3. Abnormal:
   > Thickening; no/abnormal lipid lamellae/vacuole; less lamellar granule exocytosis
   > No ABCA12/HARLEQUIN (AR): no EC ATP-binding lipid transporter from LG; hyperkeratosis with thick scales