Introduction to Dermatology II Flashcards
(46 cards)
What are the functions of the hair?
● Protection against external factors
● Sebum
● Apocrine sweat
● Thermoregulation
● Social and sexual interaction
● Epithelial and melanocyte stem cells
What is the difference between eccrine and apocrine
glands?
Eccrine sweat glands occur over most of the body and open directly onto the skin’s surface.
Apocrine glands open into the hair follicle, leading to the surface of the skin. Apocrine glands develop in areas with many hair follicles, such as on the scalp, armpits and groin.
What are the two types of hair follicles?
vellus and terminal
What are terminal hairs?
scalp, eyebrows and eyelashes
What are the hairs on the rest of the body called?
vellus hairs (except palms, soles, mucosal regions of lips and external genitalia)
What is the hair cycle of the hair?
Anagen, catagen and telogen
Explain in more detail the stages of the hair cycle?
● Anagen (where new hair forms and grows)
➢ 85% of hair; lasts 2-6 years
● Catagen (regressing phase)
➢ 1% of hair; lasts 3 weeks
● Telogen (resting phase)
➢ 10-15% of hair; lasts 3 months
● Then loss of old hair.
What is the structure of the hair within the skin?
● Human skin contains pilosebaceous follicles and sweat glands.
● Hair follicles (pilosebaceous unit)
● Pockets of epithelium continuous with superficial epidermis
● Envelop a small papilla of dermis at their base.
What are holocrine sebaceous glands?
they open into the pilary canal–> in axillae- follicles associated with apocrine glands
How are arrector pili muscles specially adapted?
Arrector pili (smooth muscle) extends at angle between surface of dermis and point in follicle wall.
What is the hair split into?
Infundibulum
Isthmus
What is the Infundubulum?
Uppermost portion of the hair follicle extending from opening of sebaceous gland to surface of the skin
What is the isthmus?
Lower portion of upper part of hair follicle between opening of sebaceous gland and insertion of arrector pili muscle
When does epithelium keratinization start?
Epithelium keratinization begins with lack of granular layer named “trichilemmal keratinization”
What is the bulge of the hair?
● Segment of the outer root sheath located at insertion of arrector pili muscle
● Hair follicle stem cells reside here
What are the types of migration of hair?
downward and upwards (distally)
What is downwards migration?
Downward → generate the new lower anagen hair follicle → enter hair bulb matrix, proliferate and undergo terminal differentiation to form hair shaft and inner root sheath.
What is upwards (distally) migration?
Upwards (distally) → form sebaceous glands and to proliferate in response to wounding
What is the bulb of the hair?
Lowermost portion of the hair follicle, includes the follicular dermal papilla and the hair matrix
What is the outer root sheath (ORS)?
Extends along from the hair bulb to the infundibulum and epidermis, serves as reservoir of stem cells
What is the inner root sheath?
● Guides / shapes hair
● Encloses follicular dermal papilla, mucopolysaccharide-rich strome, nerve fiber & capillary loop
What are the functions of the nail?
● Protection of distal phalanx
● Counterpressure effect to pulp - important for walking and tactile sensation
● Increase dexterity / manipulation of small objects
● Enhance sensory discrimination
● Scratching or grooming
What is the nail plate?
● Final product of proliferation and differentiation of nail matrix keratinocytes
● Emerges from proximal nail fold
● Grows at 1-3mm/month
● Firmly attached to nail-bed
● Detaches at hyponychium
● Lined laterally by lateral nail folds
What is the nail matrix?
● Produces nail plate
● Lies under proximal nail fold, above bone of distal phalanx (to which it is connected by a tendon
➢ Lunula only visible proportion
● Nail matrix keratinocytes differentiate → lose their nuclei and are strictly adherent - cytoplasm completely filled by hard keratins
● Also contains melanocytes
