Anatomy of brain

A presentation on anatomy of the brain in detail. Hope it will help medical students.

1. ANATOMY OF BRAIN PRESENTER: DR THOMAS JOHN

2. CENTRAL NERVOUS SYSTEM CNS consists of brain and spinal cord. Brain is situated within the cranial cavity and the spinal cord lies within the vertebral column. The adult brain constitutes about one fiftieth of total body weight and weighs about 1400g in males and 1200g in females. BRAIN- gray matter is present around the periphery and white matter in the centre.

3. BRAIN IS PROTECTED BY ..... Bony covering -THE CRANIUM The meninges CSF -in the sub arachnoid space

4. MENINGES DURA MATER -outer endosteal layer and inner meningeal layer enclosing the cranial venous sinuses between the two. ARACHNOID -thin,transparent and do not dip into the sulci. PIA MATER -thin, vascular and closely invests the brain

5. Dura mater is called as pachymeninges. Arachnoid and pia are togather known as leptomeninges. Meningeal layer of dura mater forms four folds which divide the cavity into intercommunicating compartments.

6. Folds of dura.. Falx cerebri - sickle shaped, separates the right from the left cerebral hemispheres . Tentorium cerebelli - seperates the cerebral hemispheres from the hind brain and lower part of midbrain. Falx cerebell i- separates the two cerebellar hemisphere. Diagphrama sellae - small horizontal fold .

7. Superior sagittal sinus lies along the superior margin of falx cerebri-recieves in its course the superior cerebral vein. Inferior sagittal sinus lies along the inferior margin of falx cerebri-joins great cerebral vein. Straight sinus-lies at the confluence of falx cerebri and tentorium cerebelli.

8. ARACHNOID MATER It provides sheath for the cranial nerves as far as their exit from the skull. Arachnoid villi are small finger like processes of arachnoid tissue projecting into the venous sinuses. They absorb CSF. With age these villi enlarge to form pedunculated tufts called arachnoid granulations.

9. EPIDURAL SPACE -between inner surface of the cranium and dura mater. SUBDURAL SPAC E-between dura and arachnoid. SUB ARACHNOID SPACE -Between arachnoid and pia mater,contains CSF, large vessels of the brain and cranial nerves.

10. The function of CSF is primarily as a shock absorber and a cushion for the brain so that it doesn't move around so much in the head. CSF is secreted by specialized cells within the walls of the ventricles known as choroid plexus. Re-absorption occurs in the subarachnoid space by venous structures known as "arachnoid villi"

11. PARTS OF BRAIN Developmentally brain consists of forebrain,midbrain and hindbrain . Forebrain- cerebrum+diencephalon Midbrain Hindbrain- pons,medulla,cerebellum .

12. Parts of Brain Cerebrum Diencephalon Brainstem Cerebellum

13. CEREBRUM Longitudinal cerebral fissure- divides it into two hemispheres. Corpus callosum- joins the two hemispheres across the median plane Each cerbral hemisphere consists of Outer grey matter Inner white matter Basal ganglia/basal nuclei Lateral ventricle.

14. Each cerebral hemisphere has 3 poles FRONTAL POLE TEMPORAL POLE OCCIPITAL POLE.

15. LOBES OF CEREBRAL CORTEX FRONTAL PARIETAL TEMPORAL OCCIPITAL

16. SULCI AND GYRI In order to increase the surface area of brain it is folded at places creating sulci and gyri. The grooves that make these wrinkles are called sulci and the ridges between them are called gyri .

17. MEDICOLEGAL IMPORTANCE In generalised edema of the brain flattening of the cerebral convulsions with obliteration of sulci is seen. In such cases it is difficult to appreciate the sulci and gyri correctly.

18. SULCI AND GYRI Central sulcus Lateral sulcus Parieto occipital sulcus .

19. CENTRAL SULCUS- begins on the medial surface and runs on the superolateral sulcus obliquely downwards and forwardsand ends a little abive the posterior ramus of the lateral sulcus

20. LATERAL SULCUS- inferiorly separates the orbital and tentorial surfaces,then reaches superolaterally and divides into anterior, ascending and posterior rami

21. PARIETO OCCIPITAL SULCUS -present on the medial aspect. PREOCCIPITAL NOTCH -indentation on the inferolateral boarder about 5cm in front of occipital pole.

22. SURFACES Superolateral Medial Inferior

23. INSULA

24. MEDIAL SURFACE OF BRAIN Central part of medial suface is occupied by corpus callosum . Below this lies the septum pellucidum, the fornix and the thalamus. .

25. CORPUS CALLOSUM Parts- GENU-Anterior end BODY SPLENIUM-Posterior end

26. CINGULATE SULCUS -starts in front of the genu and runs backwards parallel to upper marginof corpus callosum SUPRASPLENIAL SULCUS- lies above and parallel to splenium. CALCARINE SULCUS -begins a little below the splenium and runs towards occipital pole. It gives off the parietooccipital sulcus.

27. INFERIOR SURFACE Divided into orbital surface and tentorial surface. ORBITAL surface-parallel to medial orbital boarder there is olfatory sulcus. The rest of the orbital surface is divided by an ‘ H’ shaped sulcus.

28. TENTORIAL SURFACE -medially collateral sulcus and laterally occipitotemporal sulcus. On the medial side of temporal pole there is rhinal sulcus.

29. Part medial to collateral sulcus is parahippocampal gyrus. Part lateral to collateral sulcus is divided into medial and lateral occipitotemporal gyri by the occipitotemporal sulcus.

30. BOARDERS SUPEROMEDIAL INFEROLATERAL MEDIAL ORBITAL MEDIAL OCCIPITAL

31. BASAL GANGLIA Large subcortical masses of gray matter located within the white matter in the basal part of cerebral hemisphere. Functionally it includes substantia nigra, red nucleus and subthalamus.

32. BASAL GANGLIA Corpus striatum Caudate nucleus Lentifom nucleus Claustram Amygdaloid body.

33. Caudate nucleus has a head, body and a tail. Lentiform nucleus-lateral surface,medial surface,inferior surface. Amygdaloid body-nuclear mass in the temporal lobe and is continuous with the tail of caudate nucleus. Claustrum-saucer shaped nucleus between the putamen and insula

34. Corpus stritum is divided by internal capsule into caudate nucleus and lentiform nucleus. Lentiform nucleus is divided into a lateral part putamen and a medial part called globus pallidus. Caudate nucleus and putamen are togather known as striatum whereas globus pallidus is the pallidum.

35. FUNCTIONS Corpus striatum regulates muscle tone and help in smoothening voluntary movements. It controls automatic associated movements and the coordinated movements of different parts of the body for emotional expression.

36. INTERNAL CAPSULE Large band of fibres situated in the inferomedial part of cerebral hemisphere. In horizontal sections of brain it appears V shaped with its concavity directed laterally. It consists of fibres going from and to the cerebral cortex.

37. PARTS Anterior limb Posterior limb Genu Retrolentiform part Sublentiform part.

38. Anterior limb -between head of caudate nucleus and lentiform nucleus. Posterior limb -between thalamus and lentiform nucleus. Genu -bend between anterior and posterior limbs. Retrolentiform part -lies behind the lentiform nucleus. Sublentiform part -below the lentiform nucleus.

39. DIENCEPHALON Is a middle structure which is embedded in the cerebrum. Thalamus Hypothalamus Metathalamus Epithalamus Subthalamus.

40. THALAMUS Large ovoid mass of grey matter above the midbrain. Largest part of diencephalon. Thalami on both sides are separated by the cavity of the 3 rd ventricle.

41. HYPOTHALAMUS Most inferior part of diencephalon and contains several small nuclei and tracts. Mamillary bodies appear as rounded elevations on the base of the brain in the region of interpeduncular fossa.

42. METATHALAMUS Consists of two rounded medial and lateral geniculate bodies which protrude from posterior inferior surface of thalamus.

43. EPITHALAMUS Lies posterosuperior to thalamus. Consists of pineal gland and habenular nuclei .

44. SUBTHALAMUS Small area that lies between thalamus and mid brain. It contains several nerve tracts and subthalamic nuclei which are associated with basal ganglia.

45. LIMBIC SYSTEM The limbic system is a complex set of structures that lies on both sides of the thalamus, just under the cerebrum.   It includes the hypothalamus, the hippocampus, the amygdala, and several other nearby areas. 

46. It appears to be primarily responsible for our emotional life, and has a lot to do with the formation of memories. HIPPOCAMPUS- is concerned with long term memories.

47. BRAINSTEM MIDBRAIN PONS MEDULLA

48. MIDBRAIN Connects forebrain with the hind brain. Cavity is called cerebral aqueduct,connects third ventricle with the fourth ventricle.

49. TRANVERSE SECTION THROUGH MIDBRAIN Tectum is the part posterior to aqueduct. Each half of the midbrain anterior to aqueduct is called cerebral peduncle. Each cerebral peduncle is divided into; CRUS CEREBRI-anteriorly SUBSTANTIA NIGRA-middle TEGMENTUM-posteriorly

50. Medial and lateral geniculate bodies are situated in the posterior apect of midbrain. Superior colliculus is connected to lateral geniculate body by the superior brachium, inferior colliculus is connected to medial geniculate body by the inferior brachium.

51. PONS Large middle part of brainstem. Has two surfaces 1. ventral 2.dorsal. Dorsal surface is hidden by the cerebellum, and forms the upper half of the floor of fourth ventricle.

52. VENTRAL SURFACE Ventral surface is convex towards both sides and is transversely striated. In the median plane it is shows a vertical basilar sulcus which lodges the basilar artery. Laterally the surface is continuous with the middle cerebellar peduncle.

53. Trigeminal nerve is attached to this surface at the junction of pons with the peduncle. Abducent, facial and vestibulocochlear nerves are attached to the lower boarder.

54. MEDULLA Lies in the anterior part of posterior cranial fossa extending down to the foramen magnum. Medulla is divided into right and left halves by the anterior and posterior median fissures. Each half is divided into anterior,lateral and posterior regions by anterolateral and posterolateral sulci.

55. Anterior region is in the form of an elevation called the pyramid. Upper part of the lateral region shows an oval elevation- the olive. The rootlets of hypoglossal nerve emerge from the anterolateral sulcus between the pyramid and the olive.

56. Rootlets of 9 th 10 th and of the cranial part of accessory nerve emerge through the posterolateral fissure. Upper part of the posterolateral region shows a V shaped depression which is the lower part of floor of fourth ventricle.

57. Below the floor three elevations are seen: fasciculus gracillis, fasciculuc cuneatus and inferior cerebellar peduncle. Upper ends of fasciculus gracillis and fasciculus cuneatus expands to form the g racile and cuneate tubercles.

58. In the lower part of medulla there is another elevation called tubercinerium produced by spinal nucleus of trigeminal nerve. Medulla is divided into two parts, the lower closed part with a central canal; upper open part where central canal opens out to form the fourth ventricle.

59. CEREBELLUM Largest part of hind brain. Grey matter is highly folded and the arrangement is called “arbor vitae”(vital tree of life)

60. Consists of two cerebellar hemispheres united to each ither through a median vermis. Superior surface is convex, the two hemispheres are continuous. Inferior surface has a notch called vallecula that separates the two hemispheres.

61. Each hemisphere is divided into three lobes Anterior lobe -lies on the anterior part of superior surface. Middle lobe -largest Flocculonodular lobe -smallest.

62. Middle lobe is limited in front by the fissura prima and by the posterolateral fissure on the inferior surface. Cerebellum is divided into numerous small parts by fissures.

63. Horizontal fissure-separates superior surface from the inferior. Fissura prima-separates anterior lobe from the middle lobe on the superior surface. Posterolateral fissure- separates middle lobe from the flocculonodular lobe on the inferior surface.

64. VENTRICLES OF BRAIN LATERAL VENTRICLES- irregular cavities situated on each cerebral hemisphere. Each communicate with the third through an interventricular foramen(foramen of Monroe). Ech lateral ventricle has; Central part Three horns-anterior, posterior, inferior.

65. THIRD VENTRICLE Median cleft between the two thalami. Developmentally it represents the cavity of the diencephalon. Posteriorly it communicates with the fourth ventricle through cerebral aqueduct .

66. THE FOURTH VENTRICLE Last and lowest ventricle of cerebrum. Tent shaped. Its roof contains three apertures for the closely guarded release of CSF into the sub arachnoid space.

67. Dorsally on the lower part of the roof there is a median aperture -foramen of Magendie. On either sides it communicates with the subarachnoid space through lateral apertures-foramina of Luchka .

68. CIRCLE 0F WILLIS Provides important communication between blood supply of forebrain and midbrain. Internal carotid artery (ICA) enters the cranial cavity bilaterally and divides into the Anterior cerebral artery (ACA) and Middle cerebral artery (MCA).

69. The anterior cerebral arteries are then united by an anterior communicating (ACOM) artery. Posteriorly, the basilar artery, formed by the left and right vertebral arteries, branches into a left and right Posterior cerebral artery(PCA), forming the posterior circulation. The PCAs complete the circle of Willis by joining the internal carotid system anteriorly via the posterior communicating (PCOM) arteries.

70. ARTERIAL CIRCLE OF WILLIS

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