Important Parts of Neurovascular Anatomy in the Human Brain

1. Main Arteries

   • The brain gets its blood from three key arteries:
     • Internal Carotid Arteries: They deliver about 80% of the blood to the brain.
     • Vertebral Arteries: They provide around 20% of the brain's blood supply.
     • Basilar Artery: This artery is made when the vertebral arteries join together.

2. Circle of Willis

   • This is a special structure at the base of the brain. It includes:
     • Anterior communicating artery
     • Anterior cerebral arteries (A1 & A2 parts)
     • Internal carotid arteries
     • Posterior communicating arteries
     • Posterior cerebral arteries
   • The Circle of Willis helps with blood flow and is important for preventing problems when the blood supply is low.

3. Tiny Blood Vessels

   • These are made up of small arteries, capillaries, and tiny veins.
   • There are about 300–400 capillaries in each square millimeter of the brain's outer layer. This helps in delivering nutrients and oxygen efficiently.

4. Blood-Brain Barrier (BBB)

   • The BBB is a special protective layer formed by different cells.
   • It keeps harmful substances out while allowing necessary nutrients to pass through.
   • The average thickness of the BBB is about 0.6–0.7 micrometers.

5. Venous Drainage

   • The main system for draining blood includes:
     • Superficial and deep venous systems, which have dural venous sinuses like the superior sagittal and transverse sinuses.
   • Blood flow from the brain to the heart is around 40 milliliters per minute.

Knowing these important parts helps us understand how the brain works and how diseases can affect it in medical science.