Histology of the Skin

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Histology of the Skin

• Kelli A. Hutchens, MD, FCAP
• Director of Dermatopathology
• Assistant Professor
• Loyola University Medical Center
• Assistant Director of Mechanisms of Human Disease
• Loyola Stritch School of Medicine

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Objectives

• Identify the epidermis, dermis, and subcutis of
  the skin
• Name and label the layers five layers of the of
  the epidermis
• Compare and contrast the anatomic and histologic
  differences between thick and thin skin
• Identify (when possible) / or know the location
  of the following cells
• Keratinocyte
• Melanoycte
• Merkel cell
• Langerhan cell
• Describe the general function and location of the
  following components of the dermal epidermal
  junction and intercellular space.
• Hemidesmosomes
• Basement membrane
• Basal layer keratinocytes
• Anchoring fibrils
• Desmosomes
• Name and identify the two regions of the dermis
• Identify and classify the following
• Eccrine gland
• Sebaceous gland
• Apocrine gland

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Overview of the Skin
Epidermis
Dermis
Subcutis
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Epidermis

• Most superficial layer of the skin
• Composed of multiple layers of keratin containing
  epithelial cells keratinocytes with
  Melanocytes, merkel cells, and Langerhans
  dispersed throughout
• Major functions
• Maintenance of fluid and electrolyte balance
• Protection from ultraviolet light
• Sensory and immune function

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Epidermis Layers

• Cancel Lab Get Some Beer

Stratum Corneum
Stratum Lucidum
Stratum Granulosum
Stratum Spinosum
Stratum Basale
Thin Skin
Thick Skin
Rete ridge
Stratum Lucindum
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Differences between thin thick skin

• Thin Skin

• Thick Skin

• Palms of hands and soles of feet acral skin
• 5 layers thick stratum corneum with increased
  granular layer
• More sensory receptors
• Lack sebaceous glands and increased eccrine
  glands
• No hair follicles

• Entire body except thick skin areas.
• Less than 5 layers of stratum corneum with no
  stratum lucidum
• Hair follicles present except lips, labia minora,
  and glans penis

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Epidermis

• Desquamatization
• Layers of epidermis represent vertical maturation
  from undifferentiated basal cells to fully
  differentiated cornified cells
• From basal cell to cornified cell takes about 25
  days
• Shorter maturation periods seen in inflammatory
  conditions such as psoriasis
• Keratin production also changes as the cell
  matures and disruption in the mechanism can
  effect the integrity of the keratinocytes such as
  in Haily-Haily and Dariers Disease.

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Epidermis
Cell to Cell Adherence
Zona occludens tight junctions prevent diffusion
across cells
Zona adherens Ca dependent cadherins that
connect to actin
Macula adherens Made of desmosomes
Gap junctions communication for electric /
metabolic function
Hemidesmosomes connect cells to BM
Basement Membrane
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Epidermis
Desmosome Intercellular Bridges
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Epidermis Melanocytes
Melanocytes clearish cells in basal layer with
dark nuclei ratio of 1 10.
Langerhanss Cells dendritic cells of the
epidermis. Sit in the mid-spinous. Not visible
by light microscopy.
Merkel Cells located in the stratum basale.
Also not visible by light microscopy. They are
receptor cells that establish synaptic contacts
with sensory nerves and contain granules of
neurotransmitters.
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Dermal-Epidermal Junction

• Connects the epidermis and dermis
• It is composed of proteins which provide a firm
  connection
• Hemidesmosome connects basal keratinocytes to
  basement membrane
• Basement membrane
• Lamina lucida collagen types XVII, XIII,
  laminin 5 6
• Lamina densa collagen type VII
• Anchoring fibrils attach the basement membrane to
  the dermis hooking on to collagen VII and
  collagen I.

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Basement Membrane
Hemidesmosomes
Basal layer keratinocytes of epidermis
Laminins 5 6
Lamina Lucida
Basement Membrane
Lamina Densa
Collagen Type VII
Collagen type XVII, XIII
Anchoring Fibrils
Dermis
Collagen type I
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Dermis

• Everything below the dermal epidermal junction /
  basement membrane
• Connective tissue layer with contains blood
  vessels, nerves, sensory receptors, adnexal
  structures

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Dermis

• Two layers
• Papillary dermis includes the dermal papilla
  which project into the epidermis
• The increases contact area preventing epidermal
  detachment
• Also results in an undulating pattern which vary
  by anatomic location and individual resulting in
  grooves in the epidermis dermatoglyphics
  (fingerprints)
• Capillaries, free nerve endings and encapsulated
  sensory receptors called Meissners corpuscles.
• Reticular dermis area between the papillary
  dermis and subcutis

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Papillary Dermis
Capillaries
Papillary Dermis
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Dermis

• The dermis is composed of two major types of
  fibers
• Type I Collagen
• Elastic fibers three types based on microfiber
  and elastin content

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Sebaceous Glands
Reticular Dermis
Erector Pili muscle
Hair Follicle
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Dermal Appendages
Sebaceous Glands
Hair Follicle
Eccrine Glands
Pilar Muscle
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Sebaceous Glands

• Usually associated with hair follicles
• Simple branched acinar glands
• Several acini that empty into single duct
• Holocrine secretion
• Empty sebum into hair follicle

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Hair Follicle
cross section (above the level of the bulb)
Connective Tissue Sheath
Outer Root Sheath
Inner Root Sheath
Hair Cuticle
Hair Cortex
Bulb
Hair Medulla
Papilla
Matrix
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Eccrine Glands

• Merocrine sweat glands
• Release to adjust body temperature
• Three cell types
• Dark cells pyramid shaped with secretory
  granules line lumen of tubule
• Clear cells located toward basement membrane
• Myoepithelial cells spindle shaped contractile
  cells

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Apocrine Glands

• Apocrine glands
• Similar to eccrine glands but larger lumens and
  ducts empty onto superficial regions of hair
  follicle
• Release product by shedding of part of cytoplasm
  apocrine snouting
• Influenced by hormones (sexual scent glands)
• Only found on axilla, areola, perianal and
  genital area

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Subcutis

• Subcutis
• Area deep to the dermis
• Includes the hypodermis
• Loose connective tissue containing adipose
  tissue, nerves, sensory receptors, arteries and
  veins
• Provides a flexible attachment to the underlying
  muscle and fascia

Pacinian Corpuscle
Adipocytes
Hair bulb in the subcutis of the scalp.