Anatomy of the Newborn Skull
The pterion is the region where the frontal, parietal, temporal, and sphenoid bones join together. It is located on the side of the skull, just behind the temple. where the parietal bones meet the occipital bone posteriorly (on back of head) where a parietal and temporal bone meet on the lateral aspect of the skull (on sides) (lower jawbone), forming the freely movaable temporomandibular joint. Each parietal bone plate meets the occipital bone plate at the lambdoid suture. They act like an expansion joint, allowing the bone to enlarge.
Bones of the Skull - Structure - Fractures - TeachMeAnatomy
The point of meeting of this angle with the occipital and the mastoid part of the temporal is named the asterion. Ossification[ edit ] The parietal bone is ossified in membrane from a single center, which appears at the parietal eminence about the eighth week of fetal life. Ossification gradually extends in a radial manner from the center toward the margins of the bone; the angles are consequently the parts last formed, and it is here that the fontanelles exist.
Occasionally the parietal bone is divided into two parts, upper and lower, by an antero-posterior suture.
In other animals[ edit ] In non-human vertebrates, the parietal bones typically form the rear or central part of the skull rooflying behind the frontal bones. In many non-mammalian tetrapodsthey are bordered to the rear by a pair of postparietal bones that may be solely in the roof of the skull, or slope downwards to contribute to the back of the skull, depending on the species.
In the living tuataraand many fossil species, a small opening, the parietal foramen, lies between the two parietal bones.
This opening is the location of a third eye in the midline of the skull, which is much smaller than the two main eyes. This bone is part of the skull roof, which is a set of bones that cover the brain, eyes and nostrils. The parietal bones make contact with several other bones in the skull.
Pterion - Wikipedia
The anterior part of the bone articulates with the frontal bone and the postorbital bone. The posterior part of the bone articulates with the squamosal bone, and less commonly the supraoccipital bone.
The bone-supported neck frills of ceratopsians were formed by extensions of the parietal bone. Fontanelle allow the child's head to be more pliable during birth to allow for an easier delivery.PARIETAL BONES
They also allow for the accelerated growth of the human brain in the first years of life. In the newborn child, there are a total of 6 fontanelle: Frontal- at the intersection of the parietal bones and the frontal bone.
Occipital- at the intersection of the parietal bones and the occipital bone. Mastoid 2 - at the intersection of the parietal, occipital, and temporal bone on either side of the head. Sphenoidal 2 - at the intersection of the parietal, temporal, frontal, and sphenoid bones on either side of the head.
The occipital and sphenoidal fontanelle being the smaller of the six close between the second and third months after birth. The mastoid usually fills in around a year after birth.
And the frontal, which is the largest, generally takes between 18 to 24 months to close. Bones of the Cranium[ edit ] Base of the skull.
Anterior cranial fossa is the grayish area above the yellow and pink middle cranial fossa. The posterior cranial fossa is shown below the pink and yellow middle cranial fossa. The calvaria, or the top hemisphere of the cranium is made up of the squamous bones, the superior part of the frontal bone, the parietal bones, and the superior part of the occipital bone. The base of the cranium consists of the ethmoid, sphenoid, and occipital bones.
There are three distinct regions in the base of the cranium which can be seen from above with the calvaria removed.
These are called fossae and are named by their position with respect to the body: