Brain Ventricles and CSF (1) PDF

FOURTH VENTRICLE  FOURTH VENTRICLE  Tent-shaped space  Situated between cerebellum (behind) and pons and upper part of medulla (anteriorly) 1- Roof of 4th ventricle: Upper part: 1) Superior cerebellar peduncle 2) Superior medullary velum Lower part: 1) Pia and ependyma (Infer...

FOURTH VENTRICLE  FOURTH VENTRICLE  Tent-shaped space  Situated between cerebellum (behind) and pons and upper part of medulla (anteriorly) 1- Roof of 4th ventricle: Upper part: 1) Superior cerebellar peduncle 2) Superior medullary velum Lower part: 1) Pia and ependyma (Inferior medullary velum) 2) Foramen of Magendie Openings in roof of fourth ventricle (3): Foramen of Magendie (Median aperture): Provides communication with the cisterna magna Lateral apertures (foramen of Luschka): Continuation of lateral ends of the lateral recesses of 4th ventricle (each lateral recess extends towards lateral margin of brain stem) with the subarachnoid space of the cerebellopontine angle Lateral boundaries of fourth ventricle : Upper part:  Superior cerebellar peduncles Lower part: 1) Gracile tubercle 2) cuneate tubercle 3) inferior cerebellar peduncle  Floor of 4th ventricle: (Rhomboid, diamond-shaped) Has 4 angles: Inferior angle: Continuous with central canal of spinal cord Superior angle: Continuous with the cerebral aqueduct Lateral angles (2): Meeting of SCP and ICP Features of floor of 4th ventricle Features of the floor of the 4th ventricle: Median sulcus: Extends from superior to inferior angles Divides floor into 2 symmetrical halves Stria medullaris bundles: Lie: between pontine and medullary parts Medial eminences: 2 Elevations on each side of median sulcus Facial colliculi: 2 Swellings on each side of median sulcus Each colliculus for abducent nucleus and loop of facial nerve Superior fovea: Small depression, between medial eminence and vestibular area Inferior fovea: Small A-depression in lower part of floor Hypoglossal triangle: Between inferior fovea and median sulcus Vagal triangle: Between the limbs of the fovea Vestibular area: Lateral to the 2 foveas THIRD VENTRICLE  THIRD VENTRICLE Slit like cavity between the 2 thalami Communicates: Posteriorly: with 4th ventricle through cerebral aqueduct Anteriorly: with lateral ventricles through interventricular foramen (foramen of Monro), which is located between columns of the fornix and anterior pole of the thalamus Third ventricle has: 1)Roof 2)Floor 3)Anterior wall 4)Posterior wall 5)Lateral wall Roof of third ventricle:  Pia-ependyma: Spans between 2 striae medullaris thalami, situated along dorsomedial border of thalamus Floor of third ventricle: 1) Optic chiasma 2) Tuber cinereum and infundibulum 3) Posterior perforated substance 4) Tegmentum of midbrain (posteriorly) Anterior wall of third ventricle: 1) Anterior commissure 2) Anterior column of fornix 3) Lamina terminalis Posterior wall of third ventricle: 1) Pineal body 2) Posterior commissure 3) Cerebral aqueduct Lateral wall of third ventricle: 1) Thalamus 2) hypothalamic sulcus 3) Hypothalamus LATERAL VENTRICLE  LATERAL VENTRICLE  Located within the cerebral hemisphere  One on each side of median plane  Communicates with the 3rd ventricle through interventricular foramen  Approximately C- shaped Consists of: 1) Anterior (frontal) horn 2) Body (central part) 3) Posterior (occipital) horn 4) Inferior (temporal) horn 1. Anterior horn of lateral ventricle: Anterior to interventricular foramen Extends into frontal lobe Roof: Corpus callosum Floor: Rostrum of corpus callosum Medial wall: Septum pellucidum Lateral wall: Head of caudate nucles  Septum pellucidum: Thin sheet spans between the corpus callosum and fornix in the midline Consists of: 2 laminae separated by narrow interval (cavity of septum pellucidum) Separates: Anterior horns and central parts of the 2 lateral ventricles 2. Body (central part) of lateral ventricle: Extends: Behind the interventricular foramen to splenium of corpus callosum Roof: Body of corpus callosum Floor: 1) Tail of caudate nucleus 2) Stria terminalis 3) Thalamostriate vein 4) Thalamus Medial wall: 1) Septum pellucidum 2) Fornix Lateral wall: Meeting of roof and floor 3. Posterior horn of lateral ventricle: Extends from: Splenium to occipital pole Roof and lateral wall: Tapetum of corpus callosum, separate them from optic radiation Floor and medial wall: 2 long elevations: 1) Bulb of posterior horn (formed by forceps major of corpus callosum) 2) Calcar avis: Produced by calcarine sulcus 4. Inferior horn of lateral ventricle:  The largest Lies in: Temporal lobe Roof: 1) Stria terminalis 2) Tail of caudate nucleus 3) Amygdala Lateral wall: Tapetum of corpus callosum Floor: 1) Collateral eminence: Produced by collateral sulcus 2) Hippocampus 3) Fimbria: Axons of hippocampus continuous with crus of fornix CEREBROSPINAL FLUID (CSF) (SUBARACHNOID FLUID)  CEREBROSPINAL FLUID (CSF) (SUBARACHNOID FLUID)  Clear colourless fluid  Contains little protein and few cells  Produced partly by an active secretory process and partly by passive diffusion Present in: 1) Ventricular system 2) Cranial subarachnoid space 3) Spinal subarachnoid space Volume of CSF: About 150 ml in combined ventricular and subarachnoid spaces Produced continuously, at rate sufficient to fill these spaces several times each day Formation of CSF: By: Choroid plexus of the ventricles: Lateral ventricles 3rd ventricle 4th ventricle Note: Most CSF is produced by choroid plexus of lateral ventricle  Choroids plexus: Formed by: Invagination of vascular pia mater into the ventricular lumen, where it becomes highly convoluted producing sponge-like appearance Enters: 3rd and 4th ventricles through their roofs Enters: Lateral ventricle through choroid fissure, along the line of fimbria/ fornix, so, present in central part and inferior horn Course of cerebrospinal fluid: - Passes from: Lateral ventricles to third ventricle through interventricular foramen of Monro Third ventricle to 4th ventricle through cerebral aqueduct 4th ventricle to subarachnoid space through 3 apertures of 4th ventricle Majority passes through median aperture (foramen of Magendie) to enter cisterna magna; located between medulla and cerebellum Lesser amounts flow through lateral apertures (foramina of Luschka) to enter subarachnoid space in region of cerebellopontine angle From these sites, majority of CSF flows superiorly, round the cerebral hemispheres to the sites of reabsorption End of cerebrospinal fluid: Reabsorbed into the venous system by passing into dural venous sinuses, principally the superior sagittal sinus Reabsorption occurs by filtration through arachnoid villi and granulations Arachnoid villi: Numerous and located along the sinuses Consist of: Invaginations of arachnoid mater through the dural wall and into the lumen of the sinus Arachnoid granulations: Hypertrophy of the arachnoid villi with age Mechanism of reabsorption of CSF: Higher hydrostatic pressure in the subarachnoid space than the sinus lumen Greater colloid osmotic pressure of venous blood than cerebrospinal fluid Hydrocephalus: Rise in fluid pressure causing swelling of the ventricles Due to: Obstruction of the flow of CSF within the ventricular system (by tumours) or the subarachnoid space (by adhesions following head injury or meningitis) Papilloedema: Seen on opthalmoscopy Decompression of dilated ventricles: By inserting shunt connecting the ventricles to jugular vein or abdominal peritoneum  Subarachnoid cisterns: The subarachnoid space is of greatly varying depth in different regions Where depressions or fissures in the brain are spanned by arachnoid mater, subarachnoid cisterns are formed 1. Cerebellomedullary cistern ( Cisterna magna ): Lies: Between the cerebellum and dorsal surface of the medulla Continuous: Inferiorly with posterior part of spinal subarachnoid space Site of: Cisternal puncture 2. Interpeduncular cistern: Located: At base of the brain, where the arachnoid spans the space between the 2 temporal lobes Contains: The optic chiasma 3. Cisterna pontis: Lies: Anterior to the pons and medulla oblongata Contains: Vertebral and basilar arteries Continuous: Posteriorly: Around medulla oblongata with cerebellomedullary cistern Inferiorly: With the spinal subarachnoid space Superiorly: With the interpeduncular cistern Thank you