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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
what are adherent junctions
Cadherin receptor linked to actin cytoskeleton
26
what are adheres and desmosomes made up of
Cadherin receptor
27
describe desmosomes
Cadherin receptor linked to keratin cytoskeleton
28
describe tight junctions
- between cells and form a tight seal and prevent the movement of water between cells - Claudin and occludin seal intercellular space
29
describe gap junctions
- 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
30
what are the three layers of the dermis
Three layers - Papillary - Reticular - Adipose
31
what is the role of the dermis
Provides strength and elasticity to skin
32
what is the structure of the dermis
Complex mix of macromolecules Vascularised and innervated
33
What is the most abundant cell in the dermis
fibroblast
34
where does a fibroblast originate from
Mesenchymal origin
35
what does a fibroblast synthesis
Collagen Elastin Proteoglycans
36
describe the papillary layer of the dermis
- Directly beneath epidermis and BM - Contains many blood capillaries - Fine, randomly oriented collagen - Type III Collagen - Elastin
37
what collagen is the papillary layer of the dermis made up of
Type III Collagen | Elastin
38
where does the papillary layer of the dermis sit
- right below the epidermis
39
describe the reticular dermis
Large and densely packed collagen fibres Provides much of mechanical strength of skin
40
in the dermis what layer provides much of mechanical strength of the skin
reticular dermis
41
what are the two different types of pilosebaceous unit
- hair follicle | - sebaceous gland
42
what are the two sweat glands
- eccrine sweat gland | - apocrine gland
43
where is the cells in the hair follicle derived form
the epidermis
44
what are the two types of hair follicle
- Vellus-body hair | - Terminal-scalp and secondary sexual hair
45
where is the hair follicle found
- found over the entree body
46
What produces hair
Matrix keratinocytes produce hair
47
what function does hair have
- they all have a sensory function
48
what controls hair growth
Dermal papilla fibroblasts control hair growth
49
describe the lifecycle of hair production
- 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
where are hair follicular stem cells
Hair follicle stem cells are in the bulge region | Express keratin 15
51
describe hair follicular stem cells
Slow cycling Give rise to hair cells under normal conditions Contribute to SG and epidermis upon wounding
52
what are the three phases of hair cycle
Anagen = active Catagen = regressive Telogen = resting after telongen the hair follcile re enters anlagen
53
How long is the hair cycle phase in human
whole thing is 3 months
54
where is the sebaceous gland
attaches to the hair follicle
55
what do sebaceous glands produce
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
what does infection of Sebaceous Gland result in
acne
57
describe sebaceous gland
Exocrine gland Androgen sensitive Enlarges at puberty
58
what is the eccrine sweat gland responsive for
Thermoregulation and sweat
59
what are the two main components of the eccrine sweat gland
Excretory duct Secretory coil - where the sweat is produced
60
how much of water is sweat
Sweat 99% water
61
what sweat gland is associated with hair follicles
apocrine gland | - secretion is odourless
62
Where are apocrine glands found
Axilla and pubic region
63
what do apocrine glands do when they are broken down by
Broken down on skin by bacteria Release volatile fatty acids
64
What are other cell types associated with the skin
Melanocytes Langerhans cell Merkel cell Mast cell
65
what do melanocytes protect against
Protect against UV
66
where are melanocytes
- Dendritic cell | - Epidemis on basement membrane and hair matrix
67
what do melanocytes produce
Produce melanin which is packaged into melanosomes - eumelanin - pheomleanin - melanosomes are then injected into keratinocytes
68
What are the two main types of melanin
- Eumelanin | - Pheomelanin
69
describe the langerhan cell and where it is found
Dendritic cell Basal and spinous layers
70
what does the langerhan cell do
Antigen presenting cell First line of defence Presents antigen to T lymphocytes
71
describe where Merkel cells are and what they do
Stratum basale Sensory perception
72
Describe where mast cells are and what they do
Dermis Immune response Secretes histamine
73
name the types of wound and what layers of the skin it involves
Superficial – epidermis Partial thickness – epidermis and dermis Full thickness – epidermis, dermis, hypodermis
74
what are the three phases of wound healing
Inflammation Proliferation Maturation
75
describe the three phases of wound healing
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
What are the complications of wound healing
- infection - chronic wounds - not healed greater than 6 weeks = venous, pressure, diabetic ulcer - scarring

Locomotor 2 (30 decks)

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