Introduction to Dermatology II Flashcards
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
Can you name A-D?
a= proximal nail fold
b= lunula
c= onychodermal band
d= nail matrix
Can you name A-D?
a= arrector pili muscle
b= dermal-epidermal junction
c= eccrine gland
d= sebaceous gland
What are apocrine glands?
modified sebaceous glands and secrete into the infundibular portion of the hair follicle
Do keratinocytes lack nuclei and organelles in stratum granulosum?
No, they lack them in the stratum corneum
Where is melanin synthesised?
in melanocytes
Where do the vascular plexuses lie?
in the dermis- they do not cross into the epidermis (they are not superficial)
What is keratinocytes role in immunity?
they synthesise antibiotics
Are T-cells resident in the skin?
Yes
Where are Langerhan cells resident?
In the epidermis
What are connexons?
form the pore for a gap junction between the cytoplasm of two adjacent cells
What are the intracellular channels in gap junctions?
connexons
What are connexons essential for?
for cell synchronisation, cell differentiation, cell growth and metabolic coordination
What phase is most of the hair if it is healthy?
anagen phase
What does catagen refer to?
The transition from the growth phase to shedding
What happens to the hair during the catagen phase?
Hair is disconnected from its blood supply and becomes a club hair.
Catagen cannot occur again until after anagen.
What happens in the telogen phase?
Then the telogen phase, the hair follicle is resting and the hair is shed.
Does staphylococcus aureus contribute to eczema?
Yes, staphylococcal superantigens stimulate Th2 lymphocyte responses and subvert T-reg
What is guttate psoriasis?
Skin condition in which small, red, scaly, teardrop-shaped spots with silvery scale appear on the arms, legs, and middle of the body
What is onycholysis?
It is characterized by a spontaneous separation of the nail plate starting at the distal free margin and progressing proximally. In onycholysis, the nail plate is separated from the underlying and/or lateral supporting structures.
Is atopic eczema usually itchy?
No, it is invariably itchy
Is psoriasis associated with liver inflammation?
Yes
What does nail involvement in psoriasis indicate?
a higher risk of psoriatic arthritis
