2) Cutaneous Histology

Front 1

KERATINOCYTES

Back 1

PRINCIPAL CELL OF THE EPIDERMIS
FILAMENTS MADE OF KERATIN
ATTACHED BY DESMOSOMES (SPINES)

Front 2

MELANOCYTES

Back 2

- Primary pigment-producing cells in the skin
- Dark-staining nucleus with clear cytoplasm
- Wedged between keratinocytes in the basal layer
- Variable number depending on region and ultraviolet light exposure
- Produce and transport melanin to other cells (especially keratinocytes)
- Stain with S-100 protein

Front 3

LANGERHANS CELLS

Back 3

- Primary antigen-presenting cell of the skin
- Clear-staining cells in the suprabasilar epidermis
- Markedly folded nucleus, no desmosomes
- Contain a unique cytoplasmic organelle, called the Birbeck granule
- Birbeck granule is a 3-dimensional, sphere-shaped entity with protruding rods that resemble a tennis racket on electron microscopy
- Stain with immunohistochemical stains for CD1a and S-100 protein, and are HLA-DR positive
- Dendritic cells

Front 4

T-CELLS

Back 4

- Migrate to the thymus and differentiate
- Small, round nucleus, deeply basophilic, with a narrow rim of cytoplasm
- Role in normal cutaneous immunosurveillance
- Aid in delayed-type hypersensitivity reactions (e.g. poison ivy)
- Accept antigen presented to them by Langerhans cells, clonally expand, and provide memory
- Major cell type in cell-mediated immunity

Front 5

B-CELLS

Back 5

- Matures in the bone marrow (“B” is for bursa of Fabricius, in birds)
- Similar histologic appearance to T-cells
- Differentiate into plasma cells, which is promoted by helper T-cells
- Plasma cells then produce and secrete immunoglobulin
- Major cell type in humoral immunity

Front 6

EOSINOPHILS

Back 6

- Bi-lobed nucleus
- Granules stain strongly eosinophilic
- Slightly larger than neutrophils
- Granules contain hydrolytic enzymes
- Phagocytize immune complexes and mast cell granules
- Reactive cells that play a major role in anaphylactic reactions (Type I)
- Present in hypersensitivity reactions (such as to drugs or contact allergens) and parasitic infections

Front 7

NEUTROPHILS

Back 7

- Polymorphonuclear cell
- Inflammatory and phagocytic cells
- Lobulated and segmented nucleus
- Granules contain enzymes
- These enzymes kill microorganisms, degrade dead bacteria, break down collagen and elastin, increase vascular permeability, lyse bacterial cell walls

Front 8

MAST CELLS

Back 8

- Oval to spindle-shaped cells
- Concentrated around blood vessels
- Contain numerous cytoplasmic granules (do not stain with hematoxylin-eosin)
- Granules contain serine proteases (tryptase and chymase)
- Stain with methylene blue, Giemsa, and Leder stains
- Degranulate after cross-linking with IgE on the cell surface
- Triggering mast cell degranulation can lead to anaphylaxis

Front 9

HISTIOCYTES AND MACROPHAGES

Back 9

- Histiocytes and macrophages are synonymous
- Bone marrow-derived precursors circulate in blood (monocytes)
- Differentiate into macrophages with proper stimulation
- Make up the “mononuclear phagocytic system”
- Aggregates of activated macrophages are referred to as granulomas

Front 10

apocrine

Back 10

Apocrine glands are found mostly in odor-producing areas, such as the axillary and anogenital regions, and the breasts, eyelids, and ear canals. Function, other than to cause body odor, is still unknown.

Front 11

Eccrine glands

Back 11

sweat glands engineered primarily for temperature regulation

Front 12

Sebaceous glands

Back 12

holocrine, unilobular and multilobular, and secrete sebum

Front 13

HAIR FOLLICLE CELLS

Back 13

- The hair follicle is a complicated structure composed of 3 portions: lower, isthmus, and infundibulum
- Lower portion of the hair follicle is composed of 5 portions, each with unique cell types:
--- Dermal hair papilla
--- Hair matrix
--- The hair shaft (medulla, cortex and cuticle)
--- Inner root sheath (inner root sheath cuticle, Huxley layer, Henle layer)
--- Outer root sheath
- Associated with the arrector pili muscle (smooth muscle) and sebaceous glands

Front 14

ENDOTHELIAL CELLS

Back 14

- Endothelial cells line the lumens of small arteries and veins
- Contain thick cytoplasmic filaments and pinocytotic vesicles
- Have a unique organelle, the Weibel-Palade body, which is an electron-dense, rod-shaped structure
- Stain with immunohistochemical stains for factor VIII antigen and CD-31
- Play roles in antigen presentation and adhesion molecule function

Front 15

NERVE CELLS

Back 15

- Composed of axons and Schwann cells (peripheral nerve sheath cells)
- Myelinated and unmyelinated nerves are present
- Meissner and Vater-Pacini end organs can be seen with routine histologic staining
- Finer nerves require special staining
- Skin has sensory nerves and autonomic nerves
- Innervate blood vessels, eccrine and apocrine glands, and hair follicles

Front 16

Papillary dermis

Back 16

immediately beneath the epidermis
- primarily type III collagen
- more cellular than the reticular dermis
- separated from the deeper dermis by horizontal, superficial blood vessel plexus

Front 17

Reticular dermis

Back 17

- the bulk of the dermis; deep to the papillary dermis
- large bundles of type I collagen fibrils and elastic fibers
- blood vessels pass vertically through the reticular dermis to connect the subcutaneous horizontal plexus with the horizontal subpapillary plexus

Front 18

Cholinergic fibers

Back 18

innervate eccrine sweat glands

Front 19

Adrenergic fibers

Back 19

innervate blood vessels (vasoconstriction), arrector pili muscles, and apocrine glands.

Front 20

Back 20

Fibroblasts
Control CT matrix
Near collagen and elastic fibers, help to produce them