Podcast
Questions and Answers
What role do proteoglycans primarily play before calcification occurs in the predentin matrix?
What role do proteoglycans primarily play before calcification occurs in the predentin matrix?
- Acting as inhibitors of calcification by binding calcium (correct)
- Enhancing the diameter of collagen fibrils
- Facilitating the transport of collagen molecules
- Promoting the formation of collagen fibrils
During the process of collagen secretion, where is procollagen packed and concentrated?
During the process of collagen secretion, where is procollagen packed and concentrated?
- In the RER only
- In the predentin matrix
- In the Golgi complex (correct)
- In the cytoplasm of the odontoblast
What initiates the labeling of odontoblasts in studies involving radiolabeled chemicals?
What initiates the labeling of odontoblasts in studies involving radiolabeled chemicals?
- Injections of collagen precursors like 3 H-proline (correct)
- Application of proteoglycans onto the odontoblasts
- Injections of calcium directly into the muscle
- Direct exposure of odontoblasts to radiation
What happens to collagen fibrils as they approach the mineralized matrix?
What happens to collagen fibrils as they approach the mineralized matrix?
Which organelle is responsible for synthesizing the protein moiety of predentin proteoglycans?
Which organelle is responsible for synthesizing the protein moiety of predentin proteoglycans?
What occurs at the base of the odontoblast process in the secretion mechanism?
What occurs at the base of the odontoblast process in the secretion mechanism?
How does the diameter of collagen fibrils compare at different locations within the predentin?
How does the diameter of collagen fibrils compare at different locations within the predentin?
What mechanism is utilized for the release of tropocollagen into the predentin matrix?
What mechanism is utilized for the release of tropocollagen into the predentin matrix?
Study Notes
Odontoblast Structure & Secretory Function
- Collagen Synthesis and Secretion:
- Odontoblasts synthesize collagen precursor (procollagen) in the rough endoplasmic reticulum (RER).
- Procollagen moves to the Golgi apparatus for packaging into secretory vesicles.
- Vesicles migrate to the base of the odontoblast process.
- Exocytosis releases tropocollagen into the predentin matrix.
- Collagen fibrils form from tropocollagen and grow in size as they move toward the mineralized matrix.
- Fibril diameter increases from 15 nm at the base of the process to 50 nm at the calcification front.
Predentin Proteoglycan Synthesis and Secretion
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Proteoglycan Synthesis and Secretion:
- Odontoblasts synthesize the protein component of proteoglycans in the RER.
- Sulfation and addition of glycosaminoglycan (GAG) moieties occur in the Golgi complex.
- Secretory vesicles transport proteoglycans to the base of the odontoblast process.
- Proteoglycans are secreted into the predentin matrix.
- Chondroitin sulfate, the main proteoglycan, accumulates near the calcification front.
-
Proteoglycan Function:
- Proteoglycans may inhibit calcification by binding calcium.
- Odontoblasts likely remove proteoglycans using lysosomal enzymes just before calcification.
- The exact role of proteoglycans in calcification remains under investigation.
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