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Questions and Answers
Which feature distinguishes fixed cells from wandering free cells in connective tissue?
What is the primary role of the extracellular matrix in connective tissue?
Which connective tissue is characterized by a fluid extracellular matrix?
What is a key characteristic of multilocular adipocytes in brown fat?
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What is NOT a function of connective tissue?
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Which of the following is NOT a component of connective tissue composition?
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Which of the following is NOT a function of macrophages?
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What type of cells are referred to as Von-Kupffer cells?
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Which type of connective tissue primarily provides resistance to stress?
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What characterizes the extracellular matrix in bone connective tissue?
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What feature distinguishes reticular cells in reticular connective tissue?
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Which of the following cells in connective tissue is primarily involved in lipid storage?
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In which situation might macrophages increase in size and form clusters?
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What is the primary function of undifferentiated mesenchymal cells (UMCs)?
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Which feature is characteristic of fibroblasts as observed under light microscopy?
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What role do myofibroblasts play in tissue repair?
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What is a distinguishing feature of unilocular adipocytes in their microscopic appearance?
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Fibrocytes are characterized by which of the following features in their morphology?
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What cellular feature is NOT typically associated with fixed macrophages?
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Which connective tissue cell type primarily supports organs and acts as a heat insulator?
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Which statement about the regenerative capacity of connective tissue is incorrect?
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Study Notes
Connective Tissue
- Originates from mesenchyme
- Composed of cells, fibers, and ground substance
- Cells are widely dispersed in a large amount of extracellular substance (matrix)
- Matrix can be firm (cartilage), hard (bone), or fluid (blood)
- Can be penetrated by blood vessels, lymphatics, and nerves
Functions of Connective Tissue
- Supports and connects cells, tissues, and organs
- Cells contribute to healing of injured tissues
- Provides resistance to stress in structures like cartilage, bone, tendons, ligaments, and organ capsules
- Acts as a medium for exchange in blood, lymph, and connective tissue proper, delivering nutrients, waste products, and signaling molecules
- Participates in immunity, as plasma, mast cells, and white blood cells leave the bloodstream to protect the body
- Stores and metabolizes lipids in the form of adipose cells and adipose tissue
Connective Tissue Cells
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Fixed Cells: Stable and long-lived
- Fibroblasts
- Fat cells
- Undifferentiated mesenchymal cells (UMCs)
- Fixed macrophages
-
Wandering (free) Cells: Transient and migrating from blood to connective tissue
- Plasma cells
- Mast cells
- Leukocytes
Undifferentiated Mesenchymal Cells (UMCs)
- Multipotent stem cells
- Can differentiate into other types of connective tissue cells
- In bone marrow, they give rise to blood cells
Fibroblasts
- Originate from UMCs and pericytes
- Found in all types of connective tissue
- Flat, branched cells with thin processes and a prominent oval nucleus
- Basophilic cytoplasm
Fibroblasts (EM)
- Euchromatic nucleus with a prominent nucleolus
- Abundant RER, ribosomes, Golgi apparatus, and mitochondria
- Function:
- Formation of connective tissue fibers
- Formation of ground substance
- Healing and repair of wounds
Fibrocytes and Myofibroblasts
- Fibrocytes: Smaller, spindle-shaped cells with fewer processes and a darker nucleus
- Myofibroblasts: Share characteristics of fibroblasts and smooth muscle cells, containing actin and myosin
- Myofibroblasts play a role in wound closure
Fat Cells - Unilocular Adipocytes (White Fat)
- Found in white adipose tissues
- Large, rounded, or oval cells with a peripheral, flattened nucleus
- Pale cytoplasm with a thin rim surrounding a large fat droplet
- In H&E staining, fat dissolves, leaving large vacuoles (signet-ring appearance)
- Stain orange with Sudan III
Fat Cells - Unilocular Adipocytes (EM)
- Fat drops appear as electron-dense inclusions
- Few cell organelles are present around the nucleus
- Function:
- Storage of fat
- Support for organs
- Heat insulation
Fat Cells - Multilocular Adipocytes (Brown Fat)
- Present in brown adipose connective tissue
- Small, rounded cells with a rounded nucleus and numerous small fat droplets
- Contain many mitochondria, giving them a brown appearance
- Function:
- Heat generation
Macrophages
- Originate from blood monocytes
- Scattered in connective tissue or fixed to collagen fibers
- Large, branched cells with irregular cell boundaries (pseudopodia) and a dark, kidney-shaped nucleus
- Pale basophilic and vacuolated cytoplasm
Macrophages (EM)
- Pseudopodia, lysosomes, RER, Golgi apparatus
- Functions:
- Phagocytosis
- Antigen-presenting cells (APCs)
Mononuclear Phagocytic System
- Macrophages are found in various organs and have different names:
- Von Kupffer cells (liver)
- Dust cells (lung)
- Langerhans cells (skin)
- Microglia (brain)
- Osteoclasts (bone)
- All share the same structure and function
Reticular Cells
- Originate from UMCs
- Found in the reticular stroma of parenchymatous organs
- Small, branched cells with many processes to which reticular fibers are attached
- Pale basophilic in H&E stain, brown in silver stain
- Central, oval, and pale nucleus
Reticular Cells - Functions
- Multipotent stem cells
- Supportive function
- Antigen-presenting cells (APCs)
- Phagocytic function
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