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The nuchal lines are four curved lines on the external surface of the occipital bone: The upper, often faintly marked, is named the highest nuchal line, but is sometimes referred to as the Mempin line or linea suprema, and it attaches to the epicranial aponeurosis. Below the highest nuchal line is the superior nuchal line.
Running across the outside of the occipital bone are three curved lines and one line (the medial line) that runs down to the foramen magnum. These are known as the nuchal lines which give attachment to various ligaments and muscles. They are named as the highest, superior and inferior nuchal lines.
Running from the middle of this line across either half of the nuchal plane is the inferior nuchal line. Several muscles are attached to the outer surface of the squamous part, thus the superior nuchal line gives origin to the occipitalis and trapezius muscles, and insertion to the sternocleidomastoid and splenius capitis muscles.
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.
The external occipital crest is part of the external surface of the squamous part of the occipital bone.It is a ridge along the midline, beginning at the external occipital protuberance and descending to the foramen magnum, that gives attachment to the nuchal ligament. [1]
It begins as a plexus at the posterior aspect of the scalp from the external occipital protuberance and superior nuchal line to the back part of the vertex of the skull. It pierces the cranial attachment of the trapezius and, dipping into the venous plexus of the suboccipital triangle, joins the deep cervical vein and the vertebral vein.
The condyles are oval or reniform (kidney-shaped) in shape, and their anterior extremities, directed forward and medialward, are closer together than their posterior, and encroach on the basilar portion of the bone; the posterior extremities extend back to the level of the middle of the foramen magnum.
Its superior attachment is onto the lateral portion of [2] the external surface of the occipital bone between the superior nuchal line and inferior nuchal line. [1] [2] Its superior attachment is situated lateral to that of the semispinalis capitis muscle, and overlaps the attachment of the rectus capitis posterior major muscle. [1]