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BIOSCI 107 Part One > Specials - Human Skin > Flashcards

Specials - Human Skin Flashcards

1
Q

What is the thinnest skin?

A

Eyelids (0.5mm)

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2
Q

What is the thicket skin?

A

Palms and soles of feet (4mm)

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3
Q

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

A 
Act as a protector/barrier to the: 
Chemicals 
Pathogens
UV light 
Heat 
Environment
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4
Q

How is human skin involved in thermoregulation?

A

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)

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5
Q

How is human skin involved in sensation?

A

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

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6
Q

What are the functions of the human skin?

A

Barrier/protection
Thermoregulation
Sensation
Blood reservoir

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7
Q

What is the human skin structure?

A

Epidermis, dermis and hypodermis

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8
Q

Describe the structure of the epidermis

A

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

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9
Q

What are keratinocytes?

A

Dead keratin cells that make up the surface of the epidermis

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10
Q

How much blood can the skin hold?

A

8-10% of the total blood volume

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11
Q

Why does the skin have no structural strength

A

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

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12
Q

What and where is thin skin?

A

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

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13
Q

What and where is thick skin?

A

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

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14
Q

Does the skin have vasculature?

A

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

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15
Q

What does stratification refer to?

A

the different layers in the epidermis

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16
Q

What is the function of stratification?

A

Crucial for barrier function and continued renewal of the epidermis

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17
Q

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

A

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

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18
Q

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

A

They undergo programmed cell death (apoptosis)

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19
Q

How long does complete epidermal turnover take?

A

A month

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20
Q

What is the acronym for the layers of the epidermis?

A

Come Lets Get Sun-Burnt

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21
Q

What is the bottom layer of the epidermis?

A

Stratum Basale

22
Q

What are keratinocyte stem cells and what do they do?

A

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

23
Q

What occurs in the Stratum Basale?

A

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

24
Q

What is the layer above the Stratum Basale?

A

Stratum Spinosum

25
Q

How thick is the Stratum Spinosum?

A

8-10 layers of cells/keratinocytes

26
Q

What happens to keratinocytes in the Stratum Spinosum

A

Keratinocytes begin to flatten out

27
Q

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

A

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

28
Q

What layer is above the Stratum Spinosum?

A

Stratum Granulosum

29
Q

What happens in the Stratum Granulosum

A

Flattened keratinocytes undergo apoptosis (programmed cell death)

30
Q

What are lamellar granules?

A

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

31
Q

What is keratohyalin?

A

Protein structure in granules of keratinocytes.

These dark granules help form keratin intermediate filaments into keratin (holds keratinocytes together)

32
Q

What layer is above the Stratum Granulosum

A

Stratum Lucidum

33
Q

Where is the Stratum Lucidum found?

A

ONLY in thick skin (fingertips, palms, soles)

34
Q

What is the top layer of the epidermis?

A

Stratum Corneum

35
Q

How thick is the Stratum Corneum?

A

25-30 layers of flattened dead keratinocytes

36
Q

What is the function of the Stratum Corneum

A

To form a barrier

Keep moisture in and outside world out

37
Q

What are keratinocytes like in the Stratum Corneum

A

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

38
Q

What is the interface between the dermis and epidermis

A

The basement membrane

39
Q

What are the proteins in the Basement Membrane

A

Collagen IV, Perlecan, Nidogen, Lamaminin 332

40
Q

What do keratinocytes in the basal layer attach to?

A

Proteins in the basement membrane

41
Q

What is the Basement membrane important for?

A

It is important for the epidermal attachment to the dermis

42
Q

What can a mutation in the basement membrane proteins cause?

A

Epidermolysis Bullosa

It is when the keratinocytes cannot attach to the BM

43
Q

What are rete ridges/dermal papillae?

A

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

44
Q

What is the function of rete ridges?

A

Their contour provides resistance to shear forces

45
Q

Where do melanocytes reside?

A

In the epidermal side of the basement membrane

46
Q

What do melanocytes make?

A

Melanosomes

47
Q

What is contained in melanosomes?

A

Melanin

48
Q

How are melanosomes transferred to keratinocytes?

A

Melanosomes are transferred to keratinocytes by dendrites on the melanocytes

36 keratinocytes at a time

49
Q

What is melanin?

A

A pigment which gives the skin colour

50
Q

What is Pheomelanin

A

Pigment in melanin

Gives skin red + yellow colours

BIOSCI 107 Part One (12 decks)

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