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Alikhan & Hocker dermatology > 1.1 Structure and Function of the Skin > Flashcards

1.1 Structure and Function of the Skin Flashcards

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1
Q

What are the 6 main functions of the skin?

A

interfaces with environment,

collects sensory data,

protects against infection and chemical penetration,

temperature regulation,

water retention,

excretion of drugs/waste

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2
Q

Name the layers that comprise the skin

A
  1. Epidermis
  2. Dermis
  3. Subcutis
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3
Q

What is the structure of the epidermis?

A

Squamous epithelium comprised of keratinocytes

connected by desmosomes, adherens junctions, tight junctions, and gap junctions

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4
Q

Name the 4 types of intercellular junction of keratinocytes

A
  1. Desmosomes
  2. Adherens junctions
  3. Tight junctions
  4. Gap junctions
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5
Q

Primary keratinocyte intercellular junction?

A

Desmosomes

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6
Q

function of desmosomes?

A

Provide structure and integrity to the epidermis by anchoring/attaching to keratins

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7
Q

Desmosomes consist of … cytoplasmic and … transmembrane proteins

A

3

vs

2

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8
Q

Cytoplasmic proteins of desmosomes?

A

desmoplakin

plakophilin

plakoglobin

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9
Q

Transmembrane proteins of desmosomes?

A

desmocollin 1/2/3

&

desmoglein 1/3

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10
Q

Desmocollin, desmoglein, and other cadherins are … dependent?

A

Calcium dependent

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11
Q

Function of adherens junction?

A

Also mediate tight intercellular binding

Anchor/attach to actin filaments

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12
Q

Adherens junctions consist of … cytoplasmic & … transmembrane proteins

A

3

vs

2

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13
Q

Cytoplasmic proteins of adherens junction

A

α-catenin

β-catenin

plakoglobin

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14
Q

Transmembrane proteins of adherens junction

A

Classic cadherins

E & P

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15
Q

Function of tight junction?

A

form tight seal against water loss in granular layer

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16
Q

Tight junctions are composed of…?

A

claudins and occludins

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17
Q

Function of gap junction?

A

facilitate intercellular communication

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18
Q

Structure of gap junctions?

A

composed of connexons

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19
Q

What are the connexons?

A

tubular channels composed of 6 connexins

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20
Q

Epidermal cells originate in the … and … as they ascend to the surface – four to five layers/strata

A

cuboidal basal layer

vs

flatten out

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21
Q

Which stratum of the epidermis is seen only on palmoplantar surface?

A

Stratum lucidum

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22
Q

Layers of the epidermis (deep to superficial)

CO.LU.GRA.SP. MNEMONIC

A

stratum basale

s. spinosum
s. granulosum
s. lucidum (only on palmoplantar surfaces),
s. corneum

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23
Q

Stratum basale is composed of … from which the upper layers of the epidermis are derived

A

mitotically active cuboidal cells

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24
Q

Stratum basale is attached to epidermis by …

Keratins … & … are produced here

A

hemidesmosomes

5 & 14

(ba5a14)

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25
Q

Cellular proliferation stimulated by various factors, including…

A

Trauma

UV

( ^ornithine decarboxylase expression is a/w proliferativa states)

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26
Q

Ornithine decarboxylase is inhibited by ..? (3)

A

corticosteroids

retinoids

vitamin D3

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27
Q

… of cells in the basal layer are stem cells, which give rise to other stem cells and transient amplifying cells that can still replicate, but only for a few cycles, until they reach a … where they move upwards and eventually desquamate

A

10%

terminal differentiation phase

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28
Q

Transit time from basal layer to stratum corneum = ….

transit through the stratum corneum/desquamation = …

(total = …. from basal layer to desquamation)

A

14 days

14 days

28 days

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29
Q

The adherens junction and desmosomes

A
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30
Q

“spiny” appearance of intercellular desmosomal connections on microscopy

A

stratum spinosum

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31
Q

Stratum spinosum functions

A

Contain multiple types of intercellular junctions

Keratins 1 and 10 are made here (sp1n0sum)

Terminal keratinocyte differentiation 2° to ↑intracellular calcium in suprabasal epidermis

Odland bodies

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32
Q

Terminal keratinocyte differentiation 2° to ↑intracellular calcium takes place in …

A

suprabasal epidermis

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33
Q

Odland bodies are …. produced by … bodies in spinous layer

They primarily contain …

A

lamellar granules

Golgi bodies

ceramide

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34
Q

Which is the most important lipid involved in epidermal barrier function; the most prevalent/important lipid in the stratum spinosum?

A

Ceramides

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35
Q

Odland bodies are specialized …. that exert most of their action in the stratum ….,

by discharging ceramides and other lipids to the extracellular space of the junction between the stratum granulosum and stratum corneum

A

lysosomes

corneum

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36
Q

ceramides help form the …

and eventually replace the cell membrane

A

Cornified cell envelope

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37
Q

… and … are 2° to ↓lamellar granules

A

Flegel’s disease

and

Harlequin ichthyosis

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38
Q

X-linked ichthyosis occurs due to … in lamellar granules

A

absent steroid sulfatase

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39
Q

Other name for Odland bodies?

A

Keratinosomes

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40
Q

flattened cells with prominent basophilic keratohyaline granules?

A

stratum granulosum

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41
Q

Stratum granulosum contains …?

A

profilaggrin

(converted to filaggrin at junction of stratum granulosum and stratum corneum)

loricrin

keratin intermediate filaments

involucrin

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42
Q

In stratum granulosum cells begin to … but …

A

lose nuclei

keep overall structure

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43
Q

Cornified cell envelope (CE) production primarily takes place in the …

A

granular layer

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44
Q

Formation of the CE, 1st step (spinous layer)

A

Terminal differentiation of keratinocytes is triggered by an ^ in the intracellular [Ca] of the suprabasal epidermis

. CE assembly is initiated in the upper spinous layer via formation of a cross-linked scaffold composed of envoplakin, periplakin, and involucrin along the inner surface of the cell membrane

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45
Q

Formation of CE, 2nd step (granular layer)

A

This is followed by (or perhaps coincident with) extrusion of lamellar granules into the extracellular space

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46
Q

Formation of CE, 3rd step

A

Complexes of keratin and filaggrin also become cross-linked to the CE.

Proteases play important roles in processing of CE proteins and the proteolysis of corneodesmosomes that is required for desquamation.

A mature and terminally differentiated cornified cell thus consists of keratin filaments covalently attached to the CE, which is composed of protein and lipid envelope components and is imbedded in the extracellular lipid lamellae

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47
Q

Reinforcement of cross-linking in CE formation occurs by…?

A

Envoplakin

Periplakin

Involucrin

Loricrin

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48
Q

Function of loricrin?

A

1 component of cornified envelope

first appears in granular layer

mutated in Vohwinkel syndrome variant lacking deafness

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49
Q

Cross-linking occurs via … ➔ γ-glutamyl lysine isopeptide bonds

A

transglutaminase I

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50
Q

… is mutated in lamellar 1chthyos1s

vs

… is antigenic target in dermatitis h3rp3tiformis

A

TG 1

vs

TG3

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51
Q

The outer surface of the cornified envelope is composed of…?

A

lipids (primarily ceramides)

=

cornified cell envelope

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52
Q

What is the main function of the cornified cell envelope?

A

provides strong waterimpermeable outer barrier

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53
Q

outermost layer

serves as a mechanical barrier btw epidermis & environment

A

Stratum corneum

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54
Q

Stratum corneum is composed primarily of

protein-rich corneocytes that contain …

keratin filaments attached to ..

embedded in a lipid matrix …

A

NO NUCLEI

CE

mortar, cornified lipid envelope

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55
Q

Epidermal cells of importance

A

Keratinocytes

Melanocytes

Langerhans cells(LCs)

Merkel cells

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56
Q

primary cells of the epidermis and produce proteins (eg, keratin filaments) and lipids important for barrier function

A

keratinocytes

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57
Q

Define keratins

A

intermediate filaments that comprise the primary cytoskeleton of the epidermis

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58
Q

Basic structure of keratins

A

an α-helical rod domain (consisting of heptad amino acid repeats) divided into four segments (1A, 1B, 2A, and 2B) that are interrupted by three nonhelical segments (“linkers”)

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59
Q

Type I keratins features:

A

low-MW

acidic

K9-28

K31-40 (hair keratins)

chromosome 17

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60
Q

Type II keratins features:

A

high-MW

basic

K1-8

K81-86 (hair keratins)

chromosome 12

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61
Q

Functional unit of keratinocytes, consists of …?

A

heterodimers of type I and type II filaments that form tetramers and ultimately filaments

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62
Q

Keratinocytes are anchored to plasma membrane by …?

A

Desmosomes

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63
Q

Keratinocytes produce …?

A

IL-1, IL-6, IL-8, IL-10, IL-12, and TNF-α, among others

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64
Q

Keratinocytes respond to …?

A

IL-2, IL-4, IL-13, IL-22, and TNF-α, among others

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65
Q

Define melanocytes

A

Neural crest-derived melanin-producing dendritic cells found in the stratum basale

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66
Q

What is the melanocyte/keratinocyte ratio when viewed in 2 dimensional plane?

A

1:10

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67
Q

… activation is needed for melanocyte development/migration

… occurs as a result of … loss ➔ impaired melanocyte migration and proliferation

… mutations are a/w mucosal and acral melanoma

A

c-kit

piebaldism, c-kit

c-kit

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68
Q

Each melanocyte interfaces with …(number) keratinocytes

when analyzed threedimensionally (epidermal melanin unit)

A

36

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69
Q

Melanin

  • site production
  • precursor
  • key enzyme
A

melanosomes (lysosome type organelles)

tyrosine

tyrosinase (copper-dependent enzyme)

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70
Q

Melanin production reaction pathway

A

Tyrosine ➔ (tyrosinase-dependent step) DOPA ➔ (tyrosinase-dependent step) DOPAquinone ➔ pheomelanin (yellow/red; made by round melanosomes) or eumelanin (black/ brown; made by elliptical melanosomes)

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71
Q

Melanosomes are transported along …

and transferred to keratinocytes through … of dendrite tips

A

dendritic processes

phagocytosis

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72
Q

Melanocyte density in dark vs light skinned individuals is …?

A

IDENTICAL

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73
Q

Racial variation in pigmentation is due to …?

A

Size, stability and distribution of melanocytes

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74
Q

melanosomes in darker skinned individuals are …

vs

in lighter skin individuals

A

larger, darker (↑melanin), more stable, and are transferred individually

vs

smaller, lighter, less stable, and clustered melanosomes

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75
Q

Melanin production is stimulated by … and … activity on … on melanocytes

also stimulated through various pathways induced by UV radiation

A

MSH & ACTH

MC1-R (melanocortin 1 receptor)

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76
Q

MC1-R(melanocortin 1 receptor)

loss of function mutations leads to ?

A

↑pheomelanin:eumelanin ratio

(phenotype = red hair/fair skin, ↑risk of melanoma)

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77
Q

What is the main role of melanin?

A

absorbs UV ➔ protects against UV-induced mutations

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78
Q

UV exposure leads to … and … tanning

A

immediate (from oxidation of existing melanin)

and

delayed tanning (requires new melanin synthesis)

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79
Q

Defects in enzymes required to convert tyrosine to melanin lead to ?

A

Oculocutaneous albinism

OCA1 (Tyrosinase), OCA2 (P gene), OCA3 (TRP-1)

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80
Q

Defects in packaging of melanosome-specific proteins lead to ?

A

Hermansky-Pudlak syndrome

rare, hereditary disorder that consists of two characteristics: decreased pigmentation (albinism) with visual impairment, and blood platelet dysfunction with prolonged bleeding

(HPS1 > HPS3 > other gene mutations)

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81
Q

Defects in lysosome and melanosome trafficking to dendrites lead to ?

A

Griscelli syndrome

(MYO5A, RAB27A, and MLPH mutations)

and

Chédiak-Higashi syndrome (LYST mutations)

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82
Q

Griscelli vs Chediak-Hegashi vs Elejalde disease

DDx

A
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83
Q

Define Langerhans cells (LCs)

A

major antigen presenting cells (APC) of the skin

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84
Q

Key features of Langerhans cells?

A

Dendritic histiocytes with reniform (kidney shaped) nuclei

tennis racket-shaped Birbeck granules on EM

Interact with keratinocytes via E-cadherin

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85
Q

7 + immunostains for Langerhans cells

A

CD207

(langerin; most sensitive IHC stain; specific for Birbeck granules)

CD1a

S100

CD34

vimentin

actin

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86
Q

LCs originate from ?

A

CD34+ progenitor cells in bone marrow

like other monocytes/ macrophages

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87
Q

Found mainly in …, where it first encounters and processes antigens

&

subsequently migrates to the LNs to activate T-cells

A

stratum spinosum

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88
Q

LCs are … in skin after UV exposure, that leads to …

A

Downregulated

↓immune surveillance

89
Q

Define Merkel cells (MCs)

A

slow-adapting mechanoreceptors

found in fingertips, lips, oral cavity, and hair follicle ORS

90
Q

MCs are found in …

communicate with …

A

stratum basale

neurons

91
Q

MCs stain + for ?

A

CK20+

(in perinuclear dot pattern sensitive/ specific for MCs)

neurofilaments

S100

synaptophysin

chromogranin A

vasoactive intestinal peptide

neuron-specific enolase

calcitonin gene-related peptide

92
Q

Define Basement membrane zone (BMZ)

A

Semipermeable barrier btw epidermis & dermis

also serves to adhere basal keratinocytes to the underlying dermis

93
Q

Name the 4 main locations of interaction within BMZ

A

Basal keratinocyte/hemidesmosome

Lamina lucida

Lamina densa

Sublamina densa

94
Q

Basal keratinocyte/hemidesmosome interactions

A

intracellular keratin filaments (K5 and K14) attach to electron-dense hemidesmosomal plaques (plectin and BPAG1 [BP230]) on the basal plasma membrane

➔ hemidesmosomal plaque proteins bind to intracellular portions of the anchoring filaments (BPAG2 and α6β4 integrin)

95
Q

Interactions on lamina lucida

A

extracellular portion of anchoring filaments (BPAG2, α6β4 integrin, and laminin 332) extend from the hemidesmosome down to the lamina densa;

the thin filaments result in an electron-lucent region; is the weakest portion of BMZ ➔ is zone of separation in salt-split skin and also in suction blisters

96
Q

Interactions on lamina densa

A

anchoring filaments attach to type IV collagen (#1 component) and other proteins (laminin 332, laminin 331, and nidogen) in the lamina densa

➔ results in attachment between basal keratinocyte and lamina densa

97
Q

Interactions on sublamina densa

A

loops of type VII collagen (anchoring fibrils) arise from the underside of lamina densa, extend down into the dermis, hooking around dermal type I and III collagen f ibers, and then loop back up to reattach to lamina densa (or anchoring plaques in dermis)

➔ firmly anchors the lamina densa (and all aforementioned structures) to the papillary dermis

98
Q

BMZ also functions as a permeability barrier:

… proteoglycan (… charged) in … is a major contributor

A

heparan sulfate

negatively charged

lamina densa

99
Q

BMZ proteins

A
100
Q

Define dermis

A

Located below the epidermis

derived from mesoderm

divided into papillary dermis (superficial) & reticular dermis (deep)

101
Q

Cells of significance in dermis

A

Fibroblasts

Mononuclear phagocytes

Mast cells

Glomus cells

Dermal dendritic cells

102
Q

What is the main function of fibroblasts?

A

create extracellular matrix and are involved in wound healing

103
Q

Define glomus cells

A

specialized smooth muscle cells derived from Sucquet-Hoyer canals,

which allow for blood shunting from arterioles to venules (bypassing capillaries)

found mainly in the palms/soles

104
Q

Overproduction of glomus cells results in?

+ clinical presentation

A

Glomus tumor

(favors acral sites because of ↑glomus cell density)

painful bluish mass located usually under the nail bed

(subungual melanoma is not painful)

105
Q

Main function of dermal dendritic cells?

A

bone marrow-derived APC that resides within dermis; highly phagocytic

106
Q

Extracellular matrix (ECM) features

A

Provides structure and support to the dermis

essential for water retention and for signal transduction

Synthesized by dermal fibroblasts

107
Q

ECM is composed of ?

A

collagens

elastin

fibrillins

fibulins

integrins

laminins

glycoproteins

proteoglycans

108
Q

Collagens are … formed by amino acid chains where every third residue is …,

with a high likelihood of … in the X and Y positions, respectively

A

triple helices

glycine (Gly-X-Y)

proline & hydroxyproline/hydroxylysine

109
Q

ECM accounts for … of dry weight of the skin

A

1 component of the dermis

75%

110
Q

What is primary type of collagen present in ECM?

What other types exist in ECM?

A

Collagen I (85%)

type III

(10%; important and prevalent in blood vessels, fetal skin, GI tract, new scars, and keloids)

type V

111
Q

crosslinking of collagen is a … dependent process

(deficiency …)

catalyzed by …

A

Vitamin C dependent

scurvy

Lysyl hydroxylase and proline hydroxylase

112
Q

What is the weakest point of BMZ?

A

lamina lucida

zone of separation in salt-split skin & also in suction blisters

113
Q

Defects in collagen and/or collagen cross-linking result in?

A

most forms of Ehlers-Danlos syndrome

osteogenesis imperfecta

114
Q

Defect in COL1A1/2 causes?

A

EDS arthrochalasia type

osteogenesis imperfecta

115
Q

Defect in COL3A1

vs

COL5A1/2

vs

Lysyl hydroxylase/PLOD1 gene

A

EDS vascular type

vs

classical EDS

vs

EDS kyphoscoliosis type

116
Q

Role of matrix metalloproteinases?

A

degrade collagen

117
Q

Retinoids ➔ … collagen production

vs

Corticosteroids and UV ➔ … collagen production

A

increase

vs

reduce

118
Q

Role of elastic fibers?

A

provide resilience from stretching

&

modulate TGF-β and BMP signaling

119
Q

Elastic fibers account for … of dry skin weight

A

4%

120
Q

What is the synthesis of elastic fibers?

A

90% elastin (core)

&

10% fibrillin (surrounds elastin)

121
Q

elastin contains high levels of … and iso…

➔ these crosslink with fibrillin via …

A

desmosine

(iso)desmosine

lysyl oxidase

122
Q

What element is necessary for lysyl oxidase function that mediates cross linking of elastin with fibrillin?

A

Copper

123
Q

defects in elastic tissue

Fibrillin 1 vs 2 mutation?

A

Marfan syndrome

vs

congenital arachnodactyly

124
Q

Defect in fibulin 5 result in?

A

Cutis laxa or dermatochalasia

(decreased desmosine)

125
Q

LEMD3 mutation results in?

A

Buschke-Ollendorf syndrome

( ^ desmosine)

126
Q

ABCC6 mutation results in ?

A

Pseudoxanthoma elasticum

(fragmentation and calcification of elastic fibers)

tip: angioid streaks to the retina, as a result of breaks in a weakened Bruch’s membrane

127
Q

… fibers run horizontal/parallel in reticular dermis

and

… fibers run vertical/perpendicular to DEJ in papillary dermis

A

Elaunin

oxytalan

mnemonic: “stand (= vertical) up-high (= high in dermis) with OXYgen (= OXYtalan)”

128
Q

UV radiation ➔ damage of elastic fibers

T/F ?

A

True

129
Q

Fibers such as … , …/…/… sulfate

are set in a matrix of proteoglycans and glycosaminoglycans (GAGs)

that …

A

hyaluronic acid

chondroitin /dermatan /heparan sulfate

retain large quantities of water (up to 1000× their volume!)

130
Q

The before mentioned GAGs are broken down by …?

A

lysosomal hydrolases

131
Q

Importance of cutaneous vasculature

Name the 2 vascular plexuses

A

metabolic support of the skin

maintenance of body temperature

superficial (➔ vessels of the reticular dermis)

& deep (➔ follicles, glands)

132
Q

Which is the primary mediator of vasculogenesis?

A

VEGF

133
Q

^ VEGF is seen in which conditions?

A

most cancers, psoriasis, POEMS syndrome

and other diseases with increased vasculature

134
Q

Name some lymphatic vessel markers?

A

Prox1

Podoplanin (D2-40)

LYVE-1

VEGFR-3

135
Q

Nerves of the skin are responsible for …?

A

detecting touch/pressure, pain, itch, and other sensations

136
Q

Cutaneous sensory nerves are divided into … and …

A

free nerve endings

and

corpuscular nerve endings (round/globular collection of neural and other cells)

137
Q

Free nerve endings mediate … and … by …

End in the epidermis/superficial dermis

A

Itch and pain

A-δ (larger; myelinated)

and

C-polymodal nociceptor afferent fibers

(smaller; unmyelinated)

138
Q

corpuscular nerve endings are …

Name some of them

A

Specialized nerve receptors

  • Krause end bulbs
  • Meissner’s corpuscle
  • Pacinian corpuscle
  • Merkel nerve ending
  • Ruffini corpuscle
139
Q

Krause end bulbs are seen in ?

A

genitalia, perianal region, and vermillion lips

mnemonic “Krazy Krause ends on erotic areas”

140
Q

Features of Meissner’s corpuscle?

A

superficial (dermal papillae) mechanoreceptor of digits

fast adapting

suited for pressure/light touch

141
Q

Features of Pacinian corpuscle

A
  • deep (deep dermis/fat) mechanoreceptor of palmoplantar skin, nipples, and genital region
  • fast adapting
  • suited for vibration and deeper pressure
142
Q

Features of Merkel nerve endings?

A

superficial (basal epidermis) mechanoreceptor most concentrated in fingertips, lips, and external genitalia

slow adapting

suited for pressure/touch

143
Q

Features of Ruffini corpuscle?

A

deep (fat) mechanoreceptor most concentrated around fingernails

slow adapting

suited for sustained pressure

144
Q

Meissner’s corpuscle

vs

Pacinian corpuscle

A
  • superficial (dermal papillae) mechanoreceptor of digits
  • fast adapting
  • suited for pressure/light touch

vs

  • deep (deep dermis/fat) mechanoreceptor of palmoplantar skin, nipples, and genital region
  • fast adapting
  • suited for vibration and deeper pressure
145
Q

Merkel nerve endings

vs

Ruffini corpuscle

A
  • superficial (basal epidermis) mechanoreceptor most concentrated in fingertips, lips, and external genitalia
  • slow adapting
  • suited for pressure/touch

vs

  • deep (fat) mechanoreceptor most concentrated around fingernails
  • slow adapting
  • suited for sustained pressure
146
Q

vascular smooth muscle, apocrine glands, and arrector pili contraction are under … control

while eccrine glands are under … control

A

adrenergic

cholinergic

147
Q

Difference btw apocrine and eccrine(merocrine) glands

A

apocrine glands secrete substances indirectly

whereas eccrine glands secrete directly through a duct

148
Q

Eccrine glands are Eccrine glands secretory exocrine gland primarily responsible for ..?

They are found on all cutaneous surfaces except:

Their highest concentration is seen in:

A
  • thermoregulation
  • waste excretion
  • external auditory canal, lips, glans penis, clitoris, and labia minora
  • palms and soles
149
Q

Eccrine glands are controlled by …

innervated by postganglionic sympathetic fibers,

which synapse with … on the glands

A

hypothalamus

muscarinic Ach receptors

150
Q

… sweat secreted in secretory gland

➔ NaCl reabsorbed in duct

➔ … sweat is delivered to surface

A

Isotonic

hypotonic

151
Q

↑rate of sweating leads to ?

A

more isotonic solution

(less time to reabsorb in duct)

152
Q

What is the maximal rate of sweating?

A

~ 3 L/hr

153
Q

What are the components(deep to superficial) of eccrine glands?

A
  • secretory coil (deep dermis)
  • intradermal/ straight duct (eosinophilic cuticle seen on histology)
  • acrosyringium (intraepidermal portion; spiral duct that opens onto the skin surface)
154
Q

Eccrine(merocrine) glands stain + for?

A
  • S100
  • keratin
  • CEA
155
Q

Apocrine glands are secretory exocrine glands with … in humans

though in animals mediate … through pheromone release

Their activity begins around …

A

unclear function

sexual attraction

puberty

156
Q

Apocrine glands are located primarily in …

and empty into …?

A
  • anogenital skin, axillae, external ear canal, vermillion border, periumbilical region, eyelid margin, and breast
  • follicular infundibulum (above sebaceous duct)
157
Q

Secretory control of apocrine glands is unclear ➔ glands noninnervated, but do have …,

which are likely stimulated by …

A

β-adrenergic receptors

circulating catecholamines

158
Q

Secretory products of apocrine glands are released through … :

cholesterol and cholesterol esters, triglycerides, squalene, and fatty acids

A

decapitation secretion

159
Q

Define lipofuscin

for what condition is it responsible for?

A

pigmented mixture of lipids and proteins

responsible for yellow-brown color of chromhidrosis

160
Q

Initially … ➔ later modified by surface bacteria ➔ results in …

A

odorless secretions

body odor

161
Q

Name some ectopic or modified apocrine glands

A
  • mammary glands
  • ceruminous glands of the external auditory canal
  • Moll’s gland of the eyelids

These empty directly to the surface

162
Q

Sebaceous glands(SGs) are secretory exocrine glands found primarily on …

NOT on …

A

scalp, face, and upper anterior trunk (“seborrheic areas”)

palms & soles

163
Q

SGs

  • functions include … & …
  • consist of …
  • ass/w … and empty into
A
  • water retention and innate immune defense
  • sebocytes, which contain lipid vacuoles
  • hair follicles, inferior portion of the infundibulum
164
Q

major signal for sebaceous gland maturation?

A

Pubertal androgen production

(Transient maternal androgen stimulation present in infancy)

165
Q

Other endocrine factors stimulating maturation and sebum production

A

MSH, CRH, and substance P

166
Q

Secretory products released through …?

Composition of the products?

A

holocrine secretion (entire cell lyses to release contents)

Triglycerides (#1 component; ≈50%) > wax esters (#2) > squalene (#3)

Others: cholesterol esters, cholesterol, antimicrobial peptides, androgens, and cytokines

167
Q

Name some ectopic sebaceous glands

A
  • Meibomian glands on eyelid tarsal plate
  • Fordyce spots (vermillion lip/oral mucosa)
  • Montgomery tubercles (areolae/nipples)
  • Tysons glands (labia minora/prepuce)
  • Zeis glands (eyelid margin, close to Moll’s gland)
168
Q

Protein Components of the Epidermis (Including Nonepidermal Keratins)

A
169
Q

Loricrin & involucrin are both present in the … layer of the epidermis

In psoriasis:

  • loricrin is …
  • involucrin is …
A

Granular layer

  • decreased
  • increased
170
Q

In psoriasis and other hyperproliferative states:

  • keratin .. and .. are upregulated
  • keratin .. and .. are downregulated
A
  • 6 , 16 ^
  • 1 , 10
171
Q

Define hair

A

Epithelial-derived appendage important for

  • temperature regulation
  • protection of other structures (nasal mucosa, eyes, and ears)
  • social and sexual cues
  • tactile sensory input
172
Q

What are the 3 types of hair?

A
  • Lanugo
  • vellus
  • terminal
173
Q

Define lanugo

A
  • fine hairs shed late in gestation and during the first month of life
174
Q

Define vellus

A
  • fine hairs over face, trunk, and extremities early in life
175
Q

Define terminal hair

A
  • coarse, darker hairs of scalp, eyebrows, and eyelashes
  • postpubertal androgens induce switch to terminal hairs in other sites
176
Q

Hair density on scalp is estimated around …?

A

100.000

more in blonde and fewer in red-haired individuals

177
Q

Hair anatomy

A
178
Q

Define hair bulb

A

Lowermost portion of the hair follicle

179
Q

Define Hair matrix

A

Rapidly proliferating keratinocytes that terminally differentiate to produce the hair shaft

180
Q

Define Infundibulum

A
  • Region extending from the skin surface down to the point where the sebaceous gland opens into the hair follicle
  • ORS displays cornification similar to that of the interfollicular epidermis (i.e., contains keratohyaline granules)
181
Q

Define Isthmus

A
  • Region located between the opening of the sebaceous gland, down to the site of insertion of the arrector pili muscle
  • ORS displays trichilemmal keratinization (no inner root sheath and IRS is shed before this point)
182
Q

Define Lower hair follicle

A
  • Region located between hair bulb to proximal isthmus;
  • encapsulates dermal papilla
  • has inner and outer root sheaths
  • critical line of Auber is the widest area
183
Q

Define Arrector pili muscle

A

Inserts at the level of the bulge; pulls up hair (“goose bumps”)

184
Q

Define Bulge

A
  • Segment of the outer root sheath located at the level of arrector pili muscle insertion
  • major seat of epithelial stem cells of the hair follicle
185
Q

Define Secondary hair germ

A
  • Additional seat of epithelial and also of melanocyte stem cells
  • located between club hair and dermal papilla in telogen hair follicle
186
Q

Define Connective tissue sheath (CTS)

A
  • Special mesenchymal follicular sheath that is tightly attached to the hair follicle basement membrane and is continuous with the follicular dermal papilla
187
Q

Define Follicular dermal papilla (DP)

A
  • Onion-shaped, closely packed, specialized fibroblast population with inductive and morphogenic properties
  • hair cycle-dependent fibroblast trafficking occurs between CTS and DP
  • volume of DP determines size of hair bulb and, thus, hair shaft diameter
188
Q

Define Inner root sheath (IRS)

A
  • Packages and guides the hair shaft
  • cornifies normally
  • stains red secondary to citrulline
  • not present in telogen hairs
  • is present in lower hair follicle but not in the isthmus/infundibulum
189
Q

Define Outer root sheath (ORS)

A
  • Merges distally into the epidermis and proximally into the hair bulb
  • provides slippage plane, nutrition, regulatory molecules, and stem cells
190
Q

Define Critical line of Auber

A
  • Widest section of the hair bulb and where most mitotic activity essential for hair growth occurs
191
Q

Define Follicle pigmentary unit

A
  • Melanin-producing hair follicle melanocytes located up and around the upper one-third of the DP
  • transfer pheomelanosomes or eumelanosomes to differentiating hair follicle keratinocytes in the precortical matrix
  • goes largely into apoptosis during each catagen phase, regenerated from melanocyte stem cells in hair germ during anagen
192
Q

Name hair Follicular layers (outer to inner):

A
  • glassy membrane
  • outer root sheath
  • inner root sheath (Henle’s layer, Huxley’s layer, and cuticle)
  • hair shaft (cuticle, cortex [where most hair keratins located], and medulla)
193
Q

Function of cuticle?

A
  • Cuticle helps keeps hair intact
  • If damage ➔ split ends (trichoptilosis)
  • Cuticle from hair shaft and inner root sheath merge
194
Q

Define dermal papilla

A
  • mesenchymal structure (from embryonic mesoderm) containing vasculature
  • contributes to hair cycle regulation
195
Q

Hair Growth Cycle(HGC)

A
196
Q

Name the 3 main phases of hair growth cycle

A
  • Anagen
  • Catagen
  • Telogen
197
Q

Define exogen phase of HGC

A
  • phase of active shedding of club hair between telogen and anagen
  • Lose about 100 hairs/day
198
Q

Define anagen phase of HGC

A
  • Growth (~0.4 mm/day or ~1 cm/month on scalp); follicular melanocytes only active in anagen phase)
  • Duration: 2-6 years
  • % of scalp hairs: 85-90
199
Q

Define catagen phase of HGC

A
  • Regression (melanocytes in matrix apoptose; inner root sheath lost)
  • Duration: 2-3 weeks
  • % of scalp hairs: 1-2
200
Q

Define telogen phase of HGC

A
  • Phase activity: Resting
  • Duration: 3 months
  • % of scalp hairs: 10-15
201
Q

Define kenogen phase of HGC

A
  • subphase of telogen in which no shaft is present
202
Q

Color of hair is 2° to …?

A
  • hair melanocytes in anagen bulb/matrix
  • melanin unit = 1 melanocyte: 5 keratinocytes
  • melanocytes only produce pigment in anagen phase
  • Eumelanin (brown/black hair pigment) vs pheomelanin (red/blonde hair pigment)
203
Q

Hair follicle stem cells reside in …. and contribute to hair cycling, … , and wound healing

A

Bulge

tissue regeneration

204
Q

How can follicular melanocytes assist in diseases ass/w hypopigmentation (eg, vitiligo)?

A

can migrate to interfollicular areas to assist with repigmentation

205
Q

Both Hair follicle stem cells and interfollicular stem cells can produce …?

A

transient amplifying cells with restricted mitotic capacity

206
Q

What determines curliness of hair?

A
  • Disulfide bonding via cysteine residues
  • these bonds are broken when hair is straightened, but subsequently reform with time
207
Q

Define nail

A

Appendageal structure important for

  • protection and function of fingertips
  • proper function of the feet
  • ability to scratch
  • aesthetic appearance
208
Q

Growth rate of fingernails vs toenails?

A
  • Fingernails: 2 to 3 mm/month (~6 months to grow out)
  • Toenails: 1 mm/month (~12 months to grow out)
209
Q

Nail anatomy

A
210
Q

Define Proximal nail fold

A
  • Superficial layer continuous with skin, deep layer continuous with nail matrix
211
Q

Define Eponychium (cuticle)

A
  • Located between nail plate and nail matrix
  • acts as seal against the environment
212
Q

Define Nail matrix

A
  • At the proximal end of nail unit, generates the plate
  • Proximal matrix➔ superficial portion of nail plate
  • distal matrix ➔ ventral portion of plate
  • Melanocytes found in nail matrix
213
Q

Define Lunula (distal nail matrix)

A
  • Junction between matrix and bed
214
Q

Define Nail plate

A
  • Hard, functional unit of nail, composed primarily of keratins
  • strong attachment to nail bed
215
Q

Define Nail bed

A
  • Extends from lunula to onychodermal band
  • Provides support for nail plate
  • Very minimal contribution to nail plate synthesis
216
Q

Define Onychodermal band

A
  • Red/pink transverse band marking end of bed
217
Q

Define Hyponychium

A
  • Continuous with ventral edge of free nail plate and distal fingertip skin
218
Q

Define Lateral nail folds

A

Guide growth of nail plate

Alikhan & Hocker dermatology (16 decks)

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