Introduction to Skin Biology

Question 1

What is hypohidrotic ectodermal dysplasia?

Answer 1

People CANNOT SWEAT (abnormalities in hair follicles, sweat glands, and teeth)

Question 2

What is Raynauds’ phenomenon?

Answer 2

chronic episodic attacks of digital ischemia (provoked by cold, can ulcerate, can be associated with underlying autoimmune diseases)

Question 3

What happens if the skin fails to maintain the structural barrier?

Answer 3

dehydration

infection

Question 4

What happens if the skin fails to perform immune surveillance?

Answer 4

infection
autoimmunity
cancer

Question 5

What happens if the skin fails to repair injury?

Answer 5

skin cancer

ulcers

Question 6

What happens if the skin fails to regulate temperature?

Answer 6

hypothermia

hyperthermia

Question 7

What happens if the skin fails to maintain circulation?

Answer 7

infarction
emboli
vasculitis

Question 8

What happens if the skin fails to maintain communication?

Answer 8

itching

insensitivity

Question 9

What happens if the skin fails to photo-protect?

Answer 9

cancer

photo-aging

Question 10

What are the 3 main layers of the skin?

Answer 10

epidermis
dermis
subcutis

Question 11

How long does it take the epidermis to cycle through and self-renew?

Answer 11

28 day cycle

Question 12

Where do keratinocytes come from?

Answer 12

the basal layer of the epidermis

Question 13

What are melanocytes? Where do they come from?

Answer 13

pigment-producing cells derived from the neural crest

Question 14

What is more numerous in the epidermis, melanocytes or keratinocytes?

Answer 14

10 keratinocytes : 1 melanocyte

Question 15

True or false: melanocytes hold the pigment and are darker cells.

Answer 15

FALSE: they transfer melanin to surrounding keratinocytes via dendrites

Question 16

What do melanocytes look like under the microscope?

Answer 16

cells at the dermal-epidermal junction with a clear halo around them

Question 17

What are Langerhans cells? What do they do?

Answer 17

Dendritic cells in the mid-epidermis that recognize abnormal antigens in the skin, take them up, process them, and present them to lymphocytes in the regional lymph nodes

Question 18

What are the two major reactions where Langerhans cells are important?

Answer 18

allergic reactions

tumor surveillance

Question 19

What are Merkel cells?

Answer 19

cells involved with light-touch sensation

Question 20

In which layer of the epidermis are hemidesmosomes present?

Answer 20

basal layer

Question 21

What is the role of hemidesmosomes?

Answer 21

attach keratinocytes to the basement membrane of the dermis

Question 22

What is the name of the disease with autoimmunity to hemidesmosomes?

Answer 22

Bullous pemphigoid

• Tense, subepidermal blisters
• Not a lot of inflammation
• Autoantibodies and complement
• Localized or wide-spread

Question 23

What is the treatment for bullous pemphigoid?

Answer 23

immunosuppressive therapy for a couple of years

Question 24

What is the major action that occurs in the spinous layer of the epidermis?

Answer 24

development of lipids (lamellar granules) that are important for barrier function

Question 25

In what layer of the epidermis are desmosomes located?

Answer 25

spinous layer

Question 26

What is the role of desmosomes?

Answer 26

hold keratinocytes together

Question 27

What is the name of the disease with autoimmunity to desmosomes?

Answer 27

Pemphigus vulgaris

• Keratinocytes lose adhesions
• Epidermis falls apart (erosions)
• “chicken wire” IF pattern
• Frequently in eyes and mouth

Question 28

How do you treat pemphigus vulgaris?

Answer 28

steroids (prednisone) and immunosuppressives (rituximab)

Question 29

What population is pemphigus vulgaris most commonly seen?

Answer 29

Ashkenazi Jews

Question 30

What is the major actions of the granular layer of the epidermis?

Answer 30

• Intracellular keratohyaline granules synthesized (including profilaggrin)
• Lipids in lamellar granules secreted into intercellular space to form water barrier

Question 31

What happens with profilaggrin at the stratum corneum?

Answer 31

it is processed to filaggrin (which functions to keep water within cells)

Question 32

What are keratins?

Answer 32

cytoskeletal structural proteins that combine with filaggrin to make macrofibrils to create a protective layer

Question 33

True or false: intermediate filaments made by keratins have the same two components all over the body.

Answer 33

FALSE: pairs differ by location in the body

Question 34

Where is keratin found?

Answer 34

major fibrous structural protein in hair and nails

Question 35

Why does burning hair smell bad?

Answer 35

keratins have large amounts of sulfur-containing amino acids (like cysteine)

Question 36

True or false: the thickness of the dermis is constant throughout the body.

Answer 36

FALSE (varies from 1-4 mm thick)

Question 37

What are the two major cells of the dermis?

Answer 37

fibroplasts

mast cells

Question 38

What is the major role of fibroblasts?

Answer 38

• Synthesize and degrade CT proteins (including collagen, elastin, etc.)
• Responsible for wound healing and scar formation

Question 39

What is a keloid?

Answer 39

uncontrolled fibroblast action (no feedback inhibition on scar formation)

Question 40

What is a mast cell? What does it do?

Answer 40

Specialized tissue cells rich in histamine and heparin granules

• Release their granules when triggered by injury of when they bind IgE antibodies during allergic reactions
• Important in allergic reactions and wound healing

Question 41

What is the main “skin finding” associated with histamine release?

Answer 41

wheal and flare

Question 42

What makes up a pilosebaceous unit?

Answer 42

• Hair follicle
• Sebaceous gland
• Apocrine sweat glands (axilla and anogenital skin)
• Arrector pili muscle

Question 43

What are eccrine sweat glands?

Answer 43

“true” sweat glands—present throughout the body and open directly onto the skin—function to regulate temperature

Question 44

What is the disease associated with genetic defects in filaggrin?

Answer 44

atopic dermatitis