The Anatomy of the Cranium

The cranium is part of the skull anatomy. The entire skull is made up of 22 bones, eight of which are cranial bones. The two main parts of the cranium are the cranial roof and the cranial base.

Connected to the cranial bones are facial bones that give structure to the face and a place for the facial muscles to attach. Together, the cranial and facial bones make up the complete skull. 

The cranium has a very important job: to hold and protect the brain. It also allows passage of the cranial nerves that are essential to everyday functioning.

There are some abnormalities to craniofacial anatomy that are seen in infancy as the baby’s head grows and develops. Other conditions of the cranium include tumors and fractures.

Anatomy

The cranium is located at the top of the head and is somewhat spherical in shape, like the shape of a baseball cap. It connects to the facial skeleton.

Though the skull appears to be one big piece of bone from the outside, it is actually made up of eight cranial bones and 14 facial bones. The cranium has two main parts—the cranial roof and the cranial base.

The cranial roof consists of the frontal, occipital, and two parietal bones. The cranial base is composed of the frontal, sphenoid, ethmoid, occipital, parietal, and temporal bones. As you can see, the cranial roof and cranial base are not mutually exclusive as they share some of the same bones.

The cranial bones are fused together to keep your brain safe and sound. However, in infancy, the cranial bones have gaps between them and are connected by connective tissue. These can be felt as soft spots. This allows the brain to grow and develop before the bones fuse together to make one piece.

Function

The main function of the cranium is to protect the brain, which includes the cerebellum, cerebrum, and brain stem. It also gives a surface for the facial muscles to attach to. The cranium isn't involved with any sort of movement or activity.

The cranial nerves originate inside the cranium and exit through passages in the cranial bones. These nerves are essential to everyday functioning, including smelling, seeing, and chewing. For example, the hypoglossal nerve controls the movements of the tongue so that you can chew and speak.

Associated Conditions

There are a few categories of conditions associated with the cranium: craniofacial abnormalities, cranial tumors, and cranial fractures.

Some craniofacial abnormalities result from the skull bones fusing together too soon or in an abnormal way during infancy.

For example, craniosynostosis is a condition in which the sutures of a baby’s skull (where you feel the soft spots) close too early, causing issues with brain and skull growth. This can cause an abnormal, asymmetrical appearance of the skull or facial bones.

Some craniofacial abnormalities are sporadic, meaning they are not associated with any known genetic abnormality. Others are caused by rare genetic conditions such as:

• Apert syndrome
• Pfeiffer syndrome
• Coffin-Lowry syndrome

Other associated conditions are due to tumors on the skull base. Certain cranial tumors and conditions tend to show up in specific areas of the skull base—at the front (near the eye sockets), the middle, or the back. Skull base tumor conditions are classified by the type of tumor and its location in the skull base.

For example, meningioma is the most common type of primary brain tumor, making up about one-third of all brain tumors; they are usually benign (not cancerous). One type of meningioma is sphenoid wing meningioma, where the tumor forms on the base of the skull behind the eyes; it accounts for approximately 20% of all meningiomas.

Skull fractures are another type of condition associated with the cranium. They result from blunt force or penetrating trauma. The most common causes of traumatic head injuries are motor vehicle accidents, violence/abuse, and falls. 

There are four types of skull fractures, which may or may not require surgical intervention based on the severity. Depending on the location of the fracture, blood vessels might be injured, which can cause blood to accumulate between the skull and the brain, leading to a hematoma (blood clot).

Epidural hematoma is the most common type of hematoma resulting from a skull fracture. Like fractures, hematomas can range from mild to severe.

Treatment

Treatment of cranial injuries depends on the type of injury. For example, some craniofacial abnormalities can be corrected with surgery. 

A linear skull fracture, the most common type of skull fracture where the bone is broken but the bone does not move, usually doesn't require more intervention than brief observation in the hospital.

As for hematomas caused by fractures, a severe hematoma may require prolonged observation in the hospital, while a mild one may require only rest and ice at home.

Tumors require a medical team to treat. Radiation therapy and surgery are the most common initial treatments, while sometimes the best thing is close observation; chemotherapy is rarely used.

If surgery is indicated, some may be more difficult depending on the location of the cranial tumor. For instance, skull base meningiomas, which grow on the base of the skull, are more difficult to remove than convexity meningiomas, which grow on top of the brain.

Summary

The cranium houses and protects the brain. In infancy, the eight cranial bones are not quite sewn together, which allows for brain growth. Once fused, they help keep the brain out of harm's way. The cranium can be affected by structural abnormalities, tumors, or traumatic injury.

A Word From Verywell

The cranium is like a helmet for the brain. You can further protect your cranium and brain from traumatic injury by using safety equipment such as helmets, seat belts, and harnesses during sports, on the job, and while driving, riding, or taking transportation.

Frequently Asked Questions

Does "cranium" also mean "head"? 

Generally speaking, yes. The cranium refers to the cranial roof and base, which make up the top, sides, back, and bottom of the skull. The rest is made up of facial bones.

How many bones are in the skull? 

There are 22 bones in the skull. Fourteen are facial bones and eight are cranial bones. The bones are connected by suture lines where they grow together.

What kind of protection does the cranium provide? 

The cranium houses and protects the brain. The cranium is pretty robust because it has such a high-stakes job of protecting the brain. However, cranial bone fractures can happen, which can increase the risk of brain injury. But some fractures are mild enough that they can heal without much intervention.