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Molecular Basis Of Disease > Skin Structure > Flashcards

Skin Structure Flashcards

1
Q

What are other names for this skin?

A

cutis or integument

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2
Q

What are the 2 main layers of the skin and were are they derived from?

A
  1. epidermis
    - ectodermal origin
  2. dermis
    - mesoderm
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3
Q

What are the 3 layers of the skin?

A

epidermis
dermis
hypodermis

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4
Q

Where is the epidermis located? Which cells are located in this layer? How is this layer nourished if there is no blood supply?

A
  1. top most layer
  2. mostly cube shaped cells
    • when these die they get pushed to the surface to form the
      keratinised layer
  3. nourished by diffusion of nutrients from the dermis
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5
Q

What are the two qualities of the dermis layer?

A
  1. connective tissue layer (elastin and collagen fibres present)
  2. lots of blood vessels and nerves with specialised nerve endings
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6
Q

What are the most abundant cells in the epidermis? Where do they originate from?

A

keratinocytes

originate from stem cells in the stratum basale
- migrate to the outer layer and as they die they form a protective layer (keratinised layer)

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7
Q

What are the 3 functions of keratinocyte?

A
  1. keratin production
    • intermediate filaments for strength
  2. synthesis of vitamin D (from cholesterol)
  3. secrete IL-1 to mature T cells localised in skin
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8
Q

There are 2 specialised cell in the skin. What are these?

A

melanocytes
langerhans cells

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9
Q

What is the origin of melanocytes? What is their role?

A
  1. neural crest origin
  2. role in skin pigmentation as they can produce and distribute melanin
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10
Q

What are langerhans cells?

A

dendritic APC

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11
Q

What is the role of Langerhans cells in skin infections?

A

take up and process microbial agents
present microbial agents found in all layers of skin
mop up invading foreign substances and present them to T and B cells

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12
Q

FUNCTIONS OF SKIN. How does the skin provide mechanical protection?

A

the stratified keratinized epithelium is a tough layer which provides protection against external abrasions/injury and against invasion of foreign bodies

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13
Q

FUNCTIONS OF SKIN. How does the skin osmoregulate the body?

A

regulates bodily fluids and ions through sweat
protects against fluid loss

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14
Q

FUNCTIONS OF SKIN. How does the skin provide sensory reception?

A

receives sensory stimuli from external environment through different types of receptors (touch, pressure, heat, cold and pain)

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15
Q

FUNCTIONS OF SKIN. How does the skin provide thermoregulation?

A

regulates body temp through arteriovenous anastomoses

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16
Q

FUNCTIONS OF SKIN. How does the skin provide vitamin D?

A

skin is stimulated by ultraviolet light to provide initial stage of pathway (pro-hormone of vitamin D) leading to synthesis of vitamin D metabolites

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17
Q

FUNCTIONS OF SKIN. How is the skin involved in excretion and secretion?

A

through exocrine glands
- sweat glands
- sebaceous glands

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18
Q

FUNCTIONS OF SKIN. What substances can the skin absorb? What is this process called?

A

transdermal absorption

substance include:
- drugs
- nicotine
- estrogen etc

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19
Q

FUNCTIONS OF SKIN. How does the skin provide mobility>?

A

very mobile due to elastin and collagen

20
Q

What are the common symptoms of skin diseases?

A

burning/itching
emotional and social effects

21
Q

How can cells be linked to one another?

A

directly
or
through networks of proteins and polysaccharide chains (extracellular matrix)

22
Q

How does the environment cells live in impact the cell?

A

influences cell function
controls gene expression

23
Q

What are tissues composed of?

A

cells and ECM

24
Q

What is the difference between connective tissues and epithelium?

A

connective tissue
- few cells
- high ECM

epithelium
- many cells closely linked
- low ECM

25
Q

What are the 2 types of cell junctions?

A

cell to cell adhesion
cell to matrix adhesions

26
Q

What are the 2 types of actin filament attachment sites in anchoring junctions?

A
  1. cell to cell (adherens junctions)
  2. cell to matrix (actin linked cell matrix adhesions)
27
Q

What are the 2 types of intermediate filament attachment sites in anchoring junctions?

A
  1. cell to cell (desmosomes)
  2. cell to matrix (hemidesmosomes)
28
Q

What is the type of occluding junctions in vertebrates?

A

tight junctions

29
Q

What is the type of channel forming junctions in animals

A

gap junctions

30
Q

What are the types of signal relaying junctions?

A
  1. chemical synapses
  2. immunological synapses
31
Q

In addition to the structural roles of anchoring, occluding and channel forming junctions what is their other function?

A

singalling

32
Q

What kind of adhesion do Cadherins use?

A

homophilic (like to like)
- same type of cadherin homodimer joins each cell

33
Q

Cadherins are a diverse family of adhesion molecules (about 100 known types) which rely on Ca2+ ions. What are the 3 major types of cadherins and which cells are they found in?

A

E- cadherins
- epithelial
N-cadherins
- nerve and muscle
P-cadherins
- placental and epidermis

34
Q

each E-cadherin unit is rigid and binds to another cadherin molecule via a hinge. Ca2+ binds near the hinge why does this occur?

A

prevents flexing of the cadherin molecule

35
Q

Cadherin molecule is linked to the cytoskeleton indirectly through intracellular adaptor proteins (catenins). What cytoskeleton filament does cadehrin link to?

36
Q

What are the 3 types of catenins which indirectly link cadherin molecules to the actin filament?

A

alpha catenin
P120 catenin
beta catenin

37
Q

What is the cadherin molecule and the 3 catenin molecules known as?

A

adherens junction

38
Q

What is the function of beta catenin?

A

drives transcription of target genes involved in cell prolif

39
Q

How is beta catenin associated with cancer?

A

mutations which activate B catenin found in many cancer (oncogene)

APC mutations which cause cancer leads to loss of B catenin degradation

40
Q

Desmosomes are specialised cadherins which link to intermediate filaments rather than actin filaments. What is the function of desmosomes?

A

mechanical strength

high in heart and epithelium as they are tissues under high mechanical stress

41
Q

Integrins are molecules which bind cells to the extracellular matrix. They are heterodimers made from alpha (18 different types) and beta subunits (8 different types) which can dimerise in different combos. What do integrins bind to in the cell?

A

actin filaments

42
Q

Integrins rely on adaptor proteins (ligands). What are the main types of ligands?

A

integrin linked kinase (ILK)
alpha actinin
Talin
Filamin

43
Q

How are the ligands which indirectly link integrins to actin involved in cell signalling pathways?

A

recruit focal adhesion kinase (FAK) through Talin and paxillin linker proteins

FAK then phosphorylates proteins in the signalling pathway

44
Q

What does the extracellular portion of integrins bind to?

A

fibronectin
laminin
collagen

45
Q

Hemidesmosomes are specialised integrins which link the cell to the basal lamina. What is another name for hemidesmosomes?

A

alpha6beta4 integrin

46
Q

Hemidesmosomes are linked to keratin filaments through?

A

dystonin and plectin

47
Q

hemidesmosomes are linked to collagen fibers extracellular through?

A

collagen XVII and laminin

Molecular Basis Of Disease (17 decks)

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