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CEREBROSPINAL FLUID
Cerebrospinal fluid (CSF) is formed in the brain ventricles and circulates around the brain and spinal cord. It is produced at a rate of around 500-600 ml per day, primarily by the choroid plexuses in the ventricles. CSF is absorbed into the venous blood through arachnoid villi and lymphatic vessels. It acts as a cushion and protects the brain from mechanical injury. CSF also helps remove waste from the brain and maintain homeostasis. Abnormal CSF accumulation can cause hydrocephalus, while lumbar puncture allows sampling of CSF for analysis.
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CEREBROSPINAL FLUID
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- 2. CSF • Cerebrospinal fluid •Total volume:150ml • Rate of formation:500-600ml/day • Location : - Fills the ventricles of the brain and the subarachnoid space that surrounds the brain and the spinal cord.
- 6. Formation of CSF 50-70% : choroid plexuses 30-50%: blood vessels along the ventricular wall
- 7. Choroid Plexuses • Modifiedependymal cells. • There are four choroid plexuses (CP) in the brain, one in each of the ventricles. • The CP consists of a layer of cuboidal epithelial cells surrounding a core of capillaries and loose connective tissue.
- 8. Mechanism of formation Formedcontinuously by the choroid plexus in two stages: 1. Plasma is passively filtered across the choroidal capillary endothelium 2. Secretion of water and ions across the choroidal epithelium • Bicarbonate, Chloride, and Potassium ions, enter the CSF via channels in the epithelial cell apical membranes. • Aquaporins provide for water movement to balance osmotic gradients.
- 9. Composition • Clear, colorless,alkaline fluid. • Specific gravity 1.005 to 1.008. • pH (7.33) slightly less than that of plasma (7.4). • Iso-osmolar with plasma 289 mOsm / kg / water. • Watery solution similar in composition to blood plasma
- 10. • Contains lessprotein and different ion concentrations than plasma. Almost protein free.(20 – 30 mg%). • Almost cell free (lymphocytes 0-5 / mm3). • Contains less glucose (50mg%) than plasma. • Contains some urea & creatinine. • Also contains chloride, Na+ , K+ , HCO3 – Composition
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- 15. Absorption of CSF Arachnoidvilli - Into the subdural venous sinuses . Recent studies – more important route – via cribriform plate above the nose – to cervical lymphatics
- 16. If CSF pressureis elevated, reabsorption is more via the arachnoid villi. Abnormal increase in amount – aquaporin water channels expressed in the choroid plexus & brain microvessels – compensatory adaptation Absorption of CSF
- 17. Factors that facilitatethe movement of fluid: 1. Oncotic pressure of plasma is higher than that of CSF (as CSF has less proteins) 2. Hydrostatic pressure of CSF is higher than that of the subdural venous sinuses. Absorption of CSF
- 18. Functions of CSF •Mechanical: protective, nourishment, required for cerebral blood flow. • Therapeutical: needed for administration of drug; lumbar puncture.
- 19. Functions of CSF Protects brain from mechanical injury • Effect of buoyancy – Brain has a higher specific gravity than CSF. Therefore, the brain floats freely in the CSF. • Weighs about 1400 g in air; but only 50 g in CSF. • Protection from minor injuries during routine day-to- day activities. • Impact of major injuries is greatly diminished
- 20. Cushion effect: • CSFsupports the brain; cushion like effect • Post lumbar puncture – severe headache after CSF removal – brain hangs on the vessels & nerve roots, and traction on them stimulates pain fibers Functions of CSF
- 21. Provides microenvironment forbrain cells • Serves as a fluid buffer – buffers changes in the blood & brain interstitial fluid – • Thereby, ensures constancy in the external environment of neurons. Functions of CSF
- 22. Removal of proteins& waste products of metabolism • Lymphatics absent in the brain & the spinal cord • CSF serves the function of lymphatics Functions of CSF
- 23. Role in homeostasis •Changes in blood gases in CSF – chemoreceptors – sense & regulate respiration, BP Blood-CSF barrier Abnormalities in composition – Diagnose diseases like meningitis, encephalitis etc., Functions of CSF
- 24. Applied aspects • LUMBARPUNCTURE • HYDROCEPHALUS
- 25. Lumbar puncture • Processby which CSF is taken out from spinal subarachnoid space for study. • An LP needle is introduced usually between 3rd & 4th lumbar spines with subject lying on his side.
- 27. • Study thesample – CSF analysis • Drug delivery. ex: anaesthetics Lumbar puncture
- 28. Hydrocephalus • Pathological accumulation of CSFwithin brain spaces • Types – external & internal
- 29. Hydrocephalus Communicating (external)– excess fluid in subarachnoid space – cause – rate of formation greater than absorption. Non communicating (internal) - excess fluid accumulation in ventricular system proximal to block. • Common sites of block – Foramen of Munro, Luschka, Aqueduct of Sylvius & within ventricular system itself.
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Editor's Notes
- #8 CSF is formed as plasma is filtered from the blood through the epithelial cells. CP epithelial cells actively transport sodium, chloride and bicarbonate ions into the ventricles and water follows the resulting osmotic gradient.Have ion pumps that allow them to alter ion concentrations of the CSF Help cleanse CSF by removing wastes Plexus : a network of nerves or vessels in the body. an intricate network or web-like formation. The CP folds into many villi around each capillary, creating frond-like processes that project into the ventricles. The villi, along with a brush border of microvilli, greatly increases the surface area of the CP. The CP epithelial layer is continuous with the ependymal cell layer that lines the ventricles, but unlike the ependyma, the epithelial layer has tight gap junctions between the cells on the side facing the ventricle (apical surface). These gap junctions prevent the majority of substances from crossing the cell layer into the CSF; thus the CP acts as a blood–CSF barrier.
- #9 CSF is formed as plasma is filtered from the blood through the epithelial cells. CP epithelial cells actively transport sodium, chloride and bicarbonate ions into the ventricles and water follows the resulting osmotic gradient.Have ion pumps that allow them to alter ion concentrations of the CSF Help cleanse CSF by removing wastes Plexus : a network of nerves or vessels in the body. an intricate network or web-like formation. The CP folds into many villi around each capillary, creating frond-like processes that project into the ventricles. The villi, along with a brush border of microvilli, greatly increases the surface area of the CP. The CP epithelial layer is continuous with the ependymal cell layer that lines the ventricles, but unlike the ependyma, the epithelial layer has tight gap junctions between the cells on the side facing the ventricle (apical surface). These gap junctions prevent the majority of substances from crossing the cell layer into the CSF; thus the CP acts as a blood–CSF barrier.
- #10 CSF is formed as plasma is filtered from the blood through the epithelial cells. CP epithelial cells actively transport sodium, chloride and bicarbonate ions into the ventricles and water follows the resulting osmotic gradient.Have ion pumps that allow them to alter ion concentrations of the CSF Help cleanse CSF by removing wastes Plexus : a network of nerves or vessels in the body. an intricate network or web-like formation. The CP folds into many villi around each capillary, creating frond-like processes that project into the ventricles. The villi, along with a brush border of microvilli, greatly increases the surface area of the CP. The CP epithelial layer is continuous with the ependymal cell layer that lines the ventricles, but unlike the ependyma, the epithelial layer has tight gap junctions between the cells on the side facing the ventricle (apical surface). These gap junctions prevent the majority of substances from crossing the cell layer into the CSF; thus the CP acts as a blood–CSF barrier.
- #12 Textbook Of Clinical Neuroanatomy - Page 260 - Google Books Result https://books.google.co.in/books?isbn=8181470192 Singh – 2004 The various cisterns are large pools of CSF and communicate freely with ... Normally the CSF is clear and colourless with specific gravity of 1005-1008, and is ...
- #18 Similar, smaller villi project into veins around spinal nerve routes. These and the arachnoid villi projections contribute to outflow of CSF into the venous blood – by the process of bulk flow – unidirectional. If CSF pressure is elevated, reabsorption is more via the arachnoid villi. Abnormal increase in amount – aquaporin water channels expressed in the choroid plexus & brain microvessels – compensatory adaptation
- #21 ↑Intracranial Tension – clinical sign vomiting, headache, papilledema, hydrocephalus.
- #22 In science, buoyancy or upthrust, is an upward force exerted by a fluid that opposes the weight of an immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Knowledge of the buoyant force is important when trying to understand why some objects float while other
- #25 Small amt of protein that leaks into the interstitial fluid is drained by the CSF & returned to the blood stream.
- #29 The spinal canal is the space in the vertebral column formed by the vertebrae through which the spinal cord passes the spinal cord lies within the canal of the vertebral column
- #32 Hydro – water ; cephalo – relating to the head or skull
- #34 Skull moves along the direction of the head – brain lags behind due to inertia – vacuum created btw brain n skull – when skull comes to rest, the side of the brain opp to the blow hits the skull due to the combined effect of inertia and vacuum.