Difference Between Skull and Cranium

The main difference between skull and cranium is that the skull is composed of both facial bones and the cranium whereas the cranium is the upper part of the skull, composed of bones that do not move. Furthermore, the number of bones in the skull is 22, including 8 cranial bones and 14 facial bones, while the number of bones in the cranium is 8. 

Skull and cranium are two terms used in describing the skeletal structures of the head. The main function of them is to protect the brain and the other internal structures in the head. 

Key Areas Covered 

1. What is Skull
     – Definition, Facts, Facial Bones
2. What is Cranium
     – Definition, Cranial Bones, Sutures
3. What are the Similarities Between Skull and Cranium
     – Outline of Common Features
4. What is the Difference Between Skull and Cranium
     – Comparison of Key Differences

Key Terms 

Cranial Bones, Facial Bones, Location, Role of the Bones, Skull, Sutures

What is Skull 

Skull is the protective structure of bones, which supports the face and hosts the brain. It is composed of several bones made up through intramembranous ossification and joined together by fibrous joints called sutures. These joints are immovable and they are completely fused together at the age of 20. Cranium and face are the two main parts of the skull. The cranium is composed of 8 bones while the face is made up of 14 bones. In addition, the ossicles of the ear and the hyoid bones are also considered as the bones of the skull. Hence, the total number of bones in the skull is 29. 

Figure 1: Human Skull Front View

Facial Bones 

The facial skeleton is also called the viscerocranium and it provides sites for the attachment of muscles of the face and determines the facial features. The fusing of the 14 individual facial bones houses oral and nasal cavities, the orbits of the eyes, and the hollow spaces called sinuses. The types of facial bones and their role in the skull are described in the table below.

 Facial Bones and their Role 

What is Cranium 

Cranium is the part of the skull, which covers the brain. It is also known as neurocranium. It protects the brain along with meninges and cerebral vasculature. The two main parts of the cranium are roof or the calvarium and the cranial base. 

• Calvarium – Made up of the frontal, occipital, and two parietal bones 
• Cranial base – Made up of six bones; frontal, sphenoid, ethmoid, occipital, parietal and temporal bones. The cranial base provides the articulation point for the atlas or the first cervical vertebra, facial bones, and the mandible. 
  

  Figure 2: Human Skull Side View

Bones of the Cranium and their Role 

Sutures joints the bones of the cranium. The main sutures found in the adulthood are,

• Coronal suture – Fuses the frontal bone with the two parietal bones 
• Sagittal suture – Fuses both parietal bones to each other  
• Lambdoid suture – Fuses the occipital bone to the two parietal bones  

Similarities Between Skull and Cranium 

• Skull and cranium are two skeletal structures of the head. 
• Most bones in the skull and cranium are made up of flat bones formed by intramembranous ossification.
• Their main function is to protect the brain. 
• They also provide sites for the attachment of muscles responsible for the movement of the head, facial expressions, and chewing.  

Difference Between Skull and Cranium 

Definition 

Skull refers to the bone framework that encloses the head of a vertebrate while cranium refers to the part of the skull that encloses the brain.  

Number of Bones 

The skull is composed of 22 bones while the cranium is composed of 8 bones. 

Movement

Mandible, which is a bone of the skull, can be moved while the bones of the cranium are immobile.

Function 

The main function of the skull is to protect the brain, attach muscles of the face and determine the facial features while the main function of the cranium is to protect the brain, meninges and cerebral vasculature. 

Conclusion 

Skull is the skeletal structure which covers the head and the cranium and the face are the two components of it. In addition, the cranium is the part that covers the brain. The main difference between the skull and the cranium is their location in the head. 

Reference:

1. “Bones of the Skull.” TeachMeAnatomy, 1 Aug. 2018, Available Here

Image Courtesy:

1. “Human skull front simplified (bones)” By LadyofHats Mariana Ruiz Villarreal – Own work (Public Domain) via Commons Wikimedia 
2. “Human skull side simplified (bones)” By LadyofHats Mariana Ruiz Villarreal – made it myself (Public Domain) via Commons Wikimedia