The human skull consists of 22 bones (or 29, including the inner ear bones and hyoid bone) which are mostly connected together by ossified joints, so called sutures. The skull is divided into the braincase (neurocranium) and the facial skeleton (viscerocranium). Its main task is the protection of the most important organ in the human body: the brain.
The brain is almost entirely enclosed by the neurocranium with the exception of the foramen magnum and other foramina at the skull base which serve as entry and exit point for blood vessels and cranial nerves. Also, the skull provides support for all of the facial structures.
|Function||Protection of the brain, supporting of the facial structures|
Cranial (8): occipital, two temporal, two parietal, sphenoid, ethmoid, frontal
Facial (14): vomer, two nasal conchae, two nasal bones, two maxillae, mandible, two palatine, two zygomatic, two lacrimal
|Anterior cranial fossa||
Content: frontal lobe of the cerebral cortex, olfactory bulb, olfactory tract, optic nerve, orbital gyri
Openings: anterior ethmoidal foramen, optic canal, cribriform foramina
|Middle cranial fossa||
Content: trochlear, abducens, oculomotor, ophthalmic, maxillary, mandibular nerves, pituitary gland, internal carotid artery, temporal lobes of the brain
Openings: superior orbital fissure, foramen rotundum, foramen ovale, carotid canal, foramen lacerum, foramen spinosum
|Posterior cranial fossa||
Content: brainstem, facial, vestibulocochlear, glossopharyngeal, vagus, accessory, hypoglossal nerves, internal jugular vein
Openings: foramen magnum, internal acoustic meatus, jugular foramen, anterior condylar (hypoglossal) canal
In this article, all important landmarks and structures within the scull will be described.
- Components and features
- Foramina and contents
- Anterior (frontal) view
- Lateral (side) view
- Posterior view
- Superior view
- Base of the skull (inferior view)
- Foramina summary
Components and features
The braincase consists of the skullcap (calvarium) and the skull base. The skull cap is made up of the pairs of parietal bones and parts of the frontal bone as well as the occipital bone. The most important sutures in the human skull are:
- the coronal suture (between the frontal and parietal bone)
- the sagittal suture (dividing both the parietal bones)
- the lambdoidal suture (running horizontally between the occipital bone and both parietal bones)
These are the three most significant of all 33 sutures which are formed by the human skull bones.
The skull base is the inferior portion of the neurocranium. Looking at it from the inside it can be subdivided into the anterior, middle and posterior cranial fossae. The skull base comprises parts of the frontal, ethmoid, sphenoid, occipital and temporal bones.
The facial skeleton is referred to as all skull bones anteroinferior to the cranial cavity. Prominent representatives are the maxilla (upper jaw) and the mandible (lower jaw). The orbita and the nasal cavity are formed by the zygomatic, nasal, palatine, lacrimal bones, the vomer and the inferior nasal concha (lower turbinate).
Foramina and contents
Most foramina in which relevant nerves and blood vessels pass through are located at the base of the skull. In the following, the most important structures are discussed ordered by their location in the three cranial fossae.
The skull is a complex topic to learn - and also one of the most frequent to pop up in exams! Test yourself with our skull bones quizzes and diagrams, or use them to learn the topic from scratch.
Anterior cranial fossa
The anterior cranial fossa comprises a holey plate at the center, the so called cribriform plate (lamina cribrosa). The approximately 20 cribriform foramina serve as a passageway for the olfactory nerves to the olfactory mucosa in the nasal cavity.
Both the optic nerve and the ophthalmic artery pass through the optic canal which is centrally located on the sphenoid bone. The lesser wing of the sphenoid bone (ala minor) forms the dorsal boundary of the anterior cranial fossa.
Middle cranial fossa
The middle cranial fossa lies slightly deeper than the anterior cranial fossa. The superior orbital fissure which is bounded by the greater and lesser wings of the sphenoid bone contains the trochlear nerve, abducens nerve, oculomotor nerve and ophthalmic nerve. The sella turcica is a depression in the sphenoid bone. In the center of the middle cranial fossa it forms the pituitary fossa in which the pituitary gland sits.
Further important foramina are the:
Posterior cranial fossa
The largest opening in the skull is the foramen magnum. Here the brainstem leaves the skull and becomes the spinal cord. The foramen magnum is situated in the center of the posterior cranial fossa. It is separated from the middle cranial fossa by the dorsum sellae and the upper edge of the petrous bone.
Further important structures are the:
Anterior (frontal) view
The frontal bone is found superiorly while the mandible lies inferiorly, giving the skull an ovoid shape when looked at anteriorly. The frontal bone underlies the forehead; above the orbital cavities, the nasal bridge (which is formed jointly by the two nasal bones), and the frontal process of the zygomatic bone.
The maxilla occupies most of the space in the middle part of the facial skeleton. Together with the nasal bones, they form the boundaries of the anterior nasal aperture. Inferiorly, the mandible and the alveolar processes of the maxilla form the lower part of the anterior skull.
Lateral (side) view
The lateral aspect of the skull can be divided into three regions:
- The facial region
- The temporal region, which we will cover in detail in this section.
- The occipital region
The temporal region is subdivided by the zygomatic arch into the temporal fossa and the infratemporal fossa. The frontal bone, the parietal bone, the greater wing of the sphenoid bone, and the squamous part of the temporal bone meet at the pterion, forming the floor of the temporal fossa. The following videos, articles, and quizzes will cover everything you need to know about the temporal region of the skull, so make sure to check them out!
The posterior aspect of the skull is formed by the parietal bone superolaterally, the temporal bone inferolateral, and the occipital bone centrally. Sometimes this view of the skull is referred to as the occipital view.
From above, we can see the ellipsoid-shaped part of the skull called the calvaria. It is formed by four bones; the frontal bone, the two parietal bones, and the occipital bone. These bones articulate through three sutures:
- The coronal suture: between the frontal and parietal bones.
- The lambdoid suture: between the occipital and parietal bones.
- The sagittal suture: between the two parietal bones.
To better understand the anatomy of this region, don’t forget to watch our corresponding video tutorial, read our articles, and further strengthen your knowledge with our specially designed quiz that covers everything you need to know about the skull anatomy.
Base of the skull (inferior view)
The base of the skull extends from the superior nuchal lines of the occipital bones posteriorly to the upper incisors teeth anteriorly. This aspect of the skull contains a lot of important structures, including the largest skull foramen; the foramen magnum. We can divide this part of the skull into five, to make it easier to study:
- Anterior part: the hard palate and the upper jaw.
- Middle part: the sphenoid bone, petrous processes of the temporal bones, and the basilar part of the occipital bone.
- Lateral parts: the zygomatic arches, mandibular fossae, tympanic plates and the styloid and mastoid processes.
- Posterior part: the occipital bone.
- Cribriform plate - olfactory nerves
- Optic canal - optic nerve, opthalmic artery
- Superior orbital fissure - trochlear, abducens, oculomotor, and ophthalmic nerves
- Foramen rotundum - maxillary nerve
- Foramen ovale - mandibular nerve
- Carotid canal - internal carotid artery
- Foramen magnum - brainstem
- Internal acoustic meatus - facial and vestibulocochlear nerves
- Jugular foramen - internal jugular vein, glossopharyngeal nerve, vagus nerve, accessory nerve
- Hypoglossal canal - hypoglossal nerve)