Specials - Human Skin

Question 1

What is the thinnest skin?

Answer 1

Eyelids (0.5mm)

Question 2

What is the thicket skin?

Answer 2

Palms and soles of feet (4mm)

Question 3

To what does the human skin act as a barrier to ?

Answer 3

Act as a protector/barrier to the: 
Chemicals 
Pathogens
UV light 
Heat 
Environment

Question 4

How is human skin involved in thermoregulation?

Answer 4

Sweat glands - evaporation of sweat cools the body
Blood vessels:
Constrict = they reduce heat loss (due to reduced blood flow)

Dilate = Increase heat loss (due to more blood flowing)

Question 5

How is human skin involved in sensation?

Answer 5

Detect touch/pressure, pain and temperature
Also synthesises vitamin D
The vitamin D requires a modification by UV before the active form can be made in the liver

Question 6

What are the functions of the human skin?

Answer 6

Barrier/protection
Thermoregulation
Sensation
Blood reservoir

Question 7

What is the human skin structure?

Answer 7

Epidermis, dermis and hypodermis

Question 8

Describe the structure of the epidermis

Answer 8

Top layer of skin
Provides barrier and continued renewal
No structural strength
Consists of layers of keratinocytes

Question 9

What are keratinocytes?

Answer 9

Dead keratin cells that make up the surface of the epidermis

Question 10

How much blood can the skin hold?

Answer 10

8-10% of the total blood volume

Question 11

Why does the skin have no structural strength

Answer 11

it is mainly made of dead or dying keratinocytes, so there is no connective tissue in the epidermis to provide strength

Question 12

What and where is thin skin?

Answer 12

the majority of skin is thin skin and it is when the epidermis has 4 layers of keratinocytes (thinNEST is eyelids)

Question 13

What and where is thick skin?

Answer 13

it is in the fingertips, palms, soles and has 5 layers. The fifth layer is Stratum Lucidum

Question 14

Does the skin have vasculature?

Answer 14

No it doesn’t, all nutrient supply and waste removal through the dermis

Question 15

What does stratification refer to?

Answer 15

the different layers in the epidermis

Question 16

What is the function of stratification?

Answer 16

Crucial for barrier function and continued renewal of the epidermis

Question 17

What do cells at the bottom of the epidermis do (I.e at the stratum basale)

Answer 17

Keratinocytes proliferate at the bottom of the epidermis (Stratum Basale) which pushes cells up and away from the dermis

Question 18

What happens to cells as they move away from the dermis?

Answer 18

They undergo programmed cell death (apoptosis)

Question 19

How long does complete epidermal turnover take?

Answer 19

A month

Question 20

What is the acronym for the layers of the epidermis?

Answer 20

Come Lets Get Sun-Burnt

Question 21

What is the bottom layer of the epidermis?

Answer 21

Stratum Basale

Question 22

What are keratinocyte stem cells and what do they do?

Answer 22

They are the reservoirs of cells (keratinocytes, stem cells) for a lifetime of renewal.
Keratinocyte stem cells can divide so that one cell remains a stem cell and the others become transit amplifying keratinocytes

Question 23

What occurs in the Stratum Basale?

Answer 23

Transit amplifying keratinocytes proliferate a lot to provide cells for all the top layers
(divide rapidly but for a short period before they die)

Question 24

What is the layer above the Stratum Basale?

Answer 24

Stratum Spinosum

Question 25

How thick is the Stratum Spinosum?

Answer 25

8-10 layers of cells/keratinocytes

Question 26

What happens to keratinocytes in the Stratum Spinosum

Answer 26

Keratinocytes begin to flatten out

Question 27

What holds keratinocytes together in the Stratum Spinosum and what is this important for?

Answer 27

Keratin intermediate filaments and desmosomes. This is important for the barrier function of the skin

Question 28

What layer is above the Stratum Spinosum?

Answer 28

Stratum Granulosum

Question 29

What happens in the Stratum Granulosum

Answer 29

Flattened keratinocytes undergo apoptosis (programmed cell death)

Question 30

What are lamellar granules?

Answer 30

Organelles in keratinocytes that fuse to the plasma membrane and begin to release lipid rich secretions to help form the barrier in the Stratum Granulosum

Question 31

What is keratohyalin?

Answer 31

Protein structure in granules of keratinocytes. | These dark granules help form keratin intermediate filaments into keratin (holds keratinocytes together)

Question 32

What layer is above the Stratum Granulosum

Answer 32

Stratum Lucidum

Question 33

Where is the Stratum Lucidum found?

Answer 33

ONLY in thick skin (fingertips, palms, soles)

Question 34

What is the top layer of the epidermis?

Answer 34

Stratum Corneum

Question 35

How thick is the Stratum Corneum?

Answer 35

25-30 layers of flattened dead keratinocytes

Question 36

What is the function of the Stratum Corneum

Answer 36

To form a barrier | Keep moisture in and outside world out

Question 37

What are keratinocytes like in the Stratum Corneum

Answer 37

Have finished undergoing apoptosis and are overlapping like the scales of a snake

Question 38

What is the interface between the dermis and epidermis

Answer 38

The basement membrane

Question 39

What are the proteins in the Basement Membrane

Answer 39

Collagen IV, Perlecan, Nidogen, Lamaminin 332

Question 40

What do keratinocytes in the basal layer attach to?

Answer 40

Proteins in the basement membrane

Question 41

What is the Basement membrane important for?

Answer 41

It is important for the epidermal attachment to the dermis

Question 42

What can a mutation in the basement membrane proteins cause?

Answer 42

Epidermolysis Bullosa | It is when the keratinocytes cannot attach to the BM

Question 43

What are rete ridges/dermal papillae?

Answer 43

Wave-like ridges in the boundary between the epidermis and the dermis

Question 44

What is the function of rete ridges?

Answer 44

Their contour provides resistance to shear forces

Question 45

Where do melanocytes reside?

Answer 45

In the epidermal side of the basement membrane

Question 46

What do melanocytes make?

Answer 46

Melanosomes

Question 47

What is contained in melanosomes?

Answer 47

Melanin

Question 48

How are melanosomes transferred to keratinocytes?

Answer 48

Melanosomes are transferred to keratinocytes by dendrites on the melanocytes 36 keratinocytes at a time

Question 49

What is melanin?

Answer 49

A pigment which gives the skin colour

Question 50

What is Pheomelanin

Answer 50

Pigment in melanin | Gives skin red + yellow colours