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40 Cards in this Set
- Front
- Back
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Functions
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o Structural support
o Storage of metabolites o Defense and protection • Mediates immune, inflammatory, and allergic responses o Repair other tissues and organs • Fibrous scar |
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Connective Tissue ECM I
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o Collagen
• Principal structural component • Flexible • High tensile strength • Produced by fibroblasts • Collagen structure (cont'd) |
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Connective Tissue ECM II
Fibrils |
o Polymerized tropocollagen molecules
• Trimer of collagen molecules • Triple helix • Polymerized laterally and head-to-tail • Forms collagen fibrils o Can’t be visualized w/ electron microscope • Cartilage o Collagen or reticular fibers • Can be visualized w/ electron microscope • Can be assembled into collagen bundles • Formed only by type I |
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Collagen I
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• Principal type
• Dermis • Tendons • Ligaments • Fascia • Bone • Connective tissues proper • Forms fibrils → fibers → bundles |
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Collagen II
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• Found in cartilage
• Forms fibrils • Glassy appearance |
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Collagen III
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• Forms banded fibrils
• Supporting framework for cells of o Loose connective tissue o Walls of blood vessels o Lymphoid tissues o Bone marrow o Smooth muscle o Nerves o Lung • Use silver to stain |
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Collagen IV
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• Does not form banded fibrils
• Forms sheets • Basal lamina |
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Elastic Fibers
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• Allow tissues to respond to stretch and distension
• “Dynamic response” • Thinner than collagen fibers Elastin |
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Elastin
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o Contains a hydrophobic domain
• Coils in aqueous environment o Cross-linked by covalent bonds o Responsible for elasticity of elastic tissue • Passively return to normal tissue formation |
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Fibrillin
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o Glycoprotein
o Forms thin microfibrils • Provide substrate for elastic fiber assembly |
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GAGs
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• Most abundant components of ground substance
• Strong negative charge o Repel each other o GAGs bind water o Form a highly hydrated gel • Main component of ground substance • Helps resist compression and deformation o Several types found in connective tissue • Hyaluronic acid • Always present in ECM • Doesn’t contain sulfate • Does not form proteoglycans • Sulfated GAGs • Chondroitin sulfate • Dermatan sulfate • Keratan sulfate • Heparin sulfate • All form proteoglycans |
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Proteoglycans
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• GAGs covalently attached to core protein
• Brush-like structure • Repel one another • Form giant aggregates with hyaluronic acid • Non-covalent bond • Hydrophilic • Responsible for gel state of ECM • Resist compression w/o losing flexibility |
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Multiadhesive Glycoproteins
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• Cross-links between collagen, ECM and cells
Fibronectin and Laminin |
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Fibronectin
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o Interact w/ different ECM molecules including
• Types I, II and II collagen • GAGs • Fibrin • Integrin |
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Laminin
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o Present in basement membrane
o Binding sites for • Collagen IV • Integrin |
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Resident Cells
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• Undergo mitosis w/in connective tissue
• Fibroblast o Principal resident cell o Responsible for producing components of ECM • Collagen • Elastic fibers o Reside in close proximity to collagen |
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Resident Cell Types
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Fibroblasts -- Active and Inactive
Myofibroblasts Mesenchymal Cells Adipocytes -- Unilocular and Multilocular Macrophages Mast Cells |
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Active Fibroblasts
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• Abundant RER and Golgi
• Euchromatic • Commonly found in loose connective tissue |
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Inactive Fibroblasts
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• “fibrocytes”
• Found in dense connective tissue • Less RER and Golgi • Heterochromatic |
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Myofibroblasts
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• Have RER and Golgi
• Contain bundles of actin filaments and dense bodies similar to those of smooth muscle cells o NOT MUSCLE! • Close wound sites |
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Mesenchymal Cells
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• Present in embryonic tissue
• Euchromatic nuclei • Pluripotent o Fibroblasts o Chondroblasts o Osteoblasts o adipocytes |
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Unilocular Adipocytes
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• Most common
• Found singularly in loose connective tissue • Aggregates • White adipose tissue • Single, large liquid droplet • Large, spherical cell • Flattened nucleus • Found in periphery of cell |
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Multilocular
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• Rare in adult humans
• Found within brown adipose tissue • Multiple fat droplets • Large number of mitochondria • Centrally-placed nucleus • Not flattened • Heat generator |
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Macrophages
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o Derived from monocytes
o Kidney-shaped nucleus o Digestive vacuole o Functions • Phagocytosis of bacteria and senescent cells • Tissue cleanup • Present antigens to other immune system cells • Produce cytokines to activate immune cells o Widely distributed • Histiocytes • Connective tissue • Alveolar macrophage • Lung • Kupffer cells • Liver • Osteoclasts • Bone • Langerhans cells • Skin • Dendritic cells • Lymphoid organs |
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Mast Cells
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o Allergic response
o Most common in connective4 tissue of skin and mucous membranes • Absent in CNS o Structure • Among largest cells in connective tissue • Basophilic granules in cytoplasm • Granules contain o Histamine o Heparin sulfate o Chemotactic mediators • Surface contains receptors for immunoglobulin E (IgE) o Functions • Mediate inflammatory and hypersensitivity reacions • Allergy • Anaphylaxis |
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Mast Cell Activation
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• First exposure to antigen
• Plasma cells produce IgE o Bound to mast cell surface • Antigen binds to IgE • Degranulation occurs o Histamine causes vasodilation and increased vascular permeability • ZO junctions get leaky o Histamine and other agents cause bronchoconstriction and increased mucus production in bronchial mucosa o Chemotactic mediators attract WBC, eosinophils, and neutrophils • Transient Cells |
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Transient Cells
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• Involved in immune response
• Do not divide w/in connective tissue • Plasma cells o Derived from b-lymphocytes o Most numerous in areas of inflammation o Specialized for protein excretion • Ig • Prominent RER and Golgi o Heterochromatic AND euchromatic nucleus • Clock face pattern |
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Lymphocytes
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• Round, heterochromatic nucleus
• Production of antibodies and regulation of immune response |
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Monocytes
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• Phagocytic
• Precursor for tissue marcophages • Kidney-shaped nucleus |
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Neutrophils
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• Phagocytic to bacteria
• Elongated, segmented, multi-lobed nucleus |
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Eosinophils
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• React to parasitic infections
• Bilobed nucleus |
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Basophils
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• Rare in blood and connective tissue
• Allergic response • Bilobed nucleus • Basophilic granules in cytoplasm |
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Mesenchyme
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o Found in embryo
o Composed of mesenchymal cells • Form 3D network o Few collagen/reticular fibers o Abundant ground substance |
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Muscous connective tissue
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o Only in umbilical cord
o Large amounts of hyaluronic acid o Few collagen/reticular fibers o “Wharton’s Jelly |
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Loose connective tissue
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o Highly cellular
o Thin and sparse bundles of collagen o Abundant ground substance o Active fibroblasts o Large number of transient cells o Beneath epithelia that covers internal surfaces of body • Surrounds blood • Lymphatic vessels • Nerves o “Filter tissue” |
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Dense Irregular Connective Tissue
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o Oriented in various directions
• Resists stress from all directions o Main cell type is fibroblast • Inactive o Significant strength o Found in dermis • Capsules of internal organs • Spleen • Testes |
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Dense Regular Connective Tissue
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o Densely packed collagen bundles
o Oriented in same direction o Very little space between cells o Inactive fibroblasts • Compressed, heterochromatic nuclei o Tendons o Ligaments o Aponeuroses |
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White Adipose Tissue
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o Unilocular adipocytes
o Has receptors for growth hormone • Insulin • Noradrenalin o Poor heat conductor o Helps to keep organs in place o Shock absorption |
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Brown Adipose Tissue
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o Not present in adult humans
o Multilocular adipocytes o Oxidize fatty acids up to 20x the rate of white adipose tissue • Increase body temperature 3x |
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Reticular Connective Tissue
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• Loose connective tissue
• Found in stroma of organs o Lymphoid system • Supported by a network of reticular fibers o Form thin, branching, interconnected threads |
