cutaneous histology and the basement membrane zone

Question 1

Epidermis

Answer 1

Stratified squamous epithelium

4 layers of epidermis

Extra layer on acral skin

Mainly composed of keratinocytes

typically .5-.1 mm thick

Question 2

Layers of the epidermis

Answer 2

Stratum corneum

Stratum lucidum (acral skin only

Stratum granulosum

Stratum spinosum

Stratum basale

Question 3

Stratum corneum

Answer 3

aka cornified layer or keratin layer

Comprised of anucleate corneocytes

Primary barrier of epidermis

Thicker at acral sites

No stratum corneum at mucosal site

Question 4

Stratum lucidum

Answer 4

Aka clear layer

Only seen on acral skin

Thin eosinophilic or clear band beneath stratum corneum

3-5 cell layers thick

May function to reduce friction

Question 5

Stratum granulosum

Answer 5

cells are flat
Filled with basophilic granules

Keratohyaline granules (Fillaggrin, involucrin, loricrin)

Odland bodies (lamellar grules, descharge ceramides and other fats into intercellular space)

Barrier, cell cohesion, hydrolytic enzymes

Question 6

Stratum spinosum

Answer 6

aka prickle or spinous layer, polygonal cells

Abundant eosinophilic cytoplasm

Oval vesicular nuclei, conspicuous nucleoli

5-10 cell layer thick

Progressively flatter toward surface, contains differentiating keratinocytes, contected by intercellular bridges

(Desmosomes, adherens junctions, tight junctions)

Question 7

Stratum basale

Answer 7

cuboidal or columnar cells
Single layer
perpindicular to dermis
more basophilic cytoplasm, dark large nuclei
Periapical cap of melanin

Connected by desmosomes

Connected to basement membrane by hemidesmosomes

Most mitotic activity

Question 8

Melanocytes

Answer 8

found in basal layer

Neural crest origin

No desmosomal attachements

Pale cytoplasm

1: 10 melanocyte:keratinocytes
1: 4 on cheek

Transfer pigment to keratinocytes

Question 9

Langerhans cells

Answer 9

Bone marrow-derived, dendritic antigen presenting cells

normally in epidermis in concentration simillar to melanocytes

Question 10

Merkel cells

Answer 10

found in basal layer of the epidermis, bulge of hair follicle,
oral mucosa

Not easily identified on H and E

Closely associated with sensory nerves, function as touch receptors

Question 11

Dermis

Answer 11

composed of papillary dermis and reticular dermis

Separated by superficial vascular plexus

Question 12

Papillary dermis

Answer 12

lies directly beneath the epidermis
Connects to epidermis via dermal papillae

Papillae contain capillaries

Fine vertically orientated collagen

Question 13

Meissner’s corpuscle

Answer 13

At dermal papilla of palms, soles, and lips

thick, lamellated capsule surrounding core of cells and nerve fibers

Sensory light touch receprots

Question 14

Reticular dermis

Answer 14

coarse thicker collagen fibers parallel to surface epithelium

Also contains sweat glands, lymph vessels, hair, blood vessels

Question 15

Fibroblasts

Answer 15

Thin, spindle shaped cells with elongate ovoid nuclei interspersed between collagen bundles

Synthesize collagen and elastin fibers and ground substance

Question 16

Elastic fibers

Answer 16

Not easily visible without special stains

horizontally oriented thicker fibers in reticular dermis

Vertically oriented and more fine fibrils in papillary dermis

Question 17

Pacinian corpuscle

Answer 17

At dermal subcutneous interface
Palms, soles, digits, genitalia, ligaments, joints

Lamellated in cross section
Encapsulated sensory receptors for deep pressure and vibration

Question 18

Hair follicle

Answer 18

Infundibulum: Follicular orfice to entrance of sebaceous duct, normal keratinization

Isthmus: Sebaceous duct to insertion of erector pilli, trichilemmal keratinization (no granular layer), no inner root sheath

Lower portion: dermal papillae, matrix

Question 19

inside the hair follicle

Answer 19

central cortex surrounded by cuticle

Inner root sheath surrounds the cuticle (supports hair fiber, degenerates at level of sebaceous gland)

Outer root segments: continuous with epidermis

Question 20

sebaceous glands

Answer 20

Lobular lined with thin outer layer of basophilic germinative cells

Central bubbly clear cells filled with lipid

Nuclei scalloped

Duct lined with stratified squamous epithelium

Holocrine secretion

Eyelid (meibomian and wolf), vermillion oral mucosa (Fordyce), Tyson (penis), Montgomery (nipple)

Question 21

Apocrine gland

Answer 21

coiled secretory portion

located in lower reticular dermis subcutaneous fat

Straight duct opens into hair follicle above level of sebaceous gland

Rarely opens onto epidermal surface

found in axillae, anogentital area, external ear canal, eyelid (Moll’s), areola

Inactive until puberty

Question 22

Apocrine gland histology

Answer 22

single layer of columnar secretory cells with round nuclei

Surrounded by layer of myoepithelial cells

lumen may be larger than in eccrine tissue

Decapitation secretion: apical portion of glandular cells are pinched off into the lumen

Question 23

Eccrine gland

Answer 23

present everywhere except vermillion of lips, glans, labia minora, nail beds, inner prepuce

Greatest on palms, soles, axillae, forehead
Spiraled intraepidermal portion (acrosyringium)
Intradermal duct (straight and coiled portion)
Coiled secretory portion

Question 24

Intraepidermal spiraled portion of the eccrine gland

Answer 24

AKa acrosyringium or epidermal sweat duct unit

Empties directly onto epidermal surface

Question 25

intradermal straight portion of the eccrine gland

Answer 25

two layers of small cuboidal cells

Question 26

colloid secretory portion of the eccrine gland

Answer 26

coiled secretory portion:
one distinct layer of secretory cells, layer of myoepithelial cells

lies in lower reticular dermis

Surrounded by thick basement membrane

Question 27

Lymphatics

Answer 27

thin walled vessels lined by attenuated epithelium

Have multiple valves

Usually collapsed and difficult to detect in dermis

Seen in obstruction

Question 28

Subcutaneous fat

Answer 28

arranged in lobules, separated by vascular fibrous septa

Fat is dissolved by routine processing
large single globule of lipid that displaces nucleus and cytoplasm

Question 29

Scalp

Answer 29

many large terminal hairs, hair bulbs extends into subQ fat

Question 30

Trunk

Answer 30

dermis is very thick

Broad parallel fascicles of collagen in reticular dermis

Question 31

Nose

Answer 31

Conspicuous sebaceous glands

Often drain directly onto the skin surface

Question 32

Basement membrane Zone

Answer 32

area between epidermis and dermis

Dermo-epidermal adhesion
Regulation (cell differentiation, motility, transmission of extracellular signals)

Question 33

Layers of the BMZ

Answer 33

Hemidesmosomes
Lamina lucida
Lamina densa
Sublamina densa

Question 34

hemidesmosomes are compromised of

Answer 34

BP 230 (Bullous pemphoid Ag 1):
Belongs to the plakin family of proteins, located in cytoplasm of keratinocyte, organizes the cytoskeleton architecture

BP180 (Bullous pemphoid Ag2): AKA type 17 collagen
Transmembrane protein (connects basal keratincocytes thru BP230 to the cytoskeleton and dermal collagen 7

Question 35

Lamina lucida

Answer 35

immediately underlying hemidesmosomes is a thin structure known as the lamina lucida

may actually be an artifact of tissue prep and dehydration

one of the major component is BP180

Question 36

Lamina densa

Answer 36

Type 4 collagen and laminins

The key BMZ laminin is laminin 332

(binds to hemidesmosomal protrein integrin on the basal keratinocytes)

Also binds to type 7 collagen in the dermis

Provides adhesion between these 2 structures

Question 37

Sublamina densa

Answer 37

Type VII collagen

Large protein composed of 3 identical alpha chains
Form anchoring fibrils
Necessary to maintain epidermal dermal cohesion

Binds to both type 1 and 4 collagen

Question 38

Direct immunofluorescence (DIF)

Answer 38

helps detect molecules (Igs and C3) within biopsy

The skin

Fluorescein-conjugeteed Ab against human Ig or complement are used to detect deposits of immunoreactant in the patient skin

Question 39

Indirect immunifluorescense

Answer 39

detects circulating Ab against BMS in pt serum

PT serum applied to foreight substrate (normal human skin)

The circulating antibodies from the sera bind

Ab - Ag complex detected

Question 40

Bullous pemphigoid (BP)

Answer 40

Most common autoimmune bullous dermatosis

Seen in elderly

Tense blisters with serous/hemorrhagic content- very stable, roof is the entire dermis

Antibodies to BP Ag (Bp230) and BP Ag 2 (BP 180)

Cause subepidermal blisters

DIF shows linear deposits of IgG and C3 along the BMZ

IIF shows linear stain on the epidermal side of salt split skin

The BP 180 and BP230 ELISA show positive results correlating with the disease activity

BP better than PV, less sever cases can be treated with steroids