11.3
Cranial Bones: Superior and Posterior View
The superior view of the cranium shows the frontal and paired parietal bones.
The frontal bone is the single bone that forms the forehead. At its ante…
The skull's superior view is dominated by the frontal and parietal bones.
The frontal bone forms the forehead with thick supraorbital margins and foramina lying under the eyebrows. In between the margins is the glabella, a smooth region.
The frontal bone meets the paired parietal bones at the coronal suture. These paired parietal bones, covering the skull's top and sides, are joined by the sagittal suture.
Forming the posterior part and most of the base of the skull is the occipital bone. It connects to the parietal bones via the lambdoid suture. A midline projection, the external occipital protuberance, secures a large elastic ligament — ligamentum nuchae, which helps support the head.
The superior and inferior nuchal lines are laterally extending ridges that allow muscle attachment.
At the base, through the opening called the foramen magnum, the brain connects with the spinal cord.
On each side of the foramen, the occipital condyles, curved projections, articulate with the first vertebra.
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Q1: What bones form the superior view of the skull?
The superior view is dominated by the frontal bone and paired parietal bones. The frontal bone forms the forehead, while the parietal bones cover the skull's top and sides. These bones meet at the coronal suture anteriorly and the sagittal suture where the parietal bones join at the midline.
Q2: What is the glabella and where is it located?
The glabella is a smooth, slightly depressed region on the frontal bone located between the eyebrows at the anterior midline. It lies between the supraorbital margins, which are thickened areas that form the brow ridges. The glabella serves as a landmark on the forehead's surface.
Q3: How do the occipital condyles support the skull?
The occipital condyles are curved projections located on either side of the foramen magnum on the occipital bone's base. These oval-shaped structures articulate with the first cervical vertebra, forming joints that support the skull on top of the vertebral column and allow head movement.
Q4: What is the foramen magnum and what passes through it?
The foramen magnum is a large opening at the base of the occipital bone through which the spinal cord exits the skull and connects with the brain. This opening is essential for communication between the cranial cavity and the vertebral canal, allowing neural tissue to pass through.
Q5: What structures attach to the external occipital protuberance?
The external occipital protuberance is a midline projection on the posterior occipital bone that serves as an attachment site for the ligamentum nuchae, a large elastic ligament of the posterior neck. This ligament helps support the head and connects to the cervical vertebrae.
Q6: What are the nuchal lines and their anatomical significance?
The superior and inferior nuchal lines are laterally extending ridges on the occipital bone that mark muscle attachment sites on the posterior skull. The superior nuchal line represents the most superior point where neck muscles attach, with only the scalp covering the skull above these lines.
Q7: Where is the supraorbital foramen located and what does it transmit?
The supraorbital foramen is an opening located near the middle of the supraorbital margin of the frontal bone, just above the eyebrow. It provides passage for a sensory nerve that supplies the forehead, making it an important anatomical landmark for nerve distribution.