During childhood and adolescence, these two bones fuse into one. The frontal bones start as two paired bones. Bones of the skull (lateral) 2 Frontal bone These bones of the skull cap contain two thin layers of cortical bone separated by diploë, which is synonymous with the spongy bone seen in long bones.ĭiploë provides structural integrity and transmits forces along the length of the bones of the skull cap.įigure 3. Of particular importance is the strength of these bones relative to how thin they are. The parts of these bones that lie inferior to the brain are considered to be a part of the skull base (mentioned below). These bones protect the brain superiorly, but also provide an anchor for important muscles of facial expression and eye movement. The calvarium, also known as the roof or skull cap, consists of three bones: The fontanelles undergo complete ossification within 9 – 18 months from birth.Ĭlinical relevance: Fontanelle abnormalitiesĪn enlarged anterior fontanelle can be due to endocrine pathologies like congenital hypothyroidism.Ī bulging anterior or posterior fontanelle may suggest raised intracranial pressure, which may occur in hydrocephalus.Ī sunken anterior or posterior fontanelle may suggest dehydration. Posterior fontanelle: the soft region on the back of the infant’s head.Anterior fontanelle: the soft region on the front of the infant’s head.Base: the sphenoid, ethmoid, occipital and temporal bones tend to grow slightly laterīy week 37, the cartilaginous frame for the skull is almost entirely replaced by bone, and only two relatively small cartilaginous structures remain:.Calvarium (roof): the frontal, occipital and parietal bones tend to grow slightly earlier.This process occurs at different rates in two different regions of the skull: A cartilaginous mould begins to grow and is slowly replaced by bone in a process called intramembranous ossification. The skull begins to form prior to week 12 of embryogenesis. These markings include the external occipital protuberance, the nuchal lines, and the external occipital crest.You might also be interested in our Anatomy Flashcard Collection which contains over 2000 anatomy flashcards in addition to advanced features such as spaced repetition. This is why when you read too much anatomy and start to nod off your head falls forward. To counteract this weight difference the muscles at the back of the neck must be strong enough to resist the head falling forward. If you look at a lateral view of the skull you can see that the greater mass of the skull is anterior to the occipital condyle. Markings – The markings on the external surface of the occipital bone are all involved with attachments of the ligaments and large muscles that are necessary to hold the head erect. Parts – The two main parts of the occipital bone are the squamous part which is the flat bone part that forms the posterior part of the calvarium and the basilar part which is the part that connects the bone to the sphenoid bone. Therefore, it has a pair of condyles, the occipital condyles found on the inferior surface that articulate with the atlas as discussed earlier. The occipital bone is the cranial bone that forms the posterior part of the calvarium and also is the articulation point with the bones of the neck.
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