Adnexal Structures - Holland Flashcards
Describe the complete pilosebaceous unit.
A hair follicle (3 parts), plus a sebacious gland, erector pilae muscle, and possibly an apocrine sweat gland (depending on location).
From where does hair grow?
From the matrix of the hair bulb (keratinous).
Distinguish between the 3 types of hair/pilosebaceous units.
Lanugo (fetal, mostly shed in utero and after birth)
Vellus (fine; eg forearm hair)
Terminal (coarse, eg scalp & pubic)
What could hirsutism in a woman indicate?
Underlying androgen excess, eg Polycystic Ovarian Syndrome.
Describe the composition of sebum.
Where are sebaceous glands found? When?
Pretty much every damn lipid: FFAs, Sterols, TGs, Squalene…
Found everywhere, but especially on face & scalp, and hardly on acral skin. Stimulated by androgens in puberty.
Describe the phases of hair growth. Include the durations.
Anagen: Growth; hair becomes thick and elongates. 2-5yrs.
Catagen: Transition; roots degenerate and hair migrates. 3-6wks.
Telogen: Resting; hair is ready to be shed. 3-5mo.
What is the name of the condition where stress can cause hair loss?
How and when?
Telogen Effluvium.
Stress causes hair follicles to enter telogen phase; hair loss up to 3mo after the stressor.
What is the etiology of Alopecia Areata?
What are some clinical findings?
How is it treated?
Autoimmune.
Patches of alopecia, and sometimes nail pits.
(topical!) Corticosteroids.
Distinguish between an eccrine and apocrine sweat gland.
Eccrine are found everywhere, but especially in the palms and soles. Activated by sympathetic ACh.
Apocrine at more specific sites (axillae, anogenital, areolae…), smelly (due to bacterial action), and responds to catecholamines.
Describe the structure of a sweat gland.
How does this differ between eccrine & apocrine?
A coiled secretory gland (cuboidal) is surrounded by myoepithelium to facilitate dumping to a duct.
Eccrine dumps to the surface (acrosyringium), Apocrine to a hair follicle (above the sebaceous gland).
What is hypohidrosis? In what conditions is it seen?
Decreased sweating. Hypohidrotic Ectodermal Dysplasia (HED)
What 3 factors contribute to acne formation?
Why is puberty a very trying time for acne?
Sebum and shedded corneocytes clog a follicle >> microcomedo. Colonization by Propionibacterium Acnes causes inflammation >> Acne.
Testosterone promotes production of sebum and keratinocytes.
What are blackheads and whiteheads?
Non-inflammatory comedones. Blackheads (open) are whiteheads (closed) that have had their contents oxidized over time, turning black.
Describe the role of P. Acnes in the formation of acne.
P. Acnes is a gram-positive anaerobe that is dependent on glycerol; it hydrolyzes sebum triglycerides to this end. It also produces lipases and proinflammatory mediators.
Recall some methods of treatment of acne.
Retinoids (comedolytic; bind the RX receptor)
Benzoyl Peroxide (cleanses; anti-inflammatory?)
Antibiotics (target P Acnes)
Oral contraceptives (anti-androgen)
