Exam 4 Review:  Chapter 12:  Cerebrospinal Fluid

CSF = cerebrospinal fluid - The protein-poor serous plasma filtrate which is secreted by choroid plexus cells in each of the four ventricles of the brain and which  circulates through the ventricles of the brain, the central canal of the spinal cord, and the subarachnoid space, and returns to the blood stream at the arachnoid villi; it functions as a shock absorption fluid cushion for the brain and spinal cord and as a second circulatory fluid delivering oxygen and nutrients to the nervous tissue.  [Note:  in the near-midsaggital MRI of the skull on the right below, the CSF appears very black against the solid tissues of the brain and braincase.]

 

 

(brain) ventricles - The series of four interconnecting cavities of the brain, lined by ependymal cells and with a specialized choroid plexus which produce the cerebrospinal fluid that fills these chambers.

 

 

lateral ventricles - The largest pair (right and left) of the ventricles of the brain which are irregular with projecting horns which are located in the interior of the cerebral hemispheres; contain a choroid plexus which secretes CSF which circulates through them and passes to the third ventricle.  [Click here for an interesting clincal case, diagnosis Acute Disseminated EncephaloMyelitis, which includes an MRI image of the brain where the lateral ventricles and subarachnoid space are clearly visible.]

 

third ventricle - The third of the ventricles of the brain, a narrow vertical space within the thalamus of the diencephalon which receives CSF from the lateral ventricles and passes CSF on via the cerebral aquaduct to the fourth ventricle; contain a choroid plexus which secretes CSF.

 

fourth ventricle - The fourth of the ventricles of the brain, a narrow space between the pons and upper medulla oblongata anteriorly and the cerebellum posteriorly which receives CSF from the cerebral aquaduct  and passes CSF on to the central canal of the spinal cord and  outward into the subarachnoid space; contain a choroid plexus which secretes CSF.

 

choroid plexus - One of the delicate fringelike processes, consisting almost entirely of blood vessels, which project into each of the four ventricles of the brain which are lined by specialized ependymal cells which secrete cerebrospinal fluid.

 

 

blood-CSF barrier = blood-brain barrier - A physiological mechanism that alters the permeability of brain capillaries, so that some substances, such as certain toxins and drugs, are prevented from entering brain tissue, while other substances are allowed to enter freely; physically it consists of the capillary endothelial cells and their basement membranes and the processes of astrocytes associated with the capillary beds that serve the brain and spinal cord tissue.

 

 

interventricular foramina - The two openings or short tubes which drain the CSF from the lateral ventricles into the third ventricle.

 

cerebral aqueduct - The canal connecting and transporting CFS from the third to the fourth ventricle which is located in the midbrain.

 

median aperture - A median opening permitting CSF to move from the fourth ventricle to the subarachnoid space.

 

lateral apertures - A pair of lateral openings permitting CSF to move from the fourth ventricle to the subarachnoid space.

 

arachnoid villi - The finger-like projections of the arachnoid membrane which project into the cranial venous sinuses within the dura mater along the major fissures of the brain where they are in close proximity to the venous blood and where cerebrospinal fluid can be transferred from the subarachnoid space back into the bloodstream.

 

dural sinuses - The series of large, somewhat irregular, blood-filled venous spaces with roughly triangular cross-sections which are located within the dura mater where the dura follows the contours of the major fissures of the brain; typically there are four major dural sinuses, the superior sagittal, straight, and two transverse sinuses; these venous spaces are the locations for the arachnoid villi through which cerebrospinal fluid = CSF is reabsorbed to be returned to the venous blood supply of the brain.

 

subarachnoid space - The space in the meninges covering the brain and the spinal cord located beneath the arachnoid membrane and above the pia mater which contains the cerebrospinal fluid.

 

 

circumventricular organs - Several small structures located around the edges of the third and fourth ventricles, lacking the regular blood-brain barrier and thus serving as significant sites for neural-endocrine interaction. [They include the area postrema, the median eminence, the subcommissural organ, the subfornical organ, and the organum vasculosum of the lamina terminalis. Sometimes also included are the funiculus separans, the neurohypophysis, and the pineal body.]

 

hydrocephalus - A usually congenital (less often acquired, e.g., from tubercular meningitis) progressive condition in which an abnormal accumulation of cerebrospinal fluid in the cerebral ventricles causes enlargement of the skull and compression of the brain, destroying much of the neural tissue, and possibly increasing the size of the fontanelles and even the top of the head in newborns where skull bones have not united.  aka water on the brain.

 

 

Describe

1. the circulation of the cerebrospinal fluid including its origin and reabsorption.  (You may sketch and label and/or draw a flow chart.)

1.  CSF is synthesized by Choroid Plexus cells lining portions of the lateral ventricles.
2.  CSF is synthesized by Choroid Plexus cells lining portions of the third ventricle.
3.  CSF is synthesized by Choroid Plexus cells lining portions of the fourth ventricle.
4.  CSF flows from the lateral ventricles (through the interventricular foramen) into the third ventricle.
5.  CSF flows from the third ventricle through the cerebral aquaduct into the fourth ventricle.
6.  CSF flows from the fourth ventricle (through the median and lateral apertures) into the subarachnoid space where it circulates of the surface of the brain and spinal cord.
7.  A small quantity of CSF flows from the fourth ventricle into the central canal of the spinal cord.
8.  CSF is reabsorbed by various arachnoid villi and transferred to the blood stream in the large venous sinuses located in folds of the dura mater.