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CHAPTER 29 ■ Body Fluid Analysis 585

rom the pleural, pericardial, and peritoneal cavities; synovial T ree openings in the roo o the ourth ventricle, a pair

uid; and seminal uid is requently per ormed in the hema- o lateral apertures ( oramina o Luschka) and a median

tology laboratory. aperture ( oramen o Magendie), allow CSF to f ow into the

basal cisterns and subarachnoid space o the spinal cord.

From these basal cisterns, CSF migrates over the convexities
NOTE: This is a good time to review the de nitions of the Key toward the cerebral sinuses.

Terms in the Glossary and ash cards on .

Production of Cerebrospinal Fluid

CEREBROSPINAL FLUID CSF production is primarily a unction o the choroid plexus,

Anatomy and Physiology with a smaller proportion being derived rom the ependy-
mal lining and perivascular spaces. T e plexus is composed

CSF acts as a shock absorber or the brain and spinal cord, o two layers: the ependyma (the lining epithelium o the

circulates nutrients, lubricates the central nervous sys- ventricle) and the pia mater. T e olded projections o the

tem (CNS), and may also contribute to the nourishment highly vascularized pia lined with epithelium are re erred

o brain tissue. T e CSF circulates through the ventricles to as the choroidal epithelium. Choroidal epithelium, blood

and subarachnoid space that surrounds both the brain vessels, and interstitial connective tissue orm the choroid

and the spinal cord. T e ventricles (Fig. 29.1) consist o plexus. T e plexuses in the lateral ventricles are the largest

our hollow, f uid- lled spaces inside the brain. A lateral and produce most o the CSF. T e choroid plexus epithe-

ventricle lies inside each hemisphere o the cerebrum. T e lium and the endothelium o capillaries in contact with CSF

two lateral ventricles communicate with the third ventricle constitute the anatomical structure o the blood-brain barrier.

through the oramen o Monro. T e third ventricle, a nar- Te ependyma is a single layer o cells with villous projec-

row channel between the hemispheres through the area tions and cilia on its sur ace. Tanycytes are specialized epen-

o the thalamus, communicates with the ourth ventricle, dymal cells without cilia, located on the f oor o the third

located in the pons and medulla, by means o the aqueduct ventricle. T e main portion o this cell is directed toward

o Sylvius in the midbrain portion o the brainstem. T is the ventricle, and the neck and tail portions contact the cap-

ventricle is continuous with the central canal o the spinal illary wall. T ese cells are not believed to be involved in the

cord. production o CSF.

Longitudinal cerebral
Calvaria fissures

Anterior horn of lateral ventricle
Grey matter
Head of caudate
nucleus

Lenticular
nucleus

Thalamus

Quadrigeminal cistern

Choroid plexus (cistern of great cerebral vein)
of lateral ventricle

Cerebellum Calcification in

pineal body

Internal occipital
protuberance

FIGURE 29.1 ransverse (axial) C image o the brain. Observe the ventricles, various parts o the brain, and the
choroid plexus o the lateral ventricle. (Reprinted rom Moore KL, Dalley AF II. Clinical Oriented Anatomy, 4th ed,

Baltimore, MD: Lippincott Williams & Wilkins, 1999, with permission.)