Define the ventricular system For the lateral ventricles des

Define the ventricular system. For the lateral ventricles, describe those structures which form the boundaries. Is there a difference in these structures between the human and the sheep brain? Hydrocephalus, or the accumulation of fluid on the brain, can result from obstruction of the cerebral aqueduct; why is this?

Solution

Ventricular system of brain comprise of inconnected cavities of the brain, located within the brain parenchyma wherein the cerebrospinal fluid (CSF) is produced. CSF flows in these cavities which are continuous with the central canal of the spinal cord.There are four such inconnected cavities including 2 lateral ventricles, the third ventricle called the cerebral aqueduct and the fourth ventricle .

Lateral ventricles are the largest ventricles of the ventricular system. The C- shaped lateral ventricle starts at the inferior horn located in the temporal lobe and travels through the parietal lobe as well as frontal lobe. It terminates at the interventricular foramina where it gets connected to the central third ventricle. The an anterior horn of lateral ventricle extends into the frontal lobe whereas the posterior horn extends into the occipital lobe. The anterior horm of the lateral ventricle is the frontal horn, the posterior horn is the occipital horn and the inferior horn is the temporal horn. The apex of anterior horn reaches to the posterior of the genu of corpus callosum, it is medially bounded by the frontal part of septum pellucidum and laterally by the head of the caudate nucleus. The triangular area comprising of the temporal horn in the inferior, the occipital hornin the posterior region and the body of the lateral ventricle anteriorly is referred to as trigone of the lateral ventricle.

The human and sheep brain are quite similar in structures, however sheep brain is smaller, about one tenth of the human brain. Sheep has a elongated cerebrum, less ridges and contours and the cerebellum and brain stem are located behind the cerebrum, unlike human brain where where they are below cerebrum. This must be because sheep has a horizontal spine instead of vertical in humans. Also, the frontal lobe of sheep brain is smaller compared to overall brain size and olfactory lobe is more deveoped compared to humans.

Narrowing of the aqueduct of Sylvius can block the flow of cerebrospinal fluid, the condition referred as Aqueductal stenosis. Blockage of the aqueduct is the common cause of obstructive hydrocephalus. Aqueduct of Sylvius, is the narrowest part of the CSF pathway which connects third ventricle to the fourth ventricle. Due to this, CSF is not able to flow out of ventricles and cannot be absorbed by the surrounding tissues, thus it is more likely to get blocked, leading to accumulation of CSF in the brain. This results in higher pressure within the ventricles.