A 6 Skin as a Protective Barrier

Question 1

Name the 4 Cornified envelope proteins?

Answer 1

• Loricrin
• involucrin
• keratolinin
• transglutaminase 1 catalyzes cross-linking of the above 3.

Question 2

Corneocyte Intercellular lipid matrix (ex: ceramide) is released from?

Answer 2

-Lamellar granules (a.k.a. membrane coating granules, or Odland bodies). This is the mortar of stratum corneum.

Question 3

Main lipid in stratum corneum?

Answer 3

Ceramides. (a sphingolipid)

Question 4

Describe the 3 diseases of the stratum corneum. (Don’t need to know these!!)

Answer 4

• Staphylococcal Scalded Skin Syndrome (splits skin just below stratum corneum, sloughs off. Fluids barrier disrupted.)
• Lamellar ichthyosis (mutated transglutaminase 1, so no cornified envelope. Get large plate-like scale and ectropion.)
• Harlequin fetus (Auto recessive. Lamellar granules absent. No intercellular matrix. Severe ichthyosis, a.k.a. scales. Malformed ears, eyes, mouth.)

Question 5

Do glycoproteins belong to lamellar granules, or keratinohyalin granules?

Answer 5

-Lamellar granules. This is the exception, where a protein is in the lamellar granules.

Question 6

Which epidermal cells are interdigitated?

Answer 6

-Corneocytes

Question 7

Desmosomes are present mostly in which epidermal layers?

Answer 7

All but most superficial stratum corneum

Question 8

Elasticity of stratum corneum comes from what?

Answer 8

-H20 filled in among corneocyte proteins

Question 9

Skin temp is okay in this range without damage.

Answer 9

20-40 C

Question 10

Heat exchange w/ environment mainly happens where:

Answer 10

• Cutaneous blood vessels

- Eccrine sweat glands

Question 11

In cold environments, what happens in skin?

Answer 11

-Sympathetic stimulation. Vessel constriction. Flow down.

Question 12

Max sweat rate? Controlled by?

Answer 12

• 1.5 liter/hr. 10X normal heat loss rate.

- Controlled by hypothalamus.

Question 13

What results from UV acting on dehydrocholesterol?

Answer 13

-Cholecalciferol. (Vit D3)

Question 14

Vit D3 activation sequence

Answer 14

• 7-dehydrocholesterol: ring break by UV to…
• Cholecalcieferol (D3): hydroxylated in liver to…
• 25 hydroxycholecalcieferol: Hydroxylated again in kidney to…
• 1,25 dihydroxycholecalcieferol: Finally active.
• Acts to absorb and reabsorb more Ca from intestine and kidney.

Question 15

Langerhans do what?

Answer 15

• Present antigen to T cells
• Delayed hypersensitivity reactions
• Immunosurveillance against viruses

Question 16

Langerhans located in dermis or epidermis?

Other “inflammatory cells” located in dermis or epidermis?

Answer 16

Langerhans=epidermis (for our purposes)

“Other cells”=dermis (lymphocytes, histiocytes, neutrophils, eosinophils, mast cells)

Question 17

UV Spectrum wavelengths (in nm)

Answer 17

UVC=200-290 (ozone absorbed)
UVB=290-320 (“burning”)
UVA=320-400 (“tanning”)
-memory helper: ABC by energy level. (high freq= high energy)

Question 18

Chromophores

Answer 18

-Absorb light, excite. Then release in 1 of 3 ways:

A. Photochemical rxn: Make pyrimidine dimer or free radical
B. Photosensitized rxn: Transfer the energy to another molecule
C. Shed as heat

Question 19

Sunburn redness is due to?

Answer 19

Vasodilation, mast cell degranulation.

Question 20

3 skin cancers

Answer 20

• basal cell carcinoma
• malignant melanoma
• squamous cell carcinoma

Question 21

What Absorbs UVB in epidermis?

Answer 21

• Melanin

- Keratin, keratohyalin, nucleic acids, nucleoproteins, urocanoic acid

Question 22

UV that penetrates past epidermis?

Answer 22

• 5-10% UVB

- 50% UVA

Question 23

Function: Lamellar Granules vs Keratohyaline Granules

Answer 23

-Lamellar: Lipid contents maintain vapor barrier with signaling cell turnover. (Mortar)
-Keratohyaline: Deliver free amino acids to the outer layers of the st. corneum. (filaggrin monomers)
Conversion of profilaggrin to fillagrin. epidermal osmolarity and flexibility

Question 24

Where do you find birbeck granules?

Answer 24

In langerhans cells

Question 25

Keratinocytes release an inflamatory response through what?

Answer 25

IL-1