Title: GZ / The Grenz Zone Season 1 / Ep 1
Tags: GZ DermnetNZ

Q: What are the four major cell types of the epidermis?
[...]
A: Keratinocytes, langerhans, melanocytes, and merkel cells

Keratins 5 and 14 are expressed in the basal layer and are mutated in patients with epidermolysis bullosa simplex

Keratins 1 and 10 are expressed in the stratum spinosum layer of the epidermis and are mutated in patients with epidermolytic ichthyosis
Back Extra: aka bullous congenital ichthyosiform erythroderma

Q: The stratum [...] and [...] are layers that are absent on mucosal sites
A: corneum; granulosum
Back Extra: Dermatologists often know that a biopsy was taken from inside of the mouth without looking at the bx requisition form

Q: UV light [...] the # of Langerhans T cells
A: decreases
Back Extra: This is how PUVA can reduce inflammation in psoriasis

Q: [...] phagocytose the melanosomes made by melanocytes
A: Keratinocytes
Back Extra: "Melanocytes are apple trees, keratinocytes are deer, melanosomes are the apples"

Q: Different races and skin types actually have the same amount of melanoCYTES but differ in the number, size, type, and distribution of melanoSOMES, with fairer skin types having more lighter-colored [...]-melanin and darker skin types having more of the dark [...]-melanin
A: pheo; eu
Back Extra: Similarly, with hair, darker hair has mostly eumelanin, whereas blonde or red hair has more pheomelanin

5 stains that can identify Langerhan cells
Langerin
S100
Vimentin
Peanut agglutinin
Cd1a
Back Extra: Langerin eats 100 vitamins and peanuts so he can listen to his CDs

Clark's levels for melanoma
I. Confined to the epidermis (in situ melanoma)
II. Into the papillary dermis
III. To the papillary dermis-reticular
dermis interface (fills papillary dermis)
IV. Into the reticular dermis
V. Into the subcutaneous fat
Back Extra: Largely replaced by Breslow depth

Q: Breslow’s depth: measures tumor depth in mm’s from the [...] layer or base of an ulcerated melanoma to the bottom of the tumor
A: granular

Q: Collagens 1 and 3 are [...]-regulated by corticosteroids and UV light and [...]-regulated by retinoids
A: down; up
Back Extra: Retinoids have anti-aging effects, while steroids cause atrophy of the skin and UV light leads to photoaging

Q: Ground substances in the dermis = Glycosaminoglycans (GAGs) and mucopolysaccharides
E.g. [...] maintains water within the dermis and is often used in many cosmetic fillers
A: hyaluronic acid
Back Extra: And upregulated by retinoids

Q: [...] glands are not associated with the hair follicle and contain muscarinic receptors
A: Eccrine
Back Extra: Unlike apocrine and sebaceous glands

Locations of Apocrine glands (“4 A’s”)
Axilla
Areola of the nipple
Anogenital region
Auditory canal where they contribute to cerumen (earwax) formation
Back Extra: Also make up the Moll’s glands of the eyelids (not to be confused with Meibomian glands, which are of sebaceous origin)

Q: What gland makes smelly things and why do they smell?
[...]
A: Apocrine glands secrete odorless stuff, which is digested by bacteria that create odorous byproducts body odor
Back Extra: - Begin to function at puberty and are mainly stimulated by sympathetic adrenergic stimuli

Q: [...] glands are located everywhere except the [...] and [...] and are under hormonal influence rather than neurologic influence as is seen with other glands
A: Sebaceous; palms; soles
Back Extra: Not found on hairless skin
Forms sebum, squalene, and free fatty acids

Q: How fast does hair on the scalp grow
[...]
A: 1 cm/month
Back Extra: Can be useful when seeing a nit, you know how long lice has been present

3 zones of hair anatomy from superficial to deep
Infundibulum - From surface down to sebaceous gland insertion
Location of inflammation in lichen planopilaris
Isthmus - From sebaceous insertion down to the hair bulge (location of
arrector pili insertion)
Location of inflammation in discoid lupus
Inferior segment - Everything inferior to  hair bulge
Back Extra: Apocrine gland insertion is Above sebaceous gland insertion
Discoid = Deeper than LPP

Q: Hair from outside to inside
Glassy membrane (outermost)
Outer root sheath
Inner root sheath – itself has 3 layers...
1. [...] layer (outermost)
2. [...] layer
3. [...]
A: Henle’s; Huxley’s; Cuticle (innermost)
Back Extra: “Henle hugs Huxley”

Q: What layer of skin gives hair its shine when using conditioner?
[...]
A: Cuticle
Back Extra: Part of the hair shaft

Q: Chemotherapy exclusively affects hairs in the [...] phase
A: anagen
Back Extra: Aka anagen effluvium
Normally 85-90% of scalp hairs are in anagen phase; hairs lasts 2-6
years on average in this phase

Q: Pathogeneis of telogen effluvium
[...]
A: Early cessation of anagen phase in stress (pregnancy) so that >20% of hairs are in telogen phase
Back Extra: Normally only 10-15% are in this phase

Q: Fingernails take [...] to regrow its entire length
Toenails take [...] to regrow
A: 4-6 months; 12-18 months
Back Extra: Fingernails grow 2-3 mm per month on average
Toenails grow approximately 1 mm per month
Can be used to estimate time from trauma (Beau's lines)

Q: Lunula - white crescent-shaped region under the [...] nail plate - that represents the [proximal/distal] nail matrix
A: proximal; distal
Back Extra: Fingernails grow 2-3 mm per month on average
Toenails grow approximately 1 mm per month
Can be used to estimate time from trauma (Beau's lines)

Q: [...] - represents thickened stratum corneum with nuclei present
[...] - thickened stratum corneum without nuclei present
A: Parakeratosis; Hyperkeratosis

Q: If spiny desmosomes between cells are visible on H&E, a process known as [...] is occurring, which is often due to intercellular edema
A: spongiosis

The proximal matrix of the nail forms the top or dorsal nail plate, while the distal matrix forms the bottom or ventral nail plate

Q: [Term] - Refers to a thickened epidermal layer
[Regular/Irregular] - All rete pegs descent to the same level or
[Regular/Irregular]- Rete pegs descend to different levels within the papillary dermis
A: Acanthosis; Regular; Irregular

Q: [Male/Female] skin is generally thicker than [male/female] skin in all locations
A: Male; female

Name the 4* layers of the epidermis
Stratum corneum
Stratum granulosum
Stratum spinosum
Stratum basale
Back Extra: *Stratum lucidum found in palms and soles only and appears as thin clear strip on H&E

Merkel Cells
Located just above the basal cell layer of the epidermis and in the
bulge region of hair follicles
Believed to function as slow-adapting touch receptors
Back Extra: Give rise to Merkel cell carcinomas, which are rare, aggressive skin cancers on the head and neck of elderly Caucasian patients

Q: [...] consist of 3-5% of the cells in the stratum spinosum, are derived from bone marrow, function as antigen-presenting cells
A: Langerhans Cells
Back Extra: Contain Birbeck granules, which appear on electron
microscopy as tennis racket-shaped organelles

Q: The [papillary or reticular dermis] contains the sub-papillary plexus, which contains arterioles, capillaries, venules, lymphatics, and nerves, and also contains [...] which sense touch and pressure
A: papillary dermis (superficial); Meissner corpuscles
Back Extra: Appears wavy in 2D on biopsy specimens, as papillary dermis interdigitates with downward projections of epidermis (“rete ridges”)
Remember that these nerve fibers are affected by inflammation in leprosy patients, leading to hypoesthesia

Q: In addition to the fibroblasts, elastic fibers, ground substance, and adnexa in the dermal layer, remember that [...] comprises 70% of the dry weight of skin, important in wound healing
A: collagen
Back Extra: Important point: It is important for patients to obtain adequate protein intake for wound healing, since protein is found within collagen

Q: As wounds heal, type [...] collagen is replaced by the stronger type [...] collagen
A: III; I
Back Extra: Type III collagen (fetal collagen) is more pliable and found in granulation tissue

Q: Elastic fibers – help skin elasticity, [...] in number with aging and are also defective in Marfan’s syndrome due to [...] mutations
A: decrease; fibrillin-1

Q: The adipose layer functions as an energy store, an insulator that protects underlying muscles and bones, and as an endocrine organ where [...] converts androstenedione to estrone
A: aromatase
Back Extra: Thus possibly providing a link between obesity and breast cancer

Q: [...] glands release sweat to help regulate body temperature by cooling the skin when the sweat evaporates, and are located nearly everywhere on the skin except for the lips, the external auditory canal, the glans penis, and the labia minora and clitori
A: Eccrine
Back Extra: Can make up to 1.8 L of sweat in one hour!

Q: Eccrine glands have [...] acetylcholine receptors which bind acetylcholine released from [sympathetic/parasympathetic] nerves
A: muscarinic; sympathetic
Back Extra: Which explains why we sweat when we’re nervous
Also explains why botulinum toxin injections, which block acetylcholine
release, are effective for hyperhidrosis patients.

Q: The Moll’s glands of the eyelids are from [...] origin, which is not to be confused with Meibomian glands, which are of [...] origin
A: apocrine; sebaceous

Q: [...] glands begin to function at puberty and are mainly stimulated by sympathetic adrenergic stimuli
A: Apocrine
Back Extra: As opposed to muscarinic receptors which are associated with eccrine glands or sebaceous glands, which are under hormonal influence

Q: The deepest portion of the hair is the [...], which produces the hair shaft
A: bulb
Back Extra: In anagen hairs, this bulb is found in the deep dermis and superficial subQ
In surgery, we want to undermine beneath their hair bulbs to prevent hair loss!

Q: Hair growth is divided into 3 phases:
[...] phase (active growth) : Normally 85-90% of scalp hairs are in this phase; lasts 2-6
years on average
[...] phase (involution phase):  < 1% of scalp hairs are in this phase at any given time due to
its short length of approximately 2 weeks.
[...] phase (resting phase): Lasts 3-5 months and thus 10-15% of hairs are in this phase in a normal patient
A: Anagen; Catagen; Telogen
Back Extra: Anagen hairs fractured by chemotherapy in anagen effluvium
Telogen effluvium = early cessation of anagen phase so that >20% of hairs are in telogen phase

Nail anatomy
Nail plate – hard part of the nail
Lateral nail fold – the skin abutting the lateral sides of the nail plate
Proxima nail fold – skin proximal to cuticle
Cuticle (eponychium) - cornified epithelium overlying the lunula
Lunula - white crescent-shaped region under the proximal nail plate - that represents the distal nail matrix
Nail matrix - underneath the cuticle and proximal nail fold

Q: [...] refers to thickening of the granular layer and is classically seen in lichen planus
A: Hypergranulosis

Q: [...] refers to multiple finger-like warty projections of the epidermis
A: Papillomatosis

Q: [...] refers to a thinning of a layer of skin
A: Atrophy
Back Extra: Such as epidermal atrophy seen in lichen sclerosis