Cerebrum Anatomy Overview

Cerebrum (General Features)

• The cerebrum or cerebral hemispheres are main parts of the brain.
• It is divided into 3 surfaces:
  • Lateral surface (supero-lateral): Convex
  • Medial surface: Flat
  • Inferior surface: Irregular, divided into orbital & tentorial parts.

### Cerebral Hemispheres (Position & Borders)

• Two cerebral hemispheres are separated by a median longitudinal cerebral fissure.
• The falx cerebri projects down from the skull's vault.
• The corpus callosum is located at the floor of this fissure and connects the two cerebral hemispheres.
• The frontal lobe sits in the anterior cranial fossa.
• The temporal lobe occupies the middle cranial fossa's lateral portion.
• The occipital lobe occupies the upper posterior cranial fossa, positioned above the cerebellum and between the tentorial cerebelli.

### Central Region, Base of Brain

• The optic chiasma is a crucial structure.
•  The optic tract is a fiber bundle carrying information from the optic nerve.
• The tuber cinereum is a small region involved in hormone secretion.
• The mammillary bodies play a role in memory and sensory processing.
• Cranial nerve III (oculomotor nerve) passes through the interpeduncular fossa.
• The anterior perforated substance & posterior perforated substances are areas containing small blood vessels.

### Anterior Part, Base of Brain

• Orbitals sulci are prominent depressions on the brain's surface.
• The olfactory bulb is involved in smell.
• The olfactory tract and sulcus are part of the olfactory system.
• The olfactory trigone is a small triangular structure in this region.
• The stria lateralis are bundles of nerve fibers.
• The temporal lobe is situated in this area.
• The optic chiasma is visible.
• The tuber cinereum and mammillary bodies are identified.
• The posterior perforated substance is observed.

Division of Hemisphere into Lobes

• Three main sulci/fissures divide the hemisphere into lobes:
  • Central sulcus (Fissure of Rolando): Runs obliquely downward and forward across the lateral surface, extending from the superior border, down to the posterior ramus of the lateral fissure. It separates motor and sensory areas.
  • Lateral fissure (Fissure of Sylvius): Extends laterally between the frontal and temporal lobes to reach the lateral surface, dividing into three rami.
    • Posterior ramus: Longest, runs backward on the lateral surface, parallel to the inferior border, and penetrates the parietal lobe.
    • Anterior horizontal ramus: 2 cm long, runs forward into the frontal lobe.
    • Anterior ascending ramus: 2 cm long, runs upward into the frontal lobe.
  • Parieto-occipital sulcus: A deep sulcus on the medial surface of the hemisphere, extending a short distance on the lateral surface, separating the parietal and occipital lobes.

Lobes of Hemisphere

• The four lobes include frontal, parietal, occipital, and temporal:
  • Inferior border of temporal lobe
  • Preoccipital Notch
  • Occipital Pole
  • The insula is a buried part of the cerebral cortex located in the lateral fissure's bottom.