SKIN HISTOLOGY:UP CLOSE AND PERSONAL

A Laboratory Guide

SLIDES TO CONQUER

• 56a: Thin skin, H & E

• 56b: Thick skin, Masson, H & E

• 56e: Scalp

• 56f: Pacinian corpuscle

• 56g: Meissner corpuscle

KNOW THE HIERARCHY OF HISTOLOGIC ORGANIZATION

CELLS

TISSUEEpithelial tissue (= EPIDERMIS)

Connective tissue (=DERMIS/HYPODERMIS)Nervous tissue Muscle tissue Blood tissue

ORGANSkin

+ ECM

(Keratinocytes, etc.)

SKIN (Organ)

EPITHELIAL TISSUE(=Epidermis, glands, endothelium of blood vessels)

CONNECTIVE TISSUE(=Dermis, hypodermis)

NERVOUS TISSUE

(=Free nerve endings,

encapsulated receptors,

Merkel cell)

BLOOD TISSUE

MUSCLE TISSUE

(=Smooth muscle cells in blood vessel wall, platysma, Arrector pili)

• EPITHELIAL TISSUE

– CELLS CLOSELY PACKED TOGETHER W/ INTERCELLULAR JUNCTIONS

– SCANTY EXTRACELLULAR MATRIX

– AVASCULAR

– GLANDS

• CONNECTIVE TISSUE

– CELLS FEW AND FAR BETWEEN

– ABUNDANT EXTRACELLULAR MATRIX

• FIBERS

• GROUND SUBSTANCE

– VASCULAR

*INTIMATE RELATIONSHIP - ATTACHED TOGETHER BY A BASEMENT MEMBRANE

ORIENT THE SLIDE PROPERLY!

X

RECOGNIZE THE TISSUE COMPONENTS THAT MAKE UP THE SKIN

• EPIDERMIS– Stratified squamous

keratinized epithelium– Superficial– Thinner

• DERMIS– Dense irregular

connective tissue– Thicker

• EPIDERMAL-DERMAL INTERFACE– Wavy– Basement membrane not

visible w/ H & E

• HYPODERMIS– Loose connective tissue– May have abundant

adipose cells

IDENTIFY THE LAYERS

• EPIDERMIS– More deeply staining– Highly cellular (multiple

layers)

• DERMIS– Paler– Mostly Fibers (irregular

bundles) and some ground substance (poorly stained w/ H & E)

ARTEFACT!

• ISLANDS OF DERMAL PAPILLA WITHIN THE EPIDERMIS (due to tangential sectioning)

THIN SKIN VS THICK SKINSlide 56a Slide 56b

LAYERS OF THE EPIDERMIS (thick skin)

• S. corneum

• S. granulosum

• S. spinosum

• S. basale

• S. corneum– Anucleate

– flattened layers

– “basketweave”

• S. granulosum– Diamond shaped

– Darkly staining cytoplasmic granules

• S. spinosum– Polygonal

– Rarely see “spines”

• S. basale– Single layer, cuboidal cells

– Crowded nuclei

– Occ. Mitotic figures

MELANOCYTE (thin fair skin)

MELANOCYTE (Pigmented skin)

LANGERHANS CELL

LAYERS OF THE DERMIS

• Papillary dermis– Contains dermal papilla

– Thin collagen fibers

– More cells (fibroblasts)

– Smaller blood vessels (capillaries)

• Reticular dermis– Thick collagen fibers

– Bigger blood vessels (arterioles/venules)

– *Elastic network NOT distinguished from collagen with H&E

VELLUS vs TERMINAL(most of body) (scalp)• Superficial

• Smaller

• Lightly pigmented

• Deeper

• Bigger

• Darkly pigmented

Slide 56e: Scalp

• HAIR FOLLICLES– Terminal (up to

hypodermis)

– Various planes of section

– Mostly anagen

– Oblique

– Continuous with the surface epidermis

ANAGEN HAIR FOLLICLE

• Hair shaft

• Hair bulb

• Hair matrix

• Hair papilla

LAYERS OF THE HAIR FOLLICLE: Longitudinal section

• Hair shaft

• Inner root sheath

• Outer root sheath

• Fibrous sheath

LAYERS OF THE HAIR FOLLICLE: Cross Section

PILOSEBACEOUS UNIT(Longitudinal section)

• Arrector pili muscle

– Attaches to lower third of HF

• Sebaceous gland

– Duct enters into upper third of HF

PILOSEBACEOUS UNIT: Cross section

• Hair Follicle

• Sebaceous gland lobules

SEBACEOUS GLAND

• CENTRAL: Vacuolated lipid-filled cells w/ scalloped nuclei

• eventually disintegrating together with sebum into duct

• PERIPHERAL: row of flattened germinative cells w/ large nuclei & basophilic cytoplasm

ECCRINE GLAND: LPOCoiled portion in deep dermis

ECCRINE GLAND: Coiled portion in deep dermis (HPO)• SECRETORY PORTION

– Pale

– More cross sectional profiles, some tangential and bizarre-shaped (=tadpole)

• DUCTAL PORTION– Dark

– Fewer, more regularly rounded profiles

ECCRINE GLAND: Coiled basal portion

• Secretory portion

– Single layer

– Pale pyramidal cells

• Ductal portion

– 2 layers

– Eosinophilic cuboidal cells

– Hyaline lumenal lining

INTRAEPIDERMAL ECCRINE DUCT (=Acrosyringium)

• Corkscrew appearance

• Ductal cells are also keratinized

MEISSNER PACINIANCORPUSCLE (56g) CORPUSCLE (56f)

MEISSNER vs. PACINIAN CORPUSCLE CORPUSCLE

BLOOD VESSELS in Reticular dermis

• Arterioles

• Venules

Capillaries in Dermal papillaMEISSNER’S CORPUSCLE

LYMPHATIC VESSEL