SKULL ANATOMYCranial bones and facial bones comprise the structure known as the human skull. The cranial bones consist of eight well structured, well connected bones which protect the brain as well as the sensory organs. The facial area is supported as well as structured to form a framework consisting of 14 bones. Additionally, the teeth are supported in this structure. Each human face is unique and is formed through variations in density of the cranial and facial bones, as well as the basic underlying structure of these bones. Because of these unique formations, each human face is uniquely the sole look of the individual with the skull. The mandible, or jaw bone, is the only facial bone that moves, the rest are firmly interlocked with one another creating a firmly held together network of bones.
The bones of the skull and face create a formation of various cavities which includes the cranial cavity. With a capacity of 1,300 to 1,350 cc of area, the cranial cavity is the largest of the skull and facial cavities.
SKULL STRUCTUREThe cranial and facial bones come together to create the nasal cavity, which is segregated by two variable chambers. The chambers are segregated by the position of the nasal septum, which is a combination of both bone and cartilage. The four sets of paranasal sinuses rely on the ducts located in the nasal cavity for effective communication. The paranasal sinus cavity can be found in the bone structure which surrounds the nasal cavity.
The organs associated with hearing and balance are located in the cavity which houses the middle and inner ear. Located just inside the cranial cavity, well protected from potential damage, the tiny bones which vibrate create the sense of hearing.
Facial and cranial bones come together to form the orbits which hold the two eyeballs and develop the sense of sight. The mouth is only partially formed by bone. Also called the oral buccal cavity, it formed only by facial bones and is completely segregated in the facial region as opposed to sharing any cranial bones in its formation. The mouth is formed by bone, muscle, tissue, cartilage, and glands.
During the development of the human fetus, the skull is intentionally developed with fibrous unions throughout the cranial bones. This allows for the fetus to travel through the birth canal with a somewhat pliable head. These bones eventually fuse more than a year after birth, although the evidence of these fibrous unions disappears usually within six to eight months of birth. Gaps between developing bones are common during the developmental stages. These gaps are covered protectively by connective tissue membranes. These soft spots are known as “little fountains,” or fontanels as a baby’s heart rhythm can be felt through the soft membranes on the head. Sometimes the heart rhythm can be seen through theses soft membranes on the head. The pliable head which allowed a safer passage through the birth canal also allows for normal development patterns during the first year to eighteen months of life such as rapid brain growth, adjustments in shape and growth during the first year of life. In a normal growth rate infant the fontanels fuse together and form a permanent skull between the ages of twenty months and two years.
ANTERIOR FONTANELThe anterior fontanel is by far the most prominent and is arranged along the anteromedian portion of a baby’s skull. The anterior fontanel is also the most likely to suffer injury during the early stages of walking.
POSTERIOR FONTANELThe posterior fontanel is diamond shaped just as the anterior fontanel, although the posterior fontanel is smaller. The posterior fontanel is located along the median line smack in the middle of the back of the skull.
The two fontanels located on the sides of the skull are mirror images of each other and are known as the anterolateral fontanels. While they are smaller in size, they are irregularly shaped and viewed alone would seem to have no definition by shape. The pair of posterolateral fontanels also have no definite shape and a re considered irregular. Also mirror images of each other they are located posteriorly of the anterolateral fontanels along the posterolateral sides of the skull.
Between the fontanels the naturally occurring sutures in the skull help to hold the fontanels in place while they are undergoing the transformation into a human child’s skull. The sagittal suture is dominantly prominent and it extends down the anteroposterior median of the skull. A coronal suture holds the anterior fontanel to the anterolateral fontanel while the posterior fontanel is held to the posterolateral fontanel via the lambdoid suture. The posterolateral and the anterolateral fontanels are connected via the squamous suture. The skull is naturally designed to hold a network of nerves, vessels, and other significantly important structures which create a completed skull and head. Some bones, such as the hyoid bone and the six auditory ossicles are not technically considered part of the skull’s structure or part of the facial bones. However, due to their proximity as well as their cooperative function, they are often associated with the facial bones for simplicity.