The frontal, ethmoid, and sphenoid bones derive from the neural crest, while the parietal and occipital bones originate from the mesoderm. The critical anatomic landmarks of each fossa are listed below.Įmbryologically, the skull derives from ectodermal neural crest and mesoderm. Finally, the posterior cranial fossa forms from the occipital bone and two temporal bones. The middle cranial fossa forms from the sphenoid bone and two temporal bones. The anterior cranial fossa forms from the frontal bone, the sphenoid bone, and the ethmoid bone. There are three cranial fossae with various structural landmarks. The occipital bone is the most posterior aspect of the skull. The mastoid is a bony prominence that lies posterior to the auricle and has an associated sinus.

The petrous portion houses the inner ear. The temporal bones subdivide into petrous, squamous, zygomatic, and mastoid parts. The bregma is the junction of the coronal and sagittal sutures, and lambda is the junction of the lambdoid and sagittal sutures. The frontal sinuses lie deep to the brow ridges. It lies superior to the nasion and between the superciliary ridges. The glabella is a key midline landmark of the frontal bone. It is composed of the sphenoid and ethmoid bones (which have their associated air sinuses) and parts of the frontal, temporal, and occipital bones.Īnteriorly, the frontal bone forms the superior aspect of the orbits. Finally, the skull base allows the passage of various neurovascular structures. The asterion is the articulation of the parietal, temporal, and occipital bones. The pterion is the articulation of the frontal, parietal, temporal, and sphenoid bones just superior to the pinna. The sagittal suture lies along an anterior-posterior axis and is the articulation of the two parietal bones. The parietal bones articulate with the temporal bones inferiorly via the squamosal sutures and the occipital bone posteriorly via the lambdoid suture.

The coronal suture is the transverse mid-anterior junction of the frontal bone and the two parietal bones. It is composed of the frontal bone, parietal bones, temporal bones, and occipital bone. The calvaria, the uppermost part of the skull, protects the cerebral cortex, cerebellum, and orbital contents. In addition, it supports the muscles of the face and scalp by providing muscular and tendinous attachments, protects neurovascular structures, and houses various sinuses to accommodate increases in pressure. The skull will harden and fuse through development to protect its inner contents: the cerebrum, cerebellum, brainstem, and orbits. The function of the skull is both structurally supportive and protective. The skull features numerous foramina through which pass the cranial nerves, the spinal cord, arteries, and veins.The skull consists of 22 bones in most adult specimens, which come together via cranial sutures. The temporomandibular joint connects the lower jaw to the temporal bone and enables movement for speech and mastication. The viscerocranium consists of the unpaired mandible and vomer and the paired zygomatic bones, inferior nasal conchae, lacrimal bones, nasal bones, maxillary bones, and palatine bones. The fontanelles, which comprise the anterior, posterior, and the paired mastoid and sphenoid fontanelles, close between the age of 2 months and 18 months. The bones of the infant neurocranium are not fused but are instead connected by membranous gaps between the bone plates called fontanelles, which enable flexion of the skull to facilitate passage through the birth canal and accommodate the rapidly growing brain.

The cranial bones are connected by fibrous joints called sutures. The neurocranium consists of the frontal, the ethmoid, the sphenoid, the occipital, and the paired temporal and parietal bones. The human skull consists of approximately 30 bones, which can be anatomically divided into the cranial bones ( neurocranium) and the facial bones ( viscerocranium).

Skull bones