CorpusHuman Anatomy

Skull — Lateral View

Left lateral view (norma lateralis), Frankfort plane horizontal

Left lateral view (norma lateralis) of an adult skull, face to the left, oriented in the Frankfort horizontal plane (porion, the top of the external acoustic meatus, level with orbitale, the lowest point of the orbital margin). Each bone is a separate, tinted region: the vault (neurocranium) is formed here by the frontal, parietal, temporal and occipital bones and the greater wing of the sphenoid; the facial skeleton (viscerocranium) by the nasal, maxilla, zygomatic and mandible, with the lacrimal bone and the orbital plate of the ethmoid visible on the medial wall of the orbit.

Serrated lines are sutures (coronal, squamous and lambdoid are individually selectable; the smaller sutures are grouped). The dashed ring marks the pterion; the animated red line beneath it is the middle meningeal artery running on the inner surface of the skull, the reason a blow to the temple can cause an extradural haematoma. Hover or tap any region for details, or follow the guided steps.

Step-by-step

  1. The cranial vault

    The neurocranium has 8 bones: frontal, occipital, sphenoid and ethmoid (single) and the paired parietal and temporal bones. From the side you see the frontal bone in front, the large parietal bone forming the roof and side, the occipital bone behind, and below them the squamous temporal bone and the greater wing of the sphenoid. The vault bones ossify in membrane (intramembranous ossification), whereas most of the skull base forms in cartilage.

  2. Sutures

    Sutures are fibrous joints (synarthroses) that let the vault grow and, at birth, mould during delivery. The coronal suture separates frontal and parietal bones, the lambdoid suture separates parietal and occipital bones, and the arched squamous suture joins the temporal squama to the parietal. The sagittal suture (between the parietals, on top) is not seen in this view. Smaller sutures surround the greater wing of the sphenoid, the zygomatic bone and the nasal bones.

  3. Pterion — the danger point

    The pterion is the H-shaped junction where the frontal, parietal, sphenoid (greater wing) and temporal bones meet, about two finger-breadths (≈4 cm) above the midpoint of the zygomatic arch and a thumb's breadth (≈3 cm) behind the frontozygomatic suture. It is the thinnest part of the lateral skull, and the anterior (frontal) branch of the middle meningeal artery runs just deep to it. A fracture here can tear the artery, producing an extradural (epidural) haematoma — classically a lucid interval followed by rapid deterioration and a biconvex (lentiform) bleed on CT.

  4. Temporal bone landmarks

    Behind the arch, the temporal bone shows the external acoustic meatus, the mastoid process behind and below it, and the slender styloid process pointing forwards and downwards. The facial nerve leaves the skull through the stylomastoid foramen between styloid and mastoid. The zygomatic process of the temporal bone joins the zygomatic bone to complete the zygomatic arch, beneath which the mandibular condyle sits in the mandibular fossa.

  5. Walls of the orbit

    Seven bones build the orbit: roof — frontal (and lesser wing of sphenoid); lateral wall — zygomatic and greater wing of sphenoid; floor — maxilla (with zygomatic and palatine); medial wall — frontal process of maxilla, lacrimal, orbital plate of ethmoid and body of sphenoid. The paper-thin ethmoid plate (lamina papyracea) lets ethmoid sinusitis spread into the orbit (orbital cellulitis), and the thin floor is the usual site of a blow-out fracture. The lacrimal fossa houses the lacrimal sac.

  6. Facial skeleton

    The nasal bones form the bridge of the nose; the maxillae carry the upper teeth, form most of the cheek, the orbital floor and the hard palate, and contain the largest paranasal sinus. The zygomatic bone forms the cheek prominence; a zygomaticomaxillary complex ("tripod") fracture separates it at its sutures with the frontal, temporal and maxillary bones. The supraorbital, infraorbital and mental foramina lie roughly in one vertical line and transmit the terminal branches of V1, V2 and V3.

  7. Mandible and temporomandibular joint

    The mandible is the only freely movable bone of the skull. Its condyle articulates with the mandibular fossa of the temporal bone at the temporomandibular joint, a synovial joint divided by an articular disc into an upper gliding (translation) and a lower hinge (rotation) compartment. Temporalis inserts on the coronoid process, which passes deep to the zygomatic arch. In wide yawning the condyle can dislocate anteriorly over the articular tubercle.

Labelled parts