Adnexal Structures and Associated Disorders Flashcards
What are the 3 subunits of the hair shaft of the pilosebaceous unit?
infundibulum: (upper segment): refers to portion from the skin to the sebaceous gland
isthmus: (middlesegment) which extends from the point of insertion of the arrector pili muscle to the sebaceous gland
hair bulb: the hair shaft grows from this mitotically active undifferentiated cells of the matrix portion of the hair bulb
In what part of the pilosebaceous unit are mitotically active undifferentiated cells present?
hair bulb
what are the 3 types of pilosebaceous units?
- Lanugo (fetal)
- Vellus (fine)
- Terminal (coarse)
What are two examples of abnormal hair type for age or location signifying an undlerlying cndition
Anorexia (Lanugo)
Hirsutism (Terminal)
*females with terminal hair in male patter distribution (beard) may indicate excess androgen/ polycystic ovarian syndrome (PCOS)
Sebaceous Glands
where
what
how
when
where? greatest density on face and scalp, but everywhere
what? Produce (oil) sebum.
*triglycerides, free ftty acids, squalene, wax and sterol esters, and free sterols
How? holocrine secretion
When? Active at birth, but decreases during infacny. Sebum production stimulated by androgen production (5-alpha-dihydrotestosterone) in uberty
What is the hair cycle?
- Growth phase (anagen)
- majority of hair on scalp, duration dictates hair length
- Transition phase (catagen)
- Resting phase (telogen)
- hair shed during this phase
what is Telogen effluvium? what causes it?
Greater proportion of hair follicles (normally <15%) entering telogen phase (falling out)
**increase in hair shedding**
occurs approx 3 months after a stressful event, and slowly returns t normal. Could be pregnancy, broken bone, bad flu, psychosocial stress
What are club hairs?
instead of a typical hair bulb, you see a meek hair butt.
it is a hair follicle that is in telogen. It is a telogen bulb
What causes alopeci areata? What is it? How do we treat it?
autoimmune
smooth pathces of complete alopecia develop
nail pits (indentations in the nail plate) may be seen
topical corticosteroids are the mainstay of treatment
What is an eccrine gland and what innervates it? Where are they located?
sweaty gland
palms and soles
innervated by sympathetic fiber via Ach
What is an apocrine gland? Where are they located?
sweaty and smelly
axillae, anogenital, periumbilical, areolae, vermilion border of lips
What is hyperhidrosis?
overactive seat gland
what is anhidrosis/hypohidrosis?
occurs when sweat glands are absent/reduced
eg. ectodermal dysplasia
What are 3 disorders of the pilosebaceous unit?
acne vulgaris, acne rosacea, tinea veriscolor
How do sebaceous cells and follicular keratinocytes lead to the production of microcomedos?
- Sebaceous cells
- sebum
- fatty acids
- Follicular keratinocyte
- hyperproliferation
- keratohyaline granules increase
- disturbed desquamation
Describe the pathogenesis of acne
- Proprionibacterium acnes: releases enzymes that promote follicular rupture and stimulates the release of proinflammatory mediators leading to neutrophil recruitment and Th1 responses.
- anaerobic gram positive rod
- dependent on glycerol: hydrolysis of sebum triglycerides
- produce:
- porphyrins
- proinflammatory mediators
- lipases
Hoe do retinoids treat acne?
they target the comedone which is the inciting lesion of acne.
they work via:
- normalization of follicular keratinization, expulsion of existing kertinaceous follicular plugs, and prevention of the formation of new lesions
How does Benzoyl peroxide treat acne?
It kills the bacteria P acnes that leads to inflammatory lesions
How do antibiotics treat acne?
they kill P acnes!
What is Tinea versicolor aka Pityriasis versicolor
- Malassezia spp (globosa and furfur)
- oval to round scaly patches with fine overlying scale
- hyperpigmented (brown) or hypopigmented (lighter in color)
