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Connective Tissue Types
- Connective tissue proper (Loose, Dense-Regular or Irregular)
- Connective tissue w/ special property (Adipose, Elastic)
- Supporting connective tissue (Cartilage, Bone
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Connective Tissue Function
- • Mechanical support
- • Material that connects and binds cells into
- tissues
- • Binds tissues to each other
- • Mostly extracellular matrix, few cells
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Specific CT functions
- Capsule surrounding organs
- Internal support for organs/tissues
- Tendons, ligaments, areolar (loose) tissue
- Bone and cartilage are specialized forms of connective tissue
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Connective Tissue Composition
- • Cells (fibroblasts, immune, vascular)
- • Fibers (collagen, elastic, reticular)
- • Ground substance (glycosaminoglycans, proteoglycans, glycoproteins)
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CT Building Blocks
- •Ground substance
- Structual glycoproteins
- Basement membrane
- Connective Tissue Fibers (Collagen, Elastic, Reticular, Connective Tissue Cells (Fibroblasts, Adipocytes, Macrophages, Plasma cells, Mast cells)
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Ground Substances
Location:
Composition:
Mechanical properties:
- • Extracellular semi-fluid material in connective tissue.
- • Composed of polysaccharides (glycosaminoglycans [GAGs]). (Hyaluronic acid is the dominant polysaccharide. Others polysaccharides are linked to proteins to form proteoglycans.)
- • GAGs are hydrophilic and attract water (extracellular fluid).
- • Mechanical properties of ground substance and extracellular
- fluid are reinforced by connective tissue fibers.
- (empty spot in a microscopic view)
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ECM
ground substance with variety of fibers and structural glycoproteins that mediate adhesion of cells to the matrix
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Structural Glycoproteins
Location:
Example:
Functions
- • Proteins bound to polysaccharides
- • Examples: fibronectin, laminin, fibrillin, tenascin
- • Functions include cell adhesion and role in extracellular matrix organization
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Basement Membrane
Composition:
Interface:
Function:
- Composed of extracellular matrix proteins. (Collagen type IV, fibronectin, laminin, entactin, and GAGs)
- • Interfaces connective tissue/parenchymal cells.
- • Provides support and adhesion of parenchymal cells.
- • Acts as a barrier and permeability filter
- • Maintains differentiated functions
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Connective Tissue Fiber
- • Collagen
- • Elastic
- • Reticular
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Collagen
- • Type 1: bone, skin, tendon, etc
- • Type 2: cartilage
- • Type 3: skin, vessels, reticular fibers
- • Type 4: basement membranes
- (1,2,3 form fibers, 4 is mesh)
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Elastic
- elastin stains black
- surrounded by loose connective tissue
- Elastic connective tissue found in vertebral ligaments, and many others like large arteries.
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Reticular
- Fibrils made of collagen
- Abundant in smooth muscle, nerves, spleen ,lymph nodes, bone marrow
- Form network around cells of liver, kidney, and, endocrine organs
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Sclerodermia
autoimmune where excessive collagen deposited throughout body. Possibly fatal
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Elastic Skin
- genetic defect where collagen is not assembled correctly/ Conversion of
- procollagen to mature collagen is blocked
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CT fibers (visual description)
- 1) Collagen
- fibers (pink, wide)
- Composed of protein, collagen (most abundant protein in the body)
- Very long, hold structures
- 2) Elastic fibers
- (dark, skinny)
- Composed of protein elastin
- Not very strong
- Stretch well, and come back to original length
- 3) Reticular
- fibers (inter-lacing web)
- Reticulin
- Not very strong
- Support the tissue in the organ
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CT supporting cells
3 types:
functions:
- 1. Fibroblasts
- Function – synthesis/maintenance of extracellular material
- 2. Adipocytes
- Function – storage and metabolism of fat
- 3. Mast cells, macrophages*, lymphocytes, plasma cells
- Function – defense and immune reactions (*Note: macrophages have previously been called histiocytes)
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Fibroblasts
- • Most common cell
- • Produce and secrete fibers and ground substance
- • Flattened nuclei, sparse cytoplasm
- • More cytoplasm and altered nucleus = activated (wound healing)
- • Source of mesenchymal stem cells?
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Macrophages
- • Stem cell in bone marrow, circulating form in blood is monocyte
- • Migrate into tissues; widespread
- • Irregular membrane surface; nucleus may be oval and is usually eccentric
- • Phagocytosis of cell debris and microbes (it engulf ferritin and Carbon)
- • RBC turnover in spleen
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Mast Cells
- • Cytoplasm full of basophilic granules containing histamine, proteases, chemotactic factors, heparin
- • Originate from bone marrow stem cell
- • Dilates and increases permeability of small vessels
- • Constricts bronchioles
- • Inflammation
- • Delayed hypersensitivity (allergic reaction)
- • Widespread, most common in dermis, respiratory and digestive tracts and along capillaries
- (egg shaped appearance)
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Following injury, mast cells release Histaminecauses
a classic triple response:
- (1) vasodilation (erythema)
- (2) increased vascular permeability (edema)
- (3) an axon reflex (substance P) (further vasodilation)
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Plamsa cells
- • Common in intestinal lamina propria and glands secreting immunoglubulins such as lacrimal glands, salivary glands, and mammary gland
- • Oval cell with basophilic cytoplasm, pale centrosome, clockface nucleus
- • Loaded with rough ER
- • Differentiate from B - lymphocytes
- • Life span 10-20 days
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osteogenesis imperfecta
- brittle bone disease
- genetic disorder characterized by bones that break easily
- defective collagen structure
- example of why is CT important in dentistry
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Over growth of gingival dense fibrous connective tissue is related to:
related to poor oral hygiene, often in combination with other factors such ingestion of certain drugs
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