Fossa navicularis magna (also known as ''pharyngeal fossa'' or ''phyaryngeal fovela'') is a variant bony depression found at the midline of the occipital part of clivus. This fossa was first described by Tourtual. Its prevalence ranges from 0.9 to 5.3%.

Structure

Fossa navicularis magna is located on the anterior surface or pharyngeal surface of the clivus. Its position when present is between the spheno-occipital

synchondrosis A synchondrosis (or primary cartilaginous joint) is a type of cartilaginous joint where hyaline cartilage completely joins together two bones. Synchondroses are different than symphyses (secondary cartilaginous joints) which are formed of fibrocar ...

and 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 oblonga ...

. Size of this fossa varies considerably and its depth ranges from 3.49 to 4.94 mm. A histological study reported the presence of loose connective tissue containing collagen and

elastic fibers Elastic fibers (or yellow fibers) are an essential component of the extracellular matrix composed of bundles of proteins ( elastin) which are produced by a number of different cell types including fibroblasts, endothelial, smooth muscle, and ai ...

within the fossa navicularis magna.

Development

Two theories have been proposed to explain the formation of fossa navicularis magna. It is believed that the fossa is formed as a remnant of the

notochord In anatomy, the notochord is a flexible rod which is similar in structure to the stiffer cartilage. If a species has a notochord at any stage of its life cycle (along with 4 other features), it is, by definition, a chordate. The notochord cons ...

or residue of the channels for

emissary veins The emissary veins connect the extracranial venous system with the intracranial venous sinuses. They connect the veins outside the cranium to the venous sinuses inside the cranium. They drain from the scalp, through the skull, into the larger me ...

Clinical significance

Different pathologies were found associated with fossa navicularis magna including cancers, adenoid hypertrophy, ecchordosis physaliphora, Tornwaldt cyst and Rathke cleft cyst.{{Cite journal , last1=Murjani , first1=Bhavana , last2=Bhosale , first2=Rohini , last3=Ramaswami , first3=Easwaran , last4=Kadam , first4=Sonali , last5=Ramchandani , first5=Amit , date=2021 , title=Anatomical variations of clivus: a descriptive anatomical study , url=https://pubmed.ncbi.nlm.nih.gov/33483831/ , journal=Surgical and Radiologic Anatomy , volume=43 , issue=6 , pages=945–951 , doi=10.1007/s00276-021-02686-w , issn=1279-8517 , pmid=33483831, s2cid=231682612

References

Anatomical variations Human anatomy Skull Bones of the head and neck

Structure

Development

Clinical significance

See also

References