The function of the foramen magnum is to allow nerves, blood vessels and fluid to pass in and out of the brain. The foramen magnum is a large hole at the base of the skull.
Some of the most important parts that pass through the foramen magnum include the medulla oblongata, cranial nerves and the spinal arteries. The dura mater also passes through this opening. The dura mater is just one of the protective layers that covers the skull and the brain. It is believed that the foramen magnum plays a role in degenerative diseases such as dementia and Alzheimer's disease.