An infant's skull consists of five main bones: two frontal bones, two parietal bones, and one occipital bone. These are joined by fibrous sutures, which allow movement that facilitates childbirth and brain growth. * Posterior<unk>  is triangle-shaped. It lies at the junction between the sagittal suture and lambdoid suture. At birth, the skull features a small posterior<unk>  with an open area covered by a tough membrane, where the two parietal bones adjoin the occipital bone (at the lambda). The posterior<unk> s ossify within 6–8 weeks after birth. This is called intramembranous ossification. The mesenchymal connective tissue turns into bone tissue. * Anterior<unk>  is a diamond-shaped membrane-filled space located between the two frontal and two parietal bones of the developing fetal skull. It persists until approximately 18 months after birth. It is at the junction of the coronal suture and sagittal suture. The fetal anterior<unk>  may be palpated until 18 months. In cleidocranial dysostosis, however, it is often late in closing at 8–24 months or may never close. Examination of an infant includes palpating the anterior<unk> . * Two smaller<unk> s are located on each side of the head, more anteriorly the sphenoidal or anterolateral<unk>  (between the sphenoid, parietal, temporal, and frontal bones) and more posteriorly the mastoid or posterolateral<unk>  (between the temporal, occipital, and parietal bones). During birth,<unk> s enable the bony plates of the skull to flex, allowing the child's head to pass through the birth canal. The ossification of the bones of the skull causes the anterior<unk>  to close over by 9 to 18 months. The sphenoidal and posterior<unk> s close during the first few months of life. The closures eventually form the sutures of the neurocranium. Other than the anterior and posterior<unk> s, the mastoid<unk>  and the sphenoidal<unk>  are also significant. Closure In humans, the sequence of<unk>  closure is as follows: # The posterior<unk>  generally closes 2 to 3 months after birth; # The sphenoidal<unk>  is the next to close around 6 months after birth; # The mastoid<unk>  closes next from 6 to 18 months after birth; and # The anterior<unk>  is generally the last to close between 12 and 18 months.
Fontanelle
Hemotympanum
Orbital septum
Lacrimal groove
Optic recess
Craniopharyngeal canal
Ateronon
Rhomboid fossa