Skull Anatomy

Picture from Robswatski (http://www.flickr.com/photos/rswatski/)

The human skull is part of the skeletal system. It’s structures (namely the cranium and facial bones) provide the anchorage for the soft tissues of the face and as a result, their form (both shape and quality) dictate much of the appearance of the face. In adult humans the skull consists of 22 bones. All of these are bound together by sutures (a fibrous joint only found in the skull), the only exception being the mandible. These joints are synathroses (joints that do not allow much movement); immovable joints formed via ossification. The small amount of flexibility present is primarily as a result of Sharpey’s fibres.

Human Skull bones have many features. Extra tissue on the bones (the function being to hold muscles and ligaments) are known as Processes. Grooves in the bones (formed during development) are known as Lines. Small cavities within structures of the skull (primarily for the housing of blood vessels and nerves) are known as Foramina.

Picture from Robswatski (http://www.flickr.com/photos/rswatski/)

Perhaps the most notable part of the human skull is the cranium. This is the area which houses the human brain and brain stem in a large cavity commonly known as the cranial vault. Eight plate-like bones form the brain case (neurocranium). Of these the most profound in terms of its effect on  the appearance of the bearer’s face is the frontal bone. The human skull also contains fourteen facial bones (the splachnochranium). These bones provide the foundations of the human face. The most important facial bones (though it can be said that they’re all very important!) are the maxilla (upper jaw), mandible (lower jaw) and zygomatic (cheek bone).

Picture from Robswatski (http://www.flickr.com/photos/rswatski/)

The human skull forms many cavities such as those housing the eyes, internal ear, nose, mouth and of course the sinus cavities. The function of the sinus cavities is the subject of some scientific debate: they’re lined with respiratory epithelium and as such are considered primarily to warm and moisten air entering through the nasal cavity however it is also important to note that they reduce the overall weight of the skull without significantly effecting the strength.

Below I have divided the human skull into its 2 major components. Within these lists are the majr features of these bones.

Facial Bones

Lacrimal Bone: This is a small bon e located at the inner corner of the eye socket (medial orbit). It is the most fragile bone in the face, has two surfaces and four borders.

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Mandible: This is the lower jaw. It houses the lower teeth and is notable as the only part of the human skull that is mobile (e.g. chewing, speech etc.). It is a fusion of two halves down the mental symphysis.

Picture from Guccibear http://www.flickr.com/photos/guccibear2005/

Maxilla: This is the upper part of the jaw. It houses the upper teeth and is actually a fusion of two bones along the palatal fissure.

Piture from Cutienutt http://www.flickr.com/photos/54066547@N02/

Nasal Bone: Located between the eye sockets. They are actually two bones that together form the nasal bridge. Each has two surfaces and four borders.

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Vomer: This is located in the nasal cavity on the centreline of the nose.

Picture from RachelHermasillo http://www.flickr.com/photos/rachelhermosillo/

Zygomatic Bone: This is the primary bone in the cheek. It articulates (provides a joint) with numerous other bones within the skull (maxilla, frontal bone, sphenoid bone, temporal bone). In addition to this it forms part of the lateral wall and floor of the orbit. It has four processes and four borders.

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Cranial Bones

Ethmoid Bone: This is a bone forming part of the eye socket. It separates the nasal cavity from the brain. It articulates with fifteen other bones (the volmer, the frontal bone and sphenoid, two nasal bones, two maxillae, two lacrimals, two palatines, and two inferia nasal conchae). It has three major components: the cribriform plate, the ethmodial labyrinth, and the perpendicular plate.

Picture from Robswatski http://www.flickr.com/photos/rswatski/

Frontal Bone: This is the bone comprising what is commonly known as the forehead (squama forntalis). It houses the frontal lobes of the brain. It forms the upper regions of the eye sockets (pars orbitalis) and forms part of the nasal cavities.

Picture from Ted Zhu http://www.flickr.com/photos/47771364@N04/

Occipital Bone: This is a major structure in the cranium located at the lower back area. It has a large opening known as the Foramen Magnum (an example of previously mentioned foramina) through which the medulla oblongata enters (or exits) the cranial vault. It also transfers the spinal accessory nerve, vertebral arteries and the anterior and posterior spinal arteries.

Picture from RachelHermosillo http://www.flickr.com/photos/rachelhermosillo/

Parietal bones: These bones together form the sides and top of the human skull. They are located between the frontal and occipital bones and are roughly square (though curved as to form a rounded surface). Each bone has two surface and four borders.

Picture from RachelHermosillo

Sphenoid bone: This forms a section of the eye socket. It is butterfly shaped and has a protective cavity which houses the pituitary gland. 

Picture from Robswatski http://www.flickr.com/photos/rswatski/

Temporal bone: The temporal bones are located in the are referred to as the temple. They extend behind the ear toward the mandible  and house the temporal lobes of the brain.

Picture from RachelHermosillo http://www.flickr.com/photos/rachelhermosillo/

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