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Questions and Answers
What is the primary characteristic of fibrillar collagens?
What is the primary characteristic of fibrillar collagens?
What is the correct sequence of steps in collagen synthesis?
What is the correct sequence of steps in collagen synthesis?
What is the significance of the closely spaced transverse bands in collagen fibrils?
What is the significance of the closely spaced transverse bands in collagen fibrils?
Which feature distinguishes network-forming collagens from fibrillar collagens?
Which feature distinguishes network-forming collagens from fibrillar collagens?
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What is the typical appearance of collagen fibers when viewed under a light microscope?
What is the typical appearance of collagen fibers when viewed under a light microscope?
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Which type of collagen is primarily responsible for combining with type I collagen?
Which type of collagen is primarily responsible for combining with type I collagen?
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In what way do collagen fibers differ from epithelial tissues?
In what way do collagen fibers differ from epithelial tissues?
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What role do eosin and acidic dyes play in studying collagen fibers?
What role do eosin and acidic dyes play in studying collagen fibers?
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What is a characteristic feature of macrophages?
What is a characteristic feature of macrophages?
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Which protein primarily composes elastic fibers?
Which protein primarily composes elastic fibers?
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What feature gives plasma cells their distinct 'clock face appearance'?
What feature gives plasma cells their distinct 'clock face appearance'?
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Which type of collagen is primarily found in hyaline and elastic cartilages?
Which type of collagen is primarily found in hyaline and elastic cartilages?
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What is the primary function of leukocytes in connective tissue?
What is the primary function of leukocytes in connective tissue?
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Which of the following statements about collagen is true?
Which of the following statements about collagen is true?
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What is the primary source of collagen in the body?
What is the primary source of collagen in the body?
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Which collagen type is associated with reticular fibers?
Which collagen type is associated with reticular fibers?
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During which physiological condition does the migration of leukocytes between endothelial cells of venules significantly increase?
During which physiological condition does the migration of leukocytes between endothelial cells of venules significantly increase?
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What type of cells are responsible for antibody production?
What type of cells are responsible for antibody production?
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What is the primary structural component of connective tissue?
What is the primary structural component of connective tissue?
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Which type of connective tissue cell is primarily responsible for synthesizing collagen?
Which type of connective tissue cell is primarily responsible for synthesizing collagen?
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What is the basic classification of connective tissue based on?
What is the basic classification of connective tissue based on?
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Mast cells are known to release which of the following mediators of inflammation?
Mast cells are known to release which of the following mediators of inflammation?
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What type of connective tissue cell is characterized by its role in phagocytosis?
What type of connective tissue cell is characterized by its role in phagocytosis?
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What distinguishes an active fibroblast from a quiescent fibroblast?
What distinguishes an active fibroblast from a quiescent fibroblast?
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Which type of connective tissue fiber is most abundant in the body?
Which type of connective tissue fiber is most abundant in the body?
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Adipocytes are primarily specialized for which function?
Adipocytes are primarily specialized for which function?
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What is the primary function of ground substance in connective tissue?
What is the primary function of ground substance in connective tissue?
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Which resident cell type in connective tissue is responsible for inflammatory responses?
Which resident cell type in connective tissue is responsible for inflammatory responses?
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Mast cells are derived from which type of cells?
Mast cells are derived from which type of cells?
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What protein does NOT form large fibers in connective tissue?
What protein does NOT form large fibers in connective tissue?
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The extracellular matrix (ECM) is composed of:
The extracellular matrix (ECM) is composed of:
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Which of the following cells is considered a wandering cell in connective tissue?
Which of the following cells is considered a wandering cell in connective tissue?
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Study Notes
Learning Objectives
- Ability to describe the structural criteria of connective tissue (CT).
- Understanding of general classifications of CT categories.
- Knowledge of different cells in CT.
- Familiarity with types of CT fibers.
- Insight into collagen fibers and the steps in collagen synthesis.
Main Structural Criteria of Connective Tissue (CT)
- CT serves as major structural constituents of the body with shared qualities despite diversity.
- Primarily derived from mesoderm, forming multipotential mesenchyme leading to bones, cartilage, and blood cells.
- Functions include support, defense, transport, storage, and repair.
- Comprises cells and an extracellular matrix (ECM), contrasting epithelium which primarily consists of cells.
- ECM consists of protein fibers and ground substance, providing structural integrity.
Classification of Connective Tissue (CT)
- Classification based on composition, organization of components, and functions leading to categories like:
- Mesenchymal CT
- Mucous CT
Cells of Connective Tissue
-
Resident Cells:
- Fibroblasts, Adipocytes, Mast cells, Macrophages, Adult stem cells.
-
Wandering Cells:
- Plasma cells, Lymphocytes, Eosinophils, Neutrophils, Basophils, Monocytes.
Fibroblasts
- Most common cells in CT, critical for maintaining the extracellular components.
- Synthesize collagen and elastin fibers; produce ground substances like glycosaminoglycans (GAGs).
- Morphological differences between active and quiescent fibroblasts:
- Active fibroblasts are larger with abundant rough endoplasmic reticulum (RER).
- Quiescent fibroblasts are smaller, with darker nuclei.
Adipocytes
- Large, spherical cells (25–250 μm) derived from mesenchyme.
- Specialized for lipid storage and hormone production.
- Adipose tissue serves as insulation and cushioning for organs.
Mast Cells
- Oval cells (7-20 μm), filled with secretory granules that obscure their nucleus.
- Store inflammatory mediators like histamine and heparin; play key role in allergic reactions.
Macrophages
- Specialize in clearing debris and pathogens through phagocytosis.
- Originate from monocytes; prominent in sites of inflammation.
- Highly variable sizes and shapes based on activity; possess cytoplasmic projections.
Plasma Cells
- Derived from lymphocytes; specialize in antibody production.
- Characteristic "clock face" nucleus appearance due to euchromatin and heterochromatin.
- Rich in RER and Golgi apparatus, actively producing antibodies for immune responses.
Other White Blood Cells (Leukocytes)
- Derived from blood cells, migrate to CT during inflammation.
- Function for limited time, often a few hours or days before apoptosis.
Connective Tissue Fibers
- Comprise elongated protein structures; three main types:
- Collagen fibers
- Reticular fibers
- Elastic fibers
- Distribution varies among CT types, with collagen fibers being most abundant.
Collagen
- Major structural component with high tensile strength; most abundant protein in the human body (over 25% of total protein).
- Estimated holding capacity: a 1 mm diameter collagen fiber can suspend 10 kg without breaking.
- Various types include Type I (skin, bone), Type II (cartilage), Type III (reticular fibers), Type IV (basal lamina), Type V (placenta), and Type VII (anchoring fibrils).
Stages of Collagen Synthesis
- Formation begins with synthesis of α chains into procollagen.
- Procollagen converted into tropocollagen via procollagen peptidase.
- Tropocollagen assembles into collagen fibrils, which further form collagen fibers and bundles.
Summary
- Connective tissue differs structurally from epithelium, primarily in ECM composition.
- Recognize various resident and wandering cells with their respective functions.
- Understand the significance of collagen in structure, categories, and synthesis process.
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