[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Embryology](https://durgical.com/en/embryology/) › [Skeleton, muscles, limbs and skin](https://durgical.com/en/embryology/#a-musculoskeletal) › Skull: neurocranium, viscerocranium, sutures and fontanelles [Embryology](https://durgical.com/en/embryology/) · [Skeleton, muscles, limbs and skin](https://durgical.com/en/embryology/#a-musculoskeletal) # Skull: neurocranium, viscerocranium, sutures and fontanelles - Embryonic structure A baby's skull is plates of bone joined by flexible seams (sutures) and soft spots (fontanelles) that let the brain grow. Updated 2026-11-01 **See it in 3D:** [Frontal bone](https://durgical.com/en/anatomy/frontal-bone/) · [Parietal bones](https://durgical.com/en/anatomy/parietal-bone/) · [Base of the skull](https://durgical.com/en/anatomy/occipital-bone/) · [Temporal bones](https://durgical.com/en/anatomy/temporal-bone/) · [Sphenoid bone](https://durgical.com/en/anatomy/sphenoid-bone/) · [Ethmoid bone](https://durgical.com/en/anatomy/ethmoid-bone/) · [Mandible](https://durgical.com/en/anatomy/mandible/) · [Maxillae](https://durgical.com/en/anatomy/maxilla/) · [Nasal bones](https://durgical.com/en/anatomy/nasal-bone/) ## Key points - Vault = intramembranous ossification; base = endochondral. - Frontal = neural crest; parietal = paraxial mesoderm. - Anterior fontanelle closes around 18 months; posterior around 1 to 2 months. - Viscerocranium = neural crest of arches 1 and 2. - Achondroplasia affects the base (endochondral), not the vault (membranous). ## What it is The skull has two parts: the neurocranium, which protects the brain, and the viscerocranium, which forms the face. The vault ossifies directly in membrane, while the base passes through a cartilage stage first. Sutures and fontanelles allow moulding during birth and brain growth afterwards; their early closure is craniosynostosis. ## Key facts - Vault (membranous neurocranium): intramembranous ossification of the flat bones. - Base (chondrocranium): endochondral ossification; in front of the sella turcica it comes from neural crest, behind it from paraxial mesoderm (occipital somites). - The frontal bone comes from neural crest; the parietal bones from paraxial mesoderm. - Viscerocranium: mostly neural crest of the first two pharyngeal arches (maxilla, mandible, ossicles). - Posterior fontanelle: closes around 1 to 2 months. Anterior fontanelle: around 18 months. - At birth the vault is large and the face small; the face grows with the paranasal sinuses and the teeth. ## Structure - Membranous neurocranium: frontal, parietal bones, squamous temporal and part of the occipital. - Chondrocranium: sphenoid, ethmoid, petrous temporal and most of the occipital. - Main sutures: metopic (between the two frontal halves), coronal, sagittal and lambdoid. - Fontanelles: anterior (between frontal and parietal bones, the largest), posterior, and the sphenoid and mastoid ones on each side. ## What it becomes - Sutures are growth zones: bone is added at their edges as the brain pushes outwards. - Fontanelles let the plates overlap during birth (moulding) and then return to place. - The anterior fontanelle is part of the infant exam: tense or bulging suggests raised intracranial pressure; sunken suggests dehydration. - As they close, sutures leave a rigid skull; the sagittal and coronal sutures fuse in adult life. ## Markers - FGFR1 - FGFR2 - FGFR3 - MSX2 - TWIST1 - RUNX2 ## Clinical notes - Craniosynostosis: early closure of a suture distorts the skull according to which one closes. - Cleidocranial dysplasia (RUNX2): large, late-closing fontanelles, absent clavicles and extra teeth. - Achondroplasia (FGFR3): the endochondral base stays small with a narrow foramen magnum; the membranous vault grows normally. - Microcephaly: a small skull because the brain does not grow; the sutures are not the cause. ## Memory aid The lid is sewn from 'fabric' and the floor is cast in a 'mould': membranous vault, cartilaginous base. ## Test yourself Think of the answer, then tap the question to see it. ## What type of ossification forms the bones of the skull vault? Intramembranous: mesenchyme turns directly into bone without a cartilage model. ## Around what age does the anterior fontanelle close? In most children around 18 months; the posterior closes much earlier, around 1 to 2 months. ## Where do the frontal and parietal bones come from? The frontal bone derives from neural crest and the parietal bones from paraxial mesoderm. ## Why does achondroplasia shrink the skull base but not the vault? The base forms by endochondral ossification, which overactive FGFR3 slows; the vault is membranous. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/embryology/skull-neurocranium-viscerocranium-sutures-and-fontanelles/) ## See it in 3D The structures of Durgical's 3D anatomy where it is found. - [Frontal bone](https://durgical.com/en/anatomy/frontal-bone/) - [Parietal bones](https://durgical.com/en/anatomy/parietal-bone/) - [Base of the skull](https://durgical.com/en/anatomy/occipital-bone/) - [Temporal bones](https://durgical.com/en/anatomy/temporal-bone/) - [Sphenoid bone](https://durgical.com/en/anatomy/sphenoid-bone/) - [Ethmoid bone](https://durgical.com/en/anatomy/ethmoid-bone/) - [Mandible](https://durgical.com/en/anatomy/mandible/) - [Maxillae](https://durgical.com/en/anatomy/maxilla/) - [Nasal bones](https://durgical.com/en/anatomy/nasal-bone/) ## Related - [Neural crest cells and their derivatives](https://durgical.com/en/embryology/neural-crest-cells-and-their-derivatives/) - [Craniosynostosis](https://durgical.com/en/embryology/craniosynostosis/) - [First pharyngeal arch (mandibular arch) and the trigeminal nerve](https://durgical.com/en/embryology/first-pharyngeal-arch-and-the-trigeminal-nerve/) - [Second pharyngeal arch (hyoid arch) and the facial nerve](https://durgical.com/en/embryology/second-pharyngeal-arch-and-the-facial-nerve/) - [Achondroplasia (FGFR3)](https://durgical.com/en/embryology/achondroplasia/) - [Vertebrae: resegmentation of the sclerotomes](https://durgical.com/en/embryology/vertebrae-resegmentation-of-the-sclerotomes/) - [Teeth](https://durgical.com/en/embryology/teeth/) ## Related conditions - [Hydrocephalus](https://durgical.com/en/conditions/hydrocephalus/) - [Raised intracranial pressure and brain herniation](https://durgical.com/en/conditions/raised-intracranial-pressure-and-brain-herniation/) [← All of embryology](https://durgical.com/en/embryology/) Educational content on embryonic development; not a guide to prenatal diagnosis or to medicines in pregnancy and no substitute for a health professional's advice. No doses are given. Sources: [Cranial sutures: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/002320.htm) (MedlinePlus, US National Library of Medicine, 2026); [Cleidocranial dysplasia: MedlinePlus Genetics](https://medlineplus.gov/genetics/condition/cleidocranial-dysplasia/) (MedlinePlus, US National Library of Medicine, 2026); Langman's Medical Embryology, 13th ed., ch. 10: The Axial Skeleton (Wolters Kluwer, 2015). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/embryology/skull-neurocranium-viscerocranium-sutures-and-fontanelles/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/embryology/skull-neurocranium-viscerocranium-sutures-and-fontanelles/