Kolju

Kolju (Estonian for skull) is the bony structure that forms the head in most vertebrates, protecting the brain and supporting facial features. In humans, the skull comprises two main parts: the cranium, which encloses the brain, and the facial skeleton, which forms the face and houses the sense organs and openings for the respiratory and digestive tracts.

The cranium contains eight bones: frontal, two parietal, two temporal, occipital, sphenoid, and ethmoid. The facial skeleton consists of fourteen bones: nasal, maxillae, zygomatic, inferior nasal concha, lacrimal, palatine, vomer, and the mandible. The mandible is the only movable skull bone, joined to the temporal bones at the temporomandibular joints.

The bones are interconnected by fibrous sutures—coronal, sagittal, lambdoid, and squamous—allowing growth during childhood. Infants also have fontanelles, soft spots where the skull bones have not yet fully fused, which gradually close as development proceeds.

Functions of the skull include protecting the brain, supporting the orbits and nasal and oral cavities, and providing attachment points for muscles involved in chewing, facial expression, and speech. Growth and development of the skull involve both intramembranous and endochondral ossification, with sutures and fontanelles enabling expansion in early life and fusion later on.

There is natural variation in skull size and shape among individuals and populations. Clinical concerns include skull fractures, craniosynostosis (premature suture fusion), and changes associated with trauma or gradual disease. Imaging techniques such as X-ray, CT, and MRI aid assessment and diagnosis.

In summary, kolju denotes the skull, a complex, highly organized structure essential for protection, form, and function of the head.