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Connections of the vertebral column to the skull
Last reviewed: 06.07.2025
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The first and second cervical vertebrae are connected to the skull and its occipital bone. The joints are characterized by great strength, mobility, and complexity of structure.
The atlantooccipital joint (art. atlantooccipitalis) is a combined, condylar joint. It is formed by two condyles of the occipital bone, which connect with the corresponding superior articular fossae of the atlas. Each of these joints has its own articular capsule. Together, they are reinforced by two atlantooccipital membranes. The anterior atlantooccipital membrane (membrana atlantooccipitalis anterior) is stretched between the basilar part of the occipital bone and the anterior arch of the atlas. The posterior atlantooccipital membrane (membrana atlantooccipitalis posterior) is thinner and wider than the anterior one. It is attached to the posterior semicircle of the foramen magnum above and the posterior arch of the atlas below.
Simultaneous movements are possible at the right and left atlanto-occipital joints (combined joint). Forward and backward head tilts (nodding movements) are performed around the frontal axis. The range of motion is 20° for forward tilt and 30° for backward tilt. Around the sagittal axis, head abduction from the midline (lateral tilt) and return to the initial position are possible with a total range of up to 20°.
The median atlantoaxial joint (art. atlantoaxiilis mediana) is formed by the anterior and posterior articular surfaces of the odontoid of the axial vertebra. In front, the odontoid is connected to the fossa odontoid on the posterior surface of the anterior arch of the atlas. Behind, the odontoid articulates with the transverse ligament of the atlas (lig. transversum atlantis). This ligament is stretched between the inner surfaces of the lateral masses of the atlas. The anterior and posterior articulations of the odontoid have separate articular cavities and articular capsules, but are usually considered as a single median atlantoaxial joint. The median atlantoaxial joint is a cylindrical uniaxial joint. It allows rotation of the head relative to the vertical axis. Rotations of the atlas around the odontoid are performed together with the skull by 30-40° in each direction.
The lateral atlantoaxial joint (art. atlantoaxial lateralis) is paired, formed by the glenoid fossa on the lateral mass of the atlas and the superior articular surface on the body of the axial vertebra. The right and left atlantoaxial joints have separate articular capsules.
The medial and lateral atlantoaxial joints are strengthened by several ligaments. The ligament of the apex of the tooth (lig. apicis dentis) is unpaired, thin, stretched between the posterior edge of the anterior circumference of the foramen magnum and the apex of the tooth. The pterygoid ligaments (ligg. alaria) are paired. Each of them originates on the lateral surface of the tooth, is directed obliquely upward and laterally, and is attached to the inner surface of the condyle of the occipital bone. The pterygoid ligaments limit excessive rotation of the head at the medial atlantoaxial joint.
Behind the ligament of the apex of the tooth and the pterygoid ligaments is the cruciate ligament of the atlas (lig. cruciforme atlantis). It is formed by the transverse ligament of the atlas and the longitudinal bundles (fasciculi longitudinales) of fibrous tissue that extend upward and downward from the transverse ligament of the atlas. The upper bundle ends on the anterior semicircle of the foramen magnum, the lower bundle on the posterior surface of the body of the axial vertebra. Behind, on the side of the spinal canal, the atlantoaxial joints and their ligaments are covered with a wide and strong connective tissue integumentary membrane (membrana tectoria). At the level of the axial vertebra, the integumentary membrane passes into the posterior longitudinal ligament, and above it ends on the inner surface of the basilar part of the occipital bone. The lateral and median atlantoaxial joints are combined. Simultaneously with rotation in the medial atlantoaxial joint, in the lateral atlantoaxial joints only sliding occurs with a slight displacement of the articular surfaces.
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