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
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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
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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
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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
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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
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Macrophage in center. Stained with trypan blue (taken up by cytoplasm)
Collagen fibers stained pink-orange
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Lamina properia of stomach
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Several plasma cells: accentric nuclei, negative Golgi image, punstate herterochromatin
In lamina properia of stomach
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Dermis of the scalp (thin skin)
Papillary layer of dermis right beneath epidermis (outer layer): loosely arranged
Deeper dermis: dense irregular connective tissue
Hair follicle (arrow)
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Tendon (chromotrope): dense regular CT
Compact and homogenous, nuclei of fibroblasts(cytes?) are small dots
Muscle has white spaces (CT for neurovascular structures)
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Tendon (dense regular CT)
Arrow is pointing at fibrocyte nuclei
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Adipose tissue and surrounding capillaries (H&E)
Single fat droplet pushes nucleus flat and cytoplasm to a thin rim
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Adipose tissue with osmic acid (black), useful for showing lipid droplets
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Brown fat of a human newborn (H&E)
From posterior pharynx
Large, multiocular cells crowded together, many blood vessels
Purple nucleus usually in center of cell
Cytoplasm don’t take stain, filled with lipids
Identify
Eosinophil
Red or copper cytoplasmic granules
Bi-lobed nucleus
