Individual cells Extracellular matrix

Transcription

1 Connective Tissue

2 Connective Tissue Elements Individual cells Extracellular matrix»fibers» Collagen» Elastic» Reticular»Ground Substance» PG (proteoglycans)» GAG (glycosaminoglycan)» GP (glycoprotein)

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4 Connective tissue cells classification Resident cell populations (permanent cells) fibroblasts - fibrocytes (condro-, osteo-) myofibroblasts adipocytes (uni-, multilocular) macrophages mast cells reticular cells Wandering cell populations (transient cells) plasma cell granulocytes B and T lymphocytes monocytes

5 Fibroblasts The most frequent cell type Morphology: elongated cell branched cell processes cytoplasm - basophilic nucleus oval-shaped, euchromatic Function: Produces elements of the extracellular matrix: procollagen proelastin fibrillin GAG, PG and GP

6 Fibrocytes Less active than fibroblasts Morphology: smaller, elongated/spindle shaped, a few short unbranched processes cytoplasm scarce, acidophilic nucleus - elongated and heterochromatic

7 Fibroblasts vs Fibrocytes

8 Unilocular (white) adipocytes Morphology round (when isolated) or polygonal in groups cytoplasm a thin rim at the periphery one large lipid droplet (inclusion) nucleus - flattened, heterochromatic ( signet ring ) Location: hypodermis, around kidney, in bone cavities (adults)

9 White adipocytes, HE, 400x BV A A A A Ross HM, Histology: A Text and Atlas, 6 th ed. Adipose tissue: A white adipocyte, BV blood vessel

10 White adipocytes, Sudan III Ob. 40x Ob. 20x

11 Multilocular (brown) adipocytes Morphology: Smaller cells Cytoplasm: Many smaller lipid droplets in the foamy appearance Nucleus: round, central Mostly found before birth and in neonates Role in thermogenesis

12 Brown adipocytes Methylene blue stain, ob. 20x Azan stain, ob. 40x

13 Reticular cells Morphology star-shaped cells long and thin processes, forming networks nucleus - round, central, pale. Role: produce reticular fibers!!!!! Should not be confused with the reticulocyte, the immature erythrocyte.

14 Lymph node Reticular tissue, Giemsa, ob. 20x Reticular cells

15 Macrophages Origin: peripheral blood monocytes, a family of cells with various shapes, locations and names: Histiocytes: connective tissue Kupffer cells: liver Langerhans cells: intraepidermal Alveolar macrophages/dust Cells : lung Osteoclasts: bone Microglia: central nervous system Role: phagocytosis and inflammatory response

16 Macrophages Macrophages part of the mononuclear phagocyte system (MPS/ RES*). Morphology: irregular shapes cytoplasm: can have various heterogeneous inclusions ingested material nucleus: round, oval or kidney-shaped, eccentric *RES - reticuloendothelial system

17 Macrophages, HE Ob. 40x Ob. 100x

18 Mast cells, toluidine blue stain, ob. 60x Mast cells Distribution: in most of the loose connective tissue areas, along blood vessels Morphology: oval shaped cytoplasm has numerous basophilic, metachromatic granules nucleus: round, small and centrally located Function: immediate hypersensitivity reaction (allergies)

19 Mast cells, toluidine blue stain, ob. 100x

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21 Plasma cells Plasma cells Distribution: lymphoid organs and connective tissues associated with the mucosa of the respiratory and digestive tract Origin: terminal differentiation of B lymphocytes Morphology: ovoid/ pear shaped cells cytoplasm: basophilic, with a perinuclear pale area; +/- acidophilic Russel bodies (secretory granules) nucleus: eccentric, with hetero- and euchromatin in a characteristic pattern: cart wheel or clockface

22 Plasma cells TB stain, ob. 100x HE, ob. 40x

23 Mesenchymal cells undifferentiated cell capable of differentiation in all connective cell types found in mature connective tissue Morphology: star shaped cytoplasm: irregular branched extensions acidophilic nucleus: oval with dispersed chromatin and nucleolus

24 Mesenchymal cells

25 Fibers of the Connective Tissue Collagen Elastin Reticular Fibers

26 Fibers of the Connective Tissue

27 Collagen fibers the most abundant type of connective tissue fiber many types that differ in their origin, chemical composition, functions, distribution thicker and unbranched, wavy appearance acidophilic

28 Elastic fibers Isolated, thin fibers or arranged in networks Distribution: lung, urinary bladder, skin, aorta and elastic cartilage Special staining : orcein

29 Reticular fibers Provide a supporting framework for the cellular constituents of various tissues and organs. Thin fibers, forming networks Distribution : liver, spleen, lymph nodes, haematopoietic organs Special staining: silver impregnation

30 Spleen Reticular fibers, silver staining & HE, ob. 40x

31 Reticular fibers, silver staining

32 Ground Substance Highly hydrated semi-solid gel Participates to binding cells to fibers Colorless and transparent in usual stains Composed primarily of GAGs and PG