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The trilobite body is divided into three major sections: a cephalon (head section) with eyes, mouthparts and sensory organs such as antennae; a thorax of multiple segments which are similar to each other; and a pygidium, or tail section. In many species, the cephalon had sutures running from back to front round the outside edges of the eyes.
The calvaria is made up of the superior portions of the frontal bone, occipital bone, and parietal bones. [1] In the human skull, the sutures between the bones normally remain flexible during the first few years of postnatal development, and fontanelles are palpable. Premature complete ossification of these sutures is called craniosynostosis.
The head rests on the top part of the vertebral column, with the skull joining at C1 (the first cervical vertebra known as the atlas). The skeletal section of the head and neck forms the top part of the axial skeleton and is made up of the skull, hyoid bone, auditory ossicles, and cervical spine. The skull can be further subdivided into:
The pterion is the region where the frontal, parietal, temporal, and sphenoid bones join. [1] It is located on the side of the skull, just behind the temple.It is also considered to be the weakest part of the skull, which makes it clinically significant, as if there is a fracture around the pterion it could be accompanied by an epidural hematoma.
Skull in situ Human head skull from side Anatomy of a flat bone – the periosteum of the neurocranium is known as the pericranium Human skull from the front Side bones of skull. The human skull is the bone structure that forms the head in the human skeleton. It supports the structures of the face and forms a cavity for the brain. Like the ...
The posterior fontanelles ossify within 6–8 weeks after birth. This is called intramembranous ossification. The mesenchymal connective tissue turns into bone tissue. Anterior fontanelle is a diamond-shaped membrane-filled space located between the two frontal and two parietal bones of the developing fetal skull. It persists until ...
The frontal and parietal bones are joined by the coronal suture. The two separate parietal bones are connected at the sagittal suture. The blowhole of sperm whales is located on the crown of the head and allows the whale to breathe. Below the crown, the frontal bone and the parietal bones are separated by a range of fibrous joints called ...
If certain bones of the skull grow too fast then premature fusion of the sutures, craniosynostosis, may occur. [1] This can result in skull deformities. [1] These deformities include: [3] Brachycephaly (both sides) Plagiocephaly (one side only) Oxycephaly (both sides)