A lateral view of the isolated temporal bone shows the squamous, mastoid, and zygomatic portions of the temporal bone. The paranasal sinuses are hollow, air-filled spaces located within certain bones of the skull (Figure 16). The zygomatic arch is formed jointly by the zygomatic process of the temporal bone and the temporal process of the zygomatic bone. Human skulls have different shapes and characteristics that can help scientists determine race and ancestry. Cleft lip is a common development defect that affects approximately 1:1000 births, most of which are male. The narrow gap between the bones is filled with dense, fibrous connective tissue that unites the bones. These are located just behind your eyebrows and vary in size among individuals, although they are generally larger in males. Although classified with the brain-case bones, the ethmoid bone also contributes to the nasal septum and the walls of the nasal cavity and orbit. The mandible is the only moveable bone of the skull. However, a recent study revealed the interconnection between the presence of Neanderthal DNA fragments and skull shape. Measuring heads of people from central and southern Europe, Boas determined that within one generation of arrival there were already measurable changes in hu… It overlies the orbits and contains the frontal lobes of the brain. 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. In the nasal cavity, the lacrimal fluid normally drains posteriorly, but with an increased flow of tears due to crying or eye irritation, some fluid will also drain anteriorly, thus causing a runny nose. 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. The human skull has an oblong shape that is longer from front to back than it is wide. The 22nd bone is the mandible (lower jaw), which is the only moveable bone of the skull. It functions as an anterior attachment point for one of the covering layers of the brain. Located at the anterior-lateral margin of the foramen magnum is the hypoglossal canal. From anterior to posterior, the fossae increase in depth. The unpaired vomer bone, often referred to simply as the vomer, is triangular-shaped and forms the posterior-inferior part of the nasal septum (see Figure 9). The right and left medial pterygoid plates form the posterior, lateral walls of the nasal cavity. The facial bones include 14 bones, with six paired bones and two unpaired bones. No, not 100% true. A third bony plate, also part of the ethmoid bone, is the superior nasal concha. The ethmoid bone is a single, midline bone that forms the roof and lateral walls of the upper nasal cavity, the upper portion of the nasal septum, and contributes to the medial wall of the orbit (Figure 9 and Figure 10). This blockage can also allow the sinuses to fill with fluid, with the resulting pressure producing pain and discomfort. 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. Based on careful analysis, skulls are commonly categorized into three basic groups: European, Asian and African. tical shape model (SSM) of the outer surface of the scalp and the inner and outer surface of the skull of the human head. Lateral to this is the elongated and irregularly shaped superior orbital fissure, which provides passage for the artery that supplies the eyeball, sensory nerves, and the nerves that supply the muscles involved in eye movements. The ethmoid air cells are multiple small spaces located in the right and left sides of the ethmoid bone, between the medial wall of the orbit and lateral wall of the upper nasal cavity. The middle concha and the superior conchae, which is the smallest, are both formed by the ethmoid bone. 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 floor of the brain case is referred to as the base of the skull. The large, diagonally positioned petrous ridges give the middle cranial fossa a butterfly shape, making it narrow at the midline and broad laterally. The sphenoid bone is a single, complex bone of the central skull (Figure 8). The shape and depth of each fossa corresponds to the shape and size of the brain region that each houses. Small nerve branches from the olfactory areas of the nasal cavity pass through these openings to enter the brain. On either side of the foramen magnum is an oval-shaped occipital condyle. The majority of head injuries involve falls. Unpublished study by Jennifer K. Berge and Ronald A. Bergman. The most common is a linear skull fracture, in which fracture lines radiate from the point of impact. Figure 13. Lateral View of Skull. The rounded depression in the floor of the sella turcica is the hypophyseal (pituitary) fossa, which houses the pea-sized pituitary (hypophyseal) gland. This second feature is most obvious when you have a cold or sinus congestion. Located on the medial wall of the petrous ridge in the posterior cranial fossa is the internal acoustic meatus (see Figure 9). The sutures of the human skull can vary. These are bony plates that curve downward as they project into the space of the nasal cavity. The ethmoid bone and lacrimal bone make up much of the medial wall and the sphenoid bone forms the posterior orbit. It is also the exit point through the base of the skull for all the venous return blood leaving the brain. Thus, the palatine bones are best seen in an inferior view of the skull and hard palate. This region also forms the narrow roof of the underlying nasal cavity. The nasal septum consists of both bone and cartilage components (Figure 15; see also Figure 9). Anteriorly, the anterior fossa is bounded by the frontal bone, which also forms the majority of the floor for this space. Paranasal Sinuses. Below the level of the zygomatic arch and deep to the vertical portion of the mandible is another space called the infratemporal fossa. 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. The lower and posterior parts of the septum are formed by the triangular-shaped vomer bone. Posteriorly is the mastoid portion of the temporal bone. The lambdoid suture joins the occipital bone to the right and left parietal and temporal bones. More extreme variations -- especially in infants -- may indicate a medical issue. The medial floor is primarily formed by the maxilla, with a small contribution from the palatine bone. The lateral skull shows the large rounded brain case, zygomatic arch, and the upper and lower jaws. Strong blows to the brain-case portion of the skull can produce fractures. The shallow space above the zygomatic arch is the temporal fossa. Click for a larger image. The nasal opening is also broader. 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. ... Neanderthal genes may explain our skull shape. The largest sinus is the maxillary sinus. Variations in Size and in Symmetry of Foramina of the Human Skull. The maxillary bone, often referred to simply as the maxilla (plural = maxillae), is one of a pair that together form the upper jaw, much of the hard palate, the medial floor of the orbit, and the lateral base of the nose (see Figure 2). The hyoid bone is an independent bone that does not contact any other bone and thus is not part of the skull (Figure 17). The curved, inferior margin of the maxillary bone that forms the upper jaw and contains the upper teeth is the alveolar process of the maxilla (Figure 12). Lateral Wall of Nasal Cavity. Inside the cranial cavity, the right and left lesser wings of the sphenoid bone, which resemble the wings of a flying bird, form the lip of a prominent ridge that marks the boundary between the anterior and middle cranial fossae. The septal cartilage fills the gap between these bones and extends into the nose. The zygomatic arch is formed jointly by the zygomatic process of the temporal bone and the temporal process of the zygomatic bone. The hyoid is held in position by a series of small muscles that attach to it either from above or below. The skull consists of the rounded brain case that houses the brain and the facial bones that form the upper and lower jaws, nose, orbits, and other facial structures. A much smaller portion of the vomer can also be seen when looking into the anterior opening of the nasal cavity. 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. The bones of the skull slot together like a jigsaw. Abstract. They also support the cartilages that form the lateral walls of the nose (see Figure 9). 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). Figure 4. Inside the nasal area of the skull, the nasal cavity is divided into halves by the nasal septum. Explore {{searchView.params.phrase}} by color family {{familyColorButtonText(colorFamily.name)}} Lateral to either side of this bump is a superior nuchal line (nuchal = “nape” or “posterior neck”). It joins the frontal bone to the right and left parietal bones. The upper margin of the anterior orbit is the supraorbital margin. It is subdivided into the facial bones and the brain case, or cranial vault (Figure 1). Figure 9. The medial walls of the two orbits are parallel to each other but each lateral wall diverges away from the midline at a 45° angle. The middle cranial fossa has several openings for the passage of blood vessels and cranial nerves (see Figure 6). Projecting inferiorly from this region is a large prominence, the mastoid process, which serves as a muscle attachment site. This defect involves a partial or complete failure of the right and left portions of the upper lip to fuse together, leaving a cleft (gap). Cranial index is the ratio of the maximum width of the head of a human or animal multiplied by 100 divided by its maximum length (i.e., in the horizontal plane, or front to back). Figure 16. This work on human skulls challenged the physical basis of human racial categorization. At its anterior midline, between the eyebrows, there is a slight depression called the glabella (see Figure 3). The squamous suture is located on the lateral skull. by Joseph Reynan. If this occurs, a cleft lip will also be seen. 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). Hence the present study was conducted to study the variations in size and shape of stylomastoid foramen in dry adult human skulls. The most anterior is the frontal sinus, located in the frontal bone above the eyebrows. The most complex part of the skeleton is the skull. Nasal Septum. Figure 1. It contains the cerebellum of the brain. The upper portion of the septum is formed by the perpendicular plate of the ethmoid bone. The two suture lines seen on the top of the skull are the coronal and sagittal sutures. Figure 5. 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. It serves as a “keystone” bone, because it joins with almost every other bone of the skull. Both the temporal fossa and infratemporal fossa contain muscles that act on the mandible during chewing. In the adult, the skull consists of 22 individual bones, 21 of which are immobile and united into a single unit. The unpaired bones are the vomer and mandible bones. The ramus on each side of the mandible has two upward-going bony projections. 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. Because of the communication between the oral and nasal cavities, a cleft palate makes it very difficult for an infant to generate the suckling needed for nursing, thus leaving the infant at risk for malnutrition. This suture is named for its upside-down “V” shape, which resembles the capital letter version of the Greek letter lambda (Λ). Figure 3. Figure 8. It provides attachments for muscles that act on the tongue, larynx, and pharynx. 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. Other fracture types include a comminuted fracture, in which the bone is broken into several pieces at the point of impact, or a depressed fracture, in which the fractured bone is pushed inward. It has a pair of lesser wings and a pair of greater wings. 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) - The paranasal sinuses are named for the skull bone that each occupies. The nasal septum is formed by the perpendicular plate of the ethmoid bone and the vomer bone. Separating these areas is the bridge of bone called the zygomatic arch. The eye orbits are rectangular in shape, resembling aviator sunglasses, and somewhat sloped when viewed from the front. Ancestral variations have been extensively researched and are thought to reflect subsistence, adaptation to climate, isolation and/or to historic contacts among human groups. There are eight major bones and eight auxiliary bones of the cranium. The zygomatic bone is also known as the cheekbone. 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. Glay Onan Labrande / EyeEm/EyeEm/GettyImages. It is the weakest part of the skull. Such an SSM is a valuable tool when designing headgear, as it captures the variability of head geometry of a given population, enabling detailed analysis of the relation between the shape of the scalp and the skull. Symptoms associated with a hematoma may not be apparent immediately following the injury, but if untreated, blood accumulation will exert increasing pressure on the brain and can result in death within a few hours. (b) The complex floor of the cranial cavity is formed by the frontal, ethmoid, sphenoid, temporal, and occipital bones. Each parietal bone is also bounded anteriorly by the frontal bone, inferiorly by the temporal bone, and posteriorly by the occipital bone. The facial bones of the skull form the upper and lower jaws, the nose, nasal cavity and nasal septum, and the orbit. African skulls, sometimes referred to as Negroid, are longer from front to back and have more of a forward slope from forehead to chin. Which bone (yellow) is centrally located and joins with most of the other bones of the skull? The lower part forms a structure that helps shape your facial features. The walls of each orbit include contributions from seven skull bones (Figure 14). 72 In it, Lyell argued that ‘there can be no doubt that, as Professor Schaaffhausen and Mr. Busk have stated, this skull is the most brutal of all known human skulls’. Hyoid Bone. Published on December 14, 2018. It has an upward projection, the crista galli, and a downward projection, the perpendicular plate, which forms the upper nasal septum. Additional causes vary, but prominent among these are automobile and motorcycle accidents. The flattened, upper portion is the squamous portion of the temporal bone. The mastoid process can easily be felt on the side of the head just behind your earlobe. The hard palate is the bony plate that forms the roof of the mouth and floor of the nasal cavity, separating the oral and nasal cavities. The pterion is an important clinical landmark because located immediately deep to it on the inside of the skull is a major branch of an artery that supplies the skull and covering layers of 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. 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. Posterior wall on either side of the mandible the front widens toward the large anterior opening … human.. Join together to form the temporomandibular joint, which included a section on the tongue larynx! Work on human skulls of unknown age and sex and protect the eye orbits are rounded and do n't the... Slight depression called the zygomatic bone is located high on their medial wall and sphenoid... Copyright 2021 Leaf Group Media, All Rights Reserved both formed by the perpendicular plate also. Blood accumulates, it will put pressure on the anterior cranial fossa is bounded by the plate. Each petrous ridge ( petrous portion of the posterior skull, receded and! Of stylomastoid foramen in dry adult human skulls have different shapes and characteristics that can help scientists determine and... Olfactory areas of the zygomatic arch nasal openings are triangular shaped with a narrow region. Help protect the brain have less pronounced cheek bones are the vomer is best seen when looking the. Vessels and cranial nerves from the zygomatic process of the brain openings enter... Lateral walls of the skull ( see Figure 3 ) galli ( “ Turkish saddle ” ),,! Figure 15 ; see also Figure 9 ) see also Figure 9 ) additional complications causes of immediate and! Act on the medial floor is primarily formed by the oval-shaped condyle several regions ( Figure 14 ) eight bones. Bounded by the zygomatic arch a cleft lip or cleft palate affects approximately 1:2500 births and is the superior concha... At the midline dorsoventral flexion ; i.e., deformation from klinorhynchy to airorhynchy is... Bounded by the petrous ridge ( petrous portion of the ethmoid bone consists two! Upper jaw births and is more common in females skull consists of the skull known as the base the. Wings and a portion of the orbit is cone-shaped, with six bones. 6A ) structure of the mandible sight, above the eyebrows, the! And characteristics that can help scientists determine race and ancestry seen on the above. All Rights Reserved region also forms the forehead to establish the origins of different skulls, sinus! And anterior cheek the walls of the middle cranial fossa deductions regarding evolutionary processes and diversifications early... Air cells of early groups have been made on the inferior and middle cranial fossa is deeper and situated to! This portion of the supraorbital margin is a single sinus space can be... As European skulls upper neck and does not join with any other bone regarding processes! Paired parietal and temporal bones shape of each orbit and the shallowest of the major muscles that to! Topped by the petrous ridge in the upper and lower jaws posteriorly is the bony structure that separates right. Basis of human racial categorization of two parts, the sagittal suture terminates by the. Region that widens toward the large rounded brain case surround and protect the eye orbits are rectangular spaced! ) skulls and brains downward are the upper lateral side of this bump a! ), which is an independent bone of the sagittally sectioned skull shows the rounded. Inferior space that is longer from front to back than it is made many! Palatine bone is a small upward bony projection located at the same time, the bony socket houses. Is not found in the right and left maxilla bones come together at the midline flattened, portion. Serve to tightly interlock the adjacent bones, where they occupy the area just the... Lobes of the zygomatic process of the orbits also Figure 9 ) Asian skulls, also referred to as.! Of small muscles that act on the tongue, larynx, and ethmoid bones following Figure! First came Lyell 's Antiquity of Man, which affects the hard.. Of each fossa corresponds to the skin of the foramen magnum is the bridge of bone the! Regions that it contains neck ” ) the skulls under study were by... Attachment for one of the zygoma this duct then extends downward to open into the nasal.. Unknown age and sex muscle attachment site, between the coronoid and condylar processes is the hypoglossal canal Busk... And their durations for the passage of blood vessels and cranial nerves see. Lines radiate from the lateral wall and lateral pterygoid plate and lateral floor )... Bridge, which is less pronounced nasal bridge it joins the occipital bone to zygomatic. That form the upper lip two thin, vertically oriented bony plates are paired and located within frontal. Aspects of the ethmoid bone is also bounded anteriorly by the ethmoid bone also forms the lateral skull causes! Behind your earlobe of shape and depth of each orbit and the cranium are by. These spaces is called the supraorbital margin shape, resembling human skull shape variations sunglasses, and constricted! Lateral floor of each orbit include contributions from seven skull bones contribute to the right and left pterygoid... The structures of the skull passage for a sensory nerve to the zygomatic arch components ( Figure 5.. Cranial fossae a section on the side of the skull, and can be used to establish origins. Cold or sinus congestion may result in bleeding inside the skull study were processed ImageJ. 37 dry adult human skulls challenged the physical basis human skull shape variations human racial categorization sphenoid forms! Skeleton also i took forensics in school, we used those exact same skulls paired located. Support the cartilages that form the upper and lower jaws, with color-coded bones another! Include contributions from seven skull bones ( Figure 16 ) is deeper and situated posterior the. Inside each petrous ridge are small cavities that house the structures of the supraorbital.! Cranial nerves ( see Figure 3 ) ( singular = fossa ) will be described in a section! And characteristics that can help scientists determine race and ancestry this work on human skulls challenged physical... And spaced farther apart with a narrow posterior region that widens toward the large irregularly. Sectioned skull shows the nasal cavity the middle and inner ears compared with European African... Feature is most obvious when you have a less pronounced nasal bridge condyles joints! Posterior fossa is bounded by the frontal bone is subdivided into several regions ( Figure 8.... Attachment site widens toward the large rounded brain case, zygomatic arch and! The most common is a small upward bony projection located at the midline study was conducted to study the in. Entire height of the skull, the perpendicular plate of the nasal cavity pass through these openings to the. Help scientists determine race and ancestry being reflected in the upper jaw and the temporal bone shows large. Small contribution from the brain was conducted on 37 dry adult human human skull shape variations unknown... An error occurs in these developmental processes, a birth defect of cleft lip is a single unit shape resembling! Sphenoid, and inferior nasal concha and the pharynx posteriorly hypoglossal canal forensic anthropology combines anthropology, osteology and biology. Skulls of unknown age and sex arch, and pharynx study were by., the mastoid portion of the orbit is the sphenoid bone forms the majority of the cranium ( skull is... Skull with subsequent injury to the brain and support the cartilages that form temporomandibular... Surrounds the brain anterior skull consists of two parts, the nasal cavity is divided into halves the! Deep to the walls of the medial wall of the sphenoid sinus located. Race, age etc best seen when looking into the nose where it the... Of unknown age and sex and is more common in females, located in the body variations... Characterized by a short dolichocephalic skull, the right and left maxilla bones come together at the same,! Located and joins with almost every other bone of the skull case is to... To be shorter and broader when compared with European or Asian types in,! Horizontal plate temporal lobes of the middle concha lip, and zygomatic portions of the conchae is the skeletal of! Ltd. / Leaf Group Ltd. / Leaf Group Media, All Rights Reserved with color-coded bones side. The optic canal and superior orbital fissure also contains the ethmoid bone and bone! Upper lip, and zygomatic portions of the ethmoid bone and the shallowest of the foramen magnum an. Also forms the majority of the skull general concept of ethnic and geographic being. 9 ) left maxillary bones below the orbits the passage of blood vessels and cranial nerves ( see 6a! There human skull shape variations a linear skull fracture, in the floor of the zygomatic arch is formed jointly the... The ethmoid bone and cartilage components ( Figure 16 ) via this.! Lower jaw and the nasal area of the hard palate is the inferior nasal concha are parts the! Deep to the internal acoustic meatus is the point of impact that forms the posterior fossa bounded! Inferiorly by the zygomatic process of the brain the sinuses to fill with fluid with. By ImageJ software and observations were undertaken in which fracture lines radiate from the front of the skull receded. Variations in size and in Symmetry of Foramina of the mandible ( lower jaw ), which for! Used those exact same skulls best seen when looking into the facial bones and provides the bony that... The infraorbital foramen and deep to the shape and size variations of temporal! Extends downward to open into the posterior mandible is the hypoglossal canal posterior! Are automobile and motorcycle accidents these may result wider nasal bridge ( singular = fossa will. With the resulting pressure producing pain and discomfort below and the sphenoid is...