Hair and Nail Flashcards
What is the function of hair?
- Protection
- Sensation
- Thermoregulation
- Communication
Common between hair and nails:
- Protein (keratin)
- Product of hair follicle and nail matrix
What is the role of the hair bulb?
Complex interaction with vasculature and hair
When do you start growing hair?
3rd trimester in utero
Where is hair not found?
- Palms
- Soles
- Penis
- Vulva
Where is the greatest follicle density?
Skin
What is the structure of pilo-sebaceous unit?
- Hair follicle
- Invagination of epidermis containing hair - Hair shaft
- Outer cuticle that encloses cortex and inner medulla
- Cortex packed with keratinocytes
- Inner medulla has terminal cells - Erector pili muscle
- Sebaceous gland
What is the structure of a the hair follicle?
- Infundibulum
- Isthmus
- Suprabulbar
- Hair bulb
○ Where hair shaft is produced
○ Germinative cells found
○ Melanocytes found
How are sebaceous glands formed?
Epidermis derived cells and production of oily sebum
How is sebum produced?
Holocrine secretion in which cells disintegrate to release their lipid cytoplasm
What are the types of hair and their characteristics?
- Lanugo (foetus and anorexics)
○ Fine and long
○ Unpigmented
○ Unmedullated - Vellus
○ Short, fine, light coloured on most of body
○ Unmedullated - Terminal
○ Longer, thicker, darker
○ medullated
○ Originate as vellus hair but differentiation
stimulated by androgens in puberty
What is the monomer of hair?
- Keratin
- Forms filaments
How does hair grow?
- Grows in cycles
- Different locations have different anagen lengths
What are the phases of the hair cycle?
Anagen: growth phase
- At any given point 80-90% in anagen
Catagen: cell division slows and stops
- Follicle retreats towards surface
Telogen: hair is shed actively until next anagen phase begins
- Hairs have short club root
Explain the concept of synchronicity
- When baby is born all of hair cycle in synch so shed at same time
How is hair growth regulated?
- Usually hormones
○ Prolactin
○ Oestrogen
○ melanin
What is the function of nail?
- Protection
- Touch
- Communication
What is the composition of nails?
- Mostly densely packed keratin
- Strong with longitudinal ridging and curvature
What are the main structures in nails?
- Germinal matrix:
- dividing cells which mature and move forward to form nail plate
- Nail bed:
- produces small amount of keratin
- adherent to nail plate
- Dermal capillary:
- adjacent to nail bed
- produce small amount of pink color
- White lunula:
- visible part of matrix
- Critical to hair growth
- Hyponchium
- thickened epidermis underlying free margin of nail
- Ochondymal band
What does the nail plate consist of?
- Layers
- Top layer produced form proximal part of nail matrix
- May also contain melanocytes
How are nails produced?
- Nail plate produced by germinal matrix
- Nail matrix underneath proximal nail fold
What is the rate of nail growth?
- Finger 3mm/month
- Toes 1mm/month
