Chapter 15

Learning Objectives

• Describe the flow of cerebrospinal fluid (CSF) within the ventricular system.
• List and follow the branches from the internal carotid arteries.
• List and follow the branches from the vertebral arteries.
• Draw the Circle of Willis.

Ventricular System

• The ventricular system consists of a series of interconnected cavities filled with cerebrospinal fluid (CSF).

Ventricles

Lateral Ventricles

• Located in the cerebral hemispheres (telencephalon).
  • Contains three horns:
  • Anterior (frontal) horn
  • Posterior (occipital) horn
  • Inferior (temporal) horn
• Features:
  • Interventricular foramen (foramen of Monro) connects to the third ventricle.
  • Contains choroid plexus, responsible for CSF production.

Third Ventricle

• Located in the diencephalon.
• Features:
  • Central cavity communicates with the lateral ventricles via the interventricular foramen.
  • Connected to the fourth ventricle through the cerebral aqueduct.

Fourth Ventricle

• Cavity located in the hindbrain.
• Features:
  • Has three openings (apertures) for CSF inflow:
  • Two lateral apertures (foramen of Luschka)
  • One medial aperture (foramen of Magendie)
• This ventricle allows CSF to flow into the subarachnoid space.

CSF Functions

• Provides buoyancy to the brain, protecting it from injury.
• Acts as a chemical and physical buffer for the brain and spinal cord.
• Formed predominantly in the choroid plexus and resorbed via arachnoid granulations.

Clinical Correlate: Hydrocephalus

• Condition characterized by the accumulation of excess CSF in the ventricles due to:
  • Overproduction of CSF
  • Obstruction of CSF flow
  • Interference with CSF reabsorption.

Vascular Supply to the Brain

Arterial Supply

• Internal carotid arteries supply the cerebral cortex.
• Vertebral arteries supply the cerebellum and posterior cerebrum.

Cerebral Blood Supply

• Internal Carotid Arteries give rise to:
  • Anterior cerebral arteries (ACA)
  • Middle cerebral arteries (MCA)
• Vertebral Arteries eventually form:
  • Basilar artery
  • Terminal bifurcation into posterior cerebral arteries (PCA).

Anterior Cerebral Artery (ACA)

• Branches:
  • Pericallosal artery
  • Callosomarginal artery
• Supplies:
  • Primary motor cortex
  • Primary sensory cortex.
• Clinical Significance: Infarcts can lead to motor and sensory dysfunctions in limbs.

Middle Cerebral Artery (MCA)

• Branches:
  • Superior and inferior divisions, including temporal branches and sulcal branches.
• Supplies:
  • Insular lobe
  • Broca’s area
  • Wernicke’s area
  • Primary motor and sensory cortices.
• Clinical Significance: Infarcts can impair language and motor functions.

Posterior Cerebral Artery (PCA)

• Branches:
  • Medial occipital arteries
  • Calcarine and parieto-occipital branches.
• Supplies:
  • Midbrain
  • Occipital lobe
  • Primary visual cortex.
• Clinical Significance: Infarcts may result in visual field deficits.

Circle of Willis

• A critical arterial structure on the base of the brain; anastomosis between anterior and posterior circulation includes:
  • Anterior communicating artery,
  • Anterior cerebral arteries (ACA),
  • Middle cerebral artery (MCA),
  • Basilar artery,
  • Posterior communicating arteries,
  • Posterior cerebral arteries (PCA).

Cerebellar Blood Supply

• Branches:
  • Superior cerebellar artery (SCA)
  • Anterior inferior cerebellar artery (AICA)
  • Posterior inferior cerebellar artery (PICA)
• Supplies: Cerebellum and its peduncles.

Spinal Cord Blood Supply

• Important arteries include:
  • Anterior spinal artery
  • Posterior spinal arteries.

Clinical Correlate: Ischemic Stroke

• Defined as the sudden onset of neurological deficits due to impaired blood flow to the brain.
• Distinction from hemorrhagic stroke, which involves bleeding.

References

• Grant’s Atlas of Anatomy, 8th edition
• Grant’s Dissector, 16th edition
• Gray’s Anatomy: the anatomical basis of clinical practice
• Hollinshead’s Textbook of Anatomy, 5th edition
• Moore’s Clinically Oriented Anatomy, 7th edition
• Netter’s Atlas of Human Anatomy, 5th edition