External occipital protuberance

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(Redirected from Inion)

External occipital protuberance
Human skull lateral view. External occipital protuberance shown in red.
Occipital bone seen from below. Outer surface. (External occipital protuberance visible at top center.)
Details
Identifiers
Latin	protuberantia occipitalis externa
TA98	A02.1.04.022
TA2	568
FMA	75752
Anatomical terminology [edit on Wikidata]

Near the middle of the squamous part of occipital bone is the external occipital protuberance, the highest point of which is referred to as the inion. The inion is the most prominent projection of the protuberance which is located at the posterioinferior (rear lower) part of the human skull. The nuchal ligament and trapezius muscle attach to it.

The inion (ἰνίον, iníon, Greek for the occipital bone) is used as a landmark in the 10-20 system in electroencephalography (EEG) recording. Extending laterally from it on either side is the superior nuchal line, and above it is the faintly marked highest nuchal line.

A study of 16th-century Anatolian remains showed that the external occipital protuberance statistically tends to be less pronounced in female remains.^[1]

Additional images

Position of external occipital protuberance (shown in red). Animation.

References

This article incorporates text in the public domain from page 185 of the 20th edition of Gray's Anatomy (1918)

^ Gülekon, IN (2003). "The external occipital protuberance: can it be used as a criterion in the determination of sex?". J Forensic Sci. 48 (3): 513–6. doi:10.1520/JFS2002183. PMID 12762519.

External links

Wikimedia Commons has media related to External occipital protuberance.

"Anatomy diagram: 34257.000-1". Roche Lexicon - illustrated navigator. Elsevier. Archived from the original on 2012-07-22.
Bones of the Skull (Lateral View) Upstate Medical University

Neurocranium of the skull

Occipital

Squamous part	external Inion/External occipital protuberance Occipital bun External occipital crest Nuchal lines Suprainiac fossa planes Occipital Nuchal internal Cruciform eminence Internal occipital protuberance Internal occipital crest Groove for transverse sinus
Lateral parts	Condyle Condyloid fossa Condylar canal Hypoglossal canal jugular Jugular process Jugular tubercle
Basilar part	Pharyngeal tubercle Clivus
Other	Foramen magnum Basion Opisthion

Parietal

Frontal

Squamous part	Frontal suture Frontal eminence external Superciliary arches Glabella foramina Supraorbital foramen Brow ridge Foramen cecum Zygomatic process internal Sagittal sulcus Frontal crest
Orbital part	Ethmoidal notch Fossa for lacrimal gland Trochlear fovea Frontal sinus Frontonasal duct

Temporal

Squamous part	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 (Aditus)
Petrous part	Carotid canal Facial canal Hiatus Internal auditory meatus Cochlear aqueduct 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 of 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 Supreme nasal concha Superior nasal concha Superior meatus Middle nasal concha Middle meatus
Labyrinth	Ethmoid sinus ethmoidal foramina Posterior Anterior

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References

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