Lesson 7 Flashcards
-stellate or spindle-shaped cells with large vesicular nucleus rich in euchromatin
-with scanty, acidophilic cytoplasm
(Scanty means sparse or small in amount)
Mesenchymal Cells
Large, vesicular, and rich in euchromatin.
Mesenchymal Cells
Where are mesenchymal cells most prominent?
Perivascular area.
Perivascular spaces (PVSs) are fluid-filled spaces around small blood vessels in the brain. They are also known as Virchow-Robin spaces.
What is the primary means through which metaplasia occurs in connective tissue?
Mesenchymal cells.
Metaplasia, a process where one type of cell changes into another type
mesenchymal cells, which are undifferentiated stem cells in connective tissue, can transform into other types of connective tissue cells under specific conditions.
They are precursors of most connective tissue cells.
mesenchymal cells
How do reticular cells compare in size to fibrocytes?
Reticular cells are larger than fibrocytes.
What connective tissue type are reticular cells associated with?
Reticular connective tissue.
Where can a network of reticular fibers be found?
Lymphoid organs.
What is the appearance of the reticular cell nucleus in H&E staining?
Large and lightly stained.
What are the functions of reticular cells?
- Producer of reticular fibers.
- Stem cell for bone marrow elements and macrophages.
- May have phagocytic action.
What is the most common fixed cell in loose connective tissue?
Fibroblasts.
What substances do fibroblasts produce?
Fibrous and amorphous intercellular substances.
How does the shape of fibroblasts vary depending on their location?
- Elongated and fusiform when associated with fibers.
- Rounded when not directly associated with fibers.
What is the general shape of the fibroblast nucleus?
Ovoid, although fusiform or elongated shapes may occur.
How does the cytoplasm of young fibroblasts appear in H&E staining?
Abundant and basophilic.
What are the potential functions of protein synthesized by young fibroblasts?
- Growth (formation of more fibroblasts).
- Secretion (production of protein intercellular substances).
How do fibrocytes differ from young fibroblasts in appearance?
- Cytoplasm is difficult to see.
- Nucleus is pale, thinner, and smaller with less chromatin.
What organelles are abundant in active fibroblasts and indicate protein synthesis?
RER and a well-developed Golgi apparatus.
What molecules do fibroblasts produce to form fibers?
Tropocollagen molecules
Where does the polymerization of tropocollagen into microfibrils occur?
Outside the fibroblasts.
What is the combination of young fibroblasts and capillary buds called , that repair sizable connective tissue defects?
Granulation tissue.
What is the initial color of granulation tissue, and why?
Pink-to-red because of numerous capillaries.
Why does granulation tissue become paler over time?
Fibroblasts produce more collagenic fibers, squeezing the capillaries and reducing blood flow.
What does granulation tissue eventually become?
A collagenic scar
These are large cells filled with granules which are metachromatic when stained with certain basic aniline dyes;
the metachromasia is due to the presence of strongly acidic sulfated mucopolysaccharides;
Mast Cells (Tissue Basophils)
What causes the metachromatic property of mast cell granules?
Strongly acidic sulfated mucopolysaccharides.
Mast Cells:
What are the differences in the size and shape of mast cells among species?
- Mouse and rat: Large, round or ovoid.
- Humans: Larger than in mice and rats, similar shape.
- Guinea pigs: Contain intensely stained granules that obscure cell shape.
What substances are contained in mast cell granules?
- Heparin,
- histamine,
- serotonin.
The substances contained in mast cell granules include heparin, histamine, and in some species like the rat and mouse, serotonin is also present.
What are the functions of histamine in mast cells?
- Causes contraction of smooth muscle cells and,
- increases the permeability of capillaries and venules.
What additional substances are found in mast cell granules?
- Eosinophil chemotactic factor,
- neutrophil chemotactic factor,
- neutral proteases (e.g., tryptase, chymase),
- enzymes like peroxidase and
- β-glucuronidase.
What are some substances synthesized by mast cells?
- Leukotrienes,
- prostaglandins,
- and cytokines (e.g., platelet-activating factor, bradykinins, interleukins).
What is the primary specialization of macrophages?
Phagocytosis.
What are macrophages also called?
Histiocytes or clasmatocytes.
What type of nucleus do macrophages have?
Oval and indented on one side, kidney- or bean-shaped.
How does the nucleus of a macrophage differ from that of fibroblasts?
is slightly smaller, darker, and indented on one side.
From what do macrophages develop?
- Pre-existing mesenchymal cells,
- macrophages in loose connective tissue,
- and monocytes.
What are some substances synthesized by macrophages?
- Lysozyme,
- interferon,
- prostaglandin,
- hydrogen peroxide,
- hydroxy radicals, and
- superoxide anion.
What is the appearance of the macrophage cell membrane?
Uneven contour with pseudopodia projecting outward and inward depressions and clefts.
What structures are commonly found in the cytoplasm of macrophages?
Granules, vacuoles, numerous lysosomes, and residual bodies.
Where are mitochondria typically located in macrophages?
Congregated (Flock together) around the centrosome.
What type of cell surrounds the endothelial cells of capillaries or small vessels?
Answer: Pericytes (Cell of Rouget).
What type of cells are pericytes classified as?
Undifferentiated mesenchymal cells.
What characteristics do pericytes possess?
- Characteristics of smooth muscle cells (contractile) and, endothelial cells.
What is the function of pericytes under certain conditions?
They may differentiate into other cells.
What are fat cells called when organized into lobules?
Adipose tissue.
How do fat cells appear in cross-section?
Like a signet ring with the nucleus bulging slightly from one side
Why do fat cells appear empty in paraffin sections?
Because fat is dissolved during preparation.
What supports individual fat cells within lobules?
Reticular fibers.
Why are abundant capillaries important in fat cells?
Because of the constant metabolic activity in fat cells.
From what substances is fat formed?
Glucose and amino acids.
What are foreign body giant cells formed from?
Fusion of monocytes or macrophages.
To enclose or wall off foreign objects or debris too large or resistant for a single phagocyte to destroy. These are-
Foreign Body Giant Cells
In which condition are foreign body giant cells common?
Lesions of tuberculosis.
What is the principal function of plasma cells?
Production of antibodies (immune globulins).
Where do plasma cells differentiate?
In connective tissue from lymphocytes, as well as in the lymph nodes and spleen.
In which type of connective tissue are plasma cells relatively uncommon?
Typical loose connective tissue.
Where are plasma cells plentiful?
In highly cellular connective tissue supporting wet epithelial membranes lining the respiratory and intestinal tracts.
What are Russell bodies in plasma cells?
Spherical inclusions in dilated portions of the ER representing large accumulations of immunoglobulins.
Spherical inclusions in dilated portions of the ER representing large accumulations of immunoglobulins.
Russell bodies
What is any cell containing pigments called?
Pigment cells (e.g., melanocytes).
To protect the body from excessive exposure to UV radiation. What cell is responsiblefor it?
melanocytes
What system consists of cells capable of phagocytosis and is also called the reticuloendothelial system?
Mononuclear macrophage system.
What are some examples of cells in the mononuclear macrophage system?
- Monocytes of the blood.
- Fixed and free macrophages of connective tissue.
- Alveolar phagocytes of the lung.
- Microglia of the brain.
- Reticular cells of bone marrow and lymphoid organs.
- Von Kupffer cells of the liver.
What are the main functions of the mononuclear macrophage system?
Answer:
Protect the body from foreign materials and microorganisms.
Rid the body of dead cells.
Participate in cell-mediated immunity and humoral antibody response.
