Human skulls side simplified
Human skull front bones
Components
Eight bones form the neurocranium (brain case), a protective vault of bone surrounding the brain and brain stem. Fourteen bones form the splanchnocranium, which comprises the bones supporting the face. Encased within the temporal bones are the six auditory ossicles of the middle ear. The hyoid bone, supporting the larynx, is usually not considered as part of the skull, as it is the only bone that does not articulate with other bones of the skull.
The skull also contains the sinus cavities, which are air-filled cavities lined with respiratory epithelium, which also lines the large airways. The exact functions of the sinuses are debatable; they contribute to lessening the weight of the skull with a minimal reduction in strength, they contribute to resonance of the voice, and assist in the warming and moistening of air drawn in through the nasal cavities.
Development of the skull
At birth, the human skull is made up of 404 separate bony elements. As growth occurs, many of these bony elements gradually fuse together into solid bone (for example, the frontal bone). The bones of the roof of the skull are initially separated by regions of dense connective tissue called "cranial sutures". There are five sutures: the frontal suture, sagittal suture, lambdoid suture, coronal suture, and squamosal suture. At birth these regions are fibrous and moveable, necessary for birth and later growth. This growth can put a large amount of tension on the "obstetrical hinge," which is where the squamous and lateral parts of the occipital bone meet. A possible complication of this tension is rupture of the great cerebral vein of Galen. Larger regions of connective tissue where multiple sutures meet are called fontanelles. The six fontanelles are: the anterior fontanelle, the posterior fontanelle, the two sphenoid fontanelles, and the two mastoid fontanelles. As growth and ossification progress, the connective tissue of the fontanelles is invaded and replaced by bone. The posterior fontanelle usually closes by eight weeks, but the anterior fontanelle can remain open up to eighteen months. The anterior fontanelle is located at the junction of the frontal and parietal bones; it is a "soft spot" on a baby's forehead. Careful observation will show that you can count a baby's heart rate by observing his or her pulse pulsing softly through the anterior fontanelle.
Pathology
Dating back to Neolithic times, a skull operation called trepanation was sometimes performed. This involved drilling holes in the cranium. Examination of skulls from this period reveals that the "patients" sometimes survived for many years afterward. It seems likely that trepanation was performed for ritualistic or religious reasons and not only as an attempted life-saving technique.
there are 4 main parts to the brain at birth
Craniometry and morphology of human skulls
Like the face of a living individual, a human skull and teeth can also tell, to a certain degree, the life history and origin of its owner. Forensic scientists and archaeologists use metric and nonmetric traits to estimate what the bearer of the skull looked like. When a significant amount of bones are found, such as at Spitalfields in the UK and Jōmon shell mounds in Japan, osteologists can use traits, such as proportions of length, height, width, to know the relationships of population of the study, with living or extinct populations.
The German physician Franz Joseph Gall in around 1800 formulated the theory of phrenology, which attempted to show that specific features of the skull are associated with certain personality traits or intellectual capabilities of its owner. This theory is now considered to be obsolete.
Sexual dimorphism
All of these features vary considerably within human populations, making it difficult to identify the sex of a skull without knowledge of the population from which it came.
Ancestry
Although persons' descents are occasionally stereotyped as different from other ethnic groups on the basis of a variety of traits like eye, hair and skin color, all such characters are not discrete nor preserved in bones. Among archaeologists and forensic scientists, it is still sometimes stated that the most consistent and unique trait of ancestry in skeleton is skull shape (see craniometry).
