Neurosurgery notes/Anatomy/Vascular/Artery

Artery

View Details
Status
Done
logo
Parent item
Vascular
Sub-item
ECA External carotid artery
Internal carotid artery (Anterior circulation)
Spinal artery
Embryonic vascular anastomosis
Posterior circulation- Vertebrobasillar
Choroidal arteries
Circle of willis
Clinical arterial conditions

Embryology and the circle of Willis

  • During initial embryological development, the internal carotid artery (ICA) supplies the anterior, middle, and posterior cerebral arteries.
  • Later, the posterior communicating artery (PComA) atrophies, with the basilar artery supplying the posterior cerebral artery (PCA).
    • However, if the PComA remains larger than the ipsilateral P1, this is termed a fetal PComA (found in 25% individuals).
  • In the majority of individuals, a completely intact circle of Willis is not present, with other common variants including
    • PComA hypoplasia or absence
    • A1 hypoplasia
    • Anterior communicating artery (AComA) absence

Structure of cerebral vessels

  • Cerebral arterial vessels progressively divide into
    • Smaller arteries
    • Arterioles
    • Penetrating arterioles
      • Pial vessels, surrounded by cerebrospinal fluid, form penetrating arterioles.
    • Parenchymal arterioles and capillaries.
      • As these arterioles become intracerebral, a small extension of the subarachnoid space exists surrounding them, termed the Virchow-Robin space.
        • These parenchymal vessels become encased by astrocytic end-feet.
  • The walls of cerebral arterial vessels
    • Are comprised of three layers
      • Tunica adventitia
        • Predominantly made up of collagen and fibroblasts.
        • In the small parenchymal arterioles and capillaries, the associated astrocytic end-feet connect them to astroglia.
      • Tunica media
        • contains mostly smooth muscle, the larger arteries having a generally greater number of layers.
      • Tunica intima
        • is composed of
          • Layer of endothelium
          • Internal elastic lamina
            • A layer of elastic tissue, separating it from the tunica media.
  • Structural differences exist between cerebral and other vessels
    • Cerebral arteries
      • Thinner adventitia which contains no external elastic lamina
      • The tunica intima correspondingly has a more developed internal elastic lamina.
    • Cerebral veins
      • Have thin walls
      • Unlike systemic veins do not contain valves
      • Have minimal smooth muscle
      • Less closely follow the course of the arterial system.