Skull, Cranial Nerves & Foramina Flashcards
Where do cranial nerves have their nucleus?
Brain and brain stem
How do cranial nerves pass into the cranium?
Via foramina which are potential sites for compression and restriction
What are the foramina in the ANTERIOR cranium/fossa
Cribiform plate (roof of ethmoid) - fibres from Olfactory Nerve CN I pass up through nasal cavity Optic Canal - located between body and lesser wing of sphenoid - carries optic nerve and ophthalmic artery
What are the fissures in the back of the orbit and describe location?
Superior Orbital Fissure - Between Sphenoid lesser and greater wing
Inferior Orbital Fissure - Between Greater Wing of sphenoid and Maxilla
What structures pass through the Superior Orbital Fissure?
Oculo-motor Nerve - eye movement
Trochlea Nerve - eye movement
Abducen Nerve - eye movement
Opthalmic Vein - venous drainage from orbit to cavernous sinus
Trigeminal Nerve - Opthalmic Branch - sensations from orbit and forehead
What structures pass through the Inferior Orbital Fissure?
Trigeminal Nerve - Maxillary branch
What foramina are in the Greater wing of the Sphenoid?
Foramen Ovale; Rotundum; Spinosum (ROS)
What other nerve passes through the Sphenoid?
Trigeminal Nerve
What foramina are in the Temporal Bone?
Internal Auditory Maetus = Facial Nerve and Vestibulocochlear
Stylomastoid Foramen = Facial Nerve
Where is the Internal Auditory Maetus located?
Within the medial wall of the petrous portion of the temporal bone
What nerves pass through the Internal Auditory Maetus?
Vestibular-Cochlear CN VIII
Facial Nerve CN VII
Where is the stylo-mastoid foramen>
Located between the styloid process and the mastoid process of the temporal bone
What nerve passes through the stylo-mastoid foramen?
Motor branch of Facial Nerve CN VII EXITS here
What nerves and structures pass through the Jugular Foramen?
Glosso-Pharangeal (IX)
Vagus (X)
Spinal Accessory (XI)
Internal Jugular Veins
Sigmoid and Petrosal Sinuses
Where is the Jugular Foramen located?
Between the occiput and mastoid portion of temporal bone on each side, antero and lateral to the Foramen Magnum.
What foramina are located between 2 bones and explain?
Jugular Foramen - Between the occiput and mastoid portion of temporal bone on each side
Foramen Lacerum - Between sphenoid body and petrous portion of temporal
What foramina are within the Occiput and where?
Foramen Magnum - large hole and base of skull
Hypoglossal Canal - condylar portion of occipital bone
What structures pass through the Foramen Magnum?
Spinal Cord
Spinal Roots - C4-C1 of Spinal Accessory Nerve
Vertebral Arteries
What passes through the Hypoglossal Canal?
Hypoglossal Nerve CN XII (brainstem to tongue)
Why is the Occiput prone to distortion at birth?
In 4 separate portions - surrounding the Foramen Magnum so severe birth trauma or head injuries before can affect how the bones fuse and impinge on the spinal cord and medulla.
Why are the vertebral arteries prone to compression?
They follow a vulnerable S shaped pathway. Through vertebral foramina is cervical vertebrae which turns medially around a tortuous S bend between the atlas (C1) and occiput.
What do vertebral arteries do?
The TWO vertebral arteries provide major ARTERIAL blood supply to brain (together with 2 CAROTID arteries)
Where do the vertebral arteries pass through?
Foramen Magnum
What foramina are between the temporal and occipital bone?
Jugular Foramen
What is the function of smaller foramina in the cranium?
They carry EMSSARY veins - enable drainage from veins on OUTSIDE of cranium into VENOUS sinuses INSIDE cranium
Name 1 Smaller Foramina and explain function
Foramen Caecum - carries emissary vein from nose to superior sagittal sinus, located at junction of frontal bone and ethmoid - so it is a passageway for infection from nasal cavity to meninges.
What are the face foramina and where are they found?
Supraorbital Notch - superior orbital rim on frontal bone
Infraorbital Notch - inferior orbital rim on maxilla bone
Mental Foramen - mandible
Mandibular Foramen - mandible