Dermatology 2 Flashcards
What are the 6 main functions of hair?
- Apocrine sweat
- Social and sexual interaction
- Sebum
- Protection against external factors
- Epithelial and melanocyte stem cells
- Thermoregulation
What are the 2 main types of hair?
Terminal hair
Vellus hair
Where do we find terminal hairs?
Scalp, eyebrows and eyelashes
Where do we find vellus hairs?
Everywhere on the body, except…
- Soles of feet
- Palms of hands
- Mucosal regions of lips and external genitalia.
What are the three components of the hair cycle?
Anagen
Catagen
Telogen
What occurs in anagen?
Occurs right after hair is lost
Generation of a new follicle and with it new hair forms and grows
What occurs in catagen?
Hair regresses due to a restriction of vascular supply.
What occurs in telogen?
Hair is resting and after telogen, hair is lost and the cycle restarts
How much hair at a time is in anagen?
85% of hair, this is because anagen occurs over 2-6 years
How much hair at a time is in catagen?
1% of hair, this is because catagen only lasts fro 3 weeks
How much hair at a time is in telogen?
10-15% of hair as telogens lasts for about 3 months
Describe the structure of hair
Pilosebaceous follicles and sweat glands. Hair follicles are pilosebaceous units. The pockets of epithelium containing hair follicles are continuous with the superficial epidermis and encase the papilla of the dermis at the unit base.
Describe the course of the arrector pili
Extends at the angle from the surface at the dermis to a point in the follicle wall
What are holocrine sebaceous glands?
These are modified sebaceous glands that open into the pilary canal and are found in the axilla therefore are associated with apocrine glands
What are holocrine sebaceous glands associated with?
apocrine sweat glands.
What are apocrine glands?
Modified sebaceous glands and secrete into the infundibulum
What are the two main sub sections of the hair follicle?
Infundibulum
Isthmus
What is trichilemmal keratinisation?
Epithelium keratinisation begins with a lack of a granular layer.
What is the bulge?
Segment of the outer root sheath located at the insertion of the arrector pili muscle.
What is the role of the bulge?
Acts as a reservoir from hair follicle stem cells
When do stem cells migrate upwards?
Form sebaceous glands and proliferate in response to wounding.
When do stem cells migrate downwards?
Form new hair follicles during anagen - enter the hair bulb matrix to undergo terminal differentiation to form the hair shaft and inner root sheath.
What is the bulb?
Lowermost portion of the hair follicle - it includes the hair matrix and the follicular papilla.
What is the outer root sheath?
Extends from the bulb to the infundibulum and acts as a stem cell reservoir.
What is the inner root sheath?
Important structure of the lower part of the hair follicle that surrounds and protects the growing hair.
Encloses the dermal follicular papilla, multipolysaccharide rich strome , nerve fibre and capillary loop
What is the role of the inner root sheath?
Guide and shape hair.
What are the 5 main functions of nails?
- Scratching and grooming
- Increase dexterity and manipulation of small objects
- Counterpressure effect to pulp important information for walking/tactile sensation
- Enhance sensory discrimination
- Protection of the distal phalanx
What are the 2 main structures within the nail?
Nail plate
Nail matrix
What is the nail plate?
Final product of proliferation and differentiation of nail matrix keratinocytes.
Attached to the nail bed and detaches from it at the hyponychium. It emerges at the proximal nail fold and is lined laterally by lateral nail folds.
What is the nail plate rate of growth?
1-3mm/month
What is the nail matrix?
Produces the nail plate, attached to the distal phalanx via a tendon.
What part of the nail matrix is visible?
Lunula
How do nail matrix keratinocytes form nail plate?
Keratinocytes differentiate and lose their nuclei - they are strictly adherent too as their cytoplasm is then filled with keratin
What else does the nail matrix contain?
Melanocytes
