L4 - Connective
Transcript of L4 - Connective
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Connective Tissue
Lecture IV
Bismark Oliver C. Lemana, M.Sc. Biological Sciences Department, College of Science University of Santo Tomas, Manila
• Originated from mesenchyme (mesoderm) – Surrounds and penetrates organs
• General function: – Body form maintenance
– Provides matrix
– Body support
• Components – Cell, fibers and ground substance
– Extracellular matrix
Connective Tissue
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• Function:
– Structural
– Reservoir for growth and differentiation hormones
– Nutrient – waste exchange
Extracellular matrix
• Mesenchymal Origin – Retained in connective tissue proper
• Fibroblasts
• Hematopoietic Stem Cells – Bone marrow derived
– Moves to different areas through blood • Mast cells, macrophages, plasma cells
Leukocytes Transient cells
Cellular Components
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Hematopoietic
Stem Cells
Mesenchymal Cells
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• Synthesis of extracellular Matrix
– Collagen, elastin, glycosaminoglycans, proteoglycans, multiadhesive proteins
• Stages of activity: (synthesis state)
– Active (Fibroblast)
• RER and Golgi complex rich
• Growth factors and differentiation
– Quiescent (Fibrocyte)
• Less RER
Fibroblasts
Fibroblast
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• Storage of fats
– Insulation
• Production of heat
Adipocytes
• Bone marrow -> Monocytes -> Macrophage • Defense/Removing elements against:
– Cell debris, abnormal ECM, neoplastic cells, bacteria
• May present immune response – Antigen-presenting cells
• Posses tumor cell-killing capabilities Activated macrophages
Increased phagocytotic capacity and intracellular digestion
Enhanced lysosomal enzyme activity
Macrophage
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Macrophage
• Monocyte derived cells
• Lymphocyte activation
• Monocyte differentiation:
– Increased cell size
– Increased protein synthesis
– Increase in # of golgi complexes and lysosomes
Mononuclear Phagocyte
System
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Mononuclear Phagocyte
System
• Originated from bone marrow (progenitor cells) • Inserted in the connective tissue proper • Main functions:
– Inflammatory response – Innate immunity – Tissue repair
• Bioactive secretions – Heparin – Histamine – Serine proteases – ECF-A and NCF – Leukotrienes (SRS-A)
Mast Cells
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• Ovoid in shape with basophilic cytoplasm
– Rich in RER
• Originated from B lymphocytes
• Function:
– Production of antibodies
IgE
• Class of an antibody
• Anti-allergy and anti-parasite antibody
Plasma Cells
Plasma Cells
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Immediate hypersensitivity
reactions
• White blood cells
• Wandering cells of connective tissues
– Migrates through diapedesis
– Increased activity during inflammation
Leukocytes
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• Polymerization of proteins
– Collagen, reticular (collagen proteins)
• Tendons, aponeuroses, organ capsules, meninges
– elastic fibers (elastin proteins)
Stroma
– Supporting tissue of organs
– Trabeculae and walls of organs
Fibers
Stroma
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• Most abundant type of fiber in humans – 30% dry weight
• Protein derived • Structural functionality
– Skin, bone, cartilage, smooth muscles and BL
• Characterized into: – Forms fibrils – Fibril-associated – Forms anchoring fibrils – Forms network
Collagen
• Visible under light microscopes
• Type I is the most abundant
• Composition of the following structures
– Tendons
– Organ capsules
– Dermis
Long Fibril-forming
Collagen
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Long Fibril-forming
Collagen
• Fibril binding collagen
– Collagen to collagen
– Collagen to ECM compounds
• FACIT
– Fibril-associated collagen with interrupted triple helices
– Non-fibril forming type
Fibril-Associated
Collagen
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• Binding basal lamina with reticular fibers of connective tissues
Anchoring Fibril-Forming
Collagen
• Major structural component of BL
– Type IV
Network-Forming
Collagen
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• Occurs in many types of cells
• Procollagen αchains – Collagen precursor
– Forms triple helices in ER from protein synthesis
• Triple helix – Homotrimetric
– Heterotrimetric
• Combinations may affect the collagen type produced
Collagen Synthesis
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• Osteogenesis Imperfecta – Mutation of genes of type I collagen – Change in the position of Glycine
• Progressive Systemic Sclerosis – Over accumulation of collagen (fibrosis) – Hardening of affected organ – Functional impairment
• Kelloids – Local swelling due to abnormal collagen amount skin
• Scurvy – Vitamin C deficiency – Degeneration of connective tissue
Collagen Associated
Diseases
• Mainly composed of Collagen III • Argyrophilic
– High affinity to silver salts
• “flexible” in nature – Can change in form or volume
• Eg. Arteries, small intestines and uterus
• Reticular cells – Fibroblast-like cells: production of RF
Ehlers-Danlos Type IV disease • Deficiency in Type III collagen • Artery and Small Intestine rupture
Reticular Fibers
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Reticular Fibers
Adrenal cortex Lymph node
• Thinner than collagen
• Network forming fibers
• Found in organs subject to stretching or bending
– Eg. Arteries
Elastic Fibers
mesentery dermis Smooth muscle
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Elastic Fiber
Formation
1. Formation of fibrillin • Microfibril
accumulation
2. Deposition of elastin • Increase in fiber
size
3. Further accumulation of Elastin
• Formation of mature Elastic fiber
• Microfibril and fibrillin – Non-elastic precursor; highly resistant to pulling forces
– Holds the lens of the eye
• Elastin – Matures in ECM
– Glycine and proline rich • Rubber-like capabilities
Combination of fibrillin and elastin can form variable types of fibers depending on their function
Elastic fiber
precursors
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• Desmosine and isodemosine
Elastin Cross-link
• Highly water-based
• Complex of:
– Anionic macromolecules (glycosaminoglycans and proteoglycans
– Multiadhesive proteins (laminin, fibronectin, etc…)
• Function:
– Strength and rigidity of the matrix
– Acts as lubricant and barrier to foreign bodies
Ground Substance
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• Composition:
– Hexosamine (galactosamine/glucosamine)
– Uronic acid (glucoronic/iduronic)
• Hyaluronic acid
– largest, most abundant GAG
– Functions:
• Diffusion of molecules in connective tissues
• Lubrication to organs
Glycosaminoglycans
Glycosaminoglycans
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• Synthesized in RER, mature in Golgi, secreted via exocytosis
• Functions:
– Structural and anchoring proteins
– Bind and sequester signalling proteins
• Fibroblast growing factors
Proteoglycans
Proteoglycans and
Glycoproteins
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Connective Tissues
• Areolar tissue
• Features: – Flexible, highly vascularized, not very resistant to
stress
• Function: – Supports structure subject to pressure and low
friction (epithelia)
• Location: – Papillae of the dermis, lining of the pleural and
peritoneal cavities,
Loose Connective
Tissue
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• Adapted for resistance and protection
• Similar with LCT but:
– More collagen
– Less resistant to stress
• Two types:
– Dense irregular
– Dense regular
Dense Connective
Tissue
• Collagen arranged in bundles but without any definite orientation
• Collagen bundles are arranged in a 3-dimensional network
– More resistant to stress
• Found always in association with LCT
Dense Irregular
Connective Tissue
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LCT and DICT
Mammary gland Esophagus
Blood vessels Mesothelial Cells
• Has a definite pattern
• Linear orientation of the fibroblast
• Offers greater resistance to traction forces
Dense Regular
Connective Tissue
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• Type III Collagen
• Framework to hematopoietic and lymphoid organs
– Bone marrow, lymph node, spleen
The mononuclear phagocyte system are dispersed in the
trabeculae to monitor the flow of materials and prevent foreign bodies through phagocytosis
Reticular Tissue
Reticular Tissue
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• Found in umbilical cord (Warton’s Jelly) and fetal tissues
Mucous Tissue