Interconnected cavities dubbed ventricles (ven"tri-klz) are located within the cerebral hemispheres and brain stem (fig. 11.3 and reference bowl 53 and also 54). These spaces are continuous with the main canal that the spinal cord and also are filled through cerebrospinal fluid.

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The largest ventricles room the lateral ventricles, which space the very first and 2nd ventricles (the very first ventricle in the left cerebral hemisphere and also the 2nd ventricle in the appropriate cerebral hemisphere). They prolong into the cerebral hemispheres and also occupy portions of the frontal, temporal, and also occipital lobes.

A narrow room that constitutes the 3rd ventricle is located in the midline of the brain beneath the corpus callosum, i beg your pardon is a bridge of axons that web links the two parts of the cerebrum. This ventricle communicates through the lateral ventricles through openings (interventricular foramina) in the anterior end.

Intraventricular foramen

Cerebral aqueduct

Lateral ventricle

Lateral ventricle

Intraventricular foramen

Cerebral aqueduct

*

Cerebral aqueduct

Fourth ventricle

To main canal the spinal cord

Figure 11.3

(a) Anterior view of the ventricles in ~ the cerebral hemispheres and mind stem. (b) Lateral view.

Cerebral aqueduct

Fourth ventricle

To main canal the spinal cord

Figure 11.3

(a) Anterior view of the ventricles in ~ the cerebral hemispheres and mind stem. (b) Lateral view.

The 4th ventricle is located in the mind stem just in prior of the cerebellum. A small canal, the cerebral aqueduct (aqueduct of Sylvius), connects it to the 3rd ventricle and also passes lengthwise with the mind stem. This ventricle is continuous with the main canal of the spinal cord and has openings in that is roof that lead into the subarachnoid an are of the meninges.

Tiny, reddish cauliflowerlike masses of devoted capillaries from the pia mater, referred to as choroid plexuses, (ko"roid plek"sus-ez) secrete cerebrospinal fluid. These structures project into the cavities of the ventricles (fig. 11.4). A solitary layer of dedicated ependymal cells (see chapter 10, p. 372) joined closely by tight junctions consist of the choroid plexuses. In much the same way that astrocytes carry out a barrier between the blood and also the brain interstitial fluid (blood-brain barrier), this cells block passage of water-soluble substances between the blood and also the cerebrospinal fluid. In ~ the exact same time, the cell selectively transfer particular substances indigenous the blood right into the cerebrospinal liquid by promoted diffusion and also transfer various other substances by energetic transport (see thing 3, p. 88), for this reason regulating the ingredient of the cerebrospinal fluid.

Most of the cerebrospinal fluid arises in the lateral ventricles, from wherein it progressively circulates right into the 3rd and fourth ventricles and also into the main canal that the spinal cord. It additionally enters the subarachnoid an are of the meninges by passing v the wall of the fourth ventricle near the cerebellum.

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Humans secrete practically 500 milliliters of cere-brospinal fluid daily. However, only around 140 milliliters room in the nervous device at any kind of time, because cere-brospinal fluid is repeatedly reabsorbed right into the blood. The CSF is reabsorbed with tiny, fingerlike structures dubbed arachnoid granulations that project from the subarachnoid space into the blood-filled dural sinuses (fig. 11.4).

Cerebrospinal fluid is a clear, rather viscid liquid that differs in ingredient from the fluid that leaves the capillaries in other parts that the body. Specifically, it includes a higher concentration that sodium