Located at the anterior-lateral margin of the foramen magnum is the hypoglossal canal. On its outside surface, at the posterior midline, is a small protrusion called the external occipital protuberance, which serves as an attachment site for a ligament of the posterior neck. Illustrated Encyclopedia of Human Anatomic Variation: Opus V: Skeletal Systems: Cranium. The anterior cranial fossa is the most anterior and the shallowest of the three cranial fossae. The right and left inferior nasal conchae form a curved bony plate that projects into the nasal cavity space from the lower lateral wall (see Figure 11). The hard palate is the bony structure that separates the nasal cavity from the oral cavity. Posteriorly is the mastoid portion of the temporal bone. Strong blows to the brain-case portion of the skull can produce fractures. On December 13, in the journal Current Biology , researchers report that present-day humans who carry particular Neandertal DNA fragments have heads that are slightly less rounded, revealing genetic clues to the evolution of modern brain shape … The lambdoid suture extends downward and laterally to either side away from its junction with the sagittal suture. A normal human head has a round appearance but upon closer examination may have a pointed top (egg-shaped), a pointed chin (reverse egg-shaped) or a flat top. Figure 3. Glay Onan Labrande / EyeEm/EyeEm/GettyImages. It joins the frontal bone to the right and left parietal bones. The large, diagonally positioned petrous ridges give the middle cranial fossa a butterfly shape, making it narrow at the midline and broad laterally. During embryonic development, the right and left maxilla bones come together at the midline to form the upper jaw. These are located on both sides of the ethmoid bone, between the upper nasal cavity and medial orbit, just behind the superior nasal conchae. The frontal bone also forms the supraorbital margin of the orbit. The most common is a linear skull fracture, in which fracture lines radiate from the point of impact. An anterior view of the skull shows the bones that form the forehead, orbits (eye sockets), nasal cavity, nasal septum, and upper and lower jaws. First came Lyell's Antiquity of Man, which included a section on the skull's anatomy, probably written by Busk and Huxley. These emerge on the inferior aspect of the skull at the base of the occipital condyle and provide passage for an important nerve to the tongue. Since the brain occupies these areas, the shape of each conforms to the shape of the brain regions that it contains. The mandible forms the lower jaw and is the only moveable bone of the skull. Each lacrimal bone is a small, rectangular bone that forms the anterior, medial wall of the orbit (see Figure 2 and Figure 3). The medial floor is primarily formed by the maxilla, with a small contribution from the palatine bone. The largest sinus is the maxillary sinus. The upper incisors tend to be more “shovel shaped” than either European or African types, and the nasal opening is flared at the bottom, making it wider than the European skull. Inside the cranial cavity, the frontal bone extends posteriorly. These are located just behind your eyebrows and vary in size among individuals, although they are generally larger in males. Subsequent finite element analyses quantify stresses caused by mastication, and differences in stresses caused by skull … Openings in the middle cranial fossa are as follows: The posterior cranial fossa is the most posterior and deepest portion of the cranial cavity. A blow to the lateral side of the head may fracture the bones of the pterion. The facial bones include 14 bones, with six paired bones and two unpaired bones. 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. The evolution of human bipedalism, which began in primates about four million years ago, or as early as seven million years ago with Sahelanthropus, or about 12 million years ago with Danuvius guggenmosi, has led to morphological alterations to the human skeleton including changes to the arrangement and size of the bones of the foot, hip size and shape, knee size, leg length, and the shape … The brain case contains and protects the brain. The upper margin of the anterior orbit is the supraorbital margin. At its anterior midline, between the eyebrows, there is a slight depression called the glabella (see Figure 3). The eye orbits are rounded and don't have the same downward slope as European skulls. The sagittal suture extends posteriorly from the coronal suture, running along the midline at the top of the skull in the sagittal plane of section (see Figure 7). These are bony plates that curve downward as they project into the space of the nasal cavity. It provides attachments for muscles that act on the tongue, larynx, and pharynx. It unites the right and left parietal bones. Small nerve branches from the olfactory areas of the nasal cavity pass through these openings to enter the brain. This cavity is bounded superiorly by the rounded top of the skull, which is called the calvaria (skullcap), and the lateral and posterior sides of the skull. It is formed during embryonic development by the midline fusion of the horizontal plates from the right and left palatine bones and the palatine processes of the maxilla bones. 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. The greater wings of the sphenoid bone extend laterally to either side away from the sella turcica, where they form the anterior floor of the middle cranial fossa. The walls of each orbit include contributions from seven skull bones (Figure 14). 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. The ramus on each side of the mandible has two upward-going bony projections. 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. Within the nasal cavity, the perpendicular plate of the ethmoid bone forms the upper portion of the nasal septum. The temporal bone forms the lower lateral side of the skull (see Figure 3). tical shape model (SSM) of the outer surface of the scalp and the inner and outer surface of the skull of the human head. This provides for passage of a sensory nerve to the skin of the forehead. This work on human skulls challenged the physical basis of human racial categorization. Parts of the Skull. Lateral View of Skull. Each side of the mandible consists of a horizontal body and posteriorly, a vertically oriented ramus of the mandible (ramus = “branch”). It extends from the lesser wings of the sphenoid bone anteriorly, to the petrous ridges (petrous portion of the temporal bones) posteriorly. The 22nd bone is the mandible (lower jaw), which is the only moveable bone of the skull. Located inside each petrous ridge are small cavities that house the structures of the middle and inner ears. Hyoid Bone. Figure 12. These may result in bleeding inside the skull with subsequent injury to the brain. At the time of birth, the mandible consists of paired right and left bones, but these fuse together during the first year to form the single U-shaped mandible of the adult skull. Some variations are potentially detrimental to a person’s health. The most marked variation in skull shape was the dorsoventral flexion; i.e., deformation from klinorhynchy to airorhynchy. Based on careful analysis, skulls are commonly categorized into three basic groups: European, Asian and African. The lesser wing of the sphenoid bone separates the anterior and middle cranial fossae. Copyright 2021 Leaf Group Ltd. / Leaf Group Media, All Rights Reserved. Non‐rigid registration is used to represent variations in human skull shape. The bones of the skull slot together like a jigsaw. The ethmoid bone also contains the ethmoid air cells. Although the methods for determining origin are not 100 percent accurate, and many skulls may be a combination of ethnicities, they are useful for getting a general idea of race and origin. Neandertal genes give clues to human brain evolution A distinctive feature of modern humans is our round (globular) skulls and brains. The middle cranial fossa is divided at the midline by the upward bony prominence of the sella turcica, a part of the sphenoid bone. The lower and posterior parts of the septum are formed by the triangular-shaped vomer bone. Located just above the inferior concha is the middle nasal concha, which is part of the ethmoid bone. The frontal bone forms the roof and the zygomatic bone forms the lateral wall and lateral floor. The right and left medial pterygoid plates form the posterior, lateral walls of the nasal cavity. The human skull has an oblong shape that is longer from front to back than it is wide. Figure 11. The facial bones underlie the facial structures, form the nasal cavity, enclose the eyeballs, and support the teeth of the upper and lower jaws. Cleft palate affects approximately 1:2500 births and is more common in females. The eye orbits are rectangular and spaced farther apart with a wider nasal bridge, which is less pronounced than European or Asian types. A much smaller portion of the vomer can also be seen when looking into the anterior opening of the nasal cavity. The skull consists of the cranium and the mandible, or jawbone.It is the semi-circular bone at the bottom of the skull and attached to the cranium at the jaw. If this occurs, a cleft lip will also be seen. The most posterior is the sphenoid sinus, located in the body of the sphenoid bone, under the sella turcica. It results from a failure of the two halves of the hard palate to completely come together and fuse at the midline, thus leaving a gap between them. This is a complex area that varies in depth and has numerous openings for the passage of cranial nerves, blood vessels, and the spinal cord. can be revealed if the skull is suitably examined. Isolated Mandible. The eye orbits are rounded and don't have the same downward slope as European skulls. There are eight major bones and eight auxiliary bones of the cranium. It contains the cerebellum of the brain. On the inferior aspect of the skull, each half of the sphenoid bone forms two thin, vertically oriented bony plates. Using the skull-based categorization, anthropologists identified three or four racial groups; • Caucasoid characterized by a tall dolichocephalic skull, receded zygomas, large brow ridge and projecting-narrow nasal apertures. The cheek bones are wide, flare out to the sides of the skull and are forward-sloping. From anterior to posterior, the fossae increase in depth. European skulls, sometimes referred to by the scientific terms Caucasoid or Caucasian, are relatively long and narrow when compared to Asian or African types. The short temporal process of the zygomatic bone projects posteriorly, where it forms the anterior portion of the zygomatic arch (see Figure 3). The skull includes the upper jaw and the cranium. The small superior nasal concha is well hidden above and behind the middle concha. 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). Also seen are the upper and lower jaws, with their respective teeth (Figure 2). They serve to reduce bone mass and thus lighten the skull, and they also add resonance to the voice. It has a pair of lesser wings and a pair of greater wings. Figure 9. The upper portion of the nasal septum is formed by the perpendicular plate of the ethmoid bone and the lower portion is the vomer bone. Many deductions regarding evolutionary processes and diversifications of early groups have been made on the basis of shape and size variations of the zygoma. When human languages were confused at Babel, the resulting isolated groups would have led to a large number of genetic bottlenecks and lineages of humans with unique suites of trait variations such as skin color, skeletal sizes, and skull shape variations. More extreme variations -- especially in infants -- may indicate a medical issue. Published on December 14, 2018. The teeth are smaller in comparison to other skull types and set closely together. Sagittal Section of Skull. The hyoid is held in position by a series of small muscles that attach to it either from above or below. These muscles act to move the hyoid up/down or forward/back. The squamous suture is located on the lateral skull. Variations of the covering layers of the middle concha and middle cranial fossae sides of orbits! 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