Anatomy of Craniocervical Junction

Understanding How Your Head and Neck Work Together

The craniocervical junction connects your head (cranio) and neck (cervical), and it can be affected by different conditions. To try to simplify this complex junction, we’ve divided it into 7 key parts.  Let’s look at the key parts of this junction and how they function.
Image:  The Craniocervical Junction (CCJ)

1.  Craniocervical Junction:  This is where the base of the skull meets the upper neck. It includes the lower skull surface, upper vertebrae (C1 and C2), muscles, and connective tissues that join the skull and neck.

2.  Atlanto-occipital (AO) Joint:  This is the upper part of the craniocervical junction, where the skull (occiput) rests on the first neck vertebra (Atlas).  It allows the head to flex, extend, rotate, and tilt.  Strong ligaments, muscles, small facet joints and occipital condyles (OC) hold the head on and allow the head to move around. 

3.  Atlantoaxial (AA) Joint: This is the lower part of the craniocervical junction, where the Atlas connects with the second neck vertebra, the Axis. The atlantoaxial joint allows the head to flex, extend, and rotate. The Axis has a peg-like structure called the dens (also known as the odontoid) pointing upwards into the Atlas and is held on by ligaments, muscles and facet joints that allows head rotation.

Watch a video to learn more here.

The following information deserves to be highlighted, and cannot be overstated: 

Strong, undamaged CCJ ligaments are critical for the craniocervical junction’s biomechanical functions, meaning, the “moving parts” related to the interaction between the skull (cranio) and the upper part of the spine (cervical).   

Watch a video by Education Spine called Craniocervical Junction Model.

Image: Head with the brain stem and spinal cord highlighted.

Brainstem, Spinal Cord, and Cerebrospinal Fluid:  Inside the craniocervical junction, the brainstem connects to the spinal cord. This connection controls vital functions like heart and lung activity. Nerves, blood vessels, and cerebrospinal fluid are also part of this system.  Shepherd Center explains the anatomy of the spinal cord and how it works. The spinal cord is a very important part of our central nervous system.  It’s the overall system that controls and coordinates the activities of our body.  The main job of the spinal cord is the communication system between the brain and the body by carrying messages via nerves that allow us to move and feel sensation. 

Image:  Cranial nerves pairs with anatomical sensory functions outlined.  Neurology of the brain system & how nerves relay information to human body.

Cranial Nerves: There are cranial nerves in the head and neck that help with functions like seeing, smelling, hearing, and controlling muscle movements. The cervical spine has spinal nerves that enable communication between the brain and upper body.  To explore the functions of each of the cranial nerves and look at a diagram you can continue to learn more by referring to Medical News Today’s article on What are the cranial nerves? These nerves play important roles in sending messages to and from the spinal cord, enabling the brain to communicate with parts of the upper body.  If you wish to learn more about the anatomy of the main cranial nerves of the head and neck, watch this video by Kenhub Nerves.

Image:  Illustration of the circulatory system in neck region.

Blood Vessels: Major arteries and veins are found in the neck, supplying blood to the head and neck regions.  For more information, listen to Sam Webster who will explain these parts and systems with visuals.

Image:  Lymphatic system and skeleton system of head and neck.
Lymph Vessels: Lymph nodes in the head and neck filter lymphatic fluid and help fight infections.  You can learn more by watching:  Knowing Anatomy who will explain the lymph nodes of the head and neck.  

Understanding the basic anatomy of the craniocervical junction and cervical spine can help healthcare providers identify and address any issues causing symptoms. If you prefer, there are videos available at the end for visual explanations.  Remember, this knowledge is meant to help you and your healthcare provider investigate possible causes related to your condition.

Anatomy of the Cervical Spine

In this episode of eOrthopodTV, Orthopaedic Surgeon Randale C. Sechrest, MD narrates this animated video describing the basics of the anatomy of the cervical spine.


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