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That area of the squamous part, which lies above the highest nuchal lines is named the occipital plane (planum occipitale) and is covered by the occipitalis muscle. That below, termed the nuchal plane , is rough and irregular for the attachment of several muscles.
The squamous part is the curved, expanded plate behind the foramen magnum and is the largest part of the occipital bone. Due to its embryonic derivation from paraxial mesoderm (as opposed to neural crest, from which many other craniofacial bones are derived), it has been posited that "the occipital bone as a whole could be considered as a giant ...
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.
The spinal nerves arise from the spinal column. The top section of the spine is the cervical section, which contains nerves that innervate muscles of the head, neck and thoracic cavity, as well as transmit sensory information to the CNS. The cervical spine section contains seven vertebrae, C-1 through C-7, and eight nerve pairs, C-1 through C-8.
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 clivus (/ ˈ k l aɪ v ə s /, [1] Latin for "slope") or Blumenbach clivus is a part of the occipital bone at the base of the skull, [2] extending anteriorly from the foramen magnum. It is related to the pons and the abducens nerve (CN VI). The term is also used for the clivus ocularis, an unrelated feature of the retina.
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 is also called the median nuchal line. [2]
Anteriorly, the posterior cranial fossa is bounded by the dorsum sellae, posterior aspect of the body of sphenoid bone, and the basilar part of occipital bone/clivus. [2] Laterally, it is bounded by the petrous parts and mastoid parts of the temporal bones, and the lateral parts of occipital bone. [2]