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Locomotor 2 > Introduction to Skin > Flashcards

Introduction to Skin Flashcards

1
Q

what is the largest organ in the body

A

skin

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2
Q

how much does skin weight

A

12-15% body weight

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3
Q

what is the most common reason for visiting a GP

A

Skin - 42%

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4
Q

name some skin diseases

A

Cancer - malignant melanoma

inflammation - e.g.Psoriasis

genetic diseases

wounds - diabetic ulcers

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5
Q

What is the function of skin

A

Protection

  • Physical trauma
  • Infection
  • Penetration of drugs and chemicals
  • UV radiation
  • Water loss
  • insulation
  • provides sensory information
  • vitamin D synthesis
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6
Q

what are the two layers of the skin

A

epidermis - barreie function of the skin

dermis - made up of a large amount of collagen and connective tissue therefore responsible for the strength of the skin

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7
Q

describe the epidermis

  • epithelium
  • major cell type
  • what it also includes
A

Stratified Squamous Epithelium

Major cell type the keratinocyte

Also includes hair and sebaceous gland

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8
Q

what are the four main layers of the epidermis

A
  • Stratum basale (basal layer) - have dark nuclei
  • Stratum spinosum (spinous layer) - become more round and nuclei become lighter so not as prominent
  • Stratum granulosum (granular layer) - contains keratinohylaine granules
  • Stratum corneum (cornified layer)- become very flattened
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9
Q

What is the most abundant cell type in the skin

A
  • Keratinocytes
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10
Q

describe keratinocytes and what they produce

A
  • epithelial cell type

- produces keratins

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11
Q

describe the structure of keratin

A

intermediate filament

Mol Wt. 40-50,000 kD

Exist as acidic and basic pairs (e.g. K5/K14)

Expression pattern is specific to epidermal layer

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12
Q

where is keratin abdunant in

A

Most abundant proteins in stratum corneum, hair and nails

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13
Q

how many types of keratin are there

A

54

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14
Q

what are the two categories of keratins

A

Depends on their secondary structure

  • alpha type - soft
  • beta type - hard, beta sheets that cross over together by disulphide and hydrogen bonding which makes them harder

can classify according to there pH

  • pair together with acidic or basic pairing so the structure is normal
  • these pairing is specific to each other and to a location
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15
Q

what is the epidermis maintained by

A

Maintained by a population of adult stem cells

  • Long lived and slow cycling
  • Capable of self-renewal and terminal differentiation
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16
Q

where does proliferation occur in the epidermis

A

basal layer

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17
Q

what are the basal keratinocytes attached to

A

Basal cells adhere to ECM rich basement membrane

- helps attach the epidermis to the underlying dermis

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18
Q

what is does the basement membrane consist of

A

Consists of Laminin 332, Collagen IV, and Collagen VII

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19
Q

how are basal cell anchored to the basement membrane

A

Hemidesmosomes (integrin receptors) link keratin cytoskeleton to basement membrane

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20
Q

what is the basement membrane essential for

A

Essential for cell polarity, regulating basal cell function, and anchoring epidermis to dermis

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21
Q

describe the structure of the stratum spinosum

A

3-4 cell layers thick

Numerous desmosomes give cells spiny appearance

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22
Q

what is terminal differentiation in the keratinocytes

A

keratinocytes stop proliferating and start producing keratin

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23
Q

describe the stratum granulosum

A

2-3 cell layers

Characterised by large granules of keratohyalin

  • Filaggrin
  • Involucrin
  • Loricrin
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24
Q

describe the stratum corner

A

Main protective barrier of skin

Have a thick cornified envelope

Cross-linked by enzymes

Cells in cornified layer are dead

Intercellular lipids (ceramides) maintain moisture

keratinocytes ave complexity lost there nuclei

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25
Q

what are adherent junctions

A

Cadherin receptor linked to actin cytoskeleton

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26
Q

what are adheres and desmosomes made up of

A

Cadherin receptor

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27
Q

describe desmosomes

A

Cadherin receptor linked to keratin cytoskeleton

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28
Q

describe tight junctions

A
  • between cells and form a tight seal and prevent the movement of water between cells
  • Claudin and occludin seal intercellular space
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29
Q

describe gap junctions

A
  • pores between two adjacent cells allowing nutrients and materials to reach from the bottom to the top of the epidermis
  • Intercellular pores made up of connexins
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30
Q

what are the three layers of the dermis

A

Three layers

  • Papillary
  • Reticular
  • Adipose
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31
Q

what is the role of the dermis

A

Provides strength and elasticity to skin

32
Q

what is the structure of the dermis

A

Complex mix of macromolecules

Vascularised and innervated

33
Q

What is the most abundant cell in the dermis

A

fibroblast

34
Q

where does a fibroblast originate from

A

Mesenchymal origin

35
Q

what does a fibroblast synthesis

A

Collagen

Elastin

Proteoglycans

36
Q

describe the papillary layer of the dermis

A
  • Directly beneath epidermis and BM
  • Contains many blood capillaries
  • Fine, randomly oriented collagen
  • Type III Collagen
  • Elastin
37
Q

what collagen is the papillary layer of the dermis made up of

A

Type III Collagen

Elastin

38
Q

where does the papillary layer of the dermis sit

A
  • right below the epidermis
39
Q

describe the reticular dermis

A

Large and densely packed collagen fibres

Provides much of mechanical strength of skin

40
Q

in the dermis what layer provides much of mechanical strength of the skin

A

reticular dermis

41
Q

what are the two different types of pilosebaceous unit

A
  • hair follicle

- sebaceous gland

42
Q

what are the two sweat glands

A
  • eccrine sweat gland

- apocrine gland

43
Q

where is the cells in the hair follicle derived form

A

the epidermis

44
Q

what are the two types of hair follicle

A
  • Vellus-body hair

- Terminal-scalp and secondary sexual hair

45
Q

where is the hair follicle found

A
  • found over the entree body
46
Q

What produces hair

A

Matrix keratinocytes produce hair

47
Q

what function does hair have

A
  • they all have a sensory function
48
Q

what controls hair growth

A

Dermal papilla fibroblasts control hair growth

49
Q

describe the lifecycle of hair production

A
  • Hair follicles start form the bulge
  • At some point they are pushed out of the bulge region and migrate down the outermost part of the hair
  • When they get to the bottom of the hair they encounter dermal papilla
  • The dermal papilla causes a signal that leads to proliferation
  • And this leads to differentiation and production of the hair
  • Once the differentiation is complete the hair cells die and they are pushed through the surface of the skin as a hair
50
Q

where are hair follicular stem cells

A

Hair follicle stem cells are in the bulge region

Express keratin 15

51
Q

describe hair follicular stem cells

A

Slow cycling

Give rise to hair cells under normal conditions

Contribute to SG and epidermis upon wounding

52
Q

what are the three phases of hair cycle

A

Anagen = active

Catagen = regressive

Telogen = resting

after telongen the hair follcile re enters anlagen

53
Q

How long is the hair cycle phase in human

A

whole thing is 3 months

54
Q

where is the sebaceous gland

A

attaches to the hair follicle

55
Q

what do sebaceous glands produce

A

Mature sebocytes contain sebum = produce an oily substance which provides moisture and lubrication for the hair

  • Cell ruptures and sebum released into sebaceous duct and onto skin
56
Q

what does infection of Sebaceous Gland result in

A

acne

57
Q

describe sebaceous gland

A

Exocrine gland

Androgen sensitive

Enlarges at puberty

58
Q

what is the eccrine sweat gland responsive for

A

Thermoregulation and sweat

59
Q

what are the two main components of the eccrine sweat gland

A

Excretory duct

Secretory coil - where the sweat is produced

60
Q

how much of water is sweat

A

Sweat 99% water

61
Q

what sweat gland is associated with hair follicles

A

apocrine gland

- secretion is odourless

62
Q

Where are apocrine glands found

A

Axilla and pubic region

63
Q

what do apocrine glands do when they are broken down by

A

Broken down on skin by bacteria

Release volatile fatty acids

64
Q

What are other cell types associated with the skin

A

Melanocytes

Langerhans cell

Merkel cell

Mast cell

65
Q

what do melanocytes protect against

A

Protect against UV

66
Q

where are melanocytes

A
  • Dendritic cell

- Epidemis on basement membrane and hair matrix

67
Q

what do melanocytes produce

A

Produce melanin which is packaged into melanosomes

  • eumelanin
  • pheomleanin
  • melanosomes are then injected into keratinocytes
68
Q

What are the two main types of melanin

A
  • Eumelanin

- Pheomelanin

69
Q

describe the langerhan cell and where it is found

A

Dendritic cell

Basal and spinous layers

70
Q

what does the langerhan cell do

A

Antigen presenting cell

First line of defence

Presents antigen to T lymphocytes

71
Q

describe where Merkel cells are and what they do

A

Stratum basale

Sensory perception

72
Q

Describe where mast cells are and what they do

A

Dermis

Immune response

Secretes histamine

73
Q

name the types of wound and what layers of the skin it involves

A

Superficial – epidermis

Partial thickness – epidermis and dermis

Full thickness – epidermis, dermis, hypodermis

74
Q

what are the three phases of wound healing

A

Inflammation

Proliferation

Maturation

75
Q

describe the three phases of wound healing

A

Inflammatory response
– minutes to a few days,
- respond vascularly, haemostasis happens involving endothelium and platelets in the blood vessel
- then have response of the immune cells such as neutrophils, macrophages and then lymphocytes
- this is regulated by factors such as IL-1. IL-6 and TNF alpha

Proliferation
– matter of days
- Keratinocytes which need to migrate into the wound and increase proliferation and undergo differentiation to reform the barrier
- regulated by fibroblast growth factors and TGF beta
- At the same time there is formation of a new vascular site – angiogenic
- Fibroblasts need to migrate into this area

Maturation
– last weeks and months
- Carried out by the fibroblasts and there contractile version of the myofibroblasts
- The collagen that would have been quickly deposited is broken down and remodeled to form a more normal tissue structure

76
Q

What are the complications of wound healing

A
  • infection
  • chronic wounds - not healed greater than 6 weeks = venous, pressure, diabetic ulcer
  • scarring

Locomotor 2 (30 decks)

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