The pterion is the region where the frontal, parietal, temporal, and sphenoid bones join. It is located on the side of the

skull The skull, or cranium, is typically a bony enclosure around the brain of a vertebrate. In some fish, and amphibians, the skull is of cartilage. The skull is at the head end of the vertebrate. In the human, the skull comprises two prominent ...

, just behind the

temple A temple (from the Latin ) is a place of worship, a building used for spiritual rituals and activities such as prayer and sacrifice. By convention, the specially built places of worship of some religions are commonly called "temples" in Engli ...

. It is also considered to be the weakest part of the skull, which makes it clinically significant, as if there is a

fracture Fracture is the appearance of a crack or complete separation of an object or material into two or more pieces under the action of stress (mechanics), stress. The fracture of a solid usually occurs due to the development of certain displacemen ...

around the pterion it could be accompanied by an epidural hematoma.

Structure

The pterion is located in the

temporal fossa The temporal fossa is a fossa (shallow depression) on the side of the skull bounded by the temporal lines above, and the zygomatic arch below. Its floor is formed by the outer surfaces of four bones of the skull. The fossa is filled by the te ...

, approximately 2.6 cm behind and 1.3 cm above the posterolateral margin of the frontozygomatic suture. It is the junction between four bones: * the

parietal bone The parietal bones ( ) are two bones in the skull which, when joined at a fibrous joint known as a cranial suture, form the sides and roof of the neurocranium. In humans, each bone is roughly quadrilateral in form, and has two surfaces, four bord ...

. * the squamous part of

temporal bone The temporal bone is a paired bone situated at the sides and base of the skull, lateral to the temporal lobe of the cerebral cortex. The temporal bones are overlaid by the sides of the head known as the temples where four of the cranial bone ...

. * the greater wing of

sphenoid bone The sphenoid bone is an unpaired bone of the neurocranium. It is situated in the middle of the skull towards the front, in front of the basilar part of occipital bone, basilar part of the occipital bone. The sphenoid bone is one of the seven bon ...

. * the

frontal bone In the human skull, the frontal bone or sincipital bone is an unpaired bone which consists of two portions.'' Gray's Anatomy'' (1918) These are the vertically oriented squamous part, and the horizontally oriented orbital part, making up the bo ...

. These bones are typically joined by five

cranial sutures In anatomy, fibrous joints are joints connected by Fibrous connective tissue, fibrous tissue, consisting mainly of collagen. These are fixed joints where bones are united by a layer of white fibrous tissue of varying thickness. In the skull, the ...

: * the sphenoparietal suture joins the sphenoid and parietal bones. * the

coronal suture The coronal suture is a dense, fibrous connective tissue joint that separates the two parietal bones from the frontal bone of the skull. Structure The coronal suture lies between the paired parietal bones and the frontal bone of the skull ...

joins the frontal bone to the sphenoid and parietal bones. * the squamous suture joins the temporal bone to the sphenoid and parietal bones. * the

sphenofrontal suture The sphenofrontal suture is the cranial suture between the sphenoid bone and the frontal bone In the human skull, the frontal bone or sincipital bone is an unpaired bone which consists of two portions.'' Gray's Anatomy'' (1918) These are the v ...

joins the sphenoid and frontal bones. * the

sphenosquamosal suture The sphenosquamosal suture is a cranial suture between the sphenoid bone and the squama of the temporal bone. Additional images File:Sphenosquamosal suture - animation4.gif, Animation of sphenosquamosal suture File:Sphenosquamosal suture - ...

joins the sphenoid and temporal bones.

Clinical significance

Hematoma

The pterion is known as the weakest part of the skull. The anterior division of the

middle meningeal artery The middle meningeal artery (') is typically the third branch of the maxillary artery#First portion, first portion of the maxillary artery. After branching off the maxillary artery in the infratemporal fossa, it runs through the foramen spinosum t ...

runs underneath the pterion. Consequently, a traumatic blow to the pterion may rupture the middle meningeal artery causing an

epidural haematoma Epidural hematoma is when bleeding occurs between the tough outer membrane covering the brain (dura mater) and the skull. When this condition occurs in the spinal canal, it is known as a spinal epidural hematoma. There may be loss of consciousn ...

. The pterion may also be fractured indirectly by blows to the top or back of the head that place sufficient force on the skull to fracture the pterion.

Surgery

The pterion is a structural landmark for

neurosurgical Neurosurgery or neurological surgery, known in common parlance as brain surgery, is the medical specialty that focuses on the surgical treatment or rehabilitation of disorders which affect any portion of the nervous system including the brain, s ...

approach to middle cerebral artery

aneurysm An aneurysm is an outward :wikt:bulge, bulging, likened to a bubble or balloon, caused by a localized, abnormal, weak spot on a blood vessel wall. Aneurysms may be a result of a hereditary condition or an acquired disease. Aneurysms can also b ...

Etymology

The pterion receives its name from the

Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

root , meaning '

wing A wing is a type of fin that produces both Lift (force), lift and drag while moving through air. Wings are defined by two shape characteristics, an airfoil section and a planform (aeronautics), planform. Wing efficiency is expressed as lift-to-d ...

'. In

Greek mythology Greek mythology is the body of myths originally told by the Ancient Greece, ancient Greeks, and a genre of ancient Greek folklore, today absorbed alongside Roman mythology into the broader designation of classical mythology. These stories conc ...

Hermes Hermes (; ) is an Olympian deity in ancient Greek religion and mythology considered the herald of the gods. He is also widely considered the protector of human heralds, travelers, thieves, merchants, and orators. He is able to move quic ...

, messenger of the gods, was enabled to fly by winged sandals, and wings on his head, which were attached at the pterion.

References

External links

*
Diagram - look for #24
(sourc
here
{{Authority control Skull Otorhinolaryngology