Inside the skull, it forms the anterior cranial fossa, which contains the frontal lobes Internally, it forms the posterior cranial fossa where the occipital lobe of the. Skull & Mandible. ☠ Sutures. ☠ Bones of the Cranium. ☠ Major Landmarks of the Cranium. ☠ Functions of the Cranium. ☠ Cranial Metrics. Sutures. Sutures. The skull is one of the most complex and difficult chapters in human anatomy. It is also one of the few anatomic structures, where almost all the different medical.
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“The Anatomy of the Human Skull” the Skull Anatomy becomes transparent. This series of skull models comprises. 5 different aspects: 1.) The skull model can be. Skull: lateral view. ○ Frankfurt plane. (anatomical position,. OrbitoMeatal line): upper margin of ext. acoustic meatus - orbit floor → horizontal. ○ superior. Leopard skull (P. David Polly). Reading Benton Chapter 5 of the Dog). Mammalian skull in lateral view Exterior openings of cranial nerves on human skull.
Share This Book. 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 long sutures located between the bones of the brain case are not straight, but instead follow irregular, tightly twisting paths. This region also forms the narrow roof of the underlying nasal cavity. The larger of these is the inferior nasal concha , an independent bone of the skull. Labeled arm animation.
Animation of a human skull OUVC that yaws, rolls, and explodes into its constituent bones and then repeats with the bones labeled. See here for more human skull movies.
See here for details of the methods. Labeled hand animation. Animation of the hand anatomy of a male human showing the labeled surface anatomy, vascular anatomy, and osteology. Labeled arm animation. Animation of the upper extremity anatomy of a male human showing the labeled surface anatomy, vascular anatomy, and osteology. Labeled leg animation. Animation of the lower extremity skeletal anatomy of an elderly female human showing the labeled osteology.
Skull animation. Yaw animation of the skull of a human OUVC , revealing the labeled anatomy of the brain, nasal cavity, paranasal air sinuses, and middle ear sinuses. Roll animation of the skull of a human OUVC , revealing the labeled anatomy of the brain, nasal cavity, paranasal air sinuses, and middle ear sinuses. This website provides supplementary information as an adjunct to a published paper. Witmer, with the skilled assistance of Ryan Ridgely , is responsible for the content of the website.
Content provided here is for educational and research purposes only, and may not be used for any commercial purpose without the permission of L.
Witmer and other relevant parties. This project was funded by grants from the National Science Foundation. Last updated: The frontal bone also forms the supraorbital margin of the orbit. Near the middle of this margin, is the supraorbital foramen, the opening that provides passage for a sensory nerve to the forehead.
The frontal bone is thickened just above each supraorbital margin, forming rounded brow ridges. These are located just behind your eyebrows and vary in size among individuals, although they are generally larger in males. Inside the cranial cavity, the frontal bone extends posteriorly. This flattened region forms both the roof of the orbit below and the floor of the anterior cranial cavity above see Figure 6 b.
The occipital bone is the single bone that forms the posterior skull and posterior base of the cranial cavity Figure 7 ; see also Figure 6. 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.
The nuchal lines represent the most superior point at which muscles of the neck attach to the skull, with only the scalp covering the skull above these lines. On the base of the skull, the occipital bone contains the large opening of the foramen magnum , which allows for passage of the spinal cord as it exits the skull.
On either side of the foramen magnum is an oval-shaped occipital condyle. These condyles form joints with the first cervical vertebra and thus support the skull on top of the vertebral column. The sphenoid bone is a single, complex bone of the central skull Figure 8. The sphenoid forms much of the base of the central skull see Figure 6 and also extends laterally to contribute to the sides of the skull see Figure 3.
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. This bony region of the sphenoid bone is named for its resemblance to the horse saddles used by the Ottoman Turks, with a high back and a tall front. The rounded depression in the floor of the sella turcica is the hypophyseal pituitary fossa , which houses the pea-sized pituitary hypophyseal gland.
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 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. On the inferior aspect of the skull, each half of the sphenoid bone forms two thin, vertically oriented bony plates.
The right and left medial pterygoid plates form the posterior, lateral walls of the nasal cavity. The somewhat larger lateral pterygoid plates serve as attachment sites for chewing muscles that fill the infratemporal space and act on the mandible.
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 On the interior of the skull, the ethmoid also forms a portion of the floor of the anterior cranial cavity see Figure 6 b.
Within the nasal cavity, the perpendicular plate of the ethmoid bone forms the upper portion of the nasal septum. The ethmoid bone also forms the lateral walls of the upper nasal cavity.
Extending from each lateral wall are the superior nasal concha and middle nasal concha, which are thin, curved projections that extend into the nasal cavity Figure In the cranial cavity, the ethmoid bone forms a small area at the midline in the floor of the anterior cranial fossa. This region also forms the narrow roof of the underlying nasal cavity. This portion of the ethmoid bone consists of two parts, the crista galli and cribriform plates.
It functions as an anterior attachment point for one of the covering layers of the brain. Small nerve branches from the olfactory areas of the nasal cavity pass through these openings to enter the brain. 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. 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.
A suture is an immobile joint between adjacent bones of the skull. The narrow gap between the bones is filled with dense, fibrous connective tissue that unites the bones. The long sutures located between the bones of the brain case are not straight, but instead follow irregular, tightly twisting paths.
These twisting lines serve to tightly interlock the adjacent bones, thus adding strength to the skull for brain protection.
The two suture lines seen on the top of the skull are the coronal and sagittal sutures. The coronal suture runs from side to side across the skull, within the coronal plane of section see Figure 3. It joins the frontal bone to the right and left parietal bones.
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. It unites the right and left parietal bones. On the posterior skull, the sagittal suture terminates by joining the lambdoid suture. The lambdoid suture extends downward and laterally to either side away from its junction with the sagittal suture.
The lambdoid suture joins the occipital bone to the right and left parietal and temporal bones. The squamous suture is located on the lateral skull. It unites the squamous portion of the temporal bone with the parietal bone see Figure 3. 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.
It is the weakest part of the skull. Skeletal System Head and traumatic brain injuries are major causes of immediate death and disability, with bleeding and infections as possible additional complications.
According to the Centers for Disease Control and Prevention , approximately 30 percent of all injury-related deaths in the United States are caused by head injuries. The majority of head injuries involve falls. They are most common among young children ages 0—4 years , adolescents 15—19 years , and the elderly over 65 years. Additional causes vary, but prominent among these are automobile and motorcycle accidents.
Strong blows to the brain-case portion of the skull can produce fractures. These may result in bleeding inside the skull with subsequent injury to the brain. The most common is a linear skull fracture, in which fracture lines radiate from the point of impact. 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.
In a contrecoup counterblow fracture, the bone at the point of impact is not broken, but instead a fracture occurs on the opposite side of the 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.
A blow to the lateral side of the head may fracture the bones of the pterion. 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. A strong blow to this region can fracture the bones around the pterion. 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.
As blood accumulates, it will put pressure on the brain. 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. View this animation to see how a blow to the head may produce a contrecoup counterblow fracture of the basilar portion of the occipital bone on the base of the skull.
Why may a basilar fracture be life threatening? The facial bones of the skull form the upper and lower jaws, the nose, nasal cavity and nasal septum, and the orbit. The facial bones include 14 bones, with six paired bones and two unpaired bones. The paired bones are the maxilla, palatine, zygomatic, nasal, lacrimal, and inferior nasal conchae bones. The unpaired bones are the vomer and mandible bones.
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 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 Each tooth is anchored into a deep socket called an alveolus. On the anterior maxilla, just below the orbit, is the infraorbital foramen. This is the point of exit for a sensory nerve that supplies the nose, upper lip, and anterior cheek.
On the inferior skull, the palatine process from each maxillary bone can be seen joining together at the midline to form the anterior three-quarters of the hard palate see Figure 6 a. 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 palatine bone is one of a pair of irregularly shaped bones that contribute small areas to the lateral walls of the nasal cavity and the medial wall of each orbit. The largest region of each of the palatine bone is the horizontal plate.
The plates from the right and left palatine bones join together at the midline to form the posterior quarter of the hard palate see Figure 6 a. Thus, the palatine bones are best seen in an inferior view of the skull and hard palate. Cleft Lip and Cleft Palate During embryonic development, the right and left maxilla bones come together at the midline to form the upper jaw.
At the same time, the muscle and skin overlying these bones join together to form the upper lip. Inside the mouth, the palatine processes of the maxilla bones, along with the horizontal plates of the right and left palatine bones, join together to form the hard palate. If an error occurs in these developmental processes, a birth defect of cleft lip or cleft palate may result. Cleft lip is a common development defect that affects approximately 1: 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.
A more severe developmental defect is cleft palate, which affects the hard palate. The hard palate is the bony structure that separates the nasal cavity from the oral cavity.
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. Cleft palate affects approximately 1: 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 gap allows for communication between the nasal and oral cavities. 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. If this occurs, a cleft lip will also be seen. 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.
Surgical repair is required to correct cleft palate defects. The zygomatic bone is also known as the cheekbone. 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. The short temporal process of the zygomatic bone projects posteriorly, where it forms the anterior portion of the zygomatic arch see Figure 3. The nasal bone is one of two small bones that articulate join with each other to form the bony base bridge of the nose.
They also support the cartilages that form the lateral walls of the nose see Figure 9. These are the bones that are damaged when the nose is broken. Each lacrimal bone is a small, rectangular bone that forms the anterior, medial wall of the orbit see Figure 2 and Figure 3.
The anterior portion of the lacrimal bone forms a shallow depression called the lacrimal fossa , and extending inferiorly from this is the nasolacrimal canal. The lacrimal fluid tears of the eye , which serves to maintain the moist surface of the eye, drains at the medial corner of the eye into the nasolacrimal canal. This duct then extends downward to open into the nasal cavity, behind the inferior nasal concha. 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 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 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 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 vomer is best seen when looking from behind into the posterior openings of the nasal cavity see Figure 6 a. In this view, the vomer is seen to form the entire height of the nasal septum. A much smaller portion of the vomer can also be seen when looking into the anterior opening of the nasal cavity.
The mandible forms the lower jaw and is the only moveable bone of the skull.
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. The outside margin of the mandible, where the body and ramus come together is called the angle of the mandible Figure The ramus on each side of the mandible has two upward-going bony projections. The more anterior projection is the flattened coronoid process of the mandible , which provides attachment for one of the biting muscles.
The posterior projection is the condylar process of the mandible , which is topped by the oval-shaped condyle. The condyle of the mandible articulates joins with the mandibular fossa and articular tubercle of the temporal bone.
Together these articulations form the temporomandibular joint, which allows for opening and closing of the mouth see Figure 3. The broad U-shaped curve located between the coronoid and condylar processes is the mandibular notch. The orbit is the bony socket that houses the eyeball and contains the muscles that move the eyeball or open the upper eyelid.
Each orbit is cone-shaped, with a narrow posterior region that widens toward the large anterior opening. To help protect the eye, the bony margins of the anterior opening are thickened and somewhat constricted.
This divergence provides greater lateral peripheral vision. The walls of each orbit include contributions from seven skull bones Figure The frontal bone forms the roof and the zygomatic bone forms the lateral wall and lateral floor.
The medial floor is primarily formed by the maxilla, with a small contribution from the palatine bone. The ethmoid bone and lacrimal bone make up much of the medial wall and the sphenoid bone forms the posterior orbit. At the posterior apex of the orbit is the opening of the optic canal , which allows for passage of the optic nerve from the retina to the brain.
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 nasal septum consists of both bone and cartilage components Figure 15 ; see also Figure 9. The upper portion of the septum is formed by the perpendicular plate of the ethmoid bone.
The lower and posterior parts of the septum are formed by the triangular-shaped vomer bone. In an anterior view of the skull, the perpendicular plate of the ethmoid bone is easily seen inside the nasal opening as the upper nasal septum, but only a small portion of the vomer is seen as the inferior septum.
A better view of the vomer bone is seen when looking into the posterior nasal cavity with an inferior view of the skull, where the vomer forms the full height of the nasal septum. The anterior nasal septum is formed by the septal cartilage , a flexible plate that fills in the gap between the perpendicular plate of the ethmoid and vomer bones. This cartilage also extends outward into the nose where it separates the right and left nostrils.
The septal cartilage is not found in the dry skull. These are bony plates that curve downward as they project into the space of the nasal cavity. They serve to swirl the incoming air, which helps to warm and moisturize it before the air moves into the delicate air sacs of the lungs.
This also allows mucus, secreted by the tissue lining the nasal cavity, to trap incoming dust, pollen, bacteria, and viruses. The largest of the conchae is the inferior nasal concha, which is an independent bone of the skull. The middle concha and the superior conchae, which is the smallest, are both formed by the ethmoid bone.
When looking into the anterior nasal opening of the skull, only the inferior and middle conchae can be seen. The small superior nasal concha is well hidden above and behind the middle concha. Inside the skull, the floor of the cranial cavity is subdivided into three cranial fossae spaces , which increase in depth from anterior to posterior see Figure 4 , Figure 6 b , and Figure 9. Since the brain occupies these areas, the shape of each conforms to the shape of the brain regions that it contains.
Each cranial fossa has anterior and posterior boundaries and is divided at the midline into right and left areas by a significant bony structure or opening. The anterior cranial fossa is the most anterior and the shallowest of the three cranial fossae.
It overlies the orbits and contains the frontal lobes of the brain. Anteriorly, the anterior fossa is bounded by the frontal bone, which also forms the majority of the floor for this space. The lesser wings of the sphenoid bone form the prominent ledge that marks the boundary between the anterior and middle cranial fossae.
Located in the floor of the anterior cranial fossa at the midline is a portion of the ethmoid bone, consisting of the upward projecting crista galli and to either side of this, the cribriform plates. The middle cranial fossa is deeper and situated posterior to the anterior fossa. It extends from the lesser wings of the sphenoid bone anteriorly, to the petrous ridges petrous portion of the temporal bones posteriorly.
The large, diagonally positioned petrous ridges give the middle cranial fossa a butterfly shape, making it narrow at the midline and broad laterally. The temporal lobes of the brain occupy this fossa. 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 middle cranial fossa has several openings for the passage of blood vessels and cranial nerves see Figure 6. The posterior cranial fossa is the most posterior and deepest portion of the cranial cavity. It contains the cerebellum of the brain. The posterior fossa is bounded anteriorly by the petrous ridges, while the occipital bone forms the floor and posterior wall.