**Core Concept**
Mitral cells, also known as mitral neurons or mitral interneurons, are a type of glutamatergic interneuron in the olfactory bulb. They play a crucial role in processing and transmitting sensory information from the olfactory epithelium to the olfactory cortex. Mitral cells are characterized by their distinctive mitral-shaped dendritic tree and their axons that project to the lateral olfactory tract.

**Why the Correct Answer is Right**
Mitral cells are involved in the processing of odorant molecules, which bind to odorant receptors on the surface of the olfactory sensory neurons. The binding of these molecules triggers a signaling cascade that ultimately leads to the depolarization of mitral cells. Mitral cells then transmit this information to the olfactory cortex through their axons, where it is further processed and interpreted. The unique morphology of mitral cells, including their mitral-shaped dendritic tree, allows them to efficiently integrate and process this sensory information.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because mitral cells are not found in the retina, which is a different part of the visual system altogether.
**Option B:** This option is incorrect because granule cells are a different type of interneuron in the olfactory bulb, and while they do interact with mitral cells, they are not the same thing.
**Option C:** This option is incorrect because Purkinje cells are a type of neuron found in the cerebellum, not the olfactory bulb.

**Clinical Pearl / High-Yield Fact**
It's worth noting that the olfactory system is a unique and highly specialized sensory system that is capable of detecting a wide range of odorant molecules. The processing of this information is critical for our ability to perceive and interpret smells, and the mitral cells play a key role in this process.

**Correct Answer:** D.