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Watch this video that describes the procedure known as the lumbar puncture, a medical procedure used to sample the CSF. Because of the anatomy of the CNS, it is a relative safe location to insert a needle. Why is the lumbar puncture performed in the lower lumbar area of the vertebral column?

The ventricular system

Cerebrospinal fluid (CSF) circulates throughout and around the CNS. In other tissues, water and small molecules are filtered through capillaries as the major contributor to the interstitial fluid. In the brain, CSF is produced in special structures to perfuse through the nervous tissue of the CNS and is continuous with the interstitial fluid. Specifically, CSF circulates to remove metabolic wastes from the interstitial fluids of nervous tissues and return them to the blood stream. The ventricles    are the open spaces within the brain where CSF circulates. In some of these spaces, CSF is produced by filtering of the blood that is performed by a specialized membrane known as a choroid plexus. The CSF circulates through all of the ventricles to eventually emerge into the subarachnoid space where it will be reabsorbed into the blood.

The ventricles

There are four ventricles within the brain, all of which developed from the original hollow space within the neural tube, the central canal    . The first two are named the lateral ventricles    and are deep within the cerebrum. These ventricles are connected to the third ventricle    by two openings called the interventricular foramina    . The third ventricle is the space between the left and right sides of the diencephalon, which opens into the cerebral aqueduct    that passes through the midbrain. The aqueduct opens into the fourth ventricle    , which is the space between the cerebellum and the pons and upper medulla ( [link] ).

Cerebrospinal fluid circulation

This diagram shows the cross section of the brain and the major parts are labeled. Arrows on the figure show the direction of circulation of the cerebro-spinal fluid.
The choroid plexus in the four ventricles produce CSF, which is circulated through the ventricular system and then enters the subarachnoid space through the median and lateral apertures. The CSF is then reabsorbed into the blood at the arachnoid granulations, where the arachnoid membrane emerges into the dural sinuses.

As the telencephalon enlarges and grows into the cranial cavity, it is limited by the space within the skull. The telencephalon is the most anterior region of what was the neural tube, but cannot grow past the limit of the frontal bone of the skull. Because the cerebrum fits into this space, it takes on a C-shaped formation, through the frontal, parietal, occipital, and finally temporal regions. The space within the telencephalon is stretched into this same C-shape. The two ventricles are in the left and right sides, and were at one time referred to as the first and second ventricles. The interventricular foramina connect the frontal region of the lateral ventricles with the third ventricle.

The third ventricle is the space bounded by the medial walls of the hypothalamus and thalamus. The two thalami touch in the center in most brains as the massa intermedia, which is surrounded by the third ventricle. The cerebral aqueduct opens just inferior to the epithalamus and passes through the midbrain. The tectum and tegmentum of the midbrain are the roof and floor of the cerebral aqueduct, respectively. The aqueduct opens up into the fourth ventricle. The floor of the fourth ventricle is the dorsal surface of the pons and upper medulla (that gray matter making a continuation of the tegmentum of the midbrain). The fourth ventricle then narrows into the central canal of the spinal cord.

Questions & Answers

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why it's not advisable to not to give an intramuscular
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well l think intramuscular injection takes a long time to get to the cells of the body for action whislt an intravenous injection goes straight to the heart and then pump to the cells /tissues quickly.So in a nutshell, intramuscular is slower and takes a longer time to work
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it depends on the route of administration of drugs in an instance where the drugs to be given needs a fast action then intravenous is given but if opposite then intramuscular is advised
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Some times it is not fast in action, and again due to some complications of IM such as injection abcess, and pain.
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because of tissues inflammation the high dose of more than 2mls may cause
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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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