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Brain Anatomy and Physiology Overview in Neurosurgery

Dive into the complexities of brain anatomy and physiology with a focus on the scalp, skull, meninges, CNS, ventricles, CSF pathways, and blood supply. Understand factors affecting blood supply, autoregulation, and the blood-brain barrier.

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Brain Anatomy and Physiology Overview in Neurosurgery

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  1. Brain Anatomy and Physiology Dr. Nevo Margalit – Neurosurgery Tel Aviv Sourasky Medical Center

  2. Scalp • Skin • Connective tissue (superficial fascia) • Epicranial aponeurosis (galea aponeurotica) • Loose areolar tissue • Pericranium • Occipitofrontalis muscle

  3. Scalp

  4. The Skull

  5. The Skull

  6. The skull

  7. The MeningsThe 3 layers covering the brain • Dura: covers the brain and spinal cord. The venous sinuses run through the dura. 2 additional Parts of the dura are the Tentorium and the Falx Cerebri. • Arachnoid: Transparent, thin web structure. Creates a space around the brain called the sub arachnoid space where the CSF and the main blood vessels pass. • Pia: a very thin layer. Coats the brain and spinal cord and is inseparable from them.

  8. Dura

  9. Tentorium and Falx

  10. Tentorium

  11. Arachnoid

  12. Arachnoid – Basal Cisterns

  13. Parts of the Central Nervous System • 2 hemispheres • Brainstem • Cerebellum • Spinal cord

  14. Frontal lobe Parietal lobe Temporal lobe Occipital lobe Insular lobe Limbic lobe Each hemisphere has lobes:

  15. Lateral View

  16. Insula

  17. Gyruses and sulci • Each lobe is composed of gyruses separated by sulci • The topography can be defined by histology, anatomical relationships or function

  18. MapBrodmann

  19. Gyruses and Sulci

  20. Functional areas

  21. Function 2

  22. Function 3

  23. f-MRI

  24. The Motor Strip

  25. Fibers

  26. Ventricles and CSF

  27. Ventricles and CSF • CSF is produced by the choroid plexus in the ventricles • The circulation is from the lateral ventricles to the third through the Monroe- aqueduct- IV ventricle- sub arachnoid space in skull and spine- absorption in sss and other sinuses through arachnoid granulations

  28. CSF Pathways

  29. CSF Pathways

  30. Arteries of the brain

  31. Arteries of the brain • Anterior circulation – internal carotid artery, from common carotid in the neck. Bifurcates to MCA and ACA • Posterior circulation – vertebral arteries that join to form the basilar artery that will then bifurcate to 2 PCA

  32. Circle of Willis • Communication between 2 sides – anterior communicating (a-com) • Communication between anterior and posterior circulation – posterior communicating (p-com) • Many anomalies may exist

  33. Arteries in the neck

  34. Arteries in the subarachnoid space

  35. Arteries of the brain

  36. Physiology

  37. Blood supply to the brain • The brain gets 15% of the cardiac output and 20% of the oxygen consumption • The brain tissue gets in average 50ml of blood per 100gr of tissue per minute. The gray matter receives about 3 to 4 times more then the white matter • Total blood supply to the brain is about 500-600ml per minute

  38. Factors Affecting the blood supply • Autoregulation • Biochemical changes – O2 and CO2 • Blood brain barrier- BBB

  39. Autoregulation • Maintains a regular blood supply to the brain in changing blood pressures • The range is 50-130 mm mercury • Possible mechanisms are the myogenic control, neurogenic and biochemichal control

  40. CO2 • The most important and powerful mechanism that controls brain blood flow • A change in 1mm PCO2 changes the flow in 4-5% • PCO2 of 70 gives a maximal vasodilatation. Above that the flow is pressure dependent

  41. Hyperventilation • Hyperventilation lowers the PCO2 • It has a strong effect but it is limited in time • Could be dangerous if not regulated- ischemia • Can be regulated with a jugular bulb oximeter

  42. BLOOD BRAIN BARRIER • The BBB is composed of the tight junctions in the endothelium cells of the blood vessels • Prevents passage of large molecules and even small ions like Na and Cl • Specific substances pass the BBB like glucose and amino acids

  43. BLOOD BRAIN BARRIER • Because of the BBB, in the brain hydrostatic and oncotic pressures are not significant. The important parameter is the osmotic pressure • The BBB is damages in trauma, tumor, infarct, SAH and infection

  44. BLOOD BRAIN BARRIER

  45. Brainstem and Cranial Nerves

  46. Brain stem • Has 3 parts: midbrain, pons and medulla • Transports all the information to and from the brain • Centers for breathing and blood pressure • The origin or endpoint for cranial nerves • Contains the center of consciousness • Creates connections to the cerebellum

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