Anatomy of the Brain: Ventricular System and Cerebrospinal Fluid

Cranium

• The calvaria is composed of the frontal, parietal, and occipital bones.
• The frontal bone is unpaired and articulates with the paired parietal bones at the coronal suture.
• The parietal bones articulate with each other in the midline at the sagittal suture and with the unpaired occipital bone at the lambdoid suture.
• The four largest sutures of the skull are located where the parietal bones articulate with other bones: coronal, sagittal, lambdoid, and occipital sutures.

Cerebrospinal Fluid (CSF)

• CSF is produced by the choroid plexus in the ventricles.
• It serves three main functions: protection, buoyancy, and chemical stability.
• CSF surrounds the brain and spinal cord, and its net weight is reduced to approximately 25 grams.

Ventricular System

• The ventricular system is a set of communicating cavities within the brain.
• It is responsible for the production, transport, and removal of CSF.
• The ventricles are lined by ependymal cells, which form the choroid plexus.

Cranial Meninges

• The cranial meninges comprise three protective covers: the dura mater, arachnoid mater, and pia mater.
• The dura mater is a tough, double-layered membrane that lines the inner surface of the skull.
• The arachnoid mater intervenes between the pia and dura mater.
• The pia mater is adherent to the brain.

The Cerebrum

• The cerebrum is the largest part of the brain.
• It consists of two hemispheres separated by the median cleft or longitudinal fissure.
• Each hemisphere contains an irregular cavity containing CSF, known as the lateral ventricle.
• The two hemispheres are connected to each other by the large commissure, the corpus callosum.
• The cerebrum is composed of grey matter (cortex) and white matter.

Functions of the Cerebrum

• The frontal lobe is responsible for higher intellect, personality, mood, speech, and motor cortex.
• The parietal lobe is responsible for sensory cortex.
• The temporal lobe is responsible for memory and language, and hearing.
• The occipital lobe is responsible for visual cortex.

Sulci and Gyri

• The gyri assist in the location of certain functional areas of the brain.
• The sulci and gyri are folds on the surface of the brain.

Central Nervous System (CNS)

• The CNS comprises the brain and spinal cord.
• The brain is divided into the cerebrum, cerebellum, brain stem, midbrain, pons, and medulla.

Peripheral Nervous System (PNS)

• The PNS comprises the cranial nerves and spinal nerves.
• The cranial nerves have 12 pairs, while the spinal nerves have 31 pairs.

Grey Matter and White Matter

• In the CNS, the cell bodies of neurons are found in the grey matter of the brain in the cerebral cortex or nuclei.
• The axons of neurons in the brain are seen as white matter, arranged as fibre tracts that run in bundles or fascicles.
• Outside the CNS, the cell bodies of neurons are found as collections called ganglia.
• The axons of many neurons in the PNS are seen as nerves, which consist of many axons running together.