Brain Anatomy: Cerebellum and Metencephalon

Metencephalon

• Composed of Pons and Cerebellum

Cerebellum

• Superior surface has anterior and superior notch
• Inferior surface has vallecula cerebelli, anterior and posterior edges, and hemispheres and vermis separated by median sulcus
• Divided into three lobes: Anterior lobe, Floculonodular lobe, and Posterior or middle lobe
• Anterior lobe has culmen, central lobule, and lingula cerebelli
• Floculonodular lobe has nodulus and flocculus
• Posterior or middle lobe has declive, piramid, uvula, folium vermis, and tuber

Nuclei of the Cerebellum

• Vermis has fastigial nucleus
• Hemispheres have dentate nucleus, emboliform nucleus, and globosus nucleus

Pons

• Basal surface limited superiorly by superior cerebral peduncles
• Basal surface limited inferiorly by medulla oblongata
• Continues as middle cerebellar peduncles laterally on the basal surface of the cerebellum
• Cranial nerves leaving the brain on the borders of the pons at the basal surface of the cerebellum: Trigeminal (V), abducent (VI), facial (VII), and vestibulo-cochlear (VIII)

Dorsal Surface of the Cerebellum

• Formed by the superior part of the rhomboid fossa (floor of the IVth ventricle)
• Separated from the inferior part of the rhomboid fossa by striae medullares
• Laterally limited by superior cerebellar peduncles

Rhomboid Fossa

• Pontine part includes structures such as median sulcus, medial eminences, facial colliculi, sulcus limitans, superior foveae, upper portion of the vestibular area, and locus coeruleus

Medulla Oblongata

• Basal surface has anterior median fissure, pyramids, anterior lateral sulcus, lateral funiculus, and the olive
• Hypoglossal nerve leaves the brain at the anterior lateral sulcus on the basal surface
• Superior limits: striae medullares (dorsally) and inferior border of pons with foramen caecum (ventrally)
• Inferior limits: decussation of pyramids (ventrally) and point of emergence of C1 cranial nerves (dorsally)

Rhomboid Fossa (continued)

• Inferior part of the dorsal surface limited by sulcus limitans on the lateral side
• Vagal triangle on the dorsal surface limited by funiculus separans
• Area postrema on the dorsal surface connected with its counterpart by obex
• Vestibular area on the dorsal surface leads laterally to the lateral recess with the acoustic tubercle

Structures Found on the Rhomboid Fossa

• Median sulcus
• Sulcus limitans
• Locus coeruleus
• Medial eminance
• Vagal triangle
• Hypoglossal triangle
• Funiculus separans
• Area postrema
• Superior vestibular area

4th Ventricle

• Floor formed by the rhomboid fossa
• Superior wall composed of superior cerebellar peduncles and superior medullary vellum
• Inferior wall formed by inferior medullary velum, nodulus of the vermis, and tela choroidea
• Median aperture located at the inferior wall, leads to the cerebromedullar cisterna (subarachnoid space)
• Lateral apertures located in the apex of the lateral recessus, lead to the pons cisterna (subarachnoid space)

Spinal Cord

• Termination at L1/L2 (Lumbar vertebrae 1/Lumbar vertebrae 2)
• Cervical enlargement at C5 - T1 (Cervical vertebrae 5 - Thoracic vertebrae 1)
• Lumbosacral enlargement at L1 - S3 (Lumbar vertebrae 1 - Sacral vertebrae 3)

Fissures and Sulci in the Spinal Cord

• Anterior median fissure
• Posterior medial sulcus
• Posterolateral sulcus
• Anterolateral sulcus
• Posterior intermediate sulcus