Hair Flashcards
Upper segment consists of
infundibulum
isthmus
Hair is separated into
Shaft
cuticle, cortex, medulla
Follicle
infundibulum, sebaceous gland, isthmus, hair bulb
Specific surface properties of hair are governed by
cuticle
Cuticle acts as a barrier against
external aggression (water penetration/chemical treatment)
Top to bottom cuticle cell structure
External surface of the cell Epicuticle A-layer Exocuticle Endocuticle Cell membrane (including epicuticle) Intercellular cement Epicuticle of underneath cell
Epicuticle consists of
protein layer covered by lipid layer bound covalently by thioester linkages
Sulfur rich layers of cuticle
A-layer (30% cystine)
exocuticle (15% cystine)
In cortex, IF are embedded in matrix which is made of
KAPs (high sulfur, high glycine-tyrosine)
Proteins with the highest level of cystine are located in
matrix proteins of cortex
Much of the strength of hair is accounted for by
cross-linking of disulfide linkages between keratin chains
_____ bonds give hair flexibility
hydrogen
African hair has more ______ and less ______
KAP proteins
IF
___________ are always parallel, while _______ is anti-parallel
heptad repeat unit
tetramer
Compartments of hair follicle
- Dermal
- Epithelial
Dermal compartment of hair follicle includes
- Dermal sheath
- Dermal papilla
Epithelial compartment of hair follicle includes
hair matrix
3 concentric structures: ORS, IRS, shaft
Composition of hair lipids
fatty acids
ceramides
polar lipids
What makes up the dermal compartment
- Connective tissue sheath produced by fibroblast and collagen (I, III)
- Basement membrane (laminin type I, collagen IV, fibronectin, proteoglucans)
Stem cells that form hair are located in
basal layer of ORS bulge, it is from these cells that matrix cells are formed
Growth factors that potentiate growth of dermal papilla cells
bFGF (basic fibroblast growth factor)
PDGF (platelet-derived growth factor)
Dermal papilla cells produce _______ which influence proliferation of hair matrix cells
cytokines
Catagen
2-3 weeks Growth stops ORS shrinks Regression of hair follicles Club hair is formed when part of hair follicle in contact with lower portion of hair attaches to shaft
Anagen
2-6 years
- Rapidly dividing cells in root of hair grow upward to form hair shaft
- New hair is formed, pushes club hair up and out of follicle
- highly increased proliferative rate of hair follicle cells
