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Frontal bone

The frontal bone is an unpaired cranial bone that forms the anterior and superior portion of the skull, comprising the forehead, the superior aspect of the orbits, and the nasal segment, thereby protecting the frontal lobes of the brain and the eyes while contributing to facial structure.^[1] It originates from neural crest cells during embryonic development.^[1] Structurally, the frontal bone consists of three main parts: the squamous part, which forms the smooth, convex forehead and includes the prominent glabella at the midline between the eyebrows; the orbital part, which constitutes the roof of the orbits and contains the frontal sinuses superiorly; and the nasal segment, which articulates with the nasal bones to form the bridge of the nose.^[1] Key features include the paired supraorbital margins and foramina for neurovascular passage, the singular foramen caecum for emissary veins, and the frontal crest on the internal surface for falx cerebri attachment.^[1] The bone articulates with 12 other cranial and facial bones via sutures, including the coronal suture with the parietals superiorly, the frontozygomatic suture laterally, and the ethmoidal notch inferiorly.^[1] Functionally, the frontal bone provides robust protection for underlying neural structures and the ocular apparatus, while its squamous portion serves as an attachment site for muscles of facial expression, such as the frontalis, procerus, and orbicularis oculi.^[1] Blood supply derives from branches of both the external carotid (superficial temporal and supraorbital arteries) and internal carotid (anterior and posterior ethmoidal arteries) systems, with venous drainage occurring via the supraorbital veins, dural sinuses, and ultimately the internal jugular vein.^[1] Sensory innervation is provided by the ophthalmic division of the trigeminal nerve (CN V) through the supraorbital foramina, while motor supply to attached muscles comes from the facial nerve (CN VII).^[1] Developmentally, the frontal bone ossifies intramembranously from two primary centers beginning in the eighth week of gestation, initially as separate right and left halves divided by the metopic (frontal) suture, which typically fuses between ages 2 and 8 but persists in about 5–10% of adults as metopism.^[1] In infants, the anterior fontanelle (bregma) at the junction of the frontal and parietal bones allows for brain growth assessment and palpation of intracranial pressure.^[1] Clinically, the frontal bone's prominence makes it susceptible to fractures in 5–15% of facial traumas, often from high-impact injuries, potentially leading to complications such as cerebrospinal fluid leaks, orbital hematoma, or infection via the frontal sinuses.^[1] Its proximity to the pterion region heightens risks of middle meningeal artery damage and epidural hematomas in lateral impacts.^[1]

Anatomy

Squamous portion

The squamous portion of the frontal bone, also known as the squama, constitutes the vertically oriented upper two-thirds of the bone and forms the prominent forehead region.^[1] Its external surface is smooth and convex, providing a rounded contour to the anterior aspect of the cranium.^[2] Positioned at the midpoint of this surface is the frontal eminence (tuber frontale), a bilateral rounded elevation that contributes to the typical arched shape of the forehead.^[3] The lower border of the external surface features the superciliary arches, paired thickened ridges that form the supraorbital margins above the orbits; these serve as sites of attachment for facial muscles, including the frontalis and orbicularis oculi.^[1] Arising from the medial ends of the superciliary arches and arching posteriorly and superiorly across the external surface are the temporal lines, which diverge into a superior and an inferior line; the superior temporal line provides attachment for the epicranial aponeurosis, while the inferior temporal line anchors the temporal fascia covering the temporalis muscle.^[4] Laterally, on the temporal surface of the squamous portion, a zygomatic process projects from the lower margin, extending to articulate with the frontal process of the zygomatic bone via the zygomaticofrontal suture.^[2] The internal surface of the squamous portion is concave, conforming to the anterior cerebral contour, and exhibits several key features for dural attachments.^[3] In the midline, the frontal crest is a prominent median ridge that projects posteriorly and bifurcates superiorly to form the margins of the sagittal sulcus, a longitudinal groove housing the superior sagittal sinus.^[2] Scattered along the internal surface, particularly near the sagittal sulcus, are the granular foveolae, shallow pits formed by the pressure of arachnoid granulations that facilitate cerebrospinal fluid drainage into the venous system.^[5] The frontal crest itself serves as the primary attachment site for the anterior falx cerebri, a dural fold separating the cerebral hemispheres.^[1]

Orbital portions

The orbital portions of the frontal bone consist of two thin, triangular plates that extend posteriorly from the supraorbital margins of the squamous portion, forming the roof of the orbits on their inferior surface and contributing to the floor of the anterior cranial fossa on their superior surface.^[2]^[3] These plates are smooth and concave inferiorly to accommodate the orbital contents, while their superior surface is convex with shallow depressions corresponding to the overlying cerebral gyri.^[6] In the midline, the two orbital plates are separated by the ethmoidal notch, a quadrilateral gap that is filled by the cribriform plate of the ethmoid bone, forming the roof of the nasal cavity.^[6] The medial borders of the orbital plates feature a small depression known as the trochlear fovea near the anterior margin, providing attachment for the pulley (trochlea) of the superior oblique muscle tendon.^[7]^[8] The posterior border of each orbital plate is serrated and articulates medially with the lesser wing and laterally with the greater wing of the sphenoid bone via the sphenofrontal suture, defining the posterior extent of the orbital roof.^[2]^[3] On the superior surface of each orbital plate, anterolaterally, lies the lacrimal fossa, a shallow depression that lodges the lacrimal gland and its associated connective tissue.^[2]^[3] At the medial end of the supraorbital margin, adjacent to the orbital plate, is the frontal notch (or frontal foramen when ossified), which transmits the supratrochlear nerve and accompanying vessels from the orbit to the forehead.^[9]^[10]

Borders and articulations

The superior border of the frontal bone, located along the posterior aspect of the squamous portion, is a thick, serrated edge that articulates with the two parietal bones to form the coronal suture, which extends transversely across the cranium and meets the sagittal suture at the bregma.^[1] This suture provides a stable fibrous joint allowing for limited cranial growth during development.^[11] The orbital portions of the frontal bone feature distinct borders that facilitate connections within the orbital cavity. The posterolateral borders of these plates articulate medially with the lesser wing and laterally with the greater wing of the sphenoid bone via the sphenofrontal suture, forming a key junction in the orbital wall.^[1] The supraorbital margin, forming the superior border of the orbit, articulates laterally with the zygomatic bone via the zygomaticofrontal suture, medially with the frontal processes of the maxillae and nasal bones, with the orbital plates articulating further medially with the ethmoid and lacrimal bones, contributing to the overall orbital rim structure.^[3] The medial orbital margins articulate with the lacrimal bones through the frontolacrimal sutures and the nasal bones via the frontonasal sutures, supporting the medial boundary of the orbits.^[3] The anterior nasal border of the frontal bone, situated inferiorly between the orbital portions, forms the superior aspect of the nasal notch and articulates with the two nasal bones superiorly as well as the perpendicular plate of the ethmoid bone internally, establishing the nasion at the midline junction.^[1] Overall, the frontal bone articulates with twelve other cranial bones: the two parietal bones, sphenoid bone, ethmoid bone, two nasal bones, two maxillae, two lacrimal bones, and two zygomatic bones, underscoring its central role in cranial architecture.^[6]

Development

Ossification

The frontal bone derives from neural crest mesenchyme and undergoes intramembranous ossification, a process that forms bone directly from mesenchymal tissue without a preceding cartilage precursor.^[12]^[13] This mode of ossification contrasts with endochondral ossification seen in other skull bones, such as those of the cranial base, where cartilage models are first replaced by bone.^[12] Intramembranous ossification involves the differentiation of mesenchymal cells into osteoblasts, which deposit bone matrix around vascular-rich centers, enabling the rapid formation of flat cranial vault elements like the frontal bone.^[14] Two primary ossification centers emerge symmetrically during fetal development, one in each half of the prospective frontal bone, typically appearing in the 8th week post-conception near the frontal eminence or superciliary arch.^[14]^[15] These centers initiate in the supraorbital region and expand centrifugally, gradually forming the squamous portion superiorly and the orbital portions inferiorly, while respecting the midline metopic suture that separates the bilateral halves.^[15]^[14] Secondary ossification centers arise later in fetal life to elaborate specific projections, including pairs in the zygomatic processes laterally, the nasal part medially, and the trochlear fossae.^[14] These accessory centers integrate with the primary ones, contributing to the bone's complex architecture by the third trimester.^[14] At birth, the frontal bone remains as two distinct halves connected by the persistent metopic (frontal) suture, which allows for continued expansion during early postnatal growth.^[14]

Postnatal changes

Following birth, the frontal bone, initially formed from two separate ossification centers fused by the metopic suture, undergoes significant postnatal modifications to achieve its mature form. The metopic suture, which divides the frontal bone into right and left halves, typically obliterates between the ages of 2 and 8 years, resulting in a single, unpaired bone that provides structural integrity to the forehead.^[16] This fusion process is influenced by mechanical forces from cranial growth and is generally complete by early childhood, though incomplete or partial persistence, known as metopism, occurs in approximately 10% of adults as a benign anatomical variant.^[17] Concurrently, the frontal sinuses emerge as small evaginations from the middle nasal meatus around 1 to 2 years of age, initiating pneumatization of the orbital plates during childhood and gradually expanding into the squamous portion of the frontal bone.^[18] This pneumatization proceeds variably among individuals, with the sinuses reaching their full adult size by late adolescence or early adulthood, typically between 18 and 25 years, after continued growth through puberty.^[19] Asymmetry between the left and right frontal sinuses is common, often with one side developing larger chambers due to independent growth patterns, which can influence surgical planning in adulthood.^[20] Throughout postnatal life, the frontal bone undergoes remodeling and thickening, driven by mechanical stresses from muscle attachments, such as the frontalis and corrugator supercilii, as well as weight-bearing forces on the cranium, leading to progressive bone deposition on the external table.^[21] This remodeling is further modulated by the extent of sinus pneumatization, which replaces marrow space and alters local bone density, contributing to the bone's adaptation to functional demands over time.^[19] Sexual dimorphism becomes evident post-puberty, with males exhibiting thicker superciliary arches and more pronounced glabellar regions compared to females, attributable to androgen-driven bone apposition during adolescence.^[22]^[23]

Functions

Structural support

The frontal bone forms the anterior wall of the cranium, serving as a primary protective barrier for the frontal lobes of the cerebrum against frontal impacts.^[1] This positioning allows it to absorb and dissipate kinetic energy from direct blows to the forehead, thereby minimizing transmission of force to underlying neural tissues.^[3] By encasing the anterior aspect of the brain, the bone contributes to the overall integrity of the neurocranium, shielding delicate cortical structures involved in executive functions and decision-making.^[1] The frontal bone enhances the rigidity of the neurocranium through its articulations at the coronal and sphenofrontal sutures, which facilitate the distribution of mechanical forces across the skull.^[1] The coronal suture, connecting the squamous portion to the parietal bones, acts as a key junction for load-bearing, allowing the skull to withstand compressive and tensile stresses during everyday activities and trauma.^[3] Similarly, the sphenofrontal suture links the orbital portions to the sphenoid bone, reinforcing the anterior cranial base and preventing excessive deformation under impact.^[24] These fibrous joints collectively provide a stable framework that maintains cranial shape and volume.^[1] Specific features such as the superciliary arches and frontal tuber offer attachment sites for facial muscles, including the corrugator supercilii, while resisting localized deformation from muscular contractions and external pressures.^[25] The superciliary arches, prominent ridges above the orbits, anchor the corrugator supercilii to enable frowning and brow movements, simultaneously buttressing the supraorbital margins against superior forces.^[26] The frontal tuber, or eminence, further supports overlying soft tissues and contributes to the bone's resistance to bending.^[3] Additionally, the zygomatic process extends laterally to form part of the orbital wall and integrate with the facial buttress system, providing lateral stability and protection against side impacts to the orbit and midface.^[1] Thickness variations across the frontal bone optimize its biomechanical performance: the squamous part measures up to 1 cm thick in areas optimized for impact absorption, while the orbital plates are thinner at approximately 0.5 mm but rely on their curved architecture for enhanced strength-to-weight efficiency.^[27] This gradient allows the bone to balance protection with minimal weight, as the thicker squamous region absorbs shocks, and the thinner, arched orbital plates deflect forces without fracturing easily.^[28] The presence of frontal sinuses within the squamous part creates internal spaces that influence overall bone density, potentially lightening the structure while maintaining structural competence.^[1]

Association with sinuses

The frontal sinuses are paired, air-filled cavities housed primarily within the squamous portion of the frontal bone, with extensions into the orbital portions forming part of the roof of the orbits. These sinuses drain via narrow frontonasal ducts that open into the middle meatus of the nasal cavity, facilitating the flow of mucus and air exchange.^[29]^[30] Beyond structural roles, the frontal sinuses contribute to several physiological processes. They reduce the overall weight of the frontal bone by creating air-filled spaces within the dense bone, produce mucus from their ciliated epithelial lining to humidify inhaled air and trap airborne pathogens, and enhance vocal resonance by amplifying sound waves during speech. Additionally, the rich mucosal blood supply enables thermoregulation, as the vascular network warms cooler inhaled air before it reaches the lower respiratory tract.^[31]^[32]^[33] The frontal sinuses display significant interindividual and bilateral variability in size, shape, and degree of pneumatization, often exhibiting asymmetry between the left and right sides. They are absent (aplasia) in approximately 5-10% of individuals, with unilateral absence more common than bilateral; in some cases, extensive pneumatization extends posteriorly into the superciliary arches above the orbits. Frontal sinus pneumatization begins postnatally around the second year of life and continues into early adulthood.^[34]^[35]^[30] The arterial supply to the frontal sinuses derives from the supraorbital and anterior ethmoidal branches of the ophthalmic artery, ensuring adequate nourishment to the mucosal lining. Sensory innervation is provided by the supraorbital nerve, a terminal branch of the ophthalmic division (V1) of the trigeminal nerve (CN V), which transmits sensations from the sinus mucosa.^[36]^[37]

Clinical significance

Fractures and trauma

Frontal bone fractures are commonly associated with high-impact trauma, such as motor vehicle accidents, falls, assaults, and penetrating injuries, which account for the majority of cases due to the bone's exposed position and varying thickness.^[38] These fractures often occur in conjunction with other maxillofacial injuries, with road traffic accidents comprising up to 90.9% of incidents in some cohorts.^[39] The primary types of frontal bone fractures include linear fractures, which are simple cracks without displacement; depressed fractures, involving inward displacement of bone fragments; and comminuted fractures, characterized by multiple shattered fragments.^[40] Orbital roof fractures, stemming from the thin orbital plates of the frontal bone, are particularly vulnerable in trauma and may extend to the cribriform plate, increasing the risk of dural involvement.^[41] Bone thickness variations, with the squamous portion averaging 6-7 mm and orbital plates much thinner at 0.5-1 mm, influence fracture patterns, making the latter more prone to complex disruptions.^[38] Associated risks are significant, including dural tears that can lead to cerebrospinal fluid (CSF) rhinorrhea, intracranial hemorrhage, pneumocephalus, meningitis, and brain abscess; these complications arise in up to 65.5% of cases with intracranial injuries.^[39] Frontal sinus fractures represent 5–12% of all maxillofacial fractures, though isolated sinus fractures represent a subset of these.^[42] Le Fort fractures, particularly type III, may involve the frontal processes through extension from midfacial trauma.^[43] Diagnosis relies on non-contrast computed tomography (CT) imaging of the head and facial bones, which demonstrates bone discontinuity, displacement, and associated soft tissue injuries with high sensitivity; plain radiographs offer no additional benefit.^[38] Treatment varies by fracture characteristics: nondisplaced linear fractures are managed conservatively with observation, while displaced or comminuted fractures require surgical intervention, such as open reduction and internal fixation (ORIF) with plating for fragments depressed more than 2-5 mm.^[40] Open fractures necessitate antibiotics to prevent infection, and cases with posterior table involvement or CSF leaks may require cranialization or sinus obliteration.^[38]

Pathologies of the frontal sinuses

The frontal sinuses, paired air-filled cavities within the frontal bone that drain via the frontonasal ducts into the middle meatus of the nasal cavity, are susceptible to various non-traumatic pathologies primarily involving inflammation, obstruction, and neoplastic growth.^[44] Frontal sinusitis, an inflammation of these sinuses, is classified as acute when lasting less than 4 weeks and typically caused by viral or bacterial infections, or chronic when persisting beyond 12 weeks and often linked to persistent inflammation or structural issues.^[45]^[46] Common symptoms include frontal headache, facial pressure, fever, and nasal congestion, with acute cases frequently resolving spontaneously or with supportive care while chronic forms may require targeted intervention to prevent progression.^[45] A serious complication of untreated or severe frontal sinusitis is Pott's puffy tumor, characterized by a subperiosteal abscess overlying the frontal bone due to adjacent osteomyelitis, presenting as forehead swelling and potentially leading to intracranial extension if not promptly managed.^[47] Obstruction of the frontal sinus drainage pathways, often due to nasal polyps or a deviated nasal septum, can exacerbate sinusitis by promoting mucus retention and bacterial overgrowth.^[48] Initial treatments for obstructive frontal sinusitis include decongestants to reduce mucosal swelling, antibiotics for bacterial superinfections, and, in refractory cases, functional endoscopic sinus surgery (FESS) to widen the drainage ostia and remove obstructive tissue.^[49] Neoplasms of the frontal sinuses are rare but can arise as benign or malignant lesions; osteomas, for instance, are slow-growing benign bony tumors that may cause obstruction or erosion if large, while squamous cell carcinoma represents a more aggressive malignancy originating from the sinonasal epithelium.^[50] Detection typically involves computed tomography (CT) for bony details and magnetic resonance imaging (MRI) to assess soft tissue extension and invasion.^[51] Congenital variations, such as absence (aplasia) or underdevelopment (hypoplasia) of the frontal sinuses, occur in approximately 5% of adults bilaterally, potentially altering sinus physiology and increasing susceptibility to related nasal pathologies.^[52] Mucoceles, cystic expansions filled with mucus resulting from ductal obstruction, can develop in the frontal sinuses and lead to progressive bone erosion of surrounding walls, including the orbital roof or frontal cortex, necessitating surgical drainage to prevent complications like vision impairment.^[53] As of 2025, advances in biologic therapies have transformed management of chronic rhinosinusitis with nasal polyps affecting the frontal sinuses, with dupilumab—a monoclonal antibody targeting IL-4 and IL-13—approved by the FDA and demonstrating significant reductions in polyp size, symptom severity, and need for surgery in clinical trials and real-world studies.^[54]

Comparative anatomy

In non-mammalian vertebrates

In non-mammalian vertebrates, the frontal bones are typically paired elements of the dermatocranium that contribute to the skull roof, positioned dorsal to the orbits but separated from them by intervening bones such as the prefrontal and postfrontal, which prevent direct orbital enclosure by the frontals.^[55] These dermal bones originate from the exoskeletal armor of early vertebrates, where ossified scales integrated with the underlying chondrocranium to form protective coverings over the brain and sensory structures.^[56]^[57] This paired configuration contrasts with the midline fusion observed in many mammals, reflecting retained primitive symmetry in non-mammalian lineages.^[58] In fish and amphibians, the frontal bones are small and paired, often positioned along the orbital margins as part of the dorsal skull roofing without significant pneumatization or air-filled sinuses. In bony fish such as carp, these frontals form flat, paired plates that border the front of the braincase and orbits, sometimes fusing with adjacent dermal elements like the parietals for added stability in aquatic environments.^[59]^[60] Amphibians exhibit a similar arrangement, with compact frontals medial to the orbits, separated by the prefrontal anteriorly and postfrontal posteriorly; in salamanders, they remain distinctly paired and unfused across the midline, supporting a lightweight skull adapted for both aquatic and terrestrial transitions.^[55]^[61] Fusion with other dermal bones occurs variably, as seen in some frogs where frontals integrate with the frontoparietal complex to reinforce the reduced cranium.^[62] In reptiles, the paired frontal bones are typically flat and expansive, forming a key portion of the temporal and dorsal skull roof while articulating anteriorly with the nasals and posteriorly with the parietals to create a continuous bony vault over the brain. These bones lack paranasal sinuses, relying instead on their solid dermal structure for protection against impacts in terrestrial habitats. In lizards, for instance, the frontals exhibit a broad, rectangular shape that excludes them from the orbital margin, delegating that role to surrounding elements like the postfrontal.^[63]^[55] In birds, the frontal bones are reduced in prominence as distinct elements, often fusing along the midline and incorporating aspects of adjacent structures into a more integrated prefrontal region to facilitate the kinetic, lightweight skull essential for flight. This adaptation minimizes mass while maintaining coverage of the enlarged braincase, with the frontals forming the smooth, curved roof anterior to the parietals and directly bordering the orbits in the absence of a separate prefrontal bone.^[64]^[65]

In mammals and dinosaurs

In mammals, the frontal bone is an unpaired structure resulting from the midline fusion of two embryonic primordia during postnatal development, forming the anterior portion of the cranial vault and contributing to the forehead and the roof of the orbits. This fusion creates a single, robust bone that supports the anterior braincase and provides attachment sites for facial muscles. Frontal sinuses, air-filled cavities within the bone, are present in most terrestrial mammals, aiding in resonance and reducing skull weight, but they are absent in aquatic species such as whales, where the loss of paranasal sinuses facilitates hydrodynamic streamlining and adaptation to high-pressure diving environments.^[66]^[67] Morphological variations in the mammalian frontal bone reflect dietary and behavioral adaptations. In herbivorous ruminants like bovids, the bone is often pronounced and thickened to serve as the base for horn cores, which emerge as bony protuberances from the frontal region and provide structural support for keratinous sheaths used in defense and intraspecific combat. In contrast, the frontal bone tends to be reduced in size and less domed in many carnivores, particularly semiaquatic or fossorial species, correlating with minimized sinuses and a more streamlined skull profile optimized for predation or burrowing. Among primates, sexual dimorphism is evident in the frontal bone, with males exhibiting more robust and projecting supraorbital tori or brow ridges compared to females, a trait linked to craniofacial adaptations for display and agonistic interactions.^[68]^[69]^[70] In dinosaurs, the frontal bones are paired elements forming the central portion of the dorsal skull roof, a configuration retained from their reptilian ancestry, and they articulate rostrally with the nasals, laterally with the prefrontals and postorbitals, and caudally with the parietals. These articulations contribute to the stability of the skull roof while enclosing the forebrain and olfactory regions. In theropod and ornithischian dinosaurs, the frontals typically define the posterior and dorsal margins of the orbit, providing a bony rim that protects the eye and anchors orbital musculature, with the bone often featuring a longitudinal midline suture visible in dorsal view.^[71]^[72]^[73] Specific morphologies highlight functional diversity among dinosaurs. In sauropods, the frontals are elongated anteroposteriorly as part of the overall slender, horse-like skull adapted to their long necks and browsing habits, facilitating an extended snout for high-level foliage access without excessive cranial mass. Ceratopsian dinosaurs exhibit thickened frontals integrated into the robust skull roof, supporting the expansive parietosquamosal frill used for display and defense, with the bone's increased density enhancing resistance to impacts during head-butting behaviors. In contrast to the paranasal sinuses found in many mammals, non-avian dinosaurs exhibit diverse patterns of cranial pneumatization; while some theropods have extensive paranasal air sinuses including in the frontals, others like sauropods and ceratopsians typically lack them.^[74]^[75]^[76] The bones often bear vascular impressions and foramina indicating dense networks of blood vessels, which likely aided in thermoregulation by facilitating heat exchange in large-bodied species prone to overheating.^[77] Due to their consistent anatomical position and diagnostic features—such as ornamentation patterns, suture shapes, and vascular grooves—isolated frontal bones frequently provide key evidence for dinosaur taxonomy and phylogenetic placement in the fossil record, particularly for theropods where cranial material is often fragmentary.^[78]

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Facial fractures: classification and highlights for a useful report
Mar 19, 2020 · It is essential to categorize fracture patterns and highlight features that may affect fracture management in radiology reports of facial trauma.
[44]
7 Nasal Cavity and Paranasal Sinuses - Radiology Key
Jul 5, 2020 · The frontal sinuses are paired, often asymmetric air cells within the frontal bone. Aplasia (5% of all adults) and hypoplasia are not uncommon.
[45]
Acute Frontal Sinusitis - PMC - NIH
Strictly an infectious complication and not neoplastic in any way, Pott's Puffy Tumor may present with severe headache, fever, and photophobia.Treatment · Intracranial Complications · Table 6.3
[46]
Chronic Sinusitis - StatPearls - NCBI Bookshelf
Chronic sinusitis is an inflammation of the sinus or nasal passages occurring for more than 12 weeks at a time.Missing: FESS | Show results with:FESS
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Pott Puffy Tumor - StatPearls - NCBI Bookshelf - NIH
Feb 15, 2025 · The term "Pott puffy tumor" (PPT) refers to edema of part or all of the forehead due to a subperiosteal abscess associated with frontal bone ...
[48]
Frontal sinusitis: Causes, symptoms, treatment, and more
Frontal sinusitis often results from infections, particularly viral infections. Other possible causes include allergies, a deviated nasal septum, and nasal ...
[49]
Functional Endoscopic Sinus Surgery (FESS) - Cleveland Clinic
May 28, 2025 · Functional endoscopic sinus surgery (FESS) is a minimally invasive procedure that unblocks your sinuses to restore drainage and airflow.
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Early postoperative contrast-enhanced CT or MR imaging is recommended to detect residual tumour,. Malignant tumours. Squamous cell carcinoma and adenocarcinoma.
[51]
Nasal and Sinus Tumors | Cedars-Sinai
Squamous cell carcinoma (about 70 percent of such cancers) occurs in the ... If cancer is suspected, a MRI, CT or PET scan may be used to diagnose the condition.
[52]
Total aplasia of the paranasal sinuses - PMC - PubMed Central - NIH
Frontal sinus aplasia is present unilaterally in 15% and bilaterally in 5% of normal adults. Maxillary sinus aplasia is extremely rare, whereas maxillary sinus ...
[53]
Mucocele: Clinical Characteristics and Outcomes in 46 Operated ...
Paranasal sinus mucocele is a benign, expansive lesion associated with paranasal sinus obstruction. It affects mostly adults, and is most common in the frontal ...
[54]
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Oct 18, 2025 · As of 2025, three biologics have received US FDA approval to treat CRSwNP: dupilumab, omalizumab, and mepolizumab. These agents target distinct ...
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Amphibian and Reptile Skulls – Morphology of the Vertebrate Skeleton
Many skull bones underwent fusion, and some joints became akinetic. The evolution of internal nostrils, or choanae, was a means to pass air from outside the ...
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Postfrontal bone - Wikipedia
The postfrontal is a paired cranial bone found in many tetrapods. It occupies an area of the skull roof between and behind the orbits (eye sockets)
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It takes two: Building the vertebrate skull from chondrocranium ... - NIH
Nov 5, 2020 · Ancestral vertebrates had two distinct skulls: an outer dermatocranium which persists as parts of the modern dermal skeleton, and an inner ...
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THE STRUCTURE OF THE SKULL IN VERTEBRATES - UBC Zoology
The original dermal scales (or armour) of Ostracoderms sink down and have attach to the neurocranium and are ossified as the Dermal Bones. These are from ...Missing: frontal | Show results with:frontal
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Resolving homology in the face of shifting germ layer origins - NIH
Dec 23, 2019 · What was originally called the 'frontal' in actinopterygians, based on the location of that bone between the orbits, is actually the parietal by ...
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Carp skull anatomy (1. frontal bone, 2, 3 orbital bone, 4. Parietal...
Carp skull anatomy (1. frontal bone, 2, 3 orbital bone, 4. Parietal bone, 5. Operculum, 6. supraoccipital bone).
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Fish Skulls – Morphology of the Vertebrate Skeleton
The splanchnocranium is made of endochondral bones. Dermatocranium. The dermatocranium is composed of the dermal bones that form the superficial parts of the ...
[62]
Amphibian skull evolution: the developmental and functional context ...
Batrachians (salamanders and frogs) have simplified skulls, with dermal bones appearing rudimentary compared with fossil tetrapods, and open cheeks.
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Evolution of hyperossification expands skull diversity in frogs - PNAS
Mar 27, 2020 · Cranial hyperossification is expressed on five dermal elements (frontoparietal, nasal, premaxilla, maxilla, squamosal) and three novel bones ( ...<|separator|>
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Skull Anatomy and Ontogeny of Legless Lizard Pseudopus apodus ...
Dec 16, 2016 · Prefrontal. It is a paired bone of about triangular shape in a dorsal view posteriorly extending into a long frontal process ...
[65]
Birds have peramorphic skulls, too: anatomical network analyses ...
Apr 24, 2020 · ... frontal bones causes a reduction in the number of modules. Because bone fusion generally requires a previous contact of bones in form of a ...
[66]
Skull
Bird skulls have an enlarged braincase, reduced palatal bones, and a single occipital condyle. Bones fuse, making sutures hard to see.
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Bird anatomy - Wikipedia
The skull consists of five major bones: the frontal (top of head), parietal (back of head), premaxillary and nasal (top beak), and the mandible (bottom beak).Skeletal system · Reproductive and urogenital... · Nervous system
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Frontal Bone - an overview | ScienceDirect Topics
The temporal fossa is found behind the zygomatic process of the frontal bone. This is usually the deepest part of the temporal fossa and the line for the ...
[69]
Vascularization of Air Sinuses and Fat Bodies in the Head of the ...
Cetaceans have lost the air-filled paranasal sinus system found in terrestrial mammals (Mead, 1975; Mead and Fordyce, 2009).
[70]
The Development of Horns in Bovidae and the Genetic Mechanisms ...
Aug 11, 2025 · Horns in Bovidae develop bilaterally from the frontal bones and are distinguished by their hardness, permanence, and structural complexity. Horn ...
[71]
Repeated Loss of Frontal Sinuses in Arctoid Carnivorans - PubMed
Jul 29, 2014 · Results show that sinuses are either lost or reduced in both semiterrestrial and semiaquatic species, and that sinus size is related to skull size and shape.
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Sexual dimorphism in the cranium and endocast of the eastern ...
To explain observed sexual dimorphism in primate species, the generally advocated hypothesis is a phenomenon of sexual selection (Plavcan, 2001; Isaac, 2005; ...
[73]
Dinosaur Skeletal Anatomy - A biography of the Australian continent
Feb 12, 2012 · The frontals articulate with the nasals rostrally, with the parietals (that contribute to the braincase walls) caudally, and with the orbit- ...
[74]
The cranial anatomy of the neornithischian dinosaur ...
The prefrontal is a triradiate bone that forms the anterodorsal corner of the orbit and is exposed on the dorsal and lateral surfaces of the skull (Figs. 1 and ...<|separator|>
[75]
The Osteology of Haya griva (Dinosauria: Ornithischia) from the Late ...
Feb 26, 2021 · The frontal forms most of the dorsal margin of the orbit. It is narrowest at its midpoint over the orbit. The frontal thickens slightly in ...
[76]
A Complete Skull of an Early Cretaceous Sauropod and the ...
The new taxon also preserves the most complete skull among titanosaurians, further revealing that their low and elongated diplodocid-like skull morphology ...
[77]
New Data on Cranial Anatomy of the Ceratopsian Dinosaur ...
Jun 1, 2008 · The gently biconvex caudal margin of the frill has a cardioid shape and is strongly emarginated on the midline. Moreover, and apparently ...
[78]
Vascular Patterns in the Heads of Dinosaurs: Evidence for Blood ...
Oct 16, 2019 · Large-bodied, and often large-headed, species showed focused thermal strategies with enhanced collateral blood flow to certain sites of heat exchange.Missing: frontal bone no impressions
[79]
A megaraptorid (Dinosauria: Theropoda) frontal from the upper ...
We report the first evidence of non-mandibular cranial material of a non-avian theropod from Australia: a left frontal and fused parietal fragment.