Neuroanatomy: The Cerebrum

Introduction:

• The cerebrum is the largest part of the brain.
• Occupies the anterior, middle cranial fossae, and supratentorial part of the posterior cranial fossa.
• Consists of two cerebral hemispheres divided by the interhemispheric fissure (medial longitudinal fissure).

Interhemispheric Fissure (Medial Longitudinal Fissure):

• Deep groove separating the cerebral hemispheres.
• Contains the falx cerebri, cerebrospinal fluid, and branches of the anterior and posterior cerebral arteries.

Connecting Structures:

• Hemispheres connected by the corpus callosum (white matter bundle).
• Each hemisphere contains a lateral ventricle filled with cerebrospinal fluid.

Gross Anatomy of Cerebral Hemispheres:

• Medial Surface: Flattened, inferior surface irregular and concave (more anteriorly).
• Lateral Surface: Convex.
• Surface Features: Divided by grooves (sulci) and ridges (gyri).

Division into Lobes:

• Frontal Lobe: 41% of neocortical volume.
• Temporal Lobe: 22%.
• Parietal Lobe: 19%.
• Occipital Lobe: 18%.
• Additional regions sometimes mentioned: insular cortex (insular lobe) and cingulate gyrus with hippocampus (limbic lobe).

Relations:

• Medial Relations: Falx cerebri, contralateral cerebral hemisphere.
• Inferior Relations: Anterior cranial fossa, middle cranial fossa, tentorium cerebelli.

External Features:

• Each hemisphere has three surfaces, four borders, three poles, and is divided into four lobes.

Surfaces of the Cerebrum:

1. Superolateral Surface: Convex.
2. Medial Surface: Flat and vertical.
3. Inferior Surface: Irregular; divided into anterior (orbital surface) and posterior (tentorial surface) parts.

Borders of the Cerebrum:

1. Superior Border: Separates superolateral from medial surface.
2. Infralateral Border: Separates superolateral from inferior surface.
3. Medial Orbital Border: Separates medial from orbital surface.
4. Medial Occipital Border: Separates medial from tentorial surface.

Poles of the Cerebrum:

1. Frontal Pole: Anterior end.
2. Occipital Pole: Posterior end.
3. Temporal Pole: Anterior end of the temporal lobe.

Lobes of the Cerebrum:

1. Frontal
2. Parietal
3. Occipital
4. Temporal

Summary

• The cerebrum is a complex and largest part of the brain featuring various important anatomical structures and relations. Understanding its divisions, surfaces, and borders is crucial for grasping its functions and importance in neuroanatomy.