Interlinked cavities dubbed ventricles (ven"tri-klz) are situated within the cerebral hemispheres and also brain stem (fig. 11.3 and also recommendation plates 53 and 54). These spaces are consistent with the central canal of the spinal cord and also are filled via cerebrospinal liquid.

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The biggest ventricles are the lateral ventricles, which are the initially and second ventricles (the initially ventricle in the left cerebral hemispright here and the second ventricle in the right cerebral hemisphere). They extend into the cerebral hemispheres and occupy parts of the frontal, tempdental, and occipital lobes.

A narrow space that constitutes the third ventricle is located in the midline of the brain beneath the corpus calloamount, which is a bridge of axons that web links the 2 components of the cerebrum. This ventricle communicates via the lateral ventricles with openings (interventricular foramina) in its anterior finish.

Intraventricular foramen

Cerebral aqueduct

Lateral ventricle

Lateral ventricle

Intraventricular foramen

Cerebral aqueduct

*

Cerebral aqueduct

Fourth ventricle

To central canal of spinal cord

Figure 11.3

(a) Anterior view of the ventricles within the cerebral hemispheres and also brain stem. (b) Lateral watch.

Cerebral aqueduct

4th ventricle

To main canal of spinal cord

Figure 11.3

(a) Anterior watch of the ventricles within the cerebral hemispheres and also brain stem. (b) Lateral check out.

The fourth ventricle is situated in the brain stem just in front of the cerebellum. A narrowhead canal, the cerebral aqueduct (aqueduct of Sylvius), connects it to the third ventricle and passes lengthwise through the brain stem. This ventricle is constant via the central canal of the spinal cord and also has actually openings in its roof that lead right into the subarachnoid space of the meninges.

Tiny, reddish cauliflowerlike masses of specialized capillaries from the pia mater, referred to as choroid plexuses, (ko"roid plek"sus-ez) secrete cerebrospinal fluid. These structures job right into the cavities of the ventricles (fig. 11.4). A single layer of specialized ependymal cells (see chapter 10, p. 372) joined closely by tight junctions covers the choroid plexprovides. In much the exact same method that astrocytes carry out a obstacle between the blood and the brain interstitial fluid (blood-brain barrier), these cells block passage of water-soluble substances in between the blood and also the cerebrospinal fluid. At the exact same time, the cells selectively transport specific substances from the blood into the cerebrospinal fluid by promoted diffusion and also deliver other substances by energetic carry (view chapter 3, p. 88), for this reason regulating the complace of the cerebrospinal liquid.

Many of the cerebrospinal fluid arises in the lateral ventricles, from wright here it gradually circulates right into the third and also fourth ventricles and also into the main canal of the spinal cord. It additionally enters the subarachnoid room of the meninges by passing through the wevery one of the fourth ventricle near the cerebellum.

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Humans secrete virtually 500 milliliters of cere-brospinal liquid daily. However, just about 140 milliliters are in the nervous system at any time, because cere-brospinal fluid is continuously retook in right into the blood. The CSF is resoaked up through tiny, fingerfavor structures referred to as arachnoid granulations that job from the subarachnoid space into the blood-filled dural sinoffers (fig. 11.4).

Cerebrospinal liquid is a clear, somewhat viscid liquid that differs in complace from the liquid that leaves the capillaries in other components of the body. Specifically, it consists of a better concentration of sodium