Gross Anatomy of the Cerebellum

Study Notes

Located in the posterior cranial fossa, behind the 4th ventricle, pons, and medulla.
Covered by the tentorium cerebelli on its superior aspect.
Comprises two hemispheres connected by the narrow vermis.
Connected to the brainstem via three cerebellar peduncles: superior, middle, and inferior.
Divided into three lobes:
- Anterior lobe (paleocerebellum) on the superior surface, separated by the primary fissure.
- Middle lobe (neocerebellum), situated between the primary and uvulonodular fissures.
- Flocculonodular lobe (archicerebellum), located posterior to the uvulonodular fissure.
Horizontal fissure separates the superior and inferior surfaces.
Structurally consists of a gray matter cortex and white matter core, which contains intracerebellar nuclei.

Composed of folds called folia arranged in coronal or transverse planes.
Each folium contains a white matter core covered by gray matter.
Sectioning through the cerebellum reveals a branched appearance termed arbor vitae.
Gray matter arranged in three layers:
- Molecular layer (outermost).
- Purkinje cell layer (middle).
- Granular layer (innermost).

Four primary nuclei:
- Dentate nucleus: Largest, shaped like a crumpled bag, mainly contributes to the superior cerebellar peduncle.
- Emboliform nucleus: Ovoid, lies medial to the dentate nucleus.
- Globose nucleus: Comprises rounded cell groups, medial to the emboliform nucleus.
- Fastigial nucleus: Located near the midline in the vermis, larger than the globose nucleus.
Nuclei consist of large, multipolar neurons with simple branching dendrites.
Axons form the cerebellar outflow through the superior and inferior cerebellar peduncles.

Sparse white matter in the vermis; abundant in each cerebellar hemisphere.
Composed of three fiber groups:
- Intrinsic fibers: Connect different cerebellar regions and interconnect folia.
- Afferent fibers: Major component, predominantly entering through inferior and middle cerebellar peduncles.
- Efferent fibers: Originate from Purkinje cell axons, synapsing with cerebellar nuclei, or bypassing to exit the cerebellum.

Vermis: Influences movements of the body's long axis (neck, shoulders, thorax).
Intermediate zone: Controls distal limb muscle movements (hands and feet).
Lateral zone: Involved in planning sequential body movements and assessing movement errors.

Archicerebellum:
- Flocculonodular lobe.
- Fastigial nucleus.
- Afferents from vestibular nuclei; efferents to vestibular nuclei.
- Controls balance.
Paleocerebellum:
- Vermis and paravermis.
- Globose and emboliform nuclei.
- Afferents from spinal cord; efferents to red nucleus.
- Influences posture and muscle tone.
Neocerebellum:
- Rest of cerebellum.
- Dentate nucleus.
- Afferents from pons; efferents mainly to ventral lateral nucleus of thalamus and motor cortex.
- Coordinates voluntary movements.

Supplied by branches of the vertebrobasilar system:
- Superior cerebellar artery: Supplies the superior region.
- Anterior inferior cerebellar artery: Supplies anterior and inferior regions.
- Posterior inferior cerebellar artery: Supplies cerebellar nuclei and inferior vermis.