Cranial Fossae
Cranial fossae are depressions in the skull base that cradle and support different parts of the brain.
The cranial fossae are three depressions on the internal base of the skull that accommodate different parts of the brain. These fossae - anterior, middle, and posterior - are separated by bony ridges and are critical for understanding the organization of the cranial cavity. Each fossa has its own set of foramina for the passage of nerves and vessels and houses specific brain regions. A clear understanding of these structures is essential for students of anatomy, radiology, neurology, and surgery.
Overview
The cranial base can be divided into three fossae:
Anterior cranial fossa
Middle cranial fossa
Posterior cranial fossa
These fossae are formed by the cranial bones and shaped to cradle the brain. The anterior fossa supports the frontal lobes, the middle fossa supports the temporal lobes and pituitary gland, and the posterior fossa houses the cerebellum, pons, and medulla.
Anterior Cranial Fossa
The anterior cranial fossa is the most shallow and anterior part of the cranial base. It is formed primarily by the frontal bone (orbital plates), ethmoid bone (cribriform plate), and lesser wings of the sphenoid.
Contents:
Frontal lobes of the cerebral hemispheres
Olfactory bulbs
Key features:
Cribriform plate (ethmoid): Contains numerous tiny foramina for the passage of the olfactory nerve fibers (CN I).
Crista galli: A vertical projection of the ethmoid bone that anchors the falx cerebri.
Middle Cranial Fossa
The middle cranial fossa is deeper and wider than the anterior fossa. It is formed by the sphenoid bone (body and greater wings) and the petrous portion of the temporal bone. It lies between the lesser wings of the sphenoid and the petrous ridges of the temporal bones.
Contents:
Temporal lobes of the brain
Pituitary gland (in sella turcica)
Key features and foramina:
Optic canals: Transmit the optic nerves (CN II) and ophthalmic arteries.
Superior orbital fissure: Transmits cranial nerves III, IV, V1, VI.
Foramen rotundum: Maxillary nerve (CN V2).
Foramen ovale: Mandibular nerve (CN V3).
Foramen spinosum: Middle meningeal artery.
Sella turcica: Bony depression that houses the pituitary gland.
Posterior Cranial Fossa
The posterior cranial fossa is the deepest and largest. It is formed by the occipital bone and parts of the temporal bones. This fossa is located posterior to the petrous ridges and supports the hindbrain structures.
Contents:
Cerebellum
Pons
Medulla oblongata
Key features and foramina:
Foramen magnum: The largest opening; transmits the medulla, spinal accessory nerves (CN XI), and vertebral arteries.
Internal acoustic meatus: Facial (CN VII) and vestibulocochlear (CN VIII) nerves.
Jugular foramen: Glossopharyngeal (CN IX), vagus (CN X), accessory (CN XI) nerves, and internal jugular vein.
Hypoglossal canal: Hypoglossal nerve (CN XII).
Clinical Relevance
Trauma: Fractures involving the fossae can lead to cranial nerve injury or cerebrospinal fluid (CSF) leaks.
Tumors: Tumors of the pituitary gland can expand within the sella turcica, affecting the optic chiasm.
Posterior fossa syndrome: Tumors or hemorrhages here can compress vital brainstem structures, leading to life-threatening complications.
Last updated on April 30, 2025