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Phase 1 > Layers and Cells of the Skin > Flashcards

Layers and Cells of the Skin Flashcards

1
Q

what are the 4 layers of the epidermis (and the 5th layer that is sometimes found)?

A

(external -> internal)
1 - stratum basale (basal cell layer)
2 - stratum spinosum (prickle cell layer)
3 - stratum granulosum (granular cell layer)
( stratum lucidum - clear layer)
4 - stratum corneum

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2
Q

what type of epithelium is found in the skin epidermis

A

stratified squamous epithelium

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3
Q

what is the structure of the basal cell layer? (2)

A
  • row of columnar keratinocytes

* attached to the basement membrane by hemidesmosomes

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4
Q

why is the basal cell layer very mitotically active?

A

small proportion of keratinocytes are stem cells that continuously divide

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5
Q

what cytoplasmic structure is found in basal cells? where do they converge?

A
  • tonofilaments

* hemidesmosomes

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6
Q

what 3 cells are found in the basal layer?

A
  • keratinocytes
  • melanocytes
  • Merkel cells
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7
Q

what is the structure of the prickle cell layer? (3)

A
  • polyhedral keratinocytes
  • interconnected with desmosomes
  • give cells a spiny appearance (ie. prickle)
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8
Q

what cytoplasmic structure is found in cells of the prickle layer? where do they converge?

A
  • tonofilaments bundled together forming supportive tonofibres
  • desmosomes
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9
Q

what 2 cells are found in the prickle layer?

A
  • keratinocytes

* Langerhans cell

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10
Q

what is the structure of the granular layer?

A

flattened cells containing important granular structures

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11
Q

what 2 cell processes begin to happen in the granular layer?

A
  • removal of nuclei

* expulsion of lipids and liquid from the cytoplasm

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12
Q

what is the structure of the horny layer?

A

sheets of cornified cells with no nuclei, stuck together by lipid glue

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13
Q

where on the body is the horny layer thickest? - these areas also have a stratum lucidium

A

palms of hands and soles of feet

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14
Q

what is the cytoplasm replaced with in the cells of the horny layer?

A

keratin fibrils

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15
Q

why are cells of the horny layer stuck together with lipids?

A

makes the skin surface water tight

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16
Q

what is the top layer of their dermis and what are 2 of its features?

A

• papillary layer

  • interdiginates with epidermis
  • composed of of loosely woven collagen
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16
Q

what is the lower layer of the dermis and what is a feature of it?

A
  • reticular layer

* coarse, horizontally running bundles of collagen

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17
Q

what material makes up 70% of the dermis, and what quality does this provide the dermis?

A
  • collagen

* toughness and strength

18
Q

what fibre is incorporated into the collagen network in the dermis? what quality does this provide?

A
  • elastin

* elasticity

19
Q

what is the ground substance in the dermis and what is its purpose?

A
  • semi-solid matrix

* allows dermal structures some movement

20
Q

what cells are present in the dermis?

A
  • fibroblasts
  • dermal dendritic cells
  • mast cells
  • lymphocytes
  • macrophages
21
Q

what it is the structure of the hypodermis?

A

adipose tissue with supporting fibrous bands

22
Q

why is skin regenerating important? (2)

A
  • horny layer is important for preventing microorganisms, water etc. from entering the skin
  • epidermis prevents fluids from getting out
23
Q

what is the keratinocyte maturation sequence? (7)

A

1 - stem cells continuously divide into 1 new stem cell and a transit amplifying cell
2 - transit amplifying cells proliferate briefly before progressing upwards for terminal differentiation
3 - in prickle cell layer, cell changes shape from columnar to polygonal
4 - differentiating keratinocytes synthesise keratins
5 - in granular layer, enzymes induce degradation of nuclei and organelles
6 - in horny layer, dead and flattened corneocytes have developed cornified envelopes
7 - corneocytes eventually shed from skin surface after degradation of the lipid glue and loss of desmosomes intercellular connections

24
Q

what are 2 functions of membrane-coating granules? what is another name for these granules?

A
  • release lipid glue to increase cell adhesion
  • provide a water-tight barrier to epidermis

• lamellar bodies

25
Q

how often do dividing basal cells replicate?

A

every 200 - 400 hours (8 - 16 days)

26
Q

how long does it take skin cells to shed?

A

52 - 75 days (7-12 weeks)

27
Q

what disorder reduced the maturation time of skin cells?

A

psoriasis

28
Q

what are the name of 4 wound depths?

A
  • erosion - epidermis only
  • ulceration - structures deep in epidermis
  • partial thickness - epidermis + parts of dermis (adnexal structures serve as reservoir of epithelial cells to repopulate)
  • full thickness - epidermis + all of dermis + deeper structures (only wound edge heals)
29
Q

how long does the inflammatory phase of wound healing last?

A

24 - 28 hrs

30
Q

what are the 3 processes occurring in the inflammatory phase of wound healing?

A
  • haemostasis - vasoconstriction and primary platelet plug
  • activation of coagulation pathway
  • inflammation response
31
Q

what cells are involved in the inflammatory phase of wound healing and what are their roles? (2)

A
  • neutrophils - remove bacteria and necrotic tissue (non-programmed cells death), contribute to cytokine release
  • macrophages - phagocytosis, synthesise cytokines and growth factors
32
Q

what are the 5 processes occurring in the proliferative phase of wound healing?

A

1 - re-epithelialisation - epithelial cells loosen cell-cell adhesions and migrate towards wound site to cover granulation tissue
2 - once a single later established, keratinocytes proliferate
3 - granulation tissue forms
4 - re-angiogenesis (nourish and support fibroblasts)
5 - fibroblasts activate

33
Q

what is the role of fibroblasts in the proliferative phase of wound healing? (2)

A
  • scar formation

* collagen deposition

34
Q

what type of collagen is deposited in wound healing? what happens to collagen during the remodelling phase? (2)

A

• collagen III

  • switches to collagen I
  • organised into thick bundles and cross-link -> mature scar
35
Q

what happens to granulation tissue in the remodelling phase of wound healing?

A

matures into scar tissue - connective tissue with few cells

36
Q

what happens to some fibroblasts in the remodelling phase of wound healing?

A

differentiate into myofibroblasts - produce contractile tissue to close wound

37
Q

what is EGF? what does it signal?

A
  • epidermal growth factor

* re-epithelialisation - keratinocyte proliferation and migration

38
Q

what is PDGF? what 2 processes does it signal?

A

• platelet-derived growth factor

  • matrix formation - increases fibroblast number and activity
  • remodelling - formation of proteases
39
Q

what is VEGF? what process does it signal?

A
  • vascular endothelial growth factor

* angiogenesis

40
Q

what are 3 inflammation signally molecules?

A
  • interleukin-1
  • interleukin-6
  • activated tumour necrosis factor (TNFa)
41
Q

what 4 local factors effect wound healing?

A
  • infection
  • foreign body
  • oxygenation (highly active process)
  • vascular supply
42
Q

what 6 systemic factors effect wound healing?

A
  • age
  • disease (eg. diabetes - non-healing ulcers)
  • alcohol / smoking
  • immunocompromised conditions
  • obesity
  • medication (anti-inflammatories)

Phase 1 (14 decks)

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