Step 1: Understanding the Problem:
Neurons, the functional units of the nervous system, are classified morphologically based on the number of processes (axons and dendrites) that extend from the cell body (soma).
Step 2: Approach and Formula:
Classify neurons structurally and relate the term 'unipolar' to its anatomical definition and specific occurrence in the embryonic stage.
Step 3: Detailed Explanation:
- Multipolar neurons: Possess a cell body with one axon and two or more dendrites. These are common in the cerebral cortex.
- Bipolar neurons: Have one axon and one dendrite extending from opposite sides. They are found in the retina of the eye.
- Unipolar neurons: Have a cell body with a single process extending from it, which functions as an axon. They lack true dendrites directly on the soma. These are typically found in embryonic development stages.
- Apolar neurons: Lack distinct axons and dendrites (e.g., Hydra).
Thus, unipolar neurons strictly consist of a cell body and one axon.
Step 4: Final Answer:
They have a cell body and one axon.