An Overview of a Newborn’s Skull: Parietal Bones and Sutures

A baby’s skull is made up of six bones, as well as fontanelles ("soft spots") and sutures (fibrous tissue bands connecting the skull bones), that allow it to pass through the birth canal during delivery.

The cranial bones, including the parietal bones, will remain separated through infancy. They eventually grow together until they are connected after 18 months. They will stay that way through adulthood.

Anatomy of an Infant’s Skull

An infant’s skull is made up of bony plates, sutures, and fontanelles. The sutures act as flexible joints that allow the skull to mold during birth. They also allow the brain to grow during infancy. 

The parietal bones are the two bones located toward the back of your baby’s skull. They cover the top of the head and meet the occipital bone in the back of the head. The parietal bones also connect to the frontal bones, the two bony plates that cover your little one’s forehead and top of the head toward the front. 

The parietal bones are joined by the sagittal suture. This suture runs along the top of the head down to the back of the skull. The coronal suture attaches the parietal bones to the frontal bones, and the lambdoid suture attaches the parietal bones to the occipital bone at the back of the head. 

The sutures in your child’s skull include:

• Coronal suture: The coronal suture runs from ear to ear over the top of the head. It connects both frontal bones to the parietal bones.
• Sagittal suture: The sagittal suture runs from the top of the head to the back of the head. It joins the two parietal bones together. 
• Metopic suture: The metopic suture runs from the top of the nose up to the top of the head. It connects the two frontal bones.
• Lambdoid suture: The lambdoid suture runs across the back of the head. It joins both parietal bones to the occipital bone in the back of the skull. 

The parietal bones meet the occipital bone at the back of the head, where the posterior fontanelle is located. The fontanelles can be found in the spaces where the sutures intersect. The fontanelles are covered by thick membranes to protect your baby’s brain.

In addition to the posterior fontanelle, the anterior fontanelle is located on top of the head where the two frontal bones meet the two parietal bones. Both fontanelles will close by your child’s second birthday. 

Importance of Parietal Bones, Fontanelles, and Sutures in Newborns

The bones, sutures, and fontanelles in your baby’s skull work together to protect their brain while allowing room for growth. The bony plates that make up the parietal bones protect your child’s brain from trauma.

When your child is born, their skull bones are moldable and softer than an adult’s bones. This allows their head to fit through the birth canal. As they age, the bony plates harden and eventually fuse together. 

The flexible sutures in your child’s skull have two important functions. First, they allow your baby to fit through the birth canal during labor and delivery since the skull bones are able to shift and overlap. Second, the open spaces allow the brain to grow normally. Without open spaces in the skull, your child would be at risk for brain damage, increased intracranial pressure, and cognitive developmental delays. 

What to Look For

You may be the first to notice when something is wrong with your child’s head. Your baby’s fontanelles may even give clues when the child is seriously ill.

The fontanelles usually feel flat and firm to the touch. A sunken anterior fontanelle appears as though it is sagging inward. This indicates dehydration and needs to be treated right away. A bulging anterior fontanelle appears as though the baby’s skin is pressing upward. This could mean that your little one is experiencing increased intracranial pressure, too much pressure on their brain. This is an emergency that requires immediate treatment. 

In addition to the fontanelles, an abnormal head shape can be a sign that something is wrong. A relatively common cause of an abnormal head shape in infants is a birth defect called craniosynostosis. Craniosynostosis occurs when one or more of the sutures in the skull fuses prematurely.

When the bones fuse too early, the brain continues to grow and press against the bone. This leads to an abnormal head shape, as well as increased pressure on the brain. Craniosynostosis usually requires surgery to correct the skull’s shape and allow room for the brain to grow. 

When to Seek Treatment

Reach out to your doctor with any questions or concerns about your child’s head and skull. Call right away if your baby’s fontanelles appear to be sagging or bulging since conditions causing these changes to the fontanelles require immediate treatment. 

If you notice that your child’s head shape is changing or appears abnormal, talk with your doctor. A physician will most likely be able to make a diagnosis with a thorough physical exam and history. 

Summary

A baby's skull is made up of cranial bones, including the parietal bones, fontanelles (soft spots), and sutures. All three features protect your baby's brain and allow room for it to grow. The parietal bones form part of the side and top of the head. Fontanelles are found in spaces between skull bones where the sutures meet. Changes in your baby's fontanelles or head shape may be a sign that something is wrong. You should call your pediatrician right away.

A Word From Verywell

The bones, sutures, and fontanelles in the skull work together to both protect your child’s brain and allow the brain ample space to grow and develop. The parietal bones are two bony plates that cover the back half of your child’s head. While they start out as bony plates, they eventually fuse with the other skull bones to create one solid bone. 

If you develop any concerns about your child’s skull bones, see your pediatrician. Signs to look for include sunken fontanelles, bulging fontanelles, and a changing head shape.

Frequently Asked Questions

Which suture connects the parietal bones? 

The sagittal suture connects the two parietal bones. It runs from the top of the head down to the back of the head. 

How do I know if something is wrong with my baby's skull?

The first clue that there may be something wrong is looking at your child's fontanelles. They should appear flat and feel slightly firm to the touch. When the fontanelles sag down, your child could be dehydrated. When they are bulging out, your child may be experiencing increased intracranial pressure. Both of these conditions require treatment right away.

Where are the parietal bones?

The parietal bones are two bones that cover the backside of an infant's head. They run from the top of the head down to the back. The parietal bones connect to the occipital bone in the back of the head and the frontal bones on top of the head.