In anatomy, the atlas (C1) is the most superior (first) cervical vertebra of the spine and is located in the neck.
The occipital bone is a cranial dermal bone and the main bone of the occiput. It is trapezoidal in shape and curved on itself like a shallow dish. The occipital bone overlies the occipital lobes of the cerebrum. At the base of the skull in the occipital bone, there is a large oval opening called the foramen magnum, which allows the passage of the spinal cord.
The foramen lacerum is a triangular hole in the base of skull. It is located between the sphenoid bone, the apex of the petrous part of the temporal bone, and the basilar part of the occipital bone.
The mylohyoid muscle or diaphragma oris is a paired muscle of the neck. It runs from the mandible to the hyoid bone, forming the floor of the oral cavity of the mouth. It is named after its two attachments near the molar teeth. It forms the floor of the submental triangle. It elevates the hyoid bone and the tongue, important during swallowing and speaking.
The longus capitis muscle is broad and thick above, narrow below, and arises by four tendinous slips, from the anterior tubercles of the transverse processes of the third, fourth, fifth, and sixth cervical vertebræ, and ascends, converging toward its fellow of the opposite side, to be inserted into the inferior surface of the basilar part of the occipital bone.
The rectus capitis posterior major is a muscle in the upper back part of the neck. It is one of the suboccipital muscles. Its inferior attachment is at the spinous process of the axis ; its superior attachment is onto the outer surface of the occipital bone on and around the side part of the inferior nuchal line. The muscle is innervated by the suboccipital nerve. The muscle acts to extend the head and rorate the head to its side.
The rectus capitis posterior minor is a muscle in the upper back part of the neck. It is one of the suboccipital muscles. Its inferior attachment is at the posterior arch of atlas; its superior attachment is onto the occipital bone at and below the inferior nuchal line. The muscle is innervated by the suboccipital nerve. The muscle acts as a weak extensor of the head.
The middle pharyngeal constrictor is a fan-shaped muscle located in the neck. It is one of three pharyngeal constrictor muscles. It is smaller than the inferior pharyngeal constrictor muscle.
The superior pharyngeal constrictor muscle is a quadrilateral muscle of the pharynx. It is the uppermost and thinnest of the three pharyngeal constrictors.
The mylohyoid line is a bony ridge on the internal surface of the mandible. It runs posterosuperiorly. It is the site of origin of the mylohyoid muscle, the superior pharyngeal constrictor muscle, and the pterygomandibular raphe.
The nuchal lines are four curved lines on the external surface of the occipital bone:
The pterygoid processes of the sphenoid, one on either side, descend perpendicularly from the regions where the body and the greater wings of the sphenoid bone unite.
The temporal styloid process is a slender bony process of the temporal bone extending downward and forward from the undersurface of the temporal bone just below the ear. The styloid process gives attachments to several muscles, and ligaments.
The basilar part of the occipital bone extends forward and upward from the foramen magnum, and presents in front an area more or less quadrilateral in outline.
The lateral parts of the occipital bone are situated at the sides of the foramen magnum; on their under surfaces are the condyles for articulation with the superior facets of the atlas.
The jugular tubercle is a rounded prominence/oval elevation upon the superior surface of the occipital condyle at the junction of the basilar part and lateral part of the occipital bone, just medial to the jugular foramen on either side of the foramen magnum.
The pterygomandibular raphe is a thin tendinous band of buccopharyngeal fascia. It is attached superiorly to the pterygoid hamulus of the medial pterygoid plate, and inferiorly to the posterior end of the mylohyoid line of the mandible. It gives attachment to the buccinator muscle, and the superior pharyngeal constrictor muscle (behind).
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 clivus or Blumenbach clivus is a part of the occipital bone at the base of the skull. It is a shallow depression behind the dorsum sellae of the sphenoid bone. It slopes gradually to the anterior part of the basilar occipital bone at its junction with the sphenoid bone. It extends to the foramen magnum. It is related to the pons and the abducens nerve.
The pharyngobasilar fascia is a fascia of the pharynx. It is situated between the mucous and muscular layers of the pharynx. It is formed as a thickening of the pharyngeal mucosa superior to the superior pharyngeal constrictor muscle. It attaches to the basilar part of occipital bone, the petrous part of the temporal bone, the medial pterygoid plate, and the pterygomandibular raphe. It diminishes in thickness inferiorly. Posteriorly, it is reinforced by the pharyngeal raphe. It reinforces the pharyngeal wall where muscle is deficient.
