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The occipital condyles are undersurface protuberances of the occipital bone in vertebrates, which function in articulation with the superior facets of the atlas vertebra.. 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 ...
The basilar part of the occipital bone (also basioccipital) extends forward and upward from the foramen magnum, and presents in front an area more or less quadrilateral in outline. In the young skull, this area is rough and uneven, and is joined to the body of the sphenoid by a plate of cartilage.
The singular basioccipital is the rear lower part of the braincase, below the foramen magnum. It is homologous to the basilar part of the occipital bone . In the ancestral tetrapod, the basioccipital makes up most of a large central knob-like surface, the occipital condyle, which articulates with the vertebrae as a ball-and-socket joint .
Due to its many attachments and features, the occipital bone is described in terms of separate parts. From its front to the back is the basilar part, also called the basioccipital, at the sides of the foramen magnum are the lateral parts, also called the exoccipitals, and the back is named as the squamous part.
The under surface of the jugular process is rough, and gives attachment to the Rectus capitis lateralis muscle and the lateral atlanto-occipital ligament; from this surface an eminence, the paramastoid process, sometimes projects downward, and may be of sufficient length to reach, and articulate with, the transverse process of the atlas.
Resection of the rectus capitis posterior major and minor muscles reveals the bony recess leading to the condylar canal, which is situated posterior and lateral to the occipital condyle. It is immediately superior to the extradural vertebral artery , which makes a loop above the posterior C1 ring to enter the foramen magnum .
The occipitalis muscle (occipital belly) is a muscle which covers parts of the skull. Some sources consider the occipital muscle to be a distinct muscle. However, Terminologia Anatomica currently classifies it as part of the occipitofrontalis muscle along with the frontalis muscle. The occipitalis muscle is thin and quadrilateral in form.
To it is attached, the splenius capitis muscle, the trapezius muscle, [1] and the occipitalis. [ 2 ] From the external occipital protuberance a ridge or crest, the external occipital crest also called the median nuchal line , often faintly marked, descends to the foramen magnum , and affords attachment to the nuchal ligament .