The Skull

Skull, head, cranial vault, dome, noodle, and also thinker space all words that are used to define the very same thing: the cranium. The skull is part of the axial skeleton and is split into the two sections: the face bones and also the cranium. The is consisted of of the cranium, i m sorry is round and also houses the brain, and also the facial bones which type the upper and also lower jaws, the nose, orbits, and other facial structures. The adult skull is made up of 22 bones; 21 that them room immovable and also the 22nd one is the mandible, the reduced jaw, and also is the only moveable bone that the skull. The cranial bones kind the cranial cavity which holds and also protects the brain.

You are watching: Four major sutures of the skull

The cranium is created of eight bones: the frontal bone, two parietal bones, 2 temporal bones, the occipital bone, the sphenoid bone, and also the ethmoid bone. A suture is an synarthrosis joint, an immoveable joint, between the bones and is how the bones of the cranium space connected. They space fibrous joints. There room four major sutures that connect the bones of the cranium together: the frontal or coronal, the sagittal, the lambdoid, and also the squamous. The frontal suture connect the frontal bone come the two parietal bones. The sagittal suture connects the 2 parietal bones. The lambdoid connects the two parietal bones to the occipital bone. The squamous sutures connect the parietal bones to the temporal bones.

The Frontal Bone

The frontal bone, together seen below in pink, is the anterior roof that the skull, the bone the the forehead, and extends down to be the superior section of the orbits, the top of the eye sockets. That articulates (is linked to) v the parietal, sphenoid, ethmoid, nasal, lacrimal, maxillary, and also zygomatic bones. The form of the frontal bone dram a large part in the visual identification of a person. The supra-orbital margin is the superior, upper, rim of the eye socket. It has supra-orbital foramina, sometimes a notch, above each supra-orbital margin that enable blood vessels and nerves to reach the eyebrows, eyelids, and frontal sinuses. Supra an interpretation superior, orbital an interpretation eye socket, and also foramen definition hole; the name of the describes what the is and where the is. The smooth part above and also between her eyebrows has actually a name and also is referred to as the glabella. The zygomatic procedure of the frontal bone connects with the frontal process of the zygomatic bone i beg your pardon help form the cheekbone.

*
An anterior watch of the skull

The Parietal Bone

The parietal bones, the appropriate parietal bone highlighted in green below, do the roof the the cranium. It creates the upper lateral side of the skull. The parietal skeleton articulate through one another, and also with the frontal, sphenoid, temporal, and also occipital. The superior and inferior temporal lines are low ridges that mark the attachment sites that the temporalis muscle.

*
Lateral check out of the appropriate parietal bone

The Temporal Bone

The temporal bones are the lower lateral political parties of the skull as seen listed below in green. They are the bones one’s ears sit upon. Over there are countless features of the temporal bones. First, over there is the zygomatic process. It connects come the temporal process of the zygomatic bone. Together these kind the zygomatic arch, the cheekbone. Next, over there is the mastoid process. The is a pyramidal estimate at the ago of the temporal bone. That can quickly be felt on the next of one’s head, behind the earlobe. That is a site of muscle attachment for muscles consisting of sternocleidomastoid, splenius capitis, and also longissimus capitis. The mandibular fossa the the temporal bone is a depression the articulates through the mandible; they type the temporomandibular joint. This enables for the opening and also closing that the jaw. The temporal fossa is a depression in the temporal region. It is among the biggest landmarks of the skull. The frontal bone, sphenoid bone, parietal bone, and temporal bone all add to the concavity that the fossa. The temporal lines space the remarkable border and the zygomatic arch is the worse border. That is a site of muscle attachment because that temporalis, a mastication (chewing) muscle. Next, there is the styloid process. It is posterior to the mandibular fossa. It is a pointy, stylus like process that is just below the ear. The is one attachment suggest for muscles and also tendons of the neck and also tongue. The exterior auditory or acoustic, meatus or canal, is the canal the funnels sound into the eardrum. The is the big opening ~ above the lateral side of the skull often linked with the ear. The is a tube running from outer ear come the middle ear. The inner auditor, or acoustic, meatus or canal is a bony canal within the petrosal part of the temporal bone that permits nerves and vessels from within the posterior cranial fossa to the brain. The connects the middle and also inner ear cavities to the temporal bone.

*
Lateral check out of the skullThe Occipital Bone

The occipital bone, emphasize in environment-friendly below, is the bone the makes up the posterior and base part of the cranium. The large oval opened in the base is the foramen magnum. That is wherein the spinal cord exit the skull. There are two oval shaped occipital condyles, one on each side of the foramen magnum. These room where the skull connects to the very first cervical vertebrae that the vertebral column, atlas. In ~ the midline of the bone, over there is a protrusion called the outside occipital protuberance, the tip of it is referred to as the inion. That is easy to find and palpate. This can vary in size in people. It is a site of attachment for a ligament of the posterior neck. Lateral to either side of the protrusion is the remarkable nuchal line. This is the most superior website for muscle attachment, with just the scalp covering the skull above the lines. Just inferior come the external occipital protuberance there is the inferior nuchal line, likewise a site of muscle attachment.

*
A posterior inferior check out the the skullThe Sphenoid BoneA superior and posterior view of the sphenoid bone

The Sphenoid bone, above, is a cranial bone shaped choose a butterfly. The is situated in the anterior part of the cranium, as seen listed below in green. It forms the base of the anterior skull and also spreads laterally enough to add to the political parties of the skull. It is composed of a main body that is cubical-shaped and also two set of wing-shaped extensions that job laterally: the higher wings and the lesser wings. The sella turcica (Turkish saddle) is located at the midline of the middle cranial fossa. That is called for the same to a horse’s saddle. The hypophyseal (pituitary) fossa is the depression the the basic of the sella turcica and houses the pituitary gland. The greater wings, also known as Ala major, prolong out laterally native the sella turcica to type the anterior floor that the middle cranial fossa. They room a pair of bigger winged frameworks of the bone, curved upwards, backward and also on the lateral sides. The lesser wings, additionally known as Ala minor, are a pair that the smaller projections that space flat, triangle structures situated anterior come the higher wings. Projecting inferiorly ~ above the posterior side are the media pterygoid plate and lateral pterygoid plate. The right and left medial pterygoid plates kind the posterior, lateral walls of the nasal cavity. The bigger lateral pterygoid plates offer as attachments sites for chewing muscles.

*
An anterior lateral see of the skullThe Ethmoid BoneAn anterior see of the ethmoid bone

The ethmoid bone is located between the two orbits and also at the roof the the nose. It creates the roof and lateral walls of the upper nasal cavity, the upper portion of the nasal septum, and also contributes come the medial wall surface of the orbit. What provides it a cranial bone is the inferiorly it forms a part of the anterior cranial floor. The separates the nasal cavity indigenous the brain. That is consisted of of the perpendicular plate, the crista galli (rooster’s comb or crest), and the cribriform plate, as watched above. The perpendicular plate creates the superior part of the nasal septum. The ethmoid bone additionally forms the lateral walls of the top nasal cavity, prolonging from each lateral wall surface are the remarkable nasal concha and middle sleep concha, which space thin, curved projections that expand into the sleep cavity. The crista galli is a exceptional bony estimate that serves together an attachment suggest for a extending layer that the brain. On either next of the crista galli is the cribriform plate. It forms the roof of the nasal cavity and also contributes come the anterior cranial fossa. The is a small, flattened area v many small openings, olfactory foramina. Little nerve branches indigenous the olfactory locations of the sleep cavity pass through these openings to get in the brain. You have the right to see it emphasize in green below from a premium lateral view v the cranium.

*
A remarkable lateral watch of the ethmoid boneCranial Cavity

The inner surface ar of the cranial cavity is separated into three distinctive depressions. It is made up of the anterior, middle, and also posterior cranial fossae. Every fossa accommodates a different part of the brain. The anterior cranial fossa is the most shallow and superior the the three fossae. The fossa is made up of the frontal bone, the ethmoid bone, and the body and lesser wing of the sphenoid bone. It homes the anteroinferior part of the frontal lobe. The middle fossa is made up of the higher wings that the sphenoid bone and the temporal bone. It deserve to be stated to be butterfly shaped. It houses the pituitary gland and the two lateral components of the fossa contain the temporal lobes. The posterior cranial fossa is made up of largely the occipital bone and the posterior section of the temporal bones. It houses the brainstem and also cerebellum and associated arteries and nerves.

A superior and also lateral see of the inside of the cranium

A mnemonic to remember the skeleton of the cranium is PEST OF.

See more: How Many Ounces In A Handful ? Is A Cup A Handful

MnemonicBones
PParietal
EEthmoid
SSphenoid
TTemporal
OOccipital
FFrontal

To see an ext about the bony landmarks of the skull i beg your pardon are offered for radiological or anthropological skull measurements see: https://radiopaedia.org/articles/skull-landmarks

This video clip describes the skeleton of the cranium and face and shows lock on a model. Indigenous 3:50 onward are the cranial bones. https://www.youtube.com/watch?v=0N20150qthA

HyoidThis horseshoe-shaped bone is supplied as a solid structure for the tongue come move. This bone additionally has many locations for muscle attachment. The muscles above the hyoid are referred to as the suprahyoid muscles. The muscle below the hyoid are referred to as the infrahyoid muscles. For more information on this muscles, describe the neck muscle section. There room 3 key parts that the hyoid: the body, the greater horn, and the lesser Horn. Over there is one significant feature i beg your pardon is the tubercle the the higher horn.