Anatomy Of Epidermis

Question 1

What kind of epithelium is the epidermis?

Answer 1

Stratified squamous

Question 2

What are the layers of the epidermis?

Answer 2

• Stratum corneum
• Stratum lucidum (only palms and soles)
• Stratum granulosum
• Stratum spinosum
• Stratum basale (basal cell layer)

Question 3

What is the stratum corneum?

Answer 3

An outer layer of dead cells and keratin

Question 4

What is the purpose of the stratum corneum?

Answer 4

Presents barrier to bacterial and environmental toxins

Question 5

How does the skin epithelium change as the cells migrate to the skin surface?

Answer 5

It becomes super specialised, forming a squamous shape

Question 6

How does the skin epithelium form a squamous shape is it migrates to the surface?

Answer 6

• Filling cytoplasm with proteins, especially keratin

- Cross-linking polymer fibres into strong stable networks

Question 7

What is the purpose of the squamous shape of the skin epithelium?

Answer 7

It means the skin is resistant to mechanical trauma, and allows shedding without disruption of the whole surface

Question 8

What are the epidermal cells of the skin known as?

Answer 8

Keratinocytes

Question 9

What holds together the keratinocytes?

Answer 9

Organelles called desmosomes

Question 10

What are desmosomes?

Answer 10

Cell adhesion structures

Question 11

Where are desmosomes especially prominent?

Answer 11

In the epidermis and mucous membranes

Question 12

What is the source of new skin epidermal cells?

Answer 12

The basal cell layer

Question 13

What is the role of rete pegs in the skin?

Answer 13

Ensures attachment of the dermis to the epidermis via the basement membrane

Question 14

What are the major cell types forming the epidermis?

Answer 14

• Keratinocytes
• Melanocytes
• Merkel cells
• Langerhans cells

Question 15

What is the function of keratinocytes?

Answer 15

Produce keratin and lipids as a protective barrier

Question 16

What happens to daughter cells of keratinocytes?

Answer 16

They move to the surface to form the cornified layer (stratum corneum)

Question 17

What is the function of melanocytes?

Answer 17

Produce melanin

Question 18

What is the function of melanin?

Answer 18

• Give pigment to skin

- Protects cell nuclei from UV radiation induced DNA damage

Question 19

What happens to melanin production following UV-induced cell damage?

Answer 19

It is increased

Question 20

How is melanin production increased after UV-induced cell damage?

Answer 20

UV-induced DNA damage and/or its repeat produce initiating signals that induce an increase in melanogenesis

Question 21

Where does melanogenesis occur?

Answer 21

Specific ovoid organelles called melanosomes

Question 22

Where are melanosomes produced?

Answer 22

In dendritic melanocytes

Question 23

What is each melanocyte associated with?

Answer 23

Around 36 keratinocytes and one Langerhans cell

Question 24

What is the unit of 1 melanocyte, keratinocytes, and 1 Langerhans cell called?

Answer 24

Epidermal melanin unit

Question 25

What happens to melanin synthesised within melanosomes?

Answer 25

It is transported via dendrites to adjacent keratinocytes

Question 26

What happens to the melanin once it has been transported to keratinocyters?

Answer 26

It accumulates within keratinocytes and melanocytes in the perinuclear areas

Question 27

How does melanin protect against UV damage?

Answer 27

It serves as a physical barrier that scatters UV radiation, and reduces its penetration through the epidermis

Question 28

What is the function of Merkel cells?

Answer 28

They contain specialised nerve endings for cutaneous sensation

Question 29

What is the function of Langerhans cells?

Answer 29

They present antigens and active T-lymphocytes for immune protection

Question 30

What is meant by the epidermal turnover time?

Answer 30

The time taken for migration of cells from stratum basale to stratum corneum

Question 31

What is the epidermal turnover time?

Answer 31

Approx 30 days