Structure + function of skin

Question 1

List 5 functions of the skin.

Answer 1

Protection (barrier)
Thermoregulation
Sensation
Vitamin D production
Fluid balance

Question 2

Which 4 factors allow skin to act as a protective barrier?

Answer 2

Epidermal thickness

DNA repair mechanisms

Presence of melanin

Ability to induce apoptosis

Question 3

Describe the process of vitamin D synthesis from sunlight.

Answer 3

In the skin, 7-dehydrocholesterol is converted into D3

In the liver, D3 is converted into 25-hydroxyvitamin D

In the kidneys, 25-hydroxyvitamin D is converted into 1,25-dihydroxyvitamin D (calcitriol)

Question 4

By which 2 mechanisms does melanin provide protection against UV radiation?

Answer 4

Scatters UV radiation

Absorbs UV radiation

Question 5

What percentage of total blood volume is contained within capillary networks of the skin?

Answer 5

10%

Question 6

Which muscles make hair stand up?

Answer 6

Arrector pili

Question 7

List 3 non-epithelial cells found in the epidermis.

Answer 7

Melanocytes

Langerhans cells

Merkel cells

Question 8

Starting deep and travelling superficial, what are the 5 layers of the epidermis?

Answer 8

Stratum basale

Stratum spinosum

Stratum granulosum

Stratum lucidum

Stratum corneum

Question 9

Which junctions attach basal cells in the stratum basale to the basement membrane?

Answer 9

Hemidesmosomes

Question 10

What are the 2 main junction types found in the stratum spinosum?

Answer 10

Desmosomes
Adherens junctions

Question 11

Which junctions are found in the stratum granulosum?

Answer 11

Tight junctions

Question 12

In the epidermis, what is the function of desmosomes?

Answer 12

Mechanical strength

Question 13

In what layer of the epidermis are melanocytes found?

Answer 13

Stratum basale

Question 14

How does melanin prevent DNA damage from UV?

Answer 14

It forms a protective cap over the nucleus of cells, protecting it from DNA damage by UV light

Question 15

What is the function of Langerhans cells in the epidermis?

Answer 15

Antigen-presenting cells (immune surveillance)

Question 16

What are the 2 layers of the dermis?

Answer 16

Papillary dermis

Reticular dermis

Question 17

Which structures help strengthen the connection between the epidermis and dermis?

Answer 17

Rete ridges

Question 18

What is the principal cell of the dermis?

Answer 18

Fibroblasts

Question 19

What is the principal cell of the epidermis?

Answer 19

Keratinocytes

Question 20

During which trimester do skin appendages develop?

Answer 20

Second trimester

Question 21

What are the 2 types of sweat glands in the skin?

Answer 21

Eccrine glands

Apocrine glands

Question 22

Moving outwards, what are the epithelial layers of hair?

Answer 22

Medulla
Cortex
Cuticle
Internal root sheath
External root sheath

Question 23

Which 3 epithelial layers comprise the hair shaft?

Answer 23

Medulla
Cortex
Cuticle

Question 24

What do sebaceous glands produce and what is their function?

Answer 24

Sebum - waterproofing

Question 25

What do eccrine glands produce?

Answer 25

Sweat

Question 26

What do apocrine glands produce?

Answer 26

Odour

Question 27

What is the structural shape of sebaceous glands?

Answer 27

Branched acinar

Question 28

What are the 3 main histological changes seen in eczema?

Answer 28

Spongiosis Hyperkeratosis Parakeratosis

Question 29

What is spongiosis in eczema?

Answer 29

Swelling in the epidermis caused by the separation of keratinocytes due to fluid accumulation

Question 30

What is hyperkeratosis?

Answer 30

Thickening of the stratum corneum

Question 31

What is parakeratosis?

Answer 31

Retention of nuclei in the stratum corneum cells

Question 32

In psoriasis, which layer of the epidermis is lost?

Answer 32

Stratum granulosum

Question 33

In psoriasis, which 2 changes can be seen in the papillary dermis?

Answer 33

Elongated rete ridges Dilated capillaries

Question 34

List 5 mechanisms of blister formation.

Answer 34

1. Cells destroyed, leaving gaps 2. Fluid forces cells apart 3. Bonds between epidermal cells destroyed 4. Altered basement membrane 5. Inherited defects in skin proteins

Question 35

What is the cause of pemphigus and what kind of blistering does it cause?

Answer 35

Autoantibodies to desmosomes Intraepidermal blistering

Question 36

What is the cause of bullous pemphigoid and what kind of blistering does it cause?

Answer 36

Autoantibodies to hemidesmosomes Subepidermal blistering

Question 37

Which epidermal layer is not present in thin skin?

Answer 37

Stratum lucidum