Diameter of odontoblastic tubules at the point of origin, at their pulpal end
**Core Concept**
The **odontoblastic tubules** are tiny channels within the **dentin** of teeth, formed by the odontoblasts. These tubules play a crucial role in tooth sensitivity and dentin formation.
**Why the Correct Answer is Right**
The diameter of odontoblastic tubules at their pulpal end is approximately 2.5 micrometers, gradually decreasing as they extend towards the enamel.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because the diameter is not around 1 micrometer at the pulpal end.
**Option B:** Incorrect as 2 micrometers underestimates the diameter.
**Option C:** Incorrect because 3 micrometers overestimates the diameter at the pulpal end.
**Clinical Pearl / High-Yield Fact**
Remember, the diameter of odontoblastic tubules affects tooth sensitivity, with narrower tubules potentially causing more sensitivity due to increased resistance to fluid flow.
**Correct Answer:** D. 2.5 micrometers