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Upper surface of base of the skull. The hole indicated by an arrow is foramen magnum
Occipital bone. Inner surface.
|Anatomical terms of bone|
In anatomy, the foramen magnum (Latin: "great hole") is a large opening in the occipital bone of the cranium. It is one of the several oval or circular apertures in the base of the skull (the foramina). It is the foramen magnum through which the spinal cord (an extension of the medulla oblongata) enters and exits the skull vault.
Apart from the transmission of the medulla oblongata and its membranes, the foramen magnum transmits the vertebral arteries, the anterior and posterior spinal arteries, the membrana tectoria and alar ligaments. It also transmits the spinal component of the accessory nerve into the cranial fossa.
In humans, the foramen magnum is farther underneath the head than in the other great apes. Thus, in humans, the neck muscles (including the occipitofrontalis muscle) do not need to be as robust in order to hold the head upright. Comparisons of the position of the foramen magnum in early hominid species are useful to determine how comfortable a particular species was when walking on two limbs (bipedalism) rather than four (quadrupedalism).
|Wikimedia Commons has media related to Foramen magnum.|
- Anatomy figure: 22:4b-10 at Human Anatomy Online, SUNY Downstate Medical Center
- cranialnerves at The Anatomy Lesson by Wesley Norman (Georgetown University) (XI)
- Anatomy diagram: 34257.000-1 at Roche Lexicon - illustrated navigator, Elsevier