Foramen magnum

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Bone: Foramen magnum
Occipital bone. Inner surface.
Gray's	subject #31 129
MeSH	Foramen+Magnum

In anatomy, in the occipital bone, the foramen magnum (Latin: 'great hole') is one of the several oval or circular apertures in the base of the skull (the foramina), through which the medulla oblongata (an extension of the spinal cord) enters and exits the skull vault.

Apart from the transmission of the medulla oblongata and its membranes, the foramen magnum transmits the Spinal Accessory nerve, vertebral arteries, the anterior and posterior spinal arteries, the membrana tectoria and alar ligaments.

Contents 1 Importance 2 Additional images 3 See also 4 External links

[edit] Importance

In humans, the foramen magnum is farther underneath the head than in great apes. Thus, in humans, the neck muscles 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 (bipedality) rather than four.

The foramen magnum is the border line above which is the brain, and below, the spinal cord.

[edit] Additional images

Occipital bone. Outer surface.

Base of skull. Inferior surface.

Base of the skull. Upper surface.

Human brain dura mater (reflections)

[edit] See also

• Posterior cranial fossa

[edit] External links

• SUNY Figs 22:4b-10
• Norman/Georgetown cranialnerves (XI)
• Roche Lexicon - illustrated navigator, at Elsevier 34257.000-1

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant.

v • d • e Bones of head and neck: the cranium of the skull Occipital Squama external (Inion/External occipital protuberance, Nuchal lines) - planes (Occipital, Nuchal) - internal (Cruciform eminence, Internal occipital protuberance, Sagittal sulcus, Internal occipital crest) Lateral parts Condyle (Condyloid fossa, Condylar canal) - Hypoglossal canal - jugular (Jugular process, Jugular tubercle) Basilar part Pharyngeal tubercle Other Foramen magnum Parietal Parietal eminence - Temporal line - Parietal foramen Frontal Squama Frontal suture - Frontal eminence - external (Superciliary arches, Glabella) - foramina (Supraorbital, Cecum) - Zygomatic process - internal (Sagittal sulcus, Frontal crest) Orbital part Ethmoidal notch - Lacrimal fossa - Trochlear fovea - Frontal sinus - Frontonasal duct Temporal Squama Articular tubercle - Suprameatal triangle - Mandibular fossa - Petrotympanic fissure - Zygomatic process Mastoid part Mastoid foramen - Mastoid process (Mastoid cells) - Mastoid notch - Occipital groove - Sigmoid sulcus - Mastoid antrum (Entrance) Petrous part Carotid canal - Facial canal (Hiatus) - Internal auditory meatus - Aqueduct of cochlea - Stylomastoid foramen fossae (Subarcuate fossa, Jugular fossa) - canaliculi (Inferior tympanic, Mastoid) - Styloid process - Petrosquamous suture (note: ossicles in petrous part, but not part of temporal bone) Tympanic part Suprameatal spine Sphenoid Surfaces Superior surface: Sella turcica (Dorsum sellae, Tuberculum sellae, Hypophysial fossa, Posterior clinoid processes) - Ethmoidal spine - Chiasmatic groove - Middle clinoid process - Petrosal process - Clivus Lateral surface: Carotid groove - Sphenoidal lingula Anterior surface: Sphenoidal sinuses Great wings foramina (Rotundum, Ovale, Vesalii, Spinosum) - Spine - Infratemporal crest - Sulcus for auditory tube Small wings Superior orbital fissure - Anterior clinoid process - Optic canal Pterygoid processes fossae (Pterygoid, Scaphoid) - pterygoid plates (Lateral, Medial) - Pterygoid canal - Hamulus Other Body - Sphenoidal conchae Ethmoid Plates Cribriform plate (Crista galli, Olfactory foramina) - Perpendicular plate Surfaces Lateral surface Orbital lamina - Uncinate process Medial surface Superior nasal concha - Superior meatus - Middle nasal concha - Middle meatus Labyrinth Ethmoid sinus - ethmoidal foramina (Posterior, Anterior)

v • d • e Foramina of the skull (and canals, fissures, meati, and hiati) Anterior cranial fossa to Orbit: ethmoidal foramina (anterior, posterior) to Nasal cavity: olfactory foramina (CN-I) - foramen cecum Middle cranial fossa to Orbit: optic canal (CN-II) - superior orbital fissure (CN-III,IV,V1,VI) to Pterygopalatine fossa: foramen rotundum (CN-V2) - pterygoid canal to Infratemporal fossa: foramen ovale (CN-V3) - foramen spinosum/carotid canal other: foramen lacerum - hiatus for greater petrosal nerve - hiatus for lesser petrosal nerve - sphenoidal emissary foramen Posterior cranial fossa internal auditory meatus/facial canal/stylomastoid foramen (CN-VII,VIII) - jugular foramen (CN-IX,X,XI) - foramen magnum (CN-XI) - hypoglossal canal (CN-XII) - condylar canal - mastoid foramen Orbit to Nasal cavity: nasolacrimal canal to Face: supraorbital (notch, foramen) - infraorbital (foramen, groove) - zygomatic foramen (-facial, -temporal) to Pterygopalatine fossa: inferior orbital fissure Pterygopalatine fossa to Nasal cavity: sphenopalatine foramen to Oral cavity: greater palatine canal/greater palatine foramen - lesser palatine canals/lesser palatine foramina to Infratemporal fossa: pterygomaxillary fissure to Nasopharynx: palatovaginal canal Nasal cavity to Oral cavity: incisive canals - incisive foramen Other external acoustic meatus - mandibular foramen - mental foramen - parietal foramen - petrotympanic fissure - semilunar hiatus