41 Questions
What is the main function of fibroblasts?
Produce and secrete extracellular matrix components
Which cell type is involved in phagocytosis and engulfing foreign particles?
Macrophages
Which cell type releases mediators such as histamine and proteases?
Mast cells
What distinguishes quiescent fibroblasts from active fibroblasts?
Less active components and less cytoplasm
Which cell type plays a role in the inflammatory response by releasing mediators?
Mast cells
What is the characteristic feature of mast cells?
Granules containing mediators such as histamine and proteases
What is the main function of connective tissue?
Providing and maintaining shape and firmness in the body
Which of the following is NOT a component of connective tissue matrix?
Adipose cells
What is the role of proteoglycans in the ground substance of connective tissue?
Filling the spaces between collagen and elastic fibers
Which component exceeds the volume of cells in all types of connective tissue?
Ground substance
What is the main function of plasma cells?
Producing antibodies that mediate immunity
What is the primary function of eosinophils in the immune response?
Phagocytosing parasites
Which leukocytes migrate from the bloodstream into tissues through diapedesis?
Eosinophils
Which is the most abundant type of collagen in the human body?
Collagen I
What is the characteristic periodicity of collagen fibrils?
64 nm
What is the main content of basophilic granules in eosinophils?
Basic proteins
Which cells are involved in mediating inflammation and inactivating histamines and leukotrienes?
Eosinophils
What is the role of plasma cells in the immune response?
Producing antibodies that mediate immunity
How are collagen fibrils formed?
Through polymerization into microfibrillar units
What type of protein provides strength and structure to various tissues in the body?
Structural proteins
What constitutes the most common protein in the human body?
Collagen I
What are plasma cells involved in producing?
Antibodies
What provides structure to the mesentery?
Collagen fibers
In polarizing microscopy, what color are collagen bundles observed as in superimposed regions?
Dark
Which type of staining procedure makes elastic fibers appear darker?
Other than H&E
What are elastic fibers formed by before accumulating elastin?
Small glycoprotein microfibrils
What is the high-viscosity substance that fills the spaces between cells and fibers in connective tissue?
Ground substance
How is the ground substance revealed in electron micrographs?
As a fine granular material among collagen and elastic fibers
What are proteoglycans composed of?
A core protein and covalently bound glycosaminoglycans (GAGs)
What are GAGs?
Linear polysaccharides made up of repeating disaccharide units
What is the structure of proteoglycans?
A central protein to which GAGs are covalently bound
What distinguishes glycoproteins from proteoglycans?
Globular protein molecules with covalently attached branched chains of monosaccharides
What is the main component of collagen fibers?
Type I collagen
What is the main function of elastin fibers?
Supporting collagen fibers
How are elastin cross-links formed?
Through covalent reactions between lysine residues
Which type of collagen forms reticular fibers?
Type III collagen
What initiates the degradation of collagen fibers?
Collagenases
What is the rate of turnover for stable collagen in tendons, ligaments, and periodontal ligaments?
Low turnover rate
What process allows for the assembly of collagen fibrils?
Cleavage of proteases to form tropocollagen
What is the general composition of elastin?
High proportion of glycine, proline, and two unusual amino acids
What is the structure of elastin?
Globular molecule that polymerizes to form elastin, an amorphous rubber-like glycoprotein
Study Notes
- Collagen fibrils are assembled with a regular, overlapping pattern, resulting in cross striations with alternating dark and light bands in electron microscopy.
- Collagen fibrils are linked together to form larger collagen fibers visible by light microscopy.
- Collagen fibers form larger aggregates, typically of Type I collagen, which are bundled and linked together by other collagens.
- Collagen synthesis in RER involves the formation of polypeptide chains, injection as preprocollagen, and subsequent hydroxylation and glycosylation to form procollagen.
- The removal of signalling sequences from procollagen results in procollagen, which is then transported out of the cell.
- Procollagen is cleaved by proteases to form tropocollagen, allowing for the assembly of collagen fibrils.
- Collagen fibrils spontaneously aggregate to form fibers, and fibers are further reinforced by covalent cross-links between tropocollagen molecules.
- Collagen turnover is generally a slow process, with stable collagen in tendons, ligaments, and periodontal ligaments having a low turnover.
- Degradation of collagen fibers can be initiated by collagenases, which remove the original tropocollagen peptides and allow for further degradation by normal proteases.
- Collagen fibers are often organized into bundles in various parts of the body.
- Collagen fibers are mainly composed of Type I collagen, which is visible as acidophilic fibers in connective tissues.
- Type III collagen forms reticular fibers, which are much thinner (0.5 to 2 µm) and form a loose network in various tissues such as smooth muscles, endoneurium, and blood-forming organs.
- Elastic fibers are composed of three types of fibers: oxytalan, elaunine, and elastin.
- Elastin cross-links are formed through covalent reactions between lysine residues, resulting in desmosine and isodesmosine.
- Elastin fibers are not elastic on their own, but oxytalan fibers form a network that supports elastin, allowing for its elastic properties.
- Elastic fibers stretch easily due to the different ratio of microfibrils to elastin, which is adapted to the local tissue requirements.
- Elastin is a globular molecule that polymerizes to form elastin, an amorphous rubber-like glycoprotein.
- Elastin is made up of a high proportion of glycine, proline, and two unusual amino acids: desmosine and isodesmosine.
- Elastin fibers have a high turnover in areas such as the arterial wall.
- Deficiencies in collagen type III can result in the rupture of the arterial wall.
Test your knowledge of cell biology and immunology with this quiz covering topics such as phospholipases, leukotrienes, plasma cells, and adipose cells. Identify key cellular processes and components based on provided descriptions.
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