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2 Cell types of CT proper
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3 Fiber types of CT proper
- -Collagen
- -Elastic
- -Reticular fibers
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2 types of matrix of CT proper
- -Ground substance (PGs, GAGs)
- -Tissue fluid
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Functions of Fibrocytes
- -Quiescent cell, low activity for maintaining fibers and ground substance of ECM
- -Stimulated to become active (fibroblast) upon injury or tissue damage (for wound healing)
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Functions of Fibroblasts
- -Intesnse synthetic activity for collagen and ground substance molecules
- -Cytoplasm contains large amounts of ER and developed golgi apparatus
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4 types of Molecules found in ECM
- -Collagen
- -Elastin
- -Proteoglycans
- -Glycoproteins
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Describe collagen
- -Main fiber of ECM; resists tensile force to provide strength to tissue
- -Most abundant protein in human body - 30% of dry weight
- -25 different types of collagen - classified into groups
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Describe Elastin
Provides resiliency (allows stretching) to tissue
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Describe proteoglycans
Filamentous protein core with attached GAGs; provide framework for ECM
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Describe glycoproteins
Proteins bound to small carbohydrate molecules; provide framework for ECM
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Synthesis, Location, and Main function of:
Type I Collagen
- -Synthesis: Fibroblast or Osteoblast
- -Location: Bone tendon, ligaments
- -Main Function: Resist tension
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Synthesis, Location, and Main function of:
Type II Collagen
- -Synthesis: Chondroblast
- -Location: Cartilage
- -Main Function: Resist compressive forces, shear forces at surface
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Synthesis, Location, and Main function of:
Type III collagen
- -Synthesis: Fibroblast
- -Location: Pliable tissues (Blood vessels, uterus, GI tract, skin, muscle)
- -Main Function: Structural maintenance in expandable organs; inital collagen of wound repair
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Synthesis, Location, and Main function of:
Type IV collagen
- -Synthesis: Fibroblast
- -Location: Basement membranes (muscle cells, epithelial cells, adipocytes)
- -Main function: Support of delicate structures; Filtration
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Describe Tropocollagen
- -The protein unit that polymerized to form collagen fibrils
- -3 subunit polypeptide chains intertwined in a triple helix
- -Differenes in the chemical structure of these polypeptide chains are responsible for the variuos types of collagen
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Describe collagen fibrils
- -Thin, elongated structures
- -Several micrometers long
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Describe collagen fibers
-Fibrils aggregate to form fibers (Types I and III)
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Describe collagen bundles
- -Collection of collagen fibers (Type I)
- -Type II - no fibers/bundles
- -Type III - no fibrils or fibers
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Describe the defect and symptom of Ehlers-Danlos Type VII
- -Defect: Decrease in procollgaen peptidase activity
- -Symptoms: Increased articular mobility; Frequent subluxation
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Describe the defect and symptom of Scurvy
- -Defect: Lack of Vitamin C (no procollagen formation)
- - Symptoms: Ulceration of gums; Hemorrhages; Weak bones
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Describe the defect and symptom of Osteogensis imperfecta
- -Defect: Change of one nucleotide in genes for collagen Type I
- -Symptoms: Spontaneous fratures; Cardiac insufficiency
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Describe the defect and symptom of Keloid scarring
- -Defect: Hyper-production of collagen
- -Symptoms: Local swelling that forms in scars of the skin
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Describe Reticular Fibers
- -Composed of Type III collagen fibers
- -Very thin, small and loosely packed fibers
- -Fibers bound together and to ECM with abundant interfibrillar bridges with proteoglycans and glycoproteins
- -Reticular fibers provide framework for organs (lymph nodes, spleen, bone marrow, liver)
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Describe Elastic Fibers
- -Rich in the protein elastin
- -Rubber-like qualities
- -5X more extensible than rubber
- -Desmosine and isodesmosine provide covalent bonds that form cross-links between elastin fibers
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Give the Synthesis, Location, and Main function of:
Elastic Fibers
- -Synthesis: Fibroblast; Smooth muscle cells
- -Location: Pliable tissue (blood vessels, uterus, etc.)
- -Main function: Elongation without deformation
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What happens to Elastic fibers wth aging?
Fibers are replaced by Type I collagen; tissues lose elasticity (more easily deformed)
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Describe Marfan syndrome
- -Genetic mutation; disrupts proper elastin fiber synthesis
- -Tissues rich in elastic fibers most affected (large/medium-sized arteries contain large amounts of elastin)
- -Creates non-compliant (brittle) tissue, especially arteries, that are prone to rupture
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Describe Ground Substance
- -Highly hydrated and viscous complex of macromolecules
- -Composed mainly of PGs, GAGs, glycoproteins and small amount of tissue fluid
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Function of Ground Substance
- -Fills spaces between cells and fibers of CT and provides a pathway for waste and nutrient exchange
- -Fluid provides for lubrication of ECM
- -Provides a barrier to penetration of foreign (infectious) agents
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Properties of Tissue Fluid
- -Small quantity within ECM
- -Similar to blood plasma in content (plasma proteins, ions, diffusible substances)
- -GAGs bind to water of ECM to maintain hydration of tissue (makes overall tissue more inelastic)
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Name the location, components, functions, and cell that contain:
Loose (Areolar) CT
- -Cells: Macrophage, mast cell, endothelial cell, neuron
- -Location: surrounds muscles, nerves, adipocytes, blood and lymphatic vessels
- -Components: Loosely packed collagen fibers. More elastic and reticular fibers. Well vascularized. Innervated
- -Functions: Supports epithelial cells of organs and skin. slight resistance to stress in alld irections. Provides blood supply to tissues it surrounds
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Name the location, components, functions, and cell that contain:
Dense Irregular CT
- -Cells: Macrophage, mast cell
- -Location: Skin, fascia, joint capsule, periosteum, pericardium, leura
- -Components: Densely packed collagen fibers. Few elastic or reticular fiber. Not well vascularized. Innervated
- -Functions: Moderate resistance to stress in all directions
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Name the location, components, functions, and cell that contain:
Dense Regular CT
- -Cells: Macrophage, mast cell
- -Location: Tendon, Ligament
- -Components: Densely packed collagen fibers; Fibers oriented in parallel; Few elastic/reticular fibers; not well vascularized; innervated
- -Functions: Strong mechanical resistance to stress in a single direction
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Describe a Tendon
- -Collection of collagen fiber bundles
- -Collagen bundles are enveloped by loose CT containing blood vessels and nerves
- -Externally, many tendons are surrounded by a sheath of dense CT
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Function of Tendons
- -Connect muscle to bone
- -Transmit mechanical force generated by muscle to bone to create joine movemt
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Innervation of Tendons
- -Golgi Tendon Organ (GTO)
- -Pain fibers (free nerve endings)
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Nutrient supply of tendons
- -Limited vascular supply
- -Synovial membrane (tendon sheath)
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Describe the Synovial Sheath
- -2 layers: visceral and parietal
- -Between the layers is a cavity for fluid
- -Synovial sheath provides lubrication for tendons to slide within their fibrous sheath
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Function of Ligaments
- -Connects bone to bone
- -Controls and guides nomal movement of joints
- -Limits excess motion
- -Contain more elastic vs. tendons
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Innervation of Ligaments
- -Proprioceptive fibers
- -Free nerve endings
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Nutrient supply of ligaments
Limited vasculature
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Aging effects on Loose CT
- -↓ elasticity
- -↓ hydrophilic capabilities
- -↓ ROM
- -↑ work to overcome inelasticity
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Aging effects on Dense Irregular CT
- -↓ elasticity
- -↓ hydrophilic capabilities
- -↓ ROM
- -↑ work to overcome inelasticity
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Aging effects on Dense Regular CT
- -↓ size
- -↓ protein synthesis
- -↓ in tensile force
- -↓ load to failure
- -fiber degradation
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Effects of Immobilization of CT proper
- -Contracture
- -↓ in tensile force generation // ↓ load to failure
- -↓ GAGs/H2O
- -Cross-linking of collagen (reduces compliance)
- -Synovial sheath becomes adherent on tendons; Adhesions prevents full ROM of affected joint
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Acute Activity effects on CT proper
- -↑ temperature and ↑ in elasticity
- -Micro tears (that are repaired); repair generates stronger and larger ligament/tendon
- -Prevention of cross-links to maintain extensibility
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Chronic Activity effects on CT proper
- -Hypertrophy of ligament/tendon - allows CT to transmit increased amounts of force
- -↑ deposition of type I collagen, ↑ load to failure
- -↑ ROM is stretched
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