Pääkallo

Pääkallo, the Finnish term for the cranium, is the part of the skull that encloses the brain and forms the cranial cavity. In adults it comprises eight cranial bones: frontal, two parietal, two temporal, occipital, sphenoid, and ethmoid. Together with the fourteen facial bones, the skull typically contains 22 bones. The auditory ossicles of the middle ear are not part of the skull proper. The pääkallo protects the brain and sensory organs, supports facial structures, and provides attachment points for muscles involved in chewing, expression, and head movement. It articulates with the first cervical vertebra at the occipital condyles.

The cranial bones are joined by sutures, fibrous joints that allow growth during childhood. In infants, fontanelles—soft spots where sutures have not yet fused—permit skull expansion during birth and early development.

Development involves intramembranous ossification for the flat bones of the neurocranium and endochondral ossification for parts of the skull base. Growth continues through adolescence, after which the bones reach their adult dimensions. Variations in skull shape are common and have medical and anthropological significance.

Clinically, the skull can be affected by trauma leading to fractures or by congenital conditions such as craniosynostosis, where one or more sutures fuse prematurely. Imaging and knowledge of skull anatomy are important in neurology, neurosurgery, and dentistry.