Anatomy of meninges, ventricles, cerebrospinal fluid

1. MENINGES, VENTRICLES, CEREBROSPINAL FLUID AND BOOLD SUPPLY OF THE BRAIN Dr. Israa M. Sulaiman Dr. Mohammed Faez Department of Anatomy IMS/MSU

2. OBJECTIVES Illustrate and describe the Meninges’s three membranes. Describe the structure of the meninges, its blood supply and nerve supply. Illustrate and describe the venous blood sinuses

3. The Meninges The Meninges are the membrane covering the brain and spinal cord. The Meninges consist of three membranes: The dura mater, The arachnoid mater, The pia mater.

4. The Meninges

5. The Meninges 1. Dura mater - strong, "Tough mother" a. Falx cerebri b. Falx cerebelli c. Tentorium cerebelli d. Diaphragma sella 2. Arachnoid - spidery, holds blood vessels 3. Pia mater - "delicate mother"

6. The Meninges

7. Sagittal section showing the duramater 1) Falx cerebri 2) Tentorium cerebelli 3) Falx cerebelli 4) Diaphragma sellae

8. Superior view showing the duramater 1) Falx cerebri 2) Tentorium cerebelli

9. DURA MATER Thick dense inelastic membrane and the outermost layer of the meninges Bilaminar : Endosteal layer (outer) Meningeal layer (inner) These are closely united except along certain lines, where they separate to form venous sinuses.

10. DURA MATER Endosteal layer ; Periosteum - inner surface of the skull bones Not continuous with dura mater of spinal cord Meningeal layer ; Dura mater proper Covering the brain Continuous with dura mater of spinal cord Folded inwards as 4 septa between part of the brain The function of these septa is to restrict the rotatory displacement of the brain.

11. duramater Superior cerebral veins beneath arachnoid

12. Coronal section of the upper part of the head Endosteal layer Meningeal layer They are closely united except along certain lines; they are separated to form venous sinuses Superior sagittal sinus (Dural venous sinus) Dura mater Subdural space

13. DURA MATER Dura mater septa: Falx cerebri Falx cerebelli Tentorium cerebelli Diaphragma sella

14. Sagittal section showing the duramater 1) Falx cerebri 2) Tentorium cerebelli 3) Falx cerebelli 4) Diaphragma sellae

15. The Falx Cerebri It is a sickle-shaped fold of dura mater that lies in the midline between the two cerebral hemispheres. Its narrow end in front is attached to the internal frontal crest and the crista galli . Its broad posterior part blends in the midline with the upper surface of the tentorium cerebelli . The superior sagittal sinus runs in its upper fixed margin, the inferior sagittal sinus runs in its lower concave free margin, and the straight sinus runs along its attachment to the tentorium cerebelli .

16. Falx cerebri Superior sagittal sinus Inferior sagittal sinus Straight sinus Tentorium cerebelli * Frontal crest Crista galli

17. The Tentorium Cerebelli The tentorium cerebelli is a crescent-shaped fold of dura mater that roofs over the posterior cranial fossa. It covers the upper surface of the cerebellum and supports the occipital lobes of the cerebral hemispheres.

18. Tentorium cerebelli Falx cerebri

19. The Falx Cerebelli The falx cerebelli is a small, sickle-shaped fold of dura mater that is attached to the internal occipital crest and projects forward between the two cerebellar hemispheres. Its posterior fixed margin contains the occipital sinus.

20. The Diaphragma Sellae The diaphragma sellae is a small circular fold of dura mater that forms the roof for the sella turcica . A small opening in its center allows passage of the stalk of the pituitary gland

21. Dural Nerve Supply Branches of the trigeminal, vagus , and first three cervical nerves and branches from the sympathetic system pass to the dura. The dura is sensitive to stretching, which produces the sensation of headache.

22. Dural Blood Supply Dural Arterial Supply The dura mater’s arteries supply from the internal carotid, maxillary, ascending pharyngeal, occipital, and vertebral arteries. From a clinical standpoint, the most important is the middle meningeal artery , which is commonly damaged in head injuries. Dural Venous Drainage The meningeal veins lie in the endosteal layer of dura. The middle meningeal vein follows the branches of the middle meningeal artery and drains into the pterygoid venous plexus or the sphenoparietal sinus. The veins lie lateral to the arteries.

23. Arachnoid Mater Delicate, impermeable & avascular membrane covering the brain Lying between Pia mater (internally) & dura Mater(externally) Separated from dura mater by a potential space, the subdural space (filled by a film of fluid) Separated from pia mater by the subarachnoid space (filled with CSF) The outer and inner surfaces covered with flattened mesothelial cells

24. Superior cerebral veins beneath arachnoid Arachnoid mater

25. Arachnoid mater Arachnoid villi Arachnoid mater Subarachnoid space Arachnoid granulations Subdural space Arachnoid projects into venous sinuses - sites for CSF diffuses into bloodstream

26. Superior cerebral veins, traverse the subdural space to reach the superior sagittal sinus and its lacunae SUBDURAL SPACE : Superior cerebral veins beneath arachnoid

27. Subdural haematoma * Dura Arachnoid

28. Subarachnoid Space (SP) : Relatively narrow over the surface of cerebral hemisphere, but sometimes becomes much wider in areas at the base of the brain, the widest space is called subarachnoid cisterns The cisterna cerebellomedularis lies between inferior surface of the cerebellum and roof of 4 th ventricle The cisterna interpeduncularis lies between 2 cerebral hemispheres. All the cisternae are in free communication with one another & with the remainder of subarachnoid space

29. Median sagittal section to show the subarachnoid cisterns & circulation of CSF Superior cistern Interpeduncular cistern Cerebellomedullary cistern Chiasmatic cistern Pontine cistern

30. * Subarachnoid haemorrage Dura Arachnoid Pia mater

31. Pia Mater Pia Mater is a vascular membrane covered by mesothelial cells. Closely invests the brain, covering the gyri , descending into the deepest sulci & closely applied to the cortical surface.

32. Pia mater Pia mater

33. Pia Mater It extends out over the cranial nerves & fuses with their epineurium The cerebral arteries entering the substance of the brain, carry a sheath of pia mater with them The pia mater forms the TELA CHOROIDAE . The tela choroidae fuse with ependyma to form the choroid plexus Choroid plexus forms CSF

34. Coronal section of the interventricular foramen showing the choroid plexus of 3 rd & lateral ventricles Ependyma Choroid plexus of 3 rd ventricle Choroid plexus of lateral ventricle Pia mater of tela choroidae

35. Read About The Venous Blood Sinuses

36. VENTRICLES

37. OBJECTIVES Illustrate and describe the ventricles. Describe the structure of the ventricles. Illustrate and describe the cerebrospinal fluid (CSF) formation, absorption and circulation.

38. VENTRICLES(Ventricular System) A ventricle is an internal cavity of the brain. Within the brain, which is filled with cerebrospinal fluid(CSF). The ventricular system is composed of two lateral ventricles and two midline ventricles( third and fourth ventricles ).

39. VENTRICLES(Ventricular System) The chambers are connected to allow the flow of cerebrospinal fluid via two interventricular foramen (referred to as the foramen of Monro ) and the cerebral aqueduct (referred to as the aqueduct of Sylvius ).

40. Lateral view to show the ventricular system of the CNS Central canal of medulla oblongata & spinal cord Fourth ventricle Lateral ventricle Third ventricle Interventricular foramen (Monro) Cerebral aqueduct

41. VENTRICLES(Ventricular System) CONSISTS OF : Lateral ventricle Third ventricle Fourth ventricle Central canal of the medulla oblongata & spinal cord

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44. Lateral Ventricles The lateral ventricles are two curved shaped cavities located within the cerebrum. The lateral ventricles are separated by the septum pellucidum and do not communicate directly

45. Lateral ventricle Frontal lobe Parietal lobe Temporal lobe Occipital lobe

46. C-shaped cavity & may be divided into : 2. Anterior horn 1. Body 3. Posterior horn 4. Inferior horn Third ventricle Fourth ventricle Lateral view of the ventricular cavities of the brain Lateral ventricle

47. Anterior horn Inferior horn Posterior horn Lateral view to show the ventricular system of the CNS

48. The third ventricle is a narrow cavity or a slitlike cleft between the 2 thalamus Communicates ; Anteriorly with lateral ventricles through interventricular foramina (of monro ) Posteriorly with fourth ventricle through cerebral aqueduct (of sylvius ) Posterior view to show the ventricular system of the CNS Third ventricle

49. Frontal lobe Parietal lobe Temporal lobe Occipital lobe Third ventricle

50. Third ventricle Hypothalamus Coronal section of the brain (posterior view) Third ventricle Thalamus ROOF FLOOR Lateral wall Body of fornix

51. Fourth ventricle The fourth ventricle Is a rhomboid or diamond shaped cavity. It is a wide and flattened space located just anterior to the cerebellum and posterior to the upper, or superior, half of the medulla oblongata and the pons.

52. Cerebellum Pons Medulla oblongata (superior half) Sagittal section of the 4 th ventricle Cerebral aqueduct Central canal (spinal cord) Fourth ventricle Fourth ventricle ANTERIOR POSTERIOR

53. Frontal lobe Parietal lobe Temporal lobe Occipital lobe Fourth ventricle

54. Pons Medulla oblongata (superior half) Fig. : Sagittal section of the 4 th ventricle Cerebral aqueduct ANTERIOR POSTERIOR Superior part of the roof ; Superior medullary velum Inferior part of the roof ; Inferior medullary velum Roof or posterior wall of fourth ventricle :

55. Floor or rhomboid fossa of fourth ventricle : Formed by ; 1. Posterior surface of the pons 2. Cranial ½ of the medulla oblongata Medial sulcus (divides the floor into symmetrical halves) Medial eminence Sulcus limitans Facial colliculus Stria medullaris (strands of nerve fibers) Hypoglossal triangle Vagal triangle Posterior view of the 4 th ventricle

56. CENTRAL CANAL Opens superiorly into the fourth ventricle Fourth ventricle Inferior ½ of medulla oblongata Entire length of spinal cord Central canal (Lined with ependyma but no choroid plexus in the central canal) Extends ;

57. Frontal lobe Parietal lobe Temporal lobe Occipital lobe CENTRAL CANAL

58. Conus medullaris- Terminal ventricle

59. CEREBROSPINAL FLUID

60. It is formed by invaginating of vascular pia mater into the ventricular cavity It becomes highly convoluted & produce a spongy-like appearance It enters the 3rd and 4th ventricles through their roofs, and the lateral ventricles through the choroid fissure produces cerebrospinal fluid (CSF) CHOROID PLEXUS Lateral ventricle Third ventricle Fourth ventricle

61. Coronal section of the cavities of the lateral and 3 rd ventricles Cavity Of Lateral Ventricle Cavity Of Third Ventricle Pia Mater Ependyma CN THALAMUS CORPUS CALLOSUM Choroid Plexus of The Lateral Ventricle Pia Mater of Tela Choroidae BODY OF FORNIX Choroid Plexus of The Third Ventricle Blood supply derives from choroidal branches of the internal carotid & basilar arteries

62. Arachnoid mater Pia mater Ependyma CEREBELLUM Cavity of fourth ventricle Choroid plexus of the fourth ventricle T shaped, vertical part is double Horizontal part extends into lateral recesses of each ventricle (foramina of Luskha ) Blood supply ; posterior inferior cerebellar arteries

63. What is cerebrospinal fluid (CSF) ? Clear, colorless fluid Produced by the choroid plexus Found in the : Ventricles of the brain Subarachnoid space (between Arachnoid + Pia mater) around the brain & spinal cord The pressure of the CSF is kept remarkably constant. Based on the Monro -Kellie doctrine : “Volume of BLOOD, CSF & BRAIN at any time must be relatively constant”

64. Physical characteristics and composition of the CSF Appearance Clear and colourless Volume 130 ml Rate of production 0.5 ml/min Pressure 60-150 mm of water Composition protein 15-45 mg/100 ml glucose 50-85 mg/ 100 ml chloride 720-750 mg/100 ml No. of cells 0-3 lymphocytes/cu mm

65. Function of the CSF : Cushions & protects the CNS from trauma Provides mechanical buoyancy & support for the brain Serves as a reservoir & assists in the regulation of the contents of the skull Nourishes the CNS Removes metabolites from the CNS Serves as a pathway for pineal secretions to reach the pituitary gland

66. Sites of formation : Choroid plexus of the ventricle cavities, mostly is formed in the LATERAL VENTRICLES Some originate from the ependymal cells lining the ventricles Some from the brain substances through perivascular spaces Movement of CSF inside the ventricle is controlled by the: Pulsation of the artery in the choroid plexus By the aid of the cilia & microvilli of the ependymal cells

67. Choroid plexus of the 4 th ventricle Choroid plexus of the 3 rd ventricle 1 2 3 5 3.2 3.1 4 Superiorly = lateral aspect of each cerebral hemisphere Inferiorly = subarachnoid space around the brain & spinal cord Choroid plexus of the lateral ventricle

68. cerebrospinal fluid (CSF) The CSF is formed in the lateral ventricles escapes by the foramen of monro into the third ventricle From the third ventricle by the aqueduc t into the fourth ventricle. Then from the fourth ventricle the fluid is poured into the subarachnoid spaces through the medial foramen of majendie and the two lateral foramina of luschka . There is no evidence that functional communications between the cerebral ventricles and the subarachnoid spaces exist in any region except from the fourth ventricle.

69. Choroid plexus of the lateral ventricle Site of formation 1. Lateral ventricle 2. Third ventricle Interventricular foramina 3. Fourth ventricle Cerebral aqueduct 3.2 Lateral foramina (Luschka) 3.1 Median foramen (Magendie) 3.2 Lateral foramina (Luschka) 4. Subarachnoid space Inferiorly Superiorly Absorbed Superiorly Absorbed

70. Median sagittal section to show the subarachnoid cisterns & circulation of CSF Superior cistern Interpeduncular cistern Cerebellomedullary cistern Chiasmatic cistern Pontine cistern Circulation of CSF in subarachnoid space : Median foramen of 4 th ventricle

71. Factors that facilitate the flow of CSF in subarachnoid space ; Pulsation of the cerebral & spinal arteries Movements of the vertebral column Respiration & coughing Changing of the positions

72. Absorption of CSF into dural venous sinuses Main sites - arachnoid villi (project into dural venous sinuses, especially, superior sagittal sinus) Arachnoid villi are covered by endothelium of the venous sinus Arachnoid villi tend to be grouped together & form elevations known as arachnoid granulations CSF pressure >> the pressure in the sinus The rate of absorption of CSF through the arachnoid villi controls the CSF pressure

73. CLINICAL APPLICATION Hydrocephalus The term hydrocephalus is derived from the Greek words "hydro" meaning water and " cephalus " meaning head. It is excessive accumulation of fluid in the brain.

74. BLOOD SUPPLY OF THE BRAIN

75. OBJECTIVES Illustrate and describe the formation of the circle of willis Describe the blood supply of the brain Arterial supply Venous drainage

76. Blood Supply of The Brain The brain receives it arterial supply from two pairs of vessels, the vertebral and internal carotid arteries which are interconnected in the cranial cavity to produce an arterial circle (of Willis).

77. Internal carotid artery

78. Internal Carotid Artery Begins – bifurcation of Com Carotid A Perforates base of skull – carotid canal Enters middle cranial fossa beside dorsum sellae In the cavernous sinus Horizontal Emerge out – medial side of Ant clinoid process – perforates dura & arachnoid mater – enters subarachnoid space Turns posteriorly – below optic nerve Turns upward – lateral to optic chiasma Now is under anterior perforated susbtance Divides – into ANTERIOR & MIDDLE cerebral arteries

79. Vertebral artery Common carotid artery External carotid artery Internal carotid artery In temporal bone Internal carotid artery in cavernous sinus Basilar artery Posterior cerebral artery Posterior communicating artery Middle cerebral artery Anterior cerebral artery Basilar artery Posterior cerebral artery

80. Vertebral Artery Branch of first part of subclavian A Passes – foramen transvesarium C6 – C1 Enters through foramen magnum – perforates dura & arachnoid mater – enters subarachnoid space Turns upward, forward, medially – medulla oblongata Lower border of pons – joins opposite side BASILAR artery

81. Vertebral artery Common carotid artery External carotid artery Internal carotid artery In temporal bone Internal carotid artery in cavernous sinus Basilar artery Posterior cerebral artery Posterior communicating artery Middle cerebral artery Anterior cerebral artery Basilar artery Posterior cerebral artery

82. Blood Supply of The Brain VERTEBRAL Basilar Posterior cerebral artery INTERNAL CAROTID Middle cerebral Anterior cerebral Anterior communicating artery Posterior communicating artery CIRCLE OF WILLIS

83. VERTEBRAL Basilar PCA Pontine Labyrinthine Ant Inf CA Sup cerebellar Choroidal INTERNAL CAROTID ACA MCA Ophthalmic Ant ComA Post Com A Choroidal Branches of :-

84. CEREBRAL (ICA) Ophthalmic Post Communicating Choroidal Ant Cerebral Cortical Central Communicates with Ant Comm Art Post Cerebral Mid Cerebral Cortical Central CRANIAL (VERT) Meningeal Post Spinal Ant Spinal Post Inf Cerebellar Medullary (BASILAR) Pontine Labyrinthine Ant Inf Cerebellar Sup Cerebellar Post Cerebral Cortical Central Choroidal

85. Circle of Willis Interpeduncular fossa – base of brain Anastomosis 2 internal carotid arteries 2 vertebral arteries In the subarachnoid space

86. INFERIOR VIEW

87. Vertebral arteries Basilar A Posterior cerebral artery Posterior communicating artery Internal carotid artery Middle cerebral artery Anterior cerebral artery Anterior communicating artery Post Inf cerebellar A Sup cerebellar A Ant Inf cerebellar A

88. Middle cerebral artery Anterior cerebral artery Posterior cerebral artery

89. Anterior cerebral artery Superior frontal gyrus Central sulcus Parieto - occipital sulcus Frontal pole Superior parietal lobule Frontal pole

90. ANTERIOR CEREBRAL ARTERY LOBE AREA FRONTAL LOBE Motor – lower limb and perineum - pericentral lobule PARIETAL LOBE Sensory – lower limb and perineum - paracentral lobule

91. Lentiform nucleus Caudate nucleus Internal capsule (ANT) Hypothalamus (ANT) lentiform caudate Internal capsule Anterior cerebral artery & anterior communicating artery

92. Middle cerebral artery Central branches Temporal pole

93. Left middle cerebral artery Right middle cerebral artery Medial striate arteries Lateral striate arteries Central branches

94. MIDDLE CEREBRAL ARTERY LOBE AREA FRONTAL Motor – except for paracentral lobule Motor speech – esp left side PARIETAL Sensory – except for paracentral lobule Sensory speech TEMPORAL Auditory

95. Lentiform nucleus Caudate nucleus Internal capsule (ANT & POST) lentiform caudate Internal capsule Middle cerebral artery & anterior choroidal artery

96. Posterior cerebral artery Inferior temporal gyrus Inferior temporal gyrus

97. POSTERIOR CEREBRAL ARTERY LOBE AREA OCCIPITAL Visual TEMPORAL Olfactory

98. Hypothalamus Thalamus (ANT) Cerebral peduncle thalamus Cerebral peduncle Internal capsule Posterior cerebral artery & posterior communicating artery

99. Thalamus (POST) Geniculate bodies Cerebral peduncle thalamus Cerebral peduncle Posterior lateral arteries Lateral Geniculate bodies

100. Corpus striatum Middle & lateral striate Anterior & Middle cerebral artery Internal capsule Thalamus PComA , basilar, PCA Midbrain PCA, supCerebellarA, basilar Pons Basilar, Ant, inf, supCerebellarA, Medulla oblongata Vertebral, ASA,PSA,PICA, basilar Cerebellum supCerebellar , AICA,PICA ARTERIES to specific brain areas

101. VENOUS DRAINAGE of THE BRAIN EXTERNAL Superior cerebral Superficial middle cerebral Deep middle cerebral INTERNAL Thalamo striate choroidal SPECIFIC Midbrain Pons Medulla oblongata cerebellum

102. Superior cerebral Superficial Middle cerebral basal Superior Sagittal sinus Transverse sinus Superior Sagittal sinus Inferior Sagittal sinus Great cerebral Internal cerebral Straight sinus Occipital sinus

103. Superior cerebral Superficial Middle cerebral Superior Sagittal sinus Transverse sinus Superior anastomotic V Inferior anastomotic V

104. basal Superior Sagittal sinus Inferior Sagittal sinus Great cerebral Internal cerebral Straight sinus Occipital sinus Site of junction with transverse sinus

105. EXTERNAL CEREBRAL VEIN VEIN AREA DRAINS INTO Superior cerebral Lateral surface of cerebral hemisphere Superior sagittal sinus Superficial middle cerebral Cavernous sinus Deep middle cerebral Insula Joined by ant cerebral & striate-basal vein Sup anas V Superior sagittal sinus Inf anas V Inferior sagittal sinus

106. INTERNAL CEREBRAL VEIN VEIN AREA DRAINS INTO Thalamostriate Basal ganglia, thalamus, internal capsule,Tela choroidae of 3 rd ventricle,hippocampus Internal cerebral vein - great cerebral vein – straight sinus DURAL VENOUS SINUS Choroidal

107. VEIN of specific areas Midbrain Basal, great cerebral Pons Basal, cerebellar Medulla oblongata Anterior & posterior spinal Cerebellum Great cerebral

108. Superior sagittal sinus Inferior sagittal sinus Straight sinus Superior cerebral vein Medial aspect of hemisphere Great cerebral vein Transverse sinus (R & L) Sigmoid sinus (R & L) Confluence of sinus IntJugular vein IntJugular vein Cavernous sinus Middle cerebral vein Inferior petrosal sinus Superior petrosal sinus

109. Falx cerebri Superior sagittal sinus Inferior sagittal sinus Straight sinus Tentorium cerebelli * Superior petrosal sinus Inferior petrosal sinus Sigmoid sinus Confluence of sinus Transverse sinus

110. Straight sinus Transverse sinus Sigmoid sinus Confluence of sinus Jugular foramen Cavernous sinus Superior petrosal sinus Inferior petrosal sinus Superiorsagittal sinus

111. Cavernous sinus Lateral to body of sphenoid bone Connected to opposite – intercavernous S Receives blood Middle cerebral V Drains into Int Jugular V –via Inf petrosal sinus Transverse S – via Sup petrosal S Dural Venous sinuses – emissary veins – extracranial V

112. Stroke or cerebrovascular accident:- Blockage in the artery – cerebral infarction Carotid artery Basilar artery Bleeding within the brain – intracerebral haemorrhage Aneurysm Subarachnoid haemorrhage Intracerebral haemorrhage - hypertension Damages one side of the body - contralateral CLINICAL APPLICATION

113. CVA – due to blockage

114. CVA – due to haemorrhage

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