The Ventricles Of The Brain And Cerebrospinal Fluid

The brain has four cavities called ventricles. The first and second ventricles are referred to as the lateral ventricles and are located in the cerebral hemispheres. A midline structure, the septum pellucidum, which is a thin membrane, separates the two lateral ventricles. The lateral ventricles communicate with the third ventricle by way of a small oval opening called the foramen of Monro. The third ventricle communicates with the fourth ventricle by way of the aqueduct of Sylvius. The fourth ventricle is a cavity that lies between the inferior aspects of the brain stem and the cerebellum. The fourth ventricle has three openings: a median opening, the foramen of Magendie, and two lateral openings, the foramina of Luschka. These three foramina open into the subarachnoid space.

Cerebrospinal fluid originates from a choroid plexus located in the roof of each ventricle. The choroid plexus is a highly vascularized network of capillaries and nonconducting nerve cells. Cerebrospinal fluid is formed by filtration and secretion from each choroid plexus. Cerebrospinal fluid formed in the lateral ventricles flows into the third ventricle by way of the foramen of Monro and joins the fluid from the third ventricle. The fluid then moves down the aqueduct of Sylvius into the fourth ventricle joining the fluid from the fourth ventricle. The fluid then circulates into the subarachnoid space. The cerebrospinal fluid flows down the posterior aspect of the spinal cord, up the anterior surface of the spinal cord, and around the anterior surface of the brain. Most of the cerebrospinal fluid is absorbed into the sagittal sinus (a blood vascular cavity just under the sagittal suture of the cranium) through finger like projections of the arachnoid mater called arachnoid granulations (arachnoid villi). Cerebrospinal fluid is normally produced at the same rate that it is absorbed into the sagittal sinus.

Exercise 23.1

Using your text as a guide, fill in the labels on Figures 23.1-23.6.

Figure 23.6 Origin and Circulation of Cerebrospinal Fluid

Aqueduct of Sylvius Arachnoid granulation Choroid plexus of the fourth ventricle Choroid plexus of the third ventricle Dura mater Foramen of Luschka Foramen of Magendie Foramen of Monro Fourth ventricle Sagittal sinus Subarachnoid space Subdural space Third ventricle

Exercise 23.2

Study the model of the sagittal section of the brain. Identify the following structures on the model: aqueduct of Sylvius, cerebellum, cerebral peduncle, cerebrum, choroid plexus of the third ventricle, corpora quadrigemina, corpus callosum, fornix, gyri, hypothalamus, intermediate mass, medulla, pineal gland, pituitary gland, pons, sulci, and thalamus.

Study the model of the whole brain. Identify the following structures on the model: aqueduct of Sylvius, cerebellum, cerebral peduncle, cerebrum, choroid plexus of the third ventricle, corpora quadrigemina, corpus callosum, fornix, gyri, hypothalamus, intermediate mass, mammillary bodies, medulla, pineal gland, pituitary gland, pons, sulci, and thalamus.

Study the wall chart of the sagittal section of the brain. Identify the following structures on the wall chart: aqueduct of Sylvius, cerebellum, cerebral peduncle, cerebrum, choroid plexus of the fourth ventricle, choroid plexus of the third ventricle, corpora quadrigemina, corpus callosum, fourth ventricle, gyri, hypothalamus, infundibulum, intermediate mass, mammillary bodies, medulla, optic chiasma, pineal gland, pituitary gland, pons, subarachnoid space, sulci, thalamus, and third ventricle.

Exercise 23-3

Study a halved sheep brain. Identify the following structures of the sheep brain: aqueduct of Sylvius, cerebellum, cerebral peduncle, cerebrum, corpora quadrigemina, corpus callosum, fornix, fourth ventricle, hypothalamus, infundibulum, intermediate mass, mammillary body, medulla, olfactory bulb, optic chiasma, pineal gland, pituitary gland, pons, spinal cord, and thalamus.

Study a whole sheep brain. Find the following structures on the whole sheep brain: cerebellum, cerebrum, infundibulum, longitudinal fissure, mammillary body, medulla, midbrain, olfactory tract, olfactory bulb, optic chiasma, optic tract, optic nerve II, pituitary gland, pons, and spinal cord.

The bridge of white matter that connects the two cerebral hemispheres is called the _QX-

The convolutions of the cerebrum are referred to as (2).

Name the cranial nerves that originate from the medulla of the brain. Give name and number.

Name the four major areas of the brain.

Cerebrospinal fluid is reabsorbed back into circulation through finger like projections called £121.

Within the (13) . the medial halves of the optic nerves cross over and go to opposite sides of the brain.

The extension of the dura mater between the two cerebral hemispheres is known as the (14).

The lateral walls of the third ventricle are formed by what two parts of the brain?

The structure found within each ventricle that will serve as the site of origin of cerebrospinal fluid is called the (IT) .

18. _ Name the five lobes of the brain.

22 23

The lateral openings in the fourth ventricle that connect to the subarachnoid space are known as the 1231.

The fissure that almost completely separates the two cerebral hemispheres is called the (24).

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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Responses

  • luigina
    What joins the first and second ventricle?
    3 years ago

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