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Phase 1 > Skin Structure and function > Flashcards

Skin Structure and function Flashcards

1
Q

What are the three main functions of skin?

A

Protection, regulation/physiological & sensation.

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2
Q

What things does the skin protect from?

A
  • Mechanical impacts
  • Pressure
  • Variations in temperature
  • micro-organisms
  • radiation/chemicals
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3
Q

What is the skin’s physiological role?

A
  • body temperature regulation via sweat and hair.
  • changes in peripheral circulation.
  • Fluid balance via sweat
  • synthesis of Vitamin D
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4
Q

What is the skin’ role in sensation?

A
  • Network of nerve cells that detect and relay changes in the environment
  • heat, cold, touch and pain
  • reflexes
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5
Q

What are the three layers of the skin?

A
  • Epidermis
  • Dermis
  • subcuteus or hypodermis
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6
Q

What does the arrector pili muscle do in the skin?

A

It contracts to cause the hair to stand on end to warm the body
- goosebumps

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7
Q

What are the name of the epithelial cells in the Epidermis that make up its layers?

A

Keratinocytes

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8
Q

What structure does the epidermis sit on?

A

The basement membrane

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9
Q

What is the role of the basement membrane?

A

It seperates the Epidermis from the Dermis.

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10
Q

What are the names of the different layers in the Epidermis and their positions?

A
  • Stratum Basale (basal layer)
  • Stratum Spinosum (2nd layer)
  • Stratum Granulosum (3rd layer)
  • Stratum Corneum (top layer)
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11
Q

What is the role of Stratum Basale?

A
  • cuboidal/low columnar cells.
  • mitotically active, constant regeneration of other layers.
  • contains skin cells
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12
Q

What connects the Stratum Basale to the Basement membrane?

A

Hemidesmosomes

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13
Q

What is the Stratum Spinosum made up of?

A
  • Made up of Polyhedral Keratinocytes held together by Desmosomes (strong cell junctions).
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14
Q

What are the Stratum Granulosum features?

A
  • Cells become flattened
  • Contain Keratohyalin granules
  • start to lose nucleus and cytoplasm
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15
Q

What are the features of the Stratum Corneum?

A
  • large flat plate like cells filled with keratin
  • lost their nucleus
  • filled with lipids between cells that provide a water barrier.
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16
Q

What do some parts of the skin have?

A

An extra layer called the Stratum Lucidum (only in thick skin)

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17
Q

What process are the cells in the Stratum Basale responsible for?

A

They differentiate upwards to replace the dead skin cells.

Skin cells are constantly dying and being replaces with a complete replacement happening within a month.

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18
Q

How long does it take for skin cells to migrate from the basal layer to the top of the granular layer?

A

arorund 14 days

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19
Q

How many days for the cell to cross the stratum corneum to the surface to be shed?

A

another 14 days

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20
Q

What occurs as cells travel to the surface and differentiate?

A

They change in the amount and type of keratin they produce.

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21
Q

What is keratin?

A
  • 30 different types

- intermediate filaments that provide strong mechanical resilience to cells.

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22
Q

What are the features of the Dermis?

A
  • Connective tissue: collagen type I, Elastin & ground substance.
  • Fibroblasts
  • immune role
  • blood supply (contains BVs)
  • Tensile strength (collagen fibres)
  • Allows stretch (elastin Fibres)
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23
Q

What are the two layers of the Dermis?

A
  1. Papillary layer

2. reticular layer

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24
Q

What are features of the papillary layer of the dermis?

A
  • loose
  • contains very fine insulated collagen fibres.
  • where most BVs are found
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25
Q

What are features of the reticular layer of the dermis?

A
  • stronger collagen bundles
  • more elastic fibres and larger
  • contains BVs and nerves but not as much as the papillary layer.
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26
Q

What attaches the Dermis and Epidermis together?

A

Dermo-Epidermal junction

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27
Q

What are the functions of the Dermo-Epidermal junction?

A
  • a regulated barrier for movement from and into Epidermis
  • attachment site of Dermis and Epiderdmis
  • Aligns cells of the Epidermis
  • Serves as a base for wound healing through reepithelialisation.
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28
Q

What attach the Epidermis and Dermis together at the Dermo-Epidermal junction?

A

Hemidesmosomes

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29
Q

What is the subcutis (hypodermis) mainly composed of?

A

Adipose tissue

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30
Q

What are the functions of the Subcutis?

A
  • Energy source
  • insulation
  • Shock absorption
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31
Q

What physiological aspects of the skin allow it to act as a sensory organ?

A
  • Free nerve endings in the skin
  • Meissner’s corpuscles
  • Pacinian Corpuscles
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32
Q

Where are the free nerve endings in the skin?

A
  • in the papillary dermis and form attachments with Merkel cells to act as mechanoreceptors (touch and pressure)
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33
Q

What are Meissner’s corpuscles and where are they?

A
  • Rapidly acting mechanoreceptors responsible for touch

- Papillary dermis of hand and feet.

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34
Q

What are Pacinian Corpsucles and where are they?

A
  • Detect deep pressure and vibration

- usually in Subcutis

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35
Q

What are adnexal strucutres (structures associated with) the skin?

A
  • Hair and nails
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36
Q

What types of glands are found in the skin?

A
  • Eccrine gland
  • Apocrine gland
  • Sebaceous gland
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37
Q

What are Eccrine glands and where are they found?

A
  • These are temperature control glands -> excrete sweat
  • everywhere on skin apart from nail beds, lips, external auditory canal and some parts of genetalia.
  • mostly found on palms, soles, and axillae
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38
Q

What are Apocrine glands and where are they found?

A
  • Scent glands. Role unclear in humans.

- found in axillae and genitals.

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39
Q

What are Sebaceous glands and where are they found?

A
  • Formed from hair follicle
  • everywhere except palms and soles
  • greantly enlarge at puperty in response to androgens
  • produces sebum (oily, waxy substance to moisturise skin).
40
Q

Which cell layer increases its proliferative activity in Psoriasis as the number of epidermal cells is increased?

A

Stratum Basale

41
Q

What are the types of cells in the Epidermis?

A
  • Langerhans cell
  • Melanocyte
  • Merkel cell
  • Keratinocyte
  • stem cell
42
Q

What is the location and function of the Keratinocyte?

A

Location: Keratinised Stratified Squamous Epithelium
Function: protection & barrier; Vitamin D production

43
Q

What is the location and function of the stem cell?

A

Location: Stratum Basale
Function: self renewal and repopulation of the epidermal layers.

44
Q

What is the location and function of the Merkel Cell?

A

Location: Epidermis (mostly basal)
Function: sensation

45
Q

What is the location and function of the Langerhans cell?

A

Location: Epidermis (mostly Stratum Spinosum) and upper dermal layer.
Function: Dendritic cell; antigen presentation Phagocytosis. Part of immune system. long cytoplasm to detect antigens.

46
Q

What is the location and function of the Melanocyte?

A

Location: Basal layer
Function: Protection from Radiation. UV light.

47
Q

What amino acid does the melanocyte produce?

A

Melanin - skin pigmentation to protect from UV light.

48
Q

What does chronic UV exposure lead to in humans?

A
  • loss of skin elasticity
  • abnormal pigmentation
    = haemorrhage of BVs
  • Wrinkles
  • malanoma and non melanoms skin cancers
49
Q

What are melanosomes?

A

Organelles of pigment cells in which melanins are synthesized and stored.

50
Q

How do melanosomes protect keratinocytes?

A

melanosomes are transferred to the keratinocytes through the melanocytes cytoplasmic processes and create a protective layer over DNA.

51
Q

What are the different molecules in the Epidermis?

A
  • Keratins
  • Profilaggrin
  • involucrin
  • loricrin
  • polysaccharides glycoproteins lipids
52
Q

What are the location and function of Keratins?

A

Location: all epidermal layers
Function: major structural proteins; intermediate filaments

53
Q

What are the location and function of Profilaggrin?

A

Location: Keratohyalin granules
function: converted to filaggrin which aggregates keratin filaments into tight bundles

54
Q

What are the location and function of involucrin?

A

Location: keratohyalin granules
Function: Formation of a cell envelope around cells in the Stratum corneum

55
Q

What are the location and function of Loricrin?

A

Location: keratohyalin granules
Function: cross-links to involucrin

56
Q

What are the location and function of polysaccharides glycoproteins lipids?

A

Location: Lamellar granules
Function: extrude into intercellular space, form the cement that holds the stratum corneum cells.

57
Q

What molecules are found in the Keratohyalin granules in the Epidermis?

A
  • Profilaggrin
  • involucrin
  • loricrin
58
Q

What are the names of the cells found in the Dermis?

A
  • Fibroblast
  • lymphocytes
  • Dermal dendritic cells
  • mast cells
59
Q

What are the function of fibroblasts?

A

Synthesis (collagen, elastin & other extracellular matrix components)
Growth factors

60
Q

What are the function of Lymphocytes?

A

immunosurveillance

61
Q

What are the function of Dermal dendritic cells?

A

phagocytosis

antigen presentation

62
Q

What are the function of mast cells?

A

Produce inflammatory mediators (histamine, heparin) & chemotactic factors for eosinophils and neutrophils

63
Q

What are the types of molecules in the Dermis?

A
  • Collagen Type I
  • Elastin
  • Proteoglycans
  • Glycosaminoglycans
64
Q

What is the role of collagen type I?

A

Major structural fibrous proteins

65
Q

What is the role of Elastin?

A

Confer elasticity and recoil

66
Q

What is te role of Proteoglycans and Glycosaminoglycans?

A

Hydration

67
Q

Which cellular specialisation is found in a fibroblast?

A

Rough Endoplasmic Reticulum.

68
Q

What change in skin accounts for the collagen content in the dermis decreasing by 1% each year in adult life?

A

Decrease in Fibroblasts

69
Q

Which cell type is defective in albinism?

A

Melanocyte

70
Q

What is albinism?

A

An autosomal recessive condition where the skin is white or pink, hair white and pigmentation is lacking in the eye.

71
Q

What is a wound?

A
  • A breakdown in the protective function of the skin
  • a loss of continuity in the epitheliun with ot wirhout loss od underlying CT
  • depth of injury affects ability to heal
72
Q

What are the different depths of injury for a wound?

A
  • Erosion
  • ulceration
  • partial thickness
  • full thickness
73
Q

What depth is erosion?

A

Only epidermis lost

74
Q

What depth is ulceration?

A

Structures deep to epidermis.

75
Q

What depth is partial thickness?

A

Epidermis + varying parts of dermis.

Adnexal structures act as a reservoir of epithelial cells to repopulate wound + cells from wound edge.

76
Q

What depth is full thickness?

A

Epidermis + all of dermis + deeper structures.

wound edge only

77
Q

Define wound healing.

A

a highly coordinated and orderly process that requires the activities of a number of different cell types, including inflammatory cells, keratinocytes, fibroblasts and endothelial cells.

78
Q

What are the three overlapping phases of wound healing?

A
  1. inflammatory
  2. proliferative
  3. remodelling.
79
Q

What are the features of the inflammatory phase of healing?

A
  • 24/48 hours
  • platelets intiate haemostasis/blood clot and healing cascade.
  • other cells attracted to wound to fight infection and transition from inflammation to repair (neutrophils/macrophages)
  • signs of inflammation
  • neutrophils and macrophages phagocytose (eat) dead tissue and microorganisms.
80
Q

What are the features of the proliferative phase of healing?

A
  1. Re-epithelialisation
    - Within 1-2 days of wounding, epithelial cells loosen cell-cell adhesions and migrate to the wound site, cover the granulation tissue, and then meet in the middle.
    - Once the wound is covered in a single layer of keratinocytes -> all keratinocytes proliferate.
  2. Formation of granulation tissue; mainly type III collagen.
  3. Neovascularisation: proliferation and migration of endothelial cells. `
81
Q

What is neovascularisation?

A

Formation of new blood vessels.

82
Q

What needs to occur to close the wound?

A

Keratinocyte migration.

83
Q

What are the 2 methods of keratinocyte migration?

A
  1. Leap frog method = leap frog over eachother

2. Train method = pull eachother along

84
Q

What do fibroblasts produce to form granulation tissue?

A

Type III collagen.

85
Q

What are the features of th remodelling phase?

A
  • Switch in type III collagen to type I collagen
  • granulation tissue becomes mature scar tissue.
  • collagen is organised into thick bundles and extensively cross-linked to form a mature scar.
  • final strength is only 70-80% of preinjured skin.
86
Q

What do myofibroblasts do in the remodelling phase?

A

These are fibroblasts that develop into myofibroblasts. These contract to pull the edges of the wound together.

87
Q

How do the cells involved in the healing process know what to do?

A

Signalling molecules released from one cell to another.

88
Q

What types of signalling molecules are involved in wound healing?

A
  • Epidermal Growth Factor (EGF)
  • Platelet-derived Growth Factor (PDGF)
  • Vascular Endothelial Growth Factor (VEGF)
  • Interleukin-1
  • Interleukin-6
  • Tumour necorosis factor
89
Q

What is the function of Epidermal Growth Factor (EGF) as a signalling molecule?

A

Re-epithelisation (Keratinocyte proliferation and migration)

90
Q

What is the function of PDGF as a signalling molecule?

A 
matrix formation (increased numbers and activity of fibroblasts) 
remodelling
91
Q

What is the function of VEGF as a signalling molecule?

A

Angiogenesis (endothelial cell proliferation and migration)

92
Q

What is the function of Interleukin-1, interleukin-6, tumour necrosis factor as a signalling molecule?

A

inflammation

93
Q

What factors affect wound healing?

A
  • infection
  • forreign body
  • oxygenation
  • vascular supply
  • age
  • diseases
  • alcohol & smoking
  • immunocompromised conditions
  • obesity
  • medications
94
Q

If someone has a skin abbrasion what needs replaced in the skin?

A

the keratinocytes.

95
Q

Which part of the keratinocyte would detect an EGF signal telling it to move?

A

A trans-membrane protein on the plasma membrane

Phase 1 (4 decks)

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