The basilar part of the occipital bone is that part which forms the floor of the cranial cavity, housing the brain. The basilar part meets the vomer and sphenoid bone in the anterior, and the temporal bones at the sides. The most apparent characteristic of the basilar part of the occipital bone is the large foramen magnum, a round opening in the bone which allows the spinal cord to pass through the skull. Research Basilar Part
The foramen lacerum is a small opening in the skull near the point of articulation between the sphenoid, occipital (basilar part) and temporal bones. This opening admits the inner carotid artery into the skull from below. Research Foramen Lacerum
The jugular fossa is the surface of the skull where the temporal and occipital bones meet. It features the jugular foramen, an opening in the skull formed at the juncture of the occipital and temporal bones. The jugular foramen admits the internal jugular vein and five nerves (three cranial, the glossopharyngeal, vagus, and accessory). Research Jugular Fossa
The lambdoid suture joins the two parietal bones to the occipital bone in the back of the skull. The intersection of the sagittal suture, joining the two parietal bones together, and the
lambdoid suture forms a tripartite shape, resembling the Greek letter 'lambda,' and giving the suture its shape. The lower ends of the lambdoid suture extend to the mastoid processes of the temporal bones, joining them to the occipital bone. Research Lambdoid Suture
The occipital bone forms the back of the skull and the cranial base. It is joined to the two parietal bones and to the mastoid processes of the temporal bones on the side by the lambdoid suture. At the base of the occipital bone, at the basilar parts, the
occipital bone is attached to the sphenoid bone. The occipital bone features a significant bump, or external occipital protuberance, in the center of the back of the skull, while the Nuchal line defines the cusp at which the occipital bone curves under to the base. The large opening, or foramen magnum, in the
occipital bone can be seen in the inferior view of the skull, and allows the nerves of the upper spinal cord to pass through the skull between the brain and the rest of the spinal cord. Research Occipital Bone
The parietal bones are two of the flat cranial bones that form the roof and upper sides of the calvarium. The parietal bones are attached to each other by the sagittal suture which runs longitudinally along the roof of the skull, and both of the parietal bones are attached to the frontal bone by the coronal suture and to the occipital bone in back by the lambdoid suture. The intersection of the two parietal bones and the occipital bone is called the 'lambda' after its resemblance to that Greek letter. The sphenoid and temporal bones on each side of the skull are attached to the lower edge of the parietal bone by the squamous suture. Two ridges traverse the side of the parietal bone, extending to the frontal bone and forming a depression with the temporal fossa. These two ridges are called the superior and inferior temporal lines. Research Parietal Bones
The skull is one of the principle groups of bones in the human anatomy. The skull consists of twenty-six bones: eight bones form the skull, which houses the brain and ear ossicles, plus fourteen facial bones, which form the front of the face, jaw, nose, orbits, and the roof of the mouth, three more bones make up the inner ear ossicles, and one more, the hyoid bone, is in the neck and is attached to the temporal bone by ligaments and anchors the tongue. The skull also contains a dental arcade of teeth, which are technically not bones, though they do share some of the compositional characteristics of bonetissue. Children may grow twenty deciduousteeth, which will eventually fall out and be replaced by the permanent teeth.
The bones of the skull include the frontal bone, the occipital bone, two parietal bones, and two temporal bones. The lower rearmost part of each temporal bone is called the mastoid process, but because it is separated from the temporal bone, proper, by a suture, it is often considered a separate bone. The sphenoid bone forms the central base of the skull and spans the skull from side to side, the greater wings forming side plates of the skull. The sections of the ethmoid bone are positioned between the orbits, forming the walls and roof of the nasal cavity, while the three middle ear ossicles (stapes, malleus, and incus) are located within the temporal bones on each side of the skull. The U-shaped hyoid bone is found in the neck, and is attached by ligaments to the temporal bones. In the face, the two maxillary bones form much of the orbits, nose, upper jaw and roof of the mouth, while the zygomatic bones form the cheeks. The lachrymal bones are located on the inner sides of the orbits and are attached to the ethmoid bone and maxillary bones. Within the nasal cavity, the vomer is located in the low center and forms the thin flat bone of the nasalseptum, while two inferior urbinates form the lower sides of the cavity and two palate bones form the floor of the nasal cavity as well as the roof of the mouth.
The mandible is the only movable part of the skull, forming the lower jaw and mounting the teeth. The bones of the skull, with the exception of the mandible, are held together by very thin sutures, or seams, in which the periosteum of the individual bones interweave with each other, and are cemented by a fibrous, connective tissue. In the newborn, these sutures are not yet developed, with the bones being attached by cartilage which ossifies over time as the bones of the skull fuse together. The most evident external sutures of the skull include the coronal suture, joining the frontal bone and parietal bone, the sagittal suture, joining the parietal bones to each other, the lambdoid suture, joining the occipital and parietal bones, the squamous suture, joining the temporal and sphenoid bones to the parietal bone on each side of the skull.
The pterion is the short segment of the suture joining the squamous and parietal bones. The bones of the skull also feature a number of sinuses and foramina. Four pairs of sinuses flank the nasal cavity. Two are found in the maxillary bone, and are called maxillary sinuses. The sphenoid bone forms two paranasal sinuses called the sphenoids, and the ethmoid bone forms the two paranasal sinuses called ethmoids. Additionally, the frontal sinuses are located in the frontal bone just behind the roof of each orbit. The foramen magnum is a large, round opening in the base of the skull which admits the spinal cord, while at the base of each temporal bone is the external auditory meatus, which serve as the auditory canals. Just above each orbit in the frontal bone is a small notch or hole, called a supraorbital foramen, and just below each orbit, in the maxillary bone, is an infraorbital foramen. Two more openings, one on each side of the skull, can be found in the frontal processes of the zygomatic bones, and are called zygomatofacial foramina.
On each side of the mandible, just below the lower canines, are the mental foramina. These facial foramina serve to admit blood vessels and nerves through and into the bone. The teeth are mounted in the maxillary bone and the mandible, and are brought together for chewing by the hinge-like motion of the mandible. An average adult will have thirty-two teeth, evenly arrayed on the maxilla and mandible. Research Skull
The styloglossus is a small and short muscle. One is located on each side of the tongue. The muscles link the sides of the tongue to the base of the skull via the bony styloid process, extending downward from the temporal bones. Contraction of these two muscles pulls the tongue back and up. The genioglossus, the styloglossus, the palatoglossus and the hyoglossus work together to move the tongue. Research Styloglossus
At the base of each temporal bone is a thorn-like protrusion called the
styloid process. Located near the articulation of the occipital and temporal bones, this process connects with muscular and ligamentous tissue which attaches to the hyoid bone (the only bone in the skeleton not in direct contact with another bone). Research Styloid Process
The two temporal bones form the lower sides of the skull and part of the cranial floor. They also protect the organs responsible for hearing and equilibrium. A canal (called the external auditory meatus) passes through the lower part of the temporal bone and admits the earcanal. The temporal bone features the zygomatic process, which is a protrusion from the back part of the temporal bone which loops forward to meet the zygomatic bone to form the zygomatic arch. At the middle of this zygomatic arch is a small protrusion downward, called the articular tubercle. The front part of the temporal bone, forming the side of the skull slightly above and to the front of the ear, joins the greater wing of the sphenoid bone to compose the temple region of the skull. This frontal section of the temporal bone is called the squamous part, as it is also joined to the parietal bone at the squamous suture. The rearmost part of the temporal bone is referred to as the mastoid process. Research Temporal Bones
The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
Abbreviations
Research Basilar Part
