Skin and Function Part 1

Question 1

What is the epidermis?

Answer 1

Outer layer of skin, stratified cellular epithelium

Question 2

What is the dermis?

Answer 2

Layer beneath the epidermis, connective tissue

Question 3

What is the epidermis formed from embryonically?

Answer 3

Ectoderm-form a single layer periderm, gradual increase in layers of cells, periderm cells cast off

Question 4

What is the dermis formed from embryonically?

Answer 4

Mesoderm

Question 5

What are melanocytes?

Answer 5

Pigment producing cells from neural crests

Question 6

What is gastrulation and when does it occur?

Answer 6

Cellular organisation into germ layers; occurs days 7-10

Question 7

What does the skin look like at 4 weeks?

Answer 7

Periderm on top of basal layer, both sit atop dermis (corium)

Question 8

What does the skin look like at 16 weeks?

Answer 8

Keratin layer (top layer), then granular layer then prickle cell layer, finally basal layer atop of dermis, melanocytes migrate from neural crest

Question 9

What does the skin look like at 26 weeks?

Answer 9

Epidermis has formed, melanocytes have appeared as well as sebaceous glands, arector pili muscle and hair follicles

Question 10

What are Blaschko’s lines?

Answer 10

Developmental growth pattern of skin caused by mutations within cells, not following vessels/nerves/lymphocytes, normal development up until 18 weeks

Question 11

What is the other name for Blaschko’s lines?

Answer 11

Epidermal nevis

Question 12

What does skin consist of?

Answer 12

Epidermis, appendages, dermo-epidermal junction, dermis, sub-cutis (predominantly fat)

Question 13

What are the four layers of the epidermis, starting from the most superficial?

Answer 13

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

Question 14

What are other cells found in the epidermis?

Answer 14

Melanocytes, Langerhans cells, Merkel cells

Question 15

What is 95% of the epidermis made from?

Answer 15

Keratinocytes (contain structural keratins)

Question 16

How thick is the epidermis?

Answer 16

1.5 mm

Question 17

How are prickle cells connected?

Answer 17

Via little spikes (desmosomes) which vibrate and allow them to move upwards

Question 18

What is epidermal turnover and how is it controlled?

Answer 18

Balance of cells in/out; controlled by growth factors, cell death and hormones

Question 19

What can result from a loss of control of epidermal turnover?

Answer 19

Skin cancer and psoriasis

Question 20

How long does it take for the epidermis to fully regenerate?

Answer 20

28 days from bottom to top

Question 21

What are some features of the basal layer?

Answer 21

Usually one cell thick, small cuboidal cells, lots of intermediate filaments (keratin), stem cells so highly metabolically active

Question 22

What are some features of the prickle cell layer?

Answer 22

Larger polyhedral cells, lots of desmosomes, intermediate filaments connect to desmosomes

Question 23

What are some features of the granular layer?

Answer 23

2-3 layers of flatter cells, large keratohyalin granules, Odland bodies, high lipid content, cell nuclei loss

Question 24

What do keratohyalin granules contain?

Answer 24

Structural filaggrin and involucrin proteins

Question 25

How does eczema arise?

Answer 25

The granular area is deficient in filaggrin so people can't conserve water

Question 26

What are corneocytes?

Answer 26

Overlapping non-nucleated cell remnants

Question 27

What do lamellar bodies release in the keratin layer?

Answer 27

Lipids

Question 28

Why does HPV occur?

Answer 28

Keratinocytes become infected due to deficient skin barrier

Question 29

What are some features of the keratin layer?

Answer 29

Insoluble cornified envelope, tight waterproof barrier, 80% keratin and filaggrin, has corneocytes

Question 30

Where does the cornified envelope originate from?

Answer 30

The granular layer

Question 31

Where are areas that mucosal membranes are found?

Answer 31

Eyes, mouth, nose, genito-urinary and GI tract

Question 32

What are some specialised forms of oral mucosa?

Answer 32

Masticatory (keratinised to deal with friction/pressure), lining (non-keratinised), specialised (tongue papillae)

Question 33

What are some features of ocular mucosa?

Answer 33

Lacrimal glands, eye lashes, sebaceous glands