Connective Tissue Flashcards
Development of connective tissue
Develops from embryonic mesenchyme, which is formed from mesoderm or neural crest
Mesenchymal cells: oval nucelus, prominent nucleoli, little cytoplasm, can fx as stem cells in adut tissue
Identify
Fibroblasts: active, abundant RER
Main fx: structural
Main products: fibers (collagen, reticuar, elastic), GAGs, glycoproteins
Plays a critical role in wound healing
Identify
Fibrocytes: inactive mesenchymal cell
Minimal cytoplasm, limited RER (doesn’t seem to be involved with protein synthesis)
Reticular Cells
Fibroblast-like cells that produce reticular fibers in hematopoietic, lymphoid and adipose tissue
Stellate-shaped, oval euchromatic nucleus, prominent nucleolus
Identify
Adipocytes: white, single lipid droplet that pushes cytoplasm and nucleus to periphery
Lipid lost during H&E staining
Main product: fat, heat
Main fx: storage, heat
Immigrant Connective Tissue Cells
Macrophages
Mast Cells
Plasma Cells
Other blood-derived cells (i.e. leukocytes)
Resident (Fixed) Connective Tissue Cells
Mesenchymal cells
Fibroblasts
Fibrocytes
Reticular Cells
Adipocytes
Identify
Macrophage: monocytes travel in blood, migrate into CT and become macrophages
Main fx: phagocytosis/defense
Fixed macrophage = histiocyte
Smaller than fibroblasts
Heterochromatic, kidney-shaped nucleus
Cytoplasm filled with vacuoles and granules
*Use tryphan blue to see*
Identify
Mast cells: largest of CT cells (20-30 microns in diameter)
Main fx: defense; Main product: histamine and heparin
Cytoplasm filled with membrane-bounded basophilic (purple) granules that contain heparin, histamine, chondroitin sulfate, and ECF-4
Involved in allergic rxn
Frequently found around blood vessels
Identify
Plasma cells: large egg-shaped cells, eccentric nucleus (not centered) that has a “clock face,” clear zone near nucleus contains Golgi and centriole
Differentiate from B lymphocytes
Main product: antibodies
Main fx: immunologic
Ground substance
Viscous mixture that binds cells to CT fibers
Contains: GAGs, proteoglycans, multiadhesive glycoproteins (i.e. laminin, fibronectin)
Fx: structural and physiological, hormones and growth factors have reservoirs in ground substance
Identify
Pink squiggles are collagen, white arrow heads points at fibroblast nucleus
Collagen fibers: >50nm diameter fibrils make 1 to 20 micron diameter fibers
Stains pink in H&E
Types of Collagen
I - fibril-forming, most widespread, fx is to resist tension
II - fibril-forming, cartilage, fx is to resist pressure
III - fibril-forming, reticular fibers, fx is to form flexible meshwork
IV - forms sheet-like networks, found in basal lamina
VII - anchoring, anchors BM to collagen fibers
XII - fibril-associated, binds type II
Collagen Diseases
Osteogenesis imperfecta: single nucleotide change in type I gene produces aortic rupture, fractures
Scurvy: caused by vitamin C deficiency, impaired wound healing
Ehlers-Danlos Type IV: Type III collagen is faulty, aortic and intestinal rupture
Identify
Reticular fibers stained with silver
<50 nm diameter fibrils make 0.5 to 2 micron diameter fibers
Stains pink with H&E, but not distingushable from other collagen fibers without silver stain
Identify
Elastic fibers stained in the dermis
Elastin and fibrillin make 0.1 to 10 micron diameter fibers
*Marfan’s syndrome - mutant fibrillin
Stains pink in H&E, but not distinguishable from other collagen fibers without Resourcin-fuchsin or Picro-Orecin stain
Loose (areolar) CT
More cellular than dense CT, lots of resident cells
Found in: lamina propria, mesentery, papillary layer of dermis
Fx: positioned between tissue and allows movement
Dense Irregular CT
In the reticular layer of the dermis
More fibers than cells, fibers are interwoven (fabric-like)
Also found in: organ capsules and periosteum
Dense Regular CT
Rope-like arrangerment of fiber bundles
Found in tendons, ligaments, and cornea
Image: tendon
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Adipose tissue
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White fat (top white)
Brown fat (bottom, purple)
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Loose connective tissue. Pink collagen fibers and many nuclei. Empty space filled by ground substance
Skeletal muscle (dark pink)
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Collagen fibers
Ground substance
Mast cell in center of picture
Identify
Macrophage in center. Stained with trypan blue (taken up by cytoplasm)
Collagen fibers stained pink-orange
