cerebrospinal fluid
| Dictionary: cerebrospinal fluid |
n. (Abbr. CSF)
The serumlike fluid that circulates through the ventricles of the brain, the cavity of the spinal cord, and the subarachnoid space, functioning in shock absorption.
5min Related Video:
cerebrospinal fluid |
Britannica Concise Encyclopedia:
cerebrospinal fluid |
cerebrospinal fluid
For more information on cerebrospinal fluid, visit Britannica.com.
World of the Body:
cerebrospinal fluid |
The brain floats on a liquid cushion of cerebrospinal fluid (CSF) within the rigid bony skull. The CSF is contained between layers of the meninges, the membranes that enclose the brain. It fills the subarachnoid space between the delicate arachnoid mater that lines the tough fibrous outer covering, the dura mater, and the pia mater that covers the soft substance of the brain.
A diagrammatic vertical section through the brain showing the location of the ventricles and the direction of flow of cerebrospinal fluid (CSF). CSF is formed by the choroid plexuses (CP), mainly in the lateral ventricles, and drains into the blood via the arachnoid villi and the spinal nerve roots
Since the brain floats in CSF, the fluid acts in effect to reduce the weight of the brain from some 1000 g to about 50 g, and also protects the brain from knocks on the head. However, since the brain can move within the CS, it can be damaged on the opposite side by a sudden deceleration such as in a car accident (contra coup injury).
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 (see figure). Each of the paired lateral ventricles, in the cerebral hemispheres, contains a leaf-like, highly vascular choroid plexus. It is from these structures that the bulk of the CSF is secreted. From the lateral ventricles CSF drains into the central third ventricle, and thence through the aqueduct in the midbrain into the fourth ventricle. Both the third and fourth ventricles contribute to the flow from their own choroidal tissue. From the fourth ventricle, the CSF exits into the subarachnoid space through several openings, and fills the ‘basal cisterns’ beneath the brain. Thence the flow of CSF is mainly up and over the whole brain surface, whilst some flows down around the spinal cord. Completing the circuit back to the bloodstream, the fluid drains via the valve-like arachnoid granulations into the sagittal sinus, the large venous channel lying centrally on the top of the brain; some is also taken up into veins around spinal nerve roots and into the lymphatics of the nose.
The secretion of CSF is an active transport process that moves fluid and solutes from the blood plasma into the ventricles, the choroid plexuses being a specialized part of the blood-brain barrier. CSF secretion involves the pumping of ions and specialized ion channels, with the energy coming from glucose and oxygen in the blood. In the adult human CSF is formed at a rate of about 0.5 ml/min; the total volume is about 200 ml, of which 30 ml is in the ventricles and the remainder in the subarachnoid space. The circulation of CSF leads to the fluid being completely replaced about every 4 hours.
CSF is a weak salt solution with similar inorganic ion concentrations to plasma, but with small and significant differences, whereas the protein content is about 100 times less than that of plasma (0.5 g/litre compared to 50-70 g/litre). Abnormalities of the CSF can be important in diagnosis of some medical conditions; the fluid can be sampled by lumbar puncture from the extension of the subarachnoid space (the lumbar sac) below the lower end of the spinal cord. CSF is normally a clear, amazingly ‘bright’ fluid, and if it is cloudy or contains a raised level of protein or traces of blood this is usually an indication of brain infection, some types of brain or spinal cord tumour, or trauma.
The pressure within the brain, the intracranial pressure (ICP), is transmitted in the CSF around the spinal cord and down into the lumbar sac. With the body horizontal, it is normally low (about 10 cm H2O) ; it is markedly affected by posture, and raised by straining or coughing.
Blockage in the drainage pathways for CSF is one of the causes of a raised ICP, since the CSF is actively ‘pumped’ into the ventricular system. In an adult this raised pressure can cause expansion of the ventricles, with loss of neural tissue by compression against the rigid skull. In infants, when CSF drainage pathways have failed to develop normally, the raised ICP causes the head to swell because the junctions between the skull bones are not fused, resulting in hydrocephalus — ‘water on the brain’.
A raised intracranial pressure can often be recognized by looking into the eye with an ophthalmoscope, an instrument which shines a beam of light on to the retina at the back of the eye. The beam is focused onto the ‘optic disc’, where the nerves of the eye converge to pass to the brain. Normally this appears as a clearly-defined, pale concave disc, but if the pressure in the CSF is raised, the disc may bulge forwards into the cavity of the eye. As well as by blockage of CSF circulation, raised pressure can be caused by an expanding tumour or blood clot, or by swelling of a damaged or diseased brain.
The CSF also acts as a drainage route for waste products of brain metabolism, additional to their direct excretion into the capillary blood vessels everywhere in the brain across the blood-brain barrier.
— Malcolm Segal
See also blood-brain barrier; hydrocephalus; meninges.
Dental Dictionary:
cerebrospinal fluid |
n
The fluid that flows through and protects the four ventricles of the brain, subarachnoid space, and spinal canal.
Veterinary Dictionary:
CSF |
Cerebrospinal fluid.
Wikipedia:
Cerebrospinal fluid |
Cerebrospinal fluid (CSF), Liquor cerebrospinalis, is a clear bodily fluid that occupies the subarachnoid space and the ventricular system around and inside the brain. In essence, the brain "floats" in it.
The CSF occupies the space between the arachnoid mater (the middle layer of the brain cover, meninges), and the pia mater (the layer of the meninges closest to the brain). It constitutes the content of all intra-cerebral (inside the brain, cerebrum) ventricles, cisterns, and sulci (singular sulcus), as well as the
It acts as a "cushion" or buffer for the cortex, providing a basic mechanical and immunological protection to the brain inside the skull.
It is produced in the choroid plexus.
|
Contents
|
Circulation
CSF is produced in the brain by modified ependymal cells in the choroid plexus (approx. 50-70%), and the remainder is formed around blood vessels and along ventricular walls. It circulates from the lateral ventricles to the foramen of Monro, third ventricle, aqueduct of Sylvius, fourth ventricle, foramina of Magendie and Luschka; subarachnoid space over brain and spinal cord; reabsorption into venous sinus blood via arachnoid granulations.
It had been thought that CSF returns to the vascular system by entering the dural venous sinuses via the arachnoid granulations or villi. However, some[1] have suggested that CSF flow along the cranial nerves and spinal nerve roots allow it into the lymphatic channels; this flow may play a substantial role in CSF reabsorbtion, in particular in the neonate, in which arachnoid granulations are sparsely distributed. The flow of CSF to the nasal submucosal lymphatic channels through the cribiform plaque seems to be specially important[2].
Amount and constitution
| Reference ranges in CSF | |||
|---|---|---|---|
| Substance | Lower limit | Upper limit | Unit |
| Glucose | 50[3] | 80[3] | mg/dL |
| Protein | 15[3] | 40[4] - 45[3] | mg/dL |
| RBCs | n/a[3] | 0[3] / negative | cells/µL |
| WBCs | 0[3] | 3[3] | cells/µL |
The CSF is produced at a rate of 500 ml/day. Since the brain can contain only from 135 to 150 ml, large amounts are drained primarily into the blood through arachnoid granulations in the superior sagittal sinus. Thus the CSF turns over about 3.7 times a day. This continuous flow into the venous system dilutes the concentration of larger, lipoinsoluble molecules penetrating the brain and CSF.[5]
The CSF contains approximately 0.3% plasma proteins, or approximately 15 to 40 mg/dL, depending on sampling site.[4] CSF pressure ranges from 80 to 100 mmH2O (780–980 Pa or 4.4-7.3 mmHg) in newborns, and < 200 mmH20 (1.94 kPa) in normal children and adults, with most variations due to coughing or internal compression of jugular veins in the neck.
There are quantitative differences in the distributions of a number of proteins in the CSF. In general, globular proteins and albumin are in lower concentration in ventricular CSF compared to lumbar or cisternal fluid.[6]
Functions
CSF serves four primary purposes:
- Buoyancy-- The actual mass of the human brain is about 1400 grams; however the net weight of the brain suspended in the CSF is equivalent to a mass of 25 grams.[7] The brain therefore exists in neutral buoyancy, which allows the brain to maintain its density without being impaired by its own weight, which would cut off blood supply and kill neurons in the lower sections without CSF.[8]
- Protection-- CSF protects the brain tissue from injury when jolted or hit. In certain situations such as auto accidents or sports injuries, the CSF cannot protect the brain from forced contact with the skull case, causing hemorrhaging, brain damage, and sometimes death.[9]
- Chemical Stability-- CSF flows throughout the inner ventricular system in the brain and is absorbed back into the bloodstream, rinsing the metabolic waste from the central nervous system through the blood-brain barrier. This allows for homeostatic regulation of the distribution of neuroendocrine factors, to which slight changes can cause problems or damage to the nervous system. For example, high glycine concentration disrupts temperature and blood pressure control, and high CSF pH causes dizziness and syncope.[10]
- Prevention of brain ischemia-- The prevention of brain ischemia is made by decreasing the amount of CSF in the limited space inside the skull. This decreases total intracranial pressure and facilitates blood perfusion.
Pathology and laboratory diagnosis
When CSF pressure is elevated, cerebral blood flow may be constricted. When disorders of CSF flow occur, they may therefore affect not only CSF movement but also craniospinal compliance and the intracranial blood flow, with subsequent neuronal and glial vulnerabilities. The venous system is also important in this equation. Infants and patients shunted as small children may have particularly unexpected relationships between pressure and ventricular size, possibly due in part to venous pressure dynamics. This may have significant treatment implications, but the underlying pathophysiology needs to be further explored.
CSF connections with the lymphatic system have been demonstrated in several mammalian systems. Preliminary data suggest that these CSF-lymph connections form around the time that the CSF secretory capacity of the choroid plexus is developing (in utero). There may be some relationship between CSF disorders, including hydrocephalus and impaired CSF lymphatic transport.
CSF can be tested for the diagnosis of a variety of neurological diseases.[11] It is usually obtained by a procedure called lumbar puncture. Removal of CSF during lumber puncture can cause a severe headache after the fluid is removed, because the brain hangs on the vessels and nerve roots, and traction on them stimulates pain fibers. The pain can be relieved by intrathecal injection of sterile isotonic saline. Lumbar puncture is performed in an attempt to count the cells in the fluid and to detect the levels of protein and glucose. These parameters alone may be extremely beneficial in the diagnosis of subarachnoid hemorrhage and central nervous system infections (such as meningitis). Moreover, a CSF culture examination may yield the microorganism that has caused the infection. By using more sophisticated methods, such as the detection of the oligoclonal bands, an ongoing inflammatory condition (for example, multiple sclerosis) can be recognized. A beta-2 transferrin assay is highly specific and sensitive for the detection for, e.g., CSF leakage.
| Cause | Appearance | Polymorphonuclear cell | Lymphocyte | Protein | Glucose |
|---|---|---|---|---|---|
| Pyogenic bacterial meningitis | Yellowish, turbid | Markedly increase | Slightly increase or Normal | Markedly increase | Decrease |
| Viral meningitis | Clear fluid | Slightly increase or Normal | Markedly increase | Slightly increase or Normal | Normal |
| Tuberculous meningitis | Yellowish and viscous | Slightly increase or Normal | Markedly increase | Increase | Decrease |
| Fungal meningitis | Yellowish and viscous | Slightly increase or Normal | Markedly increase | Slightly increase or Normal | Normal or decrease |
Lumbar puncture
Lumbar puncture can also be performed to measure the intracranial pressure, which might be increased in certain types of hydrocephalus. However a lumbar puncture should never be performed if increased intracranial pressure is suspected because it could lead to brain herniation and ultimately death.
Baricity
This fluid has an importance in anesthesiology. Baricity refers to the density of a substance compared to the density of human cerebral spinal fluid. Baricity is used in anesthesia to determine the manner in which a particular drug will spread in the intrathecal space.
See also
References
- ^ Zakharov A, Papaiconomou C, Djenic J, Midha R, Johnston M (2003). "Lymphatic CSF absorption pathways in neonatal sheep revealed by subarachnoid injection of Microfil". Neuropathol. Appl. Neurobiol. 29 (6): 563–73. doi:. PMID 14636163.
- ^ Johnston M (2003). "The importance of lymphatics in cerebrospinal fluid transport.". Lymphat. Res. Biol. 1 (1): 41–4. PMID 15624320.
- ^ a b c d e f g h Normal Reference Range Table from The University of Texas Southwestern Medical Center at Dallas. Used in Interactive Case Study Companion to Pathologic basis of disease.
- ^ a b Felgenhauer K (1974). "Protein size and CSF composition". Klin. Wochenschr. 52 (24): 1158–64. doi:. PMID 4456012.
- ^ Saunders NR, Habgood MD, Dziegielewska KM (1999). "Barrier mechanisms in the brain, I. Adult brain". Clin. Exp. Pharmacol. Physiol. 26 (1): 11–9. doi:. PMID 10027064.
- ^ Merril CR, Goldman D, Sedman SA, Ebert MH (March 1981). "Ultrasensitive stain for proteins in polyacrylamide gels shows regional variation in cerebrospinal fluid proteins". Science 211: 1437–8. PMID 6162199.
- ^ Noback, Charles; Norman L. Strominger, Robert J. Demarest, David A. Ruggiero (2005). The Human Nervous System. Humana Press. p. 93. ISBN 978-1588290403.
- ^ Saladin, Kenneth (2007). Anatomy and Physiology: The Unity of Form and Function. McGraw Hill. p. 520. ISBN 978-0-07-287506-5.,
- ^ Saladin, Kenneth (2007). Anatomy and Physiology: The Unity of Form and Function. McGraw Hill. p. 520. ISBN 978-0-07-287506-5.,
- ^ Saladin, Kenneth (2007). Anatomy and Physiology: The Unity of Form and Function. McGraw Hill. p. 520. ISBN 978-0-07-287506-5.,
- ^ Seehusen DA, Reeves MM, Fomin DA (September 2003). "CSF analysis". Am Fam Physician 68 (6): 1103–8. PMID 14524396. http://www.aafp.org/afp/20030915/1103.html.
|
|||||||||||||||||||
This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
Learn More
 | blood-brain barrier |
| hydrocephalus |
| meninges |
 | What cells produce cerebrospinal fluid? Read answer... |
| Cerebrospinal fluid reabsorbed? Read answer... |
| What is the cerebrospinal fluid and what is its function? Read answer... |
Help us answer these
 | What is Cerebrospinal Fluid produced by? |
| Cerebrospinal fluid is produced in the? |
| What are the varieties of amides in cerebrospinal fluid? |
Post a question - any question - to the WikiAnswers community:
Copyrights:
 |
 | Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved. Read more |
 |
| Britannica Concise Encyclopedia. Britannica Concise Encyclopedia. © 1994-2009 Encyclopædia Britannica, Inc. All rights reserved. Read more |
 |
| World of the Body. The Oxford Companion to the Body. Copyright © 2001, 2003 by Oxford University Press. All rights reserved. Read more |
 |
| Dental Dictionary. Mosby's Dental Dictionary. Copyright © 2004 by Elsevier, Inc. All rights reserved. Read more |
|
| Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved. Read more |
 |
| Wikipedia. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article "Cerebrospinal fluid". Read more |
Related answers
- Structure that forms cerebrospinal fluid?
- What is cerebrospinal fluid?
- Structure that forms the cerebrospinal fluid?
ADVERTISEMENT
Answer these
- Where is cerebrospinal fluid?
- What contains cerebrospinal fluid?
- What is cerebrospinal fluid Treatment?
- Forms cerebrospinal fluid?
Mentioned in
- CSF (abbreviation)
- glycorrhachia
- hyperglycorrhachia
- subarachnoid hemorrhage
- erythrochromia
- Nonne–Apelt test
- pleocytosis (medicine)
- hydromicrocephaly
- hypoglycorrhachia
- hydrocephaly (medicine)
- Subarachnoid space (in medicine)
- Ventricles of the brain (in medicine)
- albuminocytologic dissociation
- hydrocephalus
