Skin Structure and Function 2

Question 1

are skin appendages preserved in scarring?

Answer 1

no

Question 2

what cells make up the epidermis?

Answer 2

95% are keratinocytes
melanocytes
Langerhans cells
merkel cells

Question 3

what are melanocytes and where do they come from?

Answer 3

pigment producing dendritic cells (can form freckles)
they migrate from the neural crest to the epidermis in first 3 months of development and sit at the basal layer and above

Question 4

what do melanocytes do?

Answer 4

contain organelles called melanosomes which convert tyrosine to melanin pigment

Question 5

what does melanin do?

Answer 5

absorbs light and acts as a neutral density filter

forms a protective cap over nucleus of basal cells to protect DNA

Question 6

what stimulates melanocytes to produce melanin?

Answer 6

UV light

hormones

Question 7

what happens to melanin granules after being produced?

Answer 7

transferred from melanocyte to a keratinocyte

Question 8

what is vitiligo?

Answer 8

autoimmune disease where melanocytes are attacked by T cells

Question 9

what is albinism?

Answer 9

genetic partial loss of pigment production

Question 10

what is nelson’s syndrome?

Answer 10

Pituitary tumour produces too much ACTH which results in over-stimulation of melanocytes and dark skin

Question 11

what is a melanoma?

Answer 11

tumour of the melanocyte cell line

Question 12

where do Langerhans cells originate and where do they end up?

Answer 12

mesenchymal origin in bone marrow and end up in the prickle layer as well as dermis and lymph nodes

Question 13

what do Langerhans cells do?

Answer 13

pick up antigens in skin and circulate to lymph nodes to present the antigen
(hence are dendritic in shape)

Question 14

what are birbeck granules?

Answer 14

tennis racket shaped organelles found in Langerhans cells that

Question 15

what are merkel cells?

Answer 15

mechanoreceptors in the basal layer between the keratinocytes and nerve fibres that detect the feeling of something crawling over you

Question 16

can merkel cells become cancerous?

Answer 16

yes
rare but very high mortality
caused by viral infection

Question 17

what is another name for hair follicles?

Answer 17

pilosebaceous unit

Question 18

describe the hair follicle

Answer 18

epidermal component + dermal papilla with adjacent sebaceous gland
specialised keratins and melanocytes above dermal papilla which give hair matrix pigmentation

Question 19

what are the 3 phases of hair growth?

Answer 19

anagen = growing
catagen = regressing
telogen = resting (will fall out)

Question 20

can growth patterns of hair vary?

Answer 20

yes
variations depending on area of body
hormones also have an influence

Question 21

which phase is most hair usually in?

Answer 21

anagen (90%)
10% in catagen
<1% in telogen

Question 22

is the telogen phase synchronous or asynchronous in humans? what does this mean?

Answer 22

asynchronous

not all hair falls out at same time (drugs can cause it to become synchronous)

Question 23

what can affect the % of hairs in the anagen phase?

Answer 23

hormones (ie - pregnancy/childbirth)

e.g - low % of anagen hairs after childbirth

Question 24

what can cause virilisation (development of male characteristics) in females?

Answer 24

excess androgen from a tumour or polycystic ovary syndrome (androgen is precursor for testosterone)

Question 25

what is alopecia areata?

Answer 25

autoimmune condition where T cells attack hair follicles causing hair loss

Question 26

what are nails made of?

Answer 26

specialised keratins

root is similar to hair bulb

Question 27

how do nails grow?

Answer 27

epidermis folds back on itself causing another lower “platform”
basal cells at this surface enter different differentiation programme so become different cells that produce lots of specialised keratin that sits on top as the nail in the same way that the keratin layer sits on top of the epidermis

Question 28

what are the 3 parts of the nail plate?

Answer 28

dorsal (on top)
intermediate (in middle)
ventral (on bottom)