A Laboratory Manual of Neuroanatomy

The following sections are included:

• PREFACE

• CONTENTS

For this exercise, students will need a whole brain and a bisected brain.

Drain off the fixation fluid and examine the gross features of the brain and identify the meninges wrapping around the brain. The dura mater may have been removed when the brain was taken out from the cadavers. Compare the thickness of the arachnoid with that of the underlying pia mater. Note that the pia mater follows closely the contours of the brain's surface whereas the arachnoid mater bridges over the surface of the brain…

In this laboratory, we shall study the basic components of the nervous system: the neurons whose axons form nerves, the supporting neuroglia and the sensory receptors.

Start by looking at examples of neurons. In a slide of Azure B stained cerebral cortex, identify the cell body of a typical neuron. Proceed to identify Nissl's bodies, the axon hillock and the centrally placed nucleus. Observe the axon and dendrites which are often only partly visible. Are there any satellite cells around the cell body? What are Nissl's bodies composed of? What is meant by the term chromatolysis? Which staining technique is applied to reveal the Nissl's bodies?…

As a preliminary exercise, embryological development may be studied by examining a series of whole mounts of chick embryos, ranging from 13 hours to 96 hours of incubation. In the young embryos of less than 20 hours' incubation, identify the head ectoderm, neural groove, notochord, Henson's node and primitive streak (Fig. 13). Appreciate the fact that no neural tube has yet developed at this stage. Around 30 hours of incubation, identify the anterior neuropore, neural tube, Henson's node and primitive streak (Fig. 14). The brain has differentiated into the prosencephalon, mesencephalon and rhombencephalon. Around 48 hours of incubation, again identify the various parts of the brain — prosencephalon, optic vesicle, infundibulum, mesencephalon, rhombencephalon, spinal cord, caudal neural groove, notochord and primitive streak…

The following sections are included:

• Blood supply of the meninges

• Blood supply of the brain

• Blood supply of the spinal cord

Before starting on the neuroanatomy, students should first revise the topographical anatomy of the spinal cord (Figs. 23, 24 & 25). The development of the spinal cord and the dura mater from birth onwards are important. Terms such as cauda equina, filum terminale, dorsal and ventral roots, cervical and lumbar enlargements must be fully understood…

External markings — Students are required to note the following external markings on the ventral, lateral and dorsal aspects of the medulla oblongata…

External markings – Using the whole brain specimen, note that the pons can be divided into ventral, dorsal and lateral aspects. From the ventral surface, identify the VI cranial nerve at the pons-medullary junction. Also observe the thick fibrous bands and the shallow furrow along the midline within which sits the basilar artery. Cut through the superior, middle and inferior cerebellar peduncles which link the cerebellum with the brainstem. Keep the cerebellum for subsequent laboratory exercises on that subject. The dorsal surface of the pons and rostral medulla forms the superior aspect of the floor of IV ventricle. Identify the median sulcus, facial colliculus, sulcus limitans, vestibular area, lateral recess of the IV ventricle, striae medullaris, middle cerebellar peduncle (sectioned), superior medullary velum, hypoglossal and vagal trigones (mainly in the medulla). Note that the hypoglossal trigone and facial colliculus form the median eminence. At the ponto-cerebellar angle, identify the VII and VIII cranial nerves. The V cranial nerve emerges from the middle pons at the lateral surface…

External markings – The midbrain represents the most rostral portion of the brain stem. Examine the foilowing gross features of this area. On the dorsal surface (Fig. 41), identify the corpora quadrigemina. What are the components and their functions? Note the IV cranial nerves emerging from behind the inferior colliculi. Bear in mind that the corpora quadrigemina represents a very important landmark of the midbrain. Proceed to the ventral surface of the midbrain and identify the two crus cerebri (also known as _____________ and containing what fibers?) as well as the interpeduncular fossa. Note that the III cranial nerve emerges from the interpeduncular fossa between the pons and the midbrain. No conspicuous gross feature can be observed on the lateral surfaces. Another very important feature of the midbrain is the narrowing of the IV ventricle rostrally to form the cerebral aqueduct in the midbrain. The tectum of the midbrain is a term used for the area above the aqueduct…

The diencephalon is a derivative of the prosencephalon – linking the mesencephalon with the telencephalon. It contains the III ventricle and is bounded laterally by the internal capsule which separates the diencephalon from the lentiform nuclei…

The following sections are included:

• General topography of the cerebral cortex

• Visual system

• Auditory system

• Olfactory system

• Deep grey matter of the telencephalon

• Fornix, caudate, hippocampus, amygdaloid nucleus

• Histology of the cerebral cortex

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The cerebellum is a motor part of the CNS and is involved with the maintenance of equilibrium and coordination of muscle action. Its function in the synchronisation of muscles is particularly important although it does not initiate voluntary movement. The cerebellum lies dorsal to the medulla oblongata, pons and fourth ventricle and occupies a major part of the posterior cranial fossa. The cerebellum has two hemispheres and a median vermis. The primary fissure and postclival sulcus can be seen on the superior side of the cerebellum (Fig. 64). The centrally located vermis is further divided into named lobules: the lingula, central lobule, culmen, declive, folium, tuber, pyramis, uvula and nodulus (Fig. 65). The major components of the cerebellum and their connections are listed in Fig. 66. Students, using the gross brain specimens, should identify and familiarize themselves with all the features listed. Trace the cerebellum into other areas of the CNS…

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The following sections are included:

• ABBREVIATIONS