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CELL 302 > Lecture B2 > Flashcards

Lecture B2 Flashcards

1
Q

Our skin is the _____ in the human body (______ total body weight)
In adults: skin’s SA is _____
Renew skin every _____ depending on age
When older, renew skin every ____ depending on age

A

-largest single organ
-15-20%
-1.5-2 m^2
-20-30 days
-50-80 days

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2
Q

main functions of skin epithelia

A

-Protective – physical barrier
-Sensory - sensory receptors in the skin
-Thermoregulation – assists in maintaining constant body temperature
-Metabolic – produces Vitamin D3, energy stored in fat, remove electrolytes through sweat

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3
Q

Following gastrulation, the skin epidermis develops from ______

A

-single layer of ectoderm

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4
Q

ectodermal progenitors forms epidermis under the influence of _____ (TFs) which does what?

A

-Wnt,BMP
-inhibits the response to FGF

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5
Q

ectodermal progenitors undergoes neurogenesis under the influence of _____ (TFs)

A

-FGFs, BMP inhibition, absence of WNT

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6
Q

FGF stands for ?

A

fibroblast growth factor

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7
Q

embryonic epidermis undergoes parallel division under the influence of ______ to form _______ (layering of skin)

A

-BMPs, Notch
-stratified epidermis

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8
Q

hair: embryonic epidermis under the influence of ______ forms _______

A

-Wnt
-Hair placodes (invaginations into CT to form hair follicle)

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9
Q

epidermis of hair placodes is under the influence of ____

A

Wnts, EGF

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10
Q

dermis of hair placodes is under the influence of ____

A

BMP inhibitors, FGFs

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11
Q

3 layers of skin

A

-epidermis (most prevalent)
-dermis
-subcutaneous layer

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12
Q

epidermis ( ____ origin) consists of _______

A

-ectoderm
-multiple layers of keratinized stratified squamous cells

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13
Q

dermis ( ____ origin) consists of _______

A

-mesoderm
-CT, blood vessels, protein fibres (collagen), nerves

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14
Q

subcutaneous layer (aka ____ ) is _______ + function?

A

-hypodermis
-loose layer of CT containing pads of adipocytes
-bind skin loosely to underlying tissue (muscle)

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15
Q

epidermal cells receive nutrients from and release their wastes into ______

A

the areolar CT layer

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16
Q

Hair follicle & Sebaceous layer are in this layer of skin?

A

dermis

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17
Q

in the skin, epidermal ridges do what?

A

invaginate and interdigitate/interconnect with dermal papillae to increase the strength of both layers

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18
Q

areolar CT does what?

A

-binds epithelial tissue to underlying tissues
-reservoir of water/salt

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19
Q

thickness of skin

A

75-150 um

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20
Q

layers of epidermis in thin skin from top to bottom (not in palms and soles) + function

A

-Stratum corneum- dead cells with keratin that have lost nucleus and cytoplasm for (waterproof) protection
-Stratum granulosum- thin layer of cells to prevent fluid loss/layer between live & dead cells, secrete lameller bodies
-Stratum spinosum- living keratinocytes, synthesis of keratin, has a lot of desmosomes for anchoring, strength & flexibility, forms ridges
-Stratum basale- single cell (cuboidal/columnar) layer, highly mitotic (stem cells), basal layer

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21
Q

thin skin vs thick skin

A

-Dermis of thin skin more cellularized and well vascularized than in thick skin
- Thin skin contains more elastin and less coarse bundles of collagen
-Thick skin epidermis is thicker

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22
Q

layers of epidermis in thick skin from top to bottom (palms and soles) + function

A

-Stratum corneum- dead cells with keratin that have lost nucleus and cytoplasm for (waterproof) protection
-Stratum lucidum- thin layer of dead cells that only appear in thick skin
-Stratum granulosum- thin layer of cells to prevent fluid loss/layer between live & dead cells, secrete lameller bodies
-Stratum spinosum- living keratinocytes, synthesis of keratin, has a lot of desmosomes for anchoring, strength & flexibility, forms ridges
-Stratum basale- single cell (cuboidal/columnar) layer, highly mitotic (stem cells), basal layer

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23
Q

Keratinocytes move from _____

A

basal layer upwards to surface

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24
Q

other cells present in skin

A

-melanocyte (pigment producing cells)
-langerhans cell (antigen presenting cells
-merkel cell (low threshold mechanoreceptors)

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25
Q

stem cells of epidermis reside _____

A

in basal layer

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26
Q

only skin layer in thick skin

A

stratum lucidum

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27
Q

basal layer of epidermis attached via ____ to underlying basement membrane

A

-intergins

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28
Q

Secreted factors from dermal fibroblasts promote _____

A

the proliferation of the basal epidermal cells

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29
Q

_____ is one of the major cues directing skin development and maintenance

A

-Wnt signaling

30
Q

Stem cells from basal layer that divide form _____

A

-Notch activated terminally differentiating cells which move up into other layers (NOTCH signalling increases)

31
Q

Stem cells of epidermis on the tip of ____ divide ______

A

-dermal papilla
-infrequently and always in sideway direction

32
Q

_____ is required to maintain epidermis

A

Wnt signaling

33
Q

marker for skin stem cells

A

B1- subunit of integrin, Lgr6+

34
Q

marker for skin differentiating cells/keratinoyctes

A

keratin 10

35
Q

transit amplifying cells of skin are ____

A

short-lived

36
Q

skin epidermis: differentiation increases as _____

A

you move up the skin layers

37
Q

Factors of epidermal SC niche (4)

A

-secreted factors (Wnt, EGF)
-cell-cell contact
-ECM
-physical factors (elasticity, topography- shape of cells)

38
Q

Rate of proliferation of epidermal SC layer is determined by _______

A

-signals (growth factors)
-direct cell-cell contact that come from the terminally
differentiated epidermal cells overlying the
stem cell layer

39
Q

Importance of the niche in the epidermis was determined by _____

A

-autologous skin graft on severe burn patients

40
Q

Hair follicles cycle through ______. Stem cells active when?

A

-bouts of hair growth and degeneration
-only periodically

41
Q

part of hair follicle

A

-hair shaft (seen above the skin)
-infundibulum
-isthmus + sebaceous gland
-bulge
-hair germ
-dermal pailla (CT)

42
Q

stem cell niche of hair follicle = ____ + ___

A

-bulge
-hair gem

43
Q

Growth cycle of hair follicle

A

-rest (telogen)
-growth (anagen)
-regression (catagen)

44
Q

stem cells in lower bulge can do what?

A

makes all the lineages of the hair follicle

45
Q

Stem cells in the epithelia produces this TF to constantly proliferate to renew epidermis

A

-Lgr6+

46
Q

Secondary hair gem TF

A

-Keratin: Krt15
-Gli1+
-Lgr5+
Wnt signalling

47
Q

Hair Bulge TF

A

-Keratin: Krt15
-Cell surface: Cd34+, Lgr5+
-TF: Sox9+

48
Q

Isthmus TF

A

-Gli1+
-Lgr6+

49
Q

Sebaceous gland TF

A

-Blimp1+ (PRDM1)
-Lgr6 (for the development of gland)

50
Q

Junctional zone (where follicle exits skin) TF

A

-Lrig1+
-EGF signaling

51
Q

Interfollicular epidermis is the _____

A

epidermis between hair follicles

52
Q

molecular identity of interfollicular epidermis (IFE) is ____

A

unclear

53
Q

____ signalling is required for hair follicle induction

A

Wnt

54
Q

____ signalling from nearby nerves to activate target Gli1

A

Shh

55
Q

Epidermal lineage commitment with multipotent stem cells contributing to ______ (3)

A

-the epidermis
-the hair follicle
-the sebaceous gland (SG)

56
Q

there is also a unipotent stem cell population in the sebaceous gland that are _____, which regulates ____ and governs activity of _____

A

-Blimp1 positive (PDRM1 positive)
-homeostasis of sebaceous gland
-Bulge SCs

57
Q

sebaceous gland buds from the ______ as a terminally differentiating structure

A

-upper ORS (outer root sheath)

58
Q

Sebaceous gland formation is regulated by ______ and produces _______

A

-Notch and Hedgehog signaling pathways
-lipid rich sebum

59
Q

Proliferative sebocytes TF

A

Ki67+, Blimp1, K14,K5, C-myc

60
Q

Differentiated sebocytes TF

A

PPARy+

61
Q

Blimp 1 inhibits ___ in sebocyte progenitor

A

C-myc

62
Q

Blimp1 SC are distinct from ____

A

multipotent SC pop’n

63
Q

sebaceous gland turnover occurs continuously during _____

A

adult homeostasis

64
Q

sebocyte creation

A

multipotent SC form isthumus & junctional zone
-sebocyte progenitor
-proliferative sebocyte/transit amplifying cells
-differentiated sebocyte (secrete sebum)

65
Q

Krt15+ progeny of SC is _____? Lgr6+, Gli1+? Lrig1+? IFE?

A

-transient
-long-lasting
-longlasting
-longlasting
-longlasting

66
Q

-Upon wounding HFSCs are able to migrate into _____.
If hair follicle stem cell pool (bulge stem cell niche) is
lost due to injury, ______ are induced to
enter and repopulate the niche. Plasticity needs ___ signalling

A

-the IFE to regenerate the epidermis and, vice versa
-IFE stem cells, HF progeny, infundibulum and sebaceous glands
-SHH

67
Q

Genes in the ______ control orientation and differentiation of hair follicles. Generally hair is in the same direction along _____. Requires ____ signalling

A

-planar cell polarity (PCP) pathway
-the body axis or orient to form a whorl
-Wnt

68
Q

Loss of HFSC niche in bulge as one ages leads to _____; young SC + old dermis = ___
young SC + young dermis = ____

A

balding
-no growth
-growth

69
Q

Bioprinting (def.)

A

-advanced manufacturing platform that enables the predefined deposition of living cells, biomaterials, and growth factors using computer-aided design to fabricate customizable constructs via a layer-by-layer printing process with a high degree of flexibility and repeatability

70
Q

bioprinting technique

A

-A skin biopsy is collected from the patient and cultured in vitro to obtain a sufficient amount of cells
-Bio-inks in the form of cell suspensions, hydrogels, or cell-encapsulated hydrogels are used to fabricate bioprinted skin constructs
-Printed construct is cultured under submerged conditions followed by an air-liquid interface to obtain mature skin suitable for transplantation

CELL 302 (18 decks)

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