The condylar canal (or condyloid canal) is a canal in the

condyloid fossa Behind either condyle of the lateral parts of occipital bone is a depression, the condyloid fossa (or condylar fossa), which receives the posterior margin of the superior facet of the atlas when the head is bent backward; the floor of this fossa is ...

of the

lateral parts of occipital bone The lateral parts of the occipital bone (also called the exoccipitals) are situated at the sides of the foramen magnum; on their under surfaces are the condyles for articulation with the superior facets of the atlas. Description The condyles are o ...

behind the

occipital condyle The occipital condyles are undersurface protuberances of the occipital bone in vertebrates, which function in articulation with the superior facets of the atlas vertebra. The condyles are oval or reniform (kidney-shaped) in shape, and their anteri ...

. Resection of the rectus capitis posterior major and minor muscles reveals the bony recess leading to the condylar canal, which is situated posterior and lateral to the occipital condyle. It is immediately superior to the extradural

vertebral artery The vertebral arteries are major arteries An artery (plural arteries) () is a blood vessel in humans and most animals that takes blood away from the heart to one or more parts of the body (tissues, lungs, brain etc.). Most arteries carry o ...

, which makes a loop above the posterior C1 ring to enter the

foramen magnum The foramen magnum ( la, great hole) is a large, oval-shaped opening in the occipital bone of the skull. It is one of the several oval or circular openings (foramina) in the base of the skull. The spinal cord, an extension of the medulla oblon ...

. The anteriomedial wall of the condylar canal thickens to join the foramen magnum rim and connect to the occipital condyle. Through the condylar canal, the

occipital emissary vein The occipital emissary vein is a small emissary vein which passes through the condylar canal The condylar canal (or condyloid canal) is a canal in the condyloid fossa of the lateral parts of occipital bone behind the occipital condyle. Resectio ...

connects to the venous system including the

suboccipital venous plexus The suboccipital venous plexus drains deoxygenated blood from the back of the head. It communicates with the external vertebral venous plexuses. The external vertebral venous plexuses travel inferiorly from this suboccipital region to drain into ...

occipital sinus The occipital sinus is the smallest of the dural venous sinuses. It is usually unpaired, and is sometimes altogether absent. It is situated in the attached margin of the falx cerebelli. It commences near the foramen magnum, and ends by draining in ...

and

sigmoid sinus The sigmoid sinuses (sigma- or s-shaped hollow curve), also known as the , are venous sinuses within the skull that receive blood from posterior dural venous sinus veins. Structure The sigmoid sinus is a dural venous sinus situated within the du ...

. It is not always present, and can have variations of being a single canal or multiple smaller canals in cluster.

Additional images

File:Condylar canal.jpg, Bilateral condylar canals (arrows) above the vertebral arteries. File:Gray187.png, Base of skull. Inferior surface.

References

External links

*
Akram Abood Jaffar: Personal website, Anatomical variations

Foramina of the skull {{musculoskeletal-stub