Missing Flashcards
What do intermediate filaments connect
Nuclear membrane to hemidesmosome
-function: maintain integrity and structure of basal epidermal cells
What do anchoring filaments connect?
hemidesmosomes to anchoring fibrils throughout the lamina lucida
-LL is fixation artefact and probably does not exist in vivo
-composition: EC collagen XVII
What is lamina densa
basal lamina sensu stricto
What is lamina densa composed of ?
collagen IV , laminin 5,6,10+ nidogen,perlecan (heparin sulphate proteoglycan), other proteoglycans+ fibulins
What do anchoring fibrils connect?
From lamina densa to dermal banded collagen fibers and to rare anchoring plaques
-they can also loop bak to lamina densa
What are focal contacts?
= are inter-hemidesmosomal adhesion structures
-mostly functional during wound healing (epidermal migration occurs)
Functions of the fur ?
-thermal regulation
-physical and immunological protection
-protection against UV light and microbes
-dispersion of sebum and pheromones
-sensory perception
-social interactions
-camouflage
Stage of skin development
1.specification-commitment of progenitor cells
2.Morphogenesis-they begin to form the specialised structures
3.Differentiation-further development towards their mature form
Hair follicles contain cells from which origin
-ectodermal
-mesenchymal
-neural-ectodermal
During elongation phase, 3 bulges appear that will give rise to:
-lowest-attachment of the arrector pills muscle
-middle- differentiate into sebaceous gland
-upper- in epitrichial sweat gland
Name 3 phases of in hair morphogenesis
1.Induction/initiation
2. Organ downgrowth
3. cellular differentiation
Name 5 stages in hair morphogenesis ( in mice 8 stages)
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
What happens in the first stage of hair morphogenesis- 1. dermal signal and epidermal placode formation
-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
What happens in stage 2, the 1. epithelial signal
-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
What happens in second dermal signal, the 3. stage ( mice 2-3)
-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
What happens in IRS and hair fiber stage (mice 3-5)
-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
What happens in stage HF polarity and control of HF shape (stages 6-8)
-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
From what structure forms HF
-from hair germs which are differentiation of stratum germinativum
What are the stages of early and late anagen
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
What happens in early catagen
Stages I, II, III, IV
-DP changes form and moves upward
-mitotic activity of the bulb stops
-incerasing numbers of apoptotic KC
What happens in late catagen
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
What happens in telogen
HS is retained in follicle
-DP in dermis
-no trailing connective tissue sheath
-full trichilemal keratinisation
What is exogen
-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
What is kenogen
-hairless telogen
-HF lost the hair and it remains empty before anagen is initiated
Name species of anagenic hair cycle
-dogs: bichon frise, Chinese crested, poodle, Yorkshire terrier,
-goats: Mohair , Angora
-merino sheep
-Angora rabbit
Which hair is always in anagen and in which species
-horse
-main, tail, fetlock
-permanent hair
What cells and glands determine cutaneous pH
- epidermal cells
- sebaceous glands
- Epitrichial (apocrine) glands
- Atrichial (eccrine) glands
Name acidic substances that determine cutaneous pH
- Free fatty acids (KCs: phospholipids; ceramides; sebum; microbes)
- filaggrin breakdown products (urocanic acid, Pyrrolidone carboxylic acid , amino acids)
3.cholesterol sulphate - alpha-hydroxy acids (sweat, microbes): LACTIC, BUTYRIC
- amino acids (KC: fillagrin breakdown products; from sweat, sebum
Name alkaline substances that determine cutaneous pH
- NH3 (atrichial sweat glands)
- CO2 (sweat)
- HCO3 (sweat)
Name functions of cutaneous pH
1.Antimicrobial
2. Influences permeability barrier
3. Influences keratinisation-desquamation
Normal values of cutaneous pH depend on:
- Species
- Depth (increased in deeper area of epidermis)
3.Age (higher at young age) - Sex (H in males, neutered females)
- Breed
- Skin area
- Sweat gland activity (atrichial Down, epitrichial up)
- Excitement (H)
- Exercise
- Circadian rhythm
- Diet
- Duration of lactation
