The sphenoid bone consists of a central body, paired medial and lateral pterygoid plates as well as paired greater and lesser wings. Nerves and vessels pass through its many foramina. The lesser wings form the back of the anterior cranial fossa and contain the optic canals (for CN II). Between the lesser and greater wings are the superior orbital fissures (for CN III, IV, VI). … Continue reading Sphenoid bone

The almost t-shaped ethmoid bone divides the cranial and nasal cavities as the roof of the nose and centre of the anterior cranial fossa. Fibres of the olfactory nerve (CN I) exit from the cranial cavity through foramina of the cribriform plate into the nose. Superiorly, the crista galli is a midline projection into the cranial cavity and serves as the anterior attachment for the … Continue reading Ethmoid bone

The brain is supplied by the internal carotid and vertebral arteries which anastomose to form the circle of Willis at the skull base. These are not the sole intracranial arteries as branches of the external carotid artery are a major supplier to the meninges. Intracranial venous drainage does not follow the course of these arteries and instead run in the dural venous sinuses. Internal carotid … Continue reading Intracranial blood supply

At certain sites, the two layers of dura mater separate to form the dural venous sinuses – the system for venous drainage of the cranium and brain. These are lined by vascular endothelium, with no valves or muscular tissue, and ultimately drain into the internal jugular veins. Sagittal sinuses The superior sagittal sinus runs in the superior margin of the falx cerebri from the crista … Continue reading Dural venous sinuses

The meninges are the three layers of connective tissue that wrap around the spine and brain. These layers are the: dura mater, arachnoid mater and pia mater. Dura mater The dura mater (“tough mother”) is the outermost layer of the meninges, made of dense connective tissue. While only one layer surrounds the spinal cord, it is divided in the cranium into an outer endosteal layer which … Continue reading Meninges & dural folds