- The primary olfactory receptors are specialized sensory cells responsible for detecting odor molecules.
- These receptors are located in the olfactory epithelium, which is a specialized epithelial tissue inside the nasal cavity, specifically in the roof of the nasal cavity.
- When odorant molecules enter the nasal passages during inhalation, they bind to these receptors and initiate a signal that is transmitted to the olfactory bulb in the brain, allowing the perception of smell.

- It is important to note that while the oral cavity, pharynx, and larynx are involved in other aspects of sensory perception and function, they do not contain olfactory receptors.
- The oral cavity is primarily involved in taste, the pharynx plays a role in both digestive and respiratory pathways, and the larynx is involved in voice production and airway protection.

Thus, the correct anatomical site for the primary olfactory receptors is the nasal cavity.

Key points:
- Primary olfactory receptors reside in the olfactory epithelium.
- The olfactory epithelium is located in the roof of the nasal cavity.
- These receptors detect odor molecules and send signals to the brain for smell perception.
- The oral cavity, pharynx, and larynx do not contain these olfactory receptors.

Reference: Gray's Anatomy, 41st Edition, Section on the Respiratory System, Chapter on Nasal Cavity and Olfaction