Structure and Function of Skin

Question 1

What does the integumentary system refer to?

Answer 1

→ skin, hair and nails

Question 2

What are the 5 main skin functions?

Answer 2

→ Barrier 
→ Thermoregulation
→ Sensation
→ Repair 
→ Vitamin D production

Question 3

What does the skin act as a barrier against?

Answer 3

→ Dehydration
→ Infection
→ Injury/abrasion
→ solar radiation

Question 4

What are the 3 layers of the skin?

Answer 4

→ Epidermis
→ Dermis
→ Hypodermis

Question 5

What is the first layer called?

Answer 5

→ Stratum basale

Question 6

Describe the stratum basale?

Answer 6

→ Contains stem cells and is attached to the dermis
→ daughter cells are constantly moving up distally through the epidermis
→ They differentiate as they go until they are shed from the outer surface

Question 7

What are the characteristics of the stratum spinosum?

Answer 7

→ Cells have many desmosomes that are visible as spines between the cells

Question 8

What does the stratum granulosum contain?

Answer 8

→ 1-4 layers of cells containing prominent granules of ‘keratohyalin’ - precursor of keratin
→ Lamellar bodies containing lipids
→ differentiating cells to form the outer layer

Question 9

What does the stratum corneum contain?

Answer 9

→ Squamous cells which have lost their nuclei
→ horn-like keratin
→ non polar lipids are between the cells

Question 10

What are the 4 main layers of the epidermis?

Answer 10

→ Stratum basale
→ Stratum Spinosum
→ Stratum Granulosum
→ Stratum corneum

Question 11

What is the stratum corneum constantly doing?

Answer 11

→ Flaking off and being constantly replaced

Question 12

What is keratin the main component of?

Answer 12

→ horns, hair, nails, claws, hooves

Question 13

What are other 3 types of epidermal cells?

Answer 13

→ Melanocytes
→ Langerhans cells
→ Merkel cells

Question 14

What do melanocytes do?

Answer 14

→ Synthesizes melanosomes

→ transfers them to basal keratinocytes through long dendrites (downwards)

Question 15

Where are the stem cells found and why?

Answer 15

→ Basal Keratinocytes

→ Need to be protected from UV damage

Question 16

Where is the melanin pigment mostly found?

Answer 16

→ Basal epidermis

Question 17

Where do keratinocytes arrange melanin and how?

Answer 17

→ They arrange melanin pigment in a cap distal to the nucleus
→ Especially in the basal layer

Question 18

What is the function of Langerhans cells?

Answer 18

→ Antigen presenting cells

→ they are also dendritic cells that form a network

Question 19

Where is vitamin D3 made?

Answer 19

→ In the epidermis

→ mostly in the basal cells but also the stratum spinosum

Question 20

What does the production of vitamin D3 require and how does this change with skin color?

Answer 20

→ UV light

→ more UV light with dark skin

Question 21

How and where is vitamin D3 converted into its active form?

Answer 21

→ 1,25 dihydroxyvitamin D3

→ In the liver and kidney

Question 22

Describe the dermis

Answer 22

→ Dense, irregular connective tissue

Question 23

Why is the dermis dense?

Answer 23

→ Full of collagen fibres

Question 24

Why is the dermis irregular?

Answer 24

→ Fibres are running in all directios

Question 25

What is the function of collagen?

Answer 25

→ provides tensile strength | → protection against abrasion and impact

Question 26

What does elastin do?

Answer 26

→ A protein complex that provides elasticity

Question 27

Why is the dermis rich in blood vessels?

Answer 27

→ it carries blood and nerve supply for the epidermis

Question 28

Why is the dermal-epidermal border wavy?

Answer 28

→ to resist shear forces

Question 29

What do fibroblasts in the dermis do?

Answer 29

→ Make and maintain the collagen

Question 30

What is an effect of UV light on skin?

Answer 30

→ Damage and loss of elastic fibres | → leads to wrinkles

Question 31

What is the hypodermis composed of?

Answer 31

``` → Fat → glands → hair follicles → nerves → blood vessels ```

Question 32

What is the function of the hypodermis?

Answer 32

→ Provides insulation → Cushioning → energy storage

Question 33

Where do subcutaneous injections go?

Answer 33

→ hypodermis

Question 34

What are the three types of gland?

Answer 34

→ Sebaceous → Eccrine sweat glands → Apocrine sweat glands

Question 35

What is the function of sebaceous glands?

Answer 35

→ Secrete oily sebum into the hair follicle

Question 36

What is the function of sebum?

Answer 36

→ Conditioner for hair and skin | → Prevents dryness and flaking

Question 37

What do eccrine sweat glands do?

Answer 37

→ Watery secretion onto skin surface | → Cool the body by evaporation

Question 38

What do apocrine sweat glands do?

Answer 38

→ secrete oily fluid into hair follicles | → source of body odour after bacterial action

Question 39

Where are apocrine sweat glands found?

Answer 39

→ Armpits | → anogenital region

Question 40

What is acne?

Answer 40

→ When a follicle becomes blocked and can get infected

Question 41

What are the 4 types of acne?

Answer 41

→ Blackhead → whiteheads → papules → infected

Question 42

Where is the nail formed?

Answer 42

→ The nail matrix

Question 43

What is the nail plate made from?

Answer 43

→ hard keratin

Question 44

What are the 4 receptors in the skin?

Answer 44

→ thermoreceptor → Meissners corpuscle → Nociceptor → Pacinian corpuscle

Question 45

What are Meissners Corpuscles receptive to?

Answer 45

→ Touch

Question 46

What are Pacinian corpuscles receptive to?

Answer 46

→ Pressure

Question 47

How does the skin protect against dehydration?

Answer 47

→ Keratin holds water | → lipids stop it evaporating

Question 48

How does the skin protect against injury?

Answer 48

→ epidermis is strong, rapid healing, thick where friction occurs → Dermis has collagen, tough and leathery → hypodermis cushions

Question 49

How does the dermis repair itself?

Answer 49

→ Fibroblasts fill gaps with new collagen that epidermis can attach to