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Structure and function by Ana > Missing > Flashcards

Missing Flashcards

1
Q

What do intermediate filaments connect

A

Nuclear membrane to hemidesmosome
-function: maintain integrity and structure of basal epidermal cells

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2
Q

What do anchoring filaments connect?

A

hemidesmosomes to anchoring fibrils throughout the lamina lucida
-LL is fixation artefact and probably does not exist in vivo
-composition: EC collagen XVII

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3
Q

What is lamina densa

A

basal lamina sensu stricto

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4
Q

What is lamina densa composed of ?

A

collagen IV , laminin 5,6,10+ nidogen,perlecan (heparin sulphate proteoglycan), other proteoglycans+ fibulins

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5
Q

What do anchoring fibrils connect?

A

From lamina densa to dermal banded collagen fibers and to rare anchoring plaques
-they can also loop bak to lamina densa

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6
Q

What are focal contacts?

A

= are inter-hemidesmosomal adhesion structures
-mostly functional during wound healing (epidermal migration occurs)

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7
Q

Functions of the fur ?

A

-thermal regulation
-physical and immunological protection
-protection against UV light and microbes
-dispersion of sebum and pheromones
-sensory perception
-social interactions
-camouflage

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8
Q

Stage of skin development

A

1.specification-commitment of progenitor cells
2.Morphogenesis-they begin to form the specialised structures
3.Differentiation-further development towards their mature form

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9
Q

Hair follicles contain cells from which origin

A

-ectodermal
-mesenchymal
-neural-ectodermal

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10
Q

During elongation phase, 3 bulges appear that will give rise to:

A

-lowest-attachment of the arrector pills muscle
-middle- differentiate into sebaceous gland
-upper- in epitrichial sweat gland

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11
Q

Name 3 phases of in hair morphogenesis

A

1.Induction/initiation
2. Organ downgrowth
3. cellular differentiation

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12
Q

Name 5 stages in hair morphogenesis ( in mice 8 stages)

A

1.The first dermal signal and epidermal placode formation
2.The first epithelial signal
3. The second dermal signal
4. Differentiation of the IRS and hair fibers
5. Induction of HF polarity and control of HF shape

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13
Q

What happens in the first stage of hair morphogenesis- 1. dermal signal and epidermal placode formation

A

-activators:
a) Wnt pathway (dermis, but also epidermis)-> beta catenin (dermis, but also epidermis)
b) ectodysplasin (EDA- for guard hair) -> NFkB- SHH
c) FGFs
d) transcription factors MSX1, MSX2
Inhibitors: BMP family

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14
Q

What happens in stage 2, the 1. epithelial signal

A

-important for formation of the dermal papilla-germ formation
-depends on:
a) Wnt (epidermis)-> beta catenin
b) platelet - derived growth factor A (PDGF-A)
c) SHH

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15
Q

What happens in second dermal signal, the 3. stage ( mice 2-3)

A

-down growth of HF -dermal papilla
-activated by :
a) SHH- activin aA (dermis)
b) SHH- hepatocyte GF (HGF) and its receptor c-Met
c) adhesion molecules like integrin

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16
Q

What happens in IRS and hair fiber stage (mice 3-5)

A

-construction of the different layers of HF
-encapsulation by nerve endings and blood vessels
-formation of associated structures ( arrector pills muscle, glands)
-infiltration of melanocytes
-formation of the bulbous peg
Formation of the IRS and hair medula: BMP, Notch-1
Formation of hair shaft cortex: Wnt, FOX N1, HOX C13, desmogelin 4
Formation of the bulge for the stem cells
Formation of the sebaceous gland bulge: c-Myc, PPARgamma
Formation of HF pigmentary unit: stem cell factor/c-kit, endothelin-1 , Notch

17
Q

What happens in stage HF polarity and control of HF shape (stages 6-8)

A

-controled by SHH, Wnt signalling pathway , TGF-alpha and its receptor , transcription factor ETS2
-secondary HF develop on the extal (caudal) side of the hair germ

18
Q

From what structure forms HF

A

-from hair germs which are differentiation of stratum germinativum

19
Q

What are the stages of early and late anagen

A

Early anagen: I, II, IIIa, IIIb
-movement of DP in the SC fat, new hair reaches up to 2/3 of the follicle length
Late anagen: IIIc, IV, V, VI
-DP fully enclosed by the bulb, HS reaches epidermal surface

20
Q

What happens in early catagen

A

Stages I, II, III, IV
-DP changes form and moves upward
-mitotic activity of the bulb stops
-incerasing numbers of apoptotic KC

21
Q

What happens in late catagen

A

Stages: V,VI, VII, VIII
-DP moves towards dermis
-tail of trailing connective tissue sheath
-apoptosis and loss pf 70% of HF
-apoptosis lower and middle ORS , hair matrix and IRS
-cessation of melanogenesis
-ECM remodeling

22
Q

What happens in telogen

A

HS is retained in follicle
-DP in dermis
-no trailing connective tissue sheath
-full trichilemal keratinisation

23
Q

What is exogen

A

-phase of hair shedding
-independent of anagen (not by the tip of the new hair)
-PROTEASES: CATHEPSIN L (enzymatic process between hair and root sheath)
-it happens during anagen IV
-ACTIVE PROCESS

24
Q

What is kenogen

A

-hairless telogen
-HF lost the hair and it remains empty before anagen is initiated

25
Q

Name species of anagenic hair cycle

A

-dogs: bichon frise, Chinese crested, poodle, Yorkshire terrier,
-goats: Mohair , Angora
-merino sheep
-Angora rabbit

26
Q

Which hair is always in anagen and in which species

A

-horse
-main, tail, fetlock
-permanent hair

27
Q

What cells and glands determine cutaneous pH

A
  1. epidermal cells
  2. sebaceous glands
  3. Epitrichial (apocrine) glands
  4. Atrichial (eccrine) glands
28
Q

Name acidic substances that determine cutaneous pH

A
  1. Free fatty acids (KCs: phospholipids; ceramides; sebum; microbes)
  2. filaggrin breakdown products (urocanic acid, Pyrrolidone carboxylic acid , amino acids)
    3.cholesterol sulphate
  3. alpha-hydroxy acids (sweat, microbes): LACTIC, BUTYRIC
  4. amino acids (KC: fillagrin breakdown products; from sweat, sebum
29
Q

Name alkaline substances that determine cutaneous pH

A
  1. NH3 (atrichial sweat glands)
  2. CO2 (sweat)
  3. HCO3 (sweat)
30
Q

Name functions of cutaneous pH

A

1.Antimicrobial
2. Influences permeability barrier
3. Influences keratinisation-desquamation

31
Q

Normal values of cutaneous pH depend on:

A
  1. Species
  2. Depth (increased in deeper area of epidermis)
    3.Age (higher at young age)
  3. Sex (H in males, neutered females)
  4. Breed
  5. Skin area
  6. Sweat gland activity (atrichial Down, epitrichial up)
  7. Excitement (H)
  8. Exercise
  9. Circadian rhythm
  10. Diet
  11. Duration of lactation

Structure and function by Ana (4 decks)

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