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Dermatology
Biology of Hair and Nails
Built from Dermatology, 5th Edition
What’s inside
4 sections · 124 slides
Overview
- What this deck covers
Principles of skin appendage formation
How hair, nails, feathers, and teeth all start the same way
- Skin appendages share one building plan
- Hair and nail as products of the same programme
- The dermal message: WNT signalling
- Single-cell studies confirm an early dermal condensate
Biology of hair
Follicle morphogenesis, patterning, the mature cycle, and hair structure
- Hair follicle morphogenesis: setting the stage
- Stages of hair follicle induction
- Signals guiding each stage of follicle induction
- Genes that build the hair shaft and inner sheath
- Nerves and blood vessels grow in step with the follicle
- Nerve network around a cycling hair follicle
- Different hair types form in successive waves
- Human hair coats change through infancy
- Trichology terms: growth stage and hair-type vocabulary
- Body-site differences in hair and skin
- Hair whorls and directional patterning
- Congenital generalized hypertrichosis
- Adult skin can still make new follicles
- Dermal papilla cells can induce new follicles
- The mature follicle cycles for life
- The hair follicle cycle
- Exogen and kenogen: shedding the old hair
- Anagen: the growth phase
- Matrix cells build the follicle's seven layers
- Catagen: controlled regression
- How the club fibre forms and the papilla is drawn up
- Genes controlling catagen: hairless and FGF-5
- Telogen: the resting phase
- From telogen back to anagen
- The hair follicle cycle and its molecular switches
- Numbers behind the human hair cycle
- Basic information on human hair follicles (a data summary)
- Source data table: basic human hair follicle statistics
- What drives faster or slower hair growth
- The three central lineages that build the hair fibre
- The inner root sheath guides the growing shaft
- The companion layer: a slippage plane
- The full layered architecture of an anagen follicle
- Hair keratins: a specialised, sulfur-rich family
- Keratin mutations and hair disease
- Which keratins mark which layer of the follicle
- Desmosomes hold follicle cells together
- Dsg4: the key desmoglein of the hair cortex
- The bulge: the follicle's main stem cell store
- The secondary hair germ and other stem cell zones
- The dermal papilla is a mesenchymal stem cell niche too
- The hair follicle is an immune-privileged site
- How the anagen hair bulb hides from the immune system
- Mechanisms contributing to the immune privilege of the hair follicle
- Mechanisms contributing to the immune privilege of the hair follicle (continued)
- Mechanisms contributing to the immune privilege of the hair follicle (continued)
- Multiple mechanisms add up to one shield
- Alopecia areata: when immune privilege collapses
- Genetics and treatment leads in alopecia areata
Biology of nails
Nail unit anatomy, development, the matrix, keratins, and nail growth
- What the nail does
- Functions of hair, the pilosebaceous unit, and nails
- Functions of hair and nails
- Functions of hair and nails (continued)
- The nail plate and the nail folds
- The matrix, lunula, and nail bed
- Nail unit anatomy, surface to cross-section
- Blood and nerve supply of the digit
- Nail embryology: an 8-to-20-week timeline
- Step-by-step nail unit development
- Genetic disorders that reveal nail development genes
- Digit tip regeneration in infants
- The nail matrix: where the nail plate is made
- Seeing the matrix directly during surgery
- Which part of the nail unit actually makes the plate?
- Theories on the origin of the nail plate
- Five decades of evidence, side by side
- The modern consensus: the matrix makes the plate
- Nail stem cells
- Melanocytes in the nail unit
- Immune privilege in the nail unit
- Nail keratins: hard, sulfur-rich, and tough
- Keratin and protein zones across the nail unit
- The nail bed does not keratinize like skin
- What else is in the nail plate
- The nail as a record of exposure
- How nail growth is measured
- Toenails vs fingernails: thickness and growth rate
- The nail apparatus: basic information and terminology
- The nail apparatus: basic information and terminology (continued)
- Factors that speed up or slow down nail growth
- Factors that can influence nail growth
- Apparent slow growth can be a change in direction
- A shared vocabulary for hair biology
- Trichology terms
- Trichology terms (continued)
- Trichology terms (continued)
- Trichology terms (continued)
- Trichology terms (continued)
- Trichology terms (continued)
- Trichology terms (continued)
- Trichology terms (continued)
- Hair and nails: what to remember
- Clinical threads worth remembering
- References
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- Dermatology, 5th Edition (2-Volume Set)