It is located within the body of the sphenoid bone, just anterior and inferior to the sella turcica, thus making it the most posterior of the paranasal sinuses. This duct then extends downward to open into the nasal cavity, behind the inferior nasal concha. External and Internal Views of Base of Skull. Each side of the nasal cavity is triangular in shape, with a broad inferior space that narrows superiorly. Human skulls have different shapes and characteristics that can help scientists determine race and ancestry. The larger of these is the inferior nasal concha, an independent bone of the skull. Posterior View of Skull. The cranium (skull) is the skeletal structure of the head that supports the face and protects the brain. The facial bones underlie the facial structures, form the nasal cavity, enclose the eyeballs, and support the teeth of the upper and lower jaws. This second feature is most obvious when you have a cold or sinus congestion. Due to the difference in the cranial index, scientists classified the human skulls into 3 main types- … To help protect the eye, the bony margins of the anterior opening are thickened and somewhat constricted. However, a recent study revealed the interconnection between the presence of Neanderthal DNA fragments and skull shape. In severe cases, the bony gap continues into the anterior upper jaw where the alveolar processes of the maxilla bones also do not properly join together above the front teeth. There are eight major bones and eight auxiliary bones of the cranium. It unites the right and left parietal bones. Still, the effects of such gene variations are probably negligible in living humans, merely adding a slight, barely discernible elongation to the skull. From anterior to posterior, the fossae increase in depth. As blood accumulates, it will put pressure on the brain. The greater wing is best seen on the outside of the lateral skull, where it forms a rectangular area immediately anterior to the squamous portion of the temporal bone. Openings in the middle cranial fossa are as follows: The posterior cranial fossa is the most posterior and deepest portion of the cranial cavity. Which bone (yellow) is centrally located and joins with most of the other bones of the skull? On the interior of the skull, the petrous portion of each temporal bone forms the prominent, diagonally oriented petrous ridge in the floor of the cranial cavity. Parts of the Skull. Watch this video to view a rotating and exploded skull, with color-coded bones. Together these articulations form the temporomandibular joint, which allows for opening and closing of the mouth (see Figure 3). Lateral View of Skull. The sphenoid sinus is a single, midline sinus. The maxillary bone forms the upper jaw and supports the upper teeth. The bones of the skull slot together like a jigsaw. The maxillary sinuses are most commonly involved during sinus infections. Each of the paired zygomatic bones forms much of the lateral wall of the orbit and the lateral-inferior margins of the anterior orbital opening (see Figure 2). If the underlying artery is damaged, bleeding can cause the formation of a hematoma (collection of blood) between the brain and interior of the skull. According to the Centers for Disease Control and Prevention (2010), approximately 30 percent of all injury-related deaths in the United States are caused by head injuries. Each of these spaces is called an ethmoid air cell. The slope causes a protrusion of the jaw, also referred to as prognathism. The crista galli (“rooster’s comb or crest”) is a small upward bony projection located at the midline. The space inferior to the zygomatic arch and deep to the posterior mandible is the infratemporal fossa. Surgical repair is required to correct cleft palate defects. Ethmoid Bone. The right and left medial pterygoid plates form the posterior, lateral walls of the nasal cavity. The temporal bone forms the lower lateral side of the skull (see Figure 3). When looking into the nasal cavity from the front of the skull, two bony plates are seen projecting from each lateral wall. The unpaired bones are the vomer and mandible bones. The lesser wings of the sphenoid bone form the prominent ledge that marks the boundary between the anterior and middle cranial fossae. The sella turcica (“Turkish saddle”) is located at the midline of the middle cranial fossa. Located at the anterior-lateral margin of the foramen magnum is the hypoglossal canal. These are the medial pterygoid plate and lateral pterygoid plate (pterygoid = “wing-shaped”). (b) The complex floor of the cranial cavity is formed by the frontal, ethmoid, sphenoid, temporal, and occipital bones. Figure 3. The temporal lobes of the brain occupy this fossa. The large, diagonally positioned petrous ridges give the middle cranial fossa a butterfly shape, making it narrow at the midline and broad laterally. These are located just behind your eyebrows and vary in size among individuals, although they are generally larger in males. Additional causes vary, but prominent among these are automobile and motorcycle accidents. Lateral View of Skull. In addition to exploding the supposed connection between race and culture, Boas measured the head shape of immigrants and their children in New York City. Non‐rigid registration is used to represent variations in human skull shape. Below this area and projecting anteriorly is the zygomatic process of the temporal bone, which forms the posterior portion of the zygomatic arch. The frontal bone is the single bone that forms the forehead. The temporal bone is subdivided into several regions (Figure 5). More extreme variations -- especially in infants -- may indicate a medical issue. Subsequent finite element analyses quantify stresses caused by mastication, and differences in stresses caused by skull … Round shape 22 % (11) 21.8 % (24) Irregular shape 18 % (9) 19.9 % (22) Oval shape 16 % (8) 8.1 % (9) Egg shape 16 % (8) - Tetragonal shape 12 % (6) 12.7 % (14) Pentagonal shape 8 % (4) - They are most common among young children (ages 0–4 years), adolescents (15–19 years), and the elderly (over 65 years). According to the 1000 Genomes Project, a typical human has 2,100 to 2,500 structural variations, which include approximately 1,000 large deletions, 160 copy-number variants, 915 Alu insertions, 128 L1 insertions, 51 SVA insertions, 4 NUMTs, and 10 inversions. The most posterior is the sphenoid sinus, located in the body of the sphenoid bone, under the sella turcica. These condyles form joints with the first cervical vertebra and thus support the skull on top of the vertebral column. Lateral Wall of Nasal Cavity. Figure 14. Utilizing the of human skull reported in the literature can be method reported by Ruan and Prasad (1995, 1998), explained by variations in skull thickness of the iso-stress in the skull and the brain were developed as samples tested and time durations of impact. It is formed by the junction of two bony processes: a short anterior component, the temporal process of the zygomatic bone (the cheekbone) and a longer posterior portion, the zygomatic process of the temporal bone, extending forward from the temporal bone. The lower and posterior parts of the septum are formed by the triangular-shaped vomer bone. Figure 17. Below the level of the zygomatic arch and deep to the vertical portion of the mandible is another space called the infratemporal fossa. List and identify the bones of the brain case and face, Locate the major suture lines of the skull and name the bones associated with each, Locate and define the boundaries of the anterior, middle, and posterior cranial fossae, the temporal fossa, and infratemporal fossa, Define the paranasal sinuses and identify the location of each, Name the bones that make up the walls of the orbit and identify the openings associated with the orbit, Identify the bones and structures that form the nasal septum and nasal conchae, and locate the hyoid bone. Sagittal Section of Skull. Fractures of the occipital bone at the base of the skull can occur in this manner, producing a basilar fracture that can damage the artery that passes through the carotid canal. Slight variations are normal. The frontal sinus is located just above the eyebrows, within the frontal bone (see Figure 15). The venous structures that carry blood inside the skull form large, curved grooves on the inner walls of the posterior cranial fossa, which terminate at each jugular foramen. The rounded depression in the floor of the sella turcica is the hypophyseal (pituitary) fossa, which houses the pea-sized pituitary (hypophyseal) gland. Figure 5. At the intersection of four bones is the pterion, a small, capital-H-shaped suture line region that unites the frontal bone, parietal bone, squamous portion of the temporal bone, and greater wing of the sphenoid bone. The lateral portions of the ethmoid bone are located between the orbit and upper nasal cavity, and thus form the lateral nasal cavity wall and a portion of the medial orbit wall. The paranasal sinuses are named for the skull bone that each occupies. Inside the skull, the base is subdivided into three large spaces, called the anterior cranial fossa, middle cranial fossa, and posterior cranial fossa (fossa = “trench or ditch”) (Figure 4). The orbit is the bony socket that houses the eyeball and muscles that move the eyeball or open the upper eyelid. The inferior concha is the largest of the nasal conchae and can easily be seen when looking into the anterior opening of the nasal cavity. It unites the squamous portion of the temporal bone with the parietal bone (see Figure 3). Because there are a variety of structural and dimensional differences between skulls of different races, careful inspection and measurements are performed on numerous parts of the skull to aid in accurate characterization. European skulls, sometimes referred to by the scientific terms Caucasoid or Caucasian, are relatively long and narrow when compared to Asian or African types. Learn more about the anatomy and function of the skull … Some variations are potentially detrimental to a person’s health. Located inside this portion of the ethmoid bone are several small, air-filled spaces that are part of the paranasal sinus system of the skull. Isolated Mandible. The superior nasal concha and middle nasal concha are parts of the ethmoid bone. This work on human skulls challenged the physical basis of human racial categorization. A lateral view of the isolated temporal bone shows the squamous, mastoid, and zygomatic portions of the temporal bone. The human skull has an oblong shape that is longer from front to back than it is wide. Figure 2. It overlies the orbits and contains the frontal lobes of the brain. This view of the posterior skull shows attachment sites for muscles and joints that support the skull. It joins the frontal bone to the right and left parietal bones. The bones that form the top and sides of the brain case are usually referred to as the “flat” bones of the skull. The middle cranial fossa is deeper and situated posterior to the anterior fossa. Figure 11. It contains the cerebellum of the brain. Inside the nasal area of the skull, the nasal cavity is divided into halves by the nasal septum. Several cranial nerves from the brain exit the skull via this opening. The paranasal sinuses are hollow, air-filled spaces named for the skull bone that each occupies. These are paired and located within the right and left maxillary bones, where they occupy the area just below the orbits. The frontal bone also forms the supraorbital margin of the orbit. Cranial Fossae. If this occurs, a cleft lip will also be seen. The superior nasal concha is located just lateral to the perpendicular plate, in the upper nasal cavity. Many deductions regarding evolutionary processes and diversifications of early groups have been made on the basis of shape and size variations of the zygoma. Figure 16. Certain people have slightly less rounded skull shapes that have that have inspired controversial questions such as alien genes having entered the human evolution process sometime in the ancient past. 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