Development & Structure of Epidermis

Question 1

describe the formation of the epidermis

Answer 1

ectoderm layers form single layer periderm, gradual increase in number of cells, periderm cells cast off

Question 2

what is the epidermis

Answer 2

the outer layer of skin, statified cellular epithelium

Question 3

what is the dermis

Answer 3

layer beneath epidermis, contains connective tissue

Question 4

describe what the dermis is formed from

Answer 4

formed from mesoderm below ectoderm

Question 5

describe what is found at 4 weeks of foetal skin development

Answer 5

periderm, basal layer and dermis

Question 6

describe what is found at 16 weeks of foetal skin development

Answer 6

keratin layer, granular layer, prickle cell layer, basal layer, dermis

Question 7

what happens to melanocytes at 16 weeks of foetal skin development

Answer 7

they migrate from the neural crest

Question 8

describe what Blaschko’s lines are

Answer 8

the development growth patterns of skin, not following nerves, blood vessels or lymphatics

Question 9

what does skin consist of

Answer 9

epidermis, appendages, dermo-epidermal junction, dermis, sub-cutis

Question 10

what type of epithelium is the epidermis and how thick it is

Answer 10

stratified squamous epithelium, 1.5mm thick

Question 11

what are the 4 defined layers of the epidermis, from outer most to inner most layer

Answer 11

keratin layer, granular layer, prickle cell layer, basal layer

Question 12

what different types of cells are found in the epidermis

Answer 12

keratinocytes(95%), melanocytes, Langerhans cells, Merkel cells

Question 13

what is the epidermal turnover regulated by

Answer 13

growth factors, cell death and hormones

Question 14

where do keratinocytes migrate from

Answer 14

the basement membrane

Question 15

describe the features of the basal layer of the epidermis (4)

Answer 15

usually one cell thick, small cuboidal, lots of intermediate filaments, highly metabolically active

Question 16

describe the features of the prickle cell layer of the epidermis (3)

Answer 16

larger polyhedral cells, lots of desmosomes(connections), intermediate filaments connect to desmosomes

Question 17

describe the features of the granular layer of the epidermis

Answer 17

large keratohyalin granules, odland(lamellar) bodies, high lipid content, origin of ‘cornified envelope’,

Question 18

how many layers of cells are found in the granular layer of the epidermis

Answer 18

2-3 layers of flatter cells

Question 19

describe the features of the keratin layer of the epidermis

Answer 19

corneocytes, insoluble cornified envelope, 80% keratin + filaggrin, lamellar granules release lipid, tight waterproof barrier

Question 20

describe what corneocytes are

Answer 20

overlapping non-nucleated cell remnants