Nissl’s substance is mainly
**Core Concept**
Nissl's substance, also known as Nissl bodies or tigroid substance, is a characteristic feature of **neurons**. It is composed of rough endoplasmic reticulum (RER) with bound **ribosomes**, which are the site of protein synthesis. This substance plays a crucial role in the metabolic activity of neurons.
**Why the Correct Answer is Right**
Since the correct answer is not provided, let's discuss the composition of Nissl's substance. Nissl's substance is mainly composed of rough endoplasmic reticulum (RER) and **ribosomes**, which are responsible for protein synthesis. The RER is studded with ribosomes, giving it a rough appearance under an electron microscope.
**Why Each Wrong Option is Incorrect**
**Option A:** Without the specific option text, it's challenging to provide a detailed explanation. However, if it's not related to RER or ribosomes, it's incorrect.
**Option B:** Similarly, without the option text, it's difficult to provide a reason. If it's not associated with protein synthesis or neuronal structure, it's incorrect.
**Option C:** If this option does not pertain to the structural components of Nissl's substance, such as RER or ribosomes, it's incorrect.
**Option D:** If this option is unrelated to the composition or function of Nissl's substance, it's incorrect.
**Clinical Pearl / High-Yield Fact**
Nissl's substance is a key feature in identifying neurons under a microscope. Damage to Nissl's substance can be an indicator of neuronal injury or disease.
**Correct Answer:** D. Rough endoplasmic reticulum with ribosomes.