What skull structure must the axons from the olfactory epithelium pass through in order to get to the olfactory bulbs?

The axons from the olfactory epithelium pass through olfactory foramen in the cribriform plate of the ethmoid bone of skull in order to get to the olfactory bulbs.

Explanation:

Olfactory foramina (also referred as cribriform foramina) are basically a number of wholes situated on the cribriform plate of the ethmoid bone in two depressions lateral to the median blade of cribriform plate (crista gilli) in the skull forming the roof of the nasal cavity.

The fibres of first cranial nerve being the olfactory nerve extends from the olfactory epithelium (axons of olfactory epithelium) to the olfactory bulb through the olfactory foramen in the cribriform plate of the ethmoid bone of skull.