BLOOD SUPPLY OF THE BRAIN, VENTRICLES , and CSF.pptx

Neuro anatomy

1. BLOOD SUPPLY OF THE BRAIN, VENTRICLES AND CEREBROSPINAL FLUID (CSF) DR RILWANU BELLO DEPARTMENT OF ANATOMY FBMS, CHS, UDUS

2. The brain gets it blood supply from 2 sources, viz. the 2 internal carotid arteries and the 2 vertebral arteries. These arteries enter the cranial cavity differently; the internal carotid artery traverses the carotid canal, while the vertebral artery passes through the foramen magnum. However, both sources join together in a free anastomosis at the base of the brain called circulus arteriosus [circle of Willis]. BLOOD SUPPLY OF BRAIN

3. It leaves the cavernous sinus opposite the anterior perforated substance and just lateral to the optic chiasma , where it gives off the following branches: Posterior communicating artery : passes posteriorly to join the posterior cerebral artery Anterior choroidal artery : passes postero -laterally to enter the inferior horn of the lateral ventricle, where it joins the choroidal plexus. Anterior cerebral artery Middle cerebral artery INTERNAL CAROTID ARTERY

4. 4th part of the vertebral artery enters the cranium through foramen magnum under the free margin of posterior atlanto -occipital membrane . Arteries of two sides join to form single median basilar artery on the ventral aspect of pons.

5. BASILAR ARTERY Branches Anterior inferior cerebellar artery: Labyrinthine artery: Pontine branches: Superior cerebellar artery: Two terminal posterior cerebral branches diverge at upper border of pons:

6. The cerebral arteries supply the cerebral cortex by cortical branches , and the white matter and nuclei inside it by central branches. The central branches arise near the origin of the cerebral arteries and are end-arteries, while the cortical branches are peripheral and anastomose freely with each other on the surface of the cortex. CEREBRAL ARTERIES

7. CIRCULUS ARTERIOSUS OR CIRCLE OF WILLIS It is a hexagonal arterial circle, situated at the base of brain in the interpeduncular fossa . It is formed by the anterior cerebral branches of internal carotid, terminal parts of internal carotid arteries and the posterior cerebral branches of basilar artery . It is an anastomosis between the basilar artery [behind] and the 2 internal carotid arteries [in front].

8. It is formed by the following arteries: a. Anteriorly : by the 2 anterior cerebral arteries which are joined together by the anterior communicating artery. b. Posteriorly : by the 2 posterior cerebral arteries which arise from the basillar artery. c. On each side: by the posterior communicating artery which joins the internal carotid with the posterior cerebral.

9. Circle of Willis and the branches of arteries supplying the brain

10. (a) Deep branches of middle cerebral artery, and (b) cortical branches of middle cerebral artery

11. Medial surface of right cerebral hemisphere with anterior cerebral artery

12. Posterior cerebral artery on: Inferior surface of left cerebral hemisphere, and medial surface of right cerebral hemisphere

13. Arterial supply of inferior surface of cerebral hemisphere

14. Cerebellum Cerebellum is supplied by following arteries: Superior cerebellar Anterior inferior cerebellar Posterior inferior cerebellar

15. The superior cerebellar artery Arises near the termination of the basilar artery It is distributed over the superior surface of the cerebellum

16. Vascular supply to the cerebellum

17. The anterior inferior cerebellar artery Arises from the basilar artery at the lower part of the pons and passes back on the inferior surface of the cerebellar hemisphere supplying this surface and the adjacent floccolus It may give rise to the labynthrine artery if it has not arisen from the basilar

18. The posterior inferior cerebellar artery Is one of the most tortuous arteries in the body and is the largest branch of the vertebral artery It arises ventrally from the vertebral artery near the lower end of the olive and spirals back around the medulla below the hypoglossal rootlets and then between the rootlets of the glossopharyngeal and vagus nerves

19. It supplied the choroid plexus of the 4 th ventricle and is distributed to the inferior vermis and the back of the cerebellar hemisphere.

20. The veins of the brain, in general, have the following characteristics: 1. Their wall are devoid of muscular layer 2. They have no valves 3. They drain into neighbouring dural sinuses The cerebral veins are divided into 2 groups : external cerebral veins draining the cortex, and internal cerebral veins draining the inside of the cerebrum. VEINS OF THE BRAIN

21. External Cerebral Veins Superior cerebral veins: Superficial middle cerebral vein Deep middle cerebral vein Inferior cerebral veins Anterior cerebral veins Internal Cerebral Veins Terminal Veins Great cerebral vein Basal vein

22. Veins on the superolateral surface of cerebral hemisphere

23. Veins on the inferior surface of cerebral hemisphere

24. Internal cerebral veins

25. LATERAL VENTRICLE There are 2 lateral ventricles in the cerebrum, one inside each hemisphere. Their central parts come in contact with each other in the median plane where they are only separated by the septum pellucidum , but their horns are more widely separated. Ventricles and Cerebrospimal fluid

26. PARTS OF LATERAL VENTRICLE : Each ventricle consists of a central part and 3 horns [anterior, posterior and inferior]. Central part : extends from the level of the interventricular foramen to the splenium of the corpus callosum . Anterior horn : extends forwards and laterally into the frontal lobe , anterior to the level of the interventricular foramen.

27. Posterior horn : extends backwards and medially into the occipital lobe behind the splenium of corpus callosum . Inferior horn : makes a curve behind the thalamus and extends forwards into the temporal lobe to end opposite the level of the uncus . It runs in the line of the superior temporal sulcus .

28. POSITION : It is a narrow cavity that lies in the midline between the 2 thalami. It is connected with the lateral ventricle on each side through the interventricular formen [foramen of Monro ] and with the 4 th ventricle below through the cerebral aqueduct of the midbrain. THIRD VENTRICLE

29. It is a tent-shaped cavity present between the pons and open medulla [ anteriorly ] and the cerebellum [ posteriorly ]. It is lined by ependyma and is continuous with the central canal in the closed medulla [below] and with the cerebral aqueduct of the midbrain [above]. FOURTH VENTRICLE

30. APPLIED ANATOMY : The median and lateral apertures of the 4th ventricle are the only sites through which the C.S.F. leaves the cavities of the brain to enter the subarchnoid space. Occlusion of these apertures leads to over distension of all ventricles by C.S.F. : a condition called hydrocephalus.

31. The cerebrospinal fluid [C.S.F.] is secreted by the arteries of the choroidal plexuses situated in all ventricles of the brain [lateral, 3rd and 4th ventricles]. It circulates from the lateral ventricles to the 3rd ventricle through the interventricular foramen. Thereafter, it reaches the 4 th ventricle through the cerebral aqueduct of the midbrain. CIRCULATION OF THE CEREBROSPINAL FLUID [C.S.F.]

32. The subarachnoid space on the outside of the brain is in continuity with a similar space around the spinal cord and also with the series of interconnected cerebral ventricles within the brain, the choroid plexus secretes CSF

33. It then leaves the 4 th ventricle to enter the subarachnoid space through the 3 openings of the ventricle : these are 1 median and 2 lateral : The median aperture : is an opening in the lower part of the roof of the 4 th ventricle, and opens into the cerebello-medullary cistern. The 2 lateral apertures lie one on each at the end of the lateral recess of the 4 th ventricle, and open into the pontine cistern.

34. The C.S.F. then ascends over the lateral surfaces of the cerebral hemispheres to reach the superior sagittal sinus where it is transferred by the arachnoid villi and granulations to enter the venous blood in the sinus.

35. The subarachnoid space on the outside of the brain is in continuity with a similar space around the spinal cord and also with the series of interconnected cerebral ventricles within the brain, the choroid plexus secretes CSF

36. So the C.S.F. is secreted by the arteries and drains eventually into the venous blood. Obstruction to this circulation results in hydrocephalus : the common site of obstruction are the interventricular foramen and the cerebral aqueduct which represent the narrowest sites.

37. Decompression of the dilated ventricles is achieved by inserting a shunt connecting the ventricles to the jugular vein or the abdominal peritoneum. clinical point

38. Thank You