2 - 14 - SKIN BARRIER

Question 1

tight junctions seal the intercellular spaces at what layer of the epidermis

Answer 1

SG2

Question 2

eventually becomes the major component of the cornified cell envelope

Answer 2

Loricrin

Question 3

Lamellar bodies are produced from the Golgi complex and stored within the cytoplasm in what cells?

Answer 3

SG3

Question 4

Defects in loricrin are known to cause what disease?

Answer 4

loricrin

Question 5

Defects in transglutaminase 1 are known to cause what disease?

Answer 5

congenital ichthyosis

Question 6

ABCA12 mutations cause what disease?

Answer 6

Harlequin ichthyosis

Question 7

major classes of lipids in the stratum corneum

Answer 7

cholesterol, free fatty acids, and ceramides

Question 8

rate-limiting step in cholesterol biosynthesis is catalyzed by what enqyme?

Answer 8

hydroxymethylglutaryl CoA (HMG CoA) reductase

Question 9

major cell–cell adhesion structure in the granular, spinous, and basal cell layers.

Answer 9

Desmosomes

Question 10

major proteases involved in the degradation of corneodesmosomes

Answer 10

serine proteases belonging to the kallikrein group

Kallikreins 5, 7, and 14 are known to exist in the stratum corneum

Question 11

congenital defects of LEKTI induce what syndrome?

Answer 11

Netherton syndrome

entire layers of the stratum corneum are prone to being peeled off, probably caused by the enhanced degradation of corneodesmosomes by kallikreins

Question 12

major protein of the stratum corneum

Answer 12

Filaggrin

Question 13

major pathway by which external molecules can penetrate the stratum corneum

Answer 13

paracellular route

Question 14

Fourteen-sided polyhedron composed of eight hexagons and six squares, proposed in 1887 by William Thomson (Lord Kelvin) as the best shape for packing equal-sized cells together to fill the space using the minimal surface area of each cell

Answer 14

Kelvin’s Tetrakaidecahedron

Question 15

pH of the skin surface

Answer 15

weakly acidic pH (a pH of 5.6 to 6.4)

The weak acidic pH is due to various substances, such as free fatty acids secreted from sebaceous glands or derived from phospholipid hydrolysis in the stratum corneum, lactic acid secreted from derived from the eccrine glands, urocanic acid mostly derived from the degradation products of filaggrin, and metabolites produced by microorganisms

Question 16

Question 17

the two major antimicrobial proteins of the skin and show a broad spectrum of antimicrobial activity in vivo

Answer 17

Cathelicidins and β-defensins

Question 18

the dominant commensal bacterium of the skin microbiota

Answer 18

Staphylococcus epidermidis

Question 19

Question 20

babies born before how many weeks of gestation lack the covering of the vernix?

Answer 20

before 28 weeks