Dermatology - Non-keratinocyte Epidermal Cells and Appendages

Question 1

4 types of epidermal cells?

Answer 1

Keratinocytes (95%)
Melanocytes
Langerhan cells
Merkel cells

Question 2

Migration of melanocytes in first 3 months of foetal development?

Answer 2

Migrate from the epidermis to the neural crest

Question 3

Function of melanocytes?

Answer 3

Convert tyrosine to melanin and store this in organelles called melanosomes

Question 4

Function of melanosomes?

Answer 4

AKA melanin granules - transferred to adjacent keratinocyte via dendrites and form a protective cap over the nucleus

Question 5

What is Nelson’s syndrome?

Answer 5

Melanin Stimulating Hormone (MSH) is produced in excess by the pituitary

Question 6

Function and location of Langerhan cells?

Answer 6

Act as antigen-presenting cells as part of the skin immune system

Question 7

Origin of Langerhan cells?

Answer 7

Mesenchymal origin (bone marrow)

Question 8

Unique feature of Langerhan cells?

Answer 8

Contain Birbeck granules/Racket organelles (tennis racket-shaped)

Question 9

Function and location of merkel cells?

Answer 9

Basal cells that are mechanoreceptors (allow sense of touch); between keratinocytes and nerve fibres

Question 10

Cause of Merkel cell carcinoma?

Answer 10

Caused by a viral infection; there is a very high mortality

Question 11

What are hair follicles?

Answer 11

AKA pilosebaceous unitThey have an epidermal component plus a dermal papilla

Question 12

Label this pilo-sebaceous unit?

Answer 12

IMAGE

Question 13

Phases of growth of a hair follicle?

Answer 13

Anagen (growing)

Catagen (involuting/cessation)

Telogen (resting/shedding phase that occurs each day in numbers of 50-100)

Question 14

Types of hair follicles?

Answer 14

Lanugo (in utero) - fine, soft woolly hair

Vellus - short, thin and light-colored that develops during childhood

Terminal - thick, long, and dark that develops during puberty due to androgen hormone increase

Question 15

Pattern of telogen phase in humans?

Answer 15

Asynchrous, so it occurs at different times and all the hair is not lost at a single time

Question 16

What is telogen effluvium?

Answer 16

Excessive shedding of hair; commonly occurs after pregnancy, due to hormone changes, and will grow back

Question 17

What is Alopecia areata?

Answer 17

Autoimmune hair loss

Question 18

Structure of nails?

Answer 18

Specialised keratins with a nail matrix/root (similar to a hair bulb)

Question 19

Injury to nail matrix?

Answer 19

Flawed differentiation can cause mini fingernail growth