Mesencephalon, cerebellum and telencephalon anatomical observation experiment
Mesencephalon, cerebellum and telencephalon anatomical observation experiment
1. Observe specimens and models of the mesencephalon and cerebellum to understand the external morphology and internal structure of the mesencephalon and cerebellum.
2. Observe and master the layering of nerve cells in the cerebellar cortex.
3. Recognize the main structures, gyrus and lobes of the cerebral hemispheres and observe the internal structure of the cerebral hemispheres.
4. Observe and master the structure of cellular stratification within the cerebral cortex.
5. Understand the ventricles and periaqueducts of the brain.
Operation method
Mesencephalon, cerebellum and telencephalon anatomical observation experiment
Materials and Instruments
Median sagittal section specimen Horizontal cerebral section stained specimen Horizontal cerebellar section stained specimen Cerebral hemisphere specimen Insula specimen Ventricular specimen and meningeal dissection specimen Specimen and model of the brain Brain in the basal nuclei Specimen and model of the brain Anatomical model of the brain Cerebral cortex slice Move I. Mesencephalon For more product details, please visit Aladdin Scientific website.
Probe Dissecting Tray Microscope
(i) Appearance of the mesencephalon
Stained specimens were taken from the brainstem, median sagittal section of the brain and horizontal section of the cerebrum, and the structures of the mesencephalon were observed in conjunction with a model of the brain.
The mesencephalon is located between the midbrain and the cerebral hemispheres and is covered by both cerebral hemispheres. The mesencephalon is divided into the dorsal thalamus, superior thalamus, posterior thalamus, hypothalamus and basal thalamus.
1. The dorsal thalamus is two ovoid gray masses. The anterior end of the thalamus is called the anterior thalamic node, and the posterior end is called the thalamic occiput. The dorsal surface of the dorsal thalamus is the floor of the lateral ventricles. In a median sagittal specimen, the medial surface of the dorsal thalamus is seen to form part of the lateral wall of the third ventricle, and there is an intermediate gray mass in the center of the medial surface, called the thalamic intergluteal fusion, which connects the left and right dorsal thalamus. Below the interthalamic fusion there is a shallow sulcus from the anterior part of the middle cerebral aqueduct to the interventricular foramen, called the hypothalamic sulcus, which is the demarcation line between the dorsal thalamus and the hypothalamus, and the rest of the dorsal thalamus is connected with the neighboring parts, which is not visible in the appearance.
The suprachiasmatic thalamus is located in the upper back of the dorsal thalamus, and its main structure is the pineal gland.
3. The posterior thalamus is located in the lower and outer part of the occipital dorsal thalamus, with the medial geniculate body and lateral geniculate body, the medial geniculate body is connected to the inferior thalamus by the inferior thalamic arm, and the lateral geniculate body is connected to the superior thalamus by the superior thalamic arm.
4. Hypothalamus In the median sagittal specimen of the brain, the hypothalamus is seen to be located below the hypothalamic sulcus. It forms the lateral wall of the lower third ventricle. Viewed from the base of the brain, the hypothalamus includes the optic cross, optic tract, gray nodule, funiculus, pituitary gland, and papillary bodies.
The optic nerves on both sides synthesize into the optic cross, which is continued into the optic tract. Posterior to the optic cross is the gray nodule, which migrates down the funiculus. The lower end of the funnel is connected to the pituitary gland and posterior to the gray nodule is a pair of rounded elevations, the papillary bodies.
5. The basal thalamus is a migratory region of the midbrain and mesencephalon and is invisible in appearance.
(i) Internal structure of the mesencephalon
The internal structure of the dorsal thalamus was observed by staining specimens of the horizontal gross section of the brain. Each side of the dorsal thalamus is divided into three parts by the white matter (inner medullary plate), i.e., the anterior nucleus, the medial nucleus, and the lateral nucleus. The medial aspect of the dorsal thalamus is also seen to form part of the lateral wall of the third ventricle. The lateral aspect of the dorsal thalamus is adjacent to the internal capsule.
II. Cerebellum
(I) Shape of the cerebellum
Specimens and models of the cerebellum were taken for observation. The cerebellum is located in the posterior fossa of the skull, flat above and covered by the cerebral hemispheres, and depressed in the middle below to accommodate the medulla oblongata.
The cerebellar vermis is the narrowed middle part of the cerebellum, which is curled like a ring. The anterior most part of the cerebellar earthworm below the cerebellum is called the tubercle.
The cerebellar hemispheres are the inflated parts of the cerebellum on both sides, with many parallel shallow grooves and a few deep grooves on the surface, the deep grooves divide the planum into several lobes. The deep grooves divide the cerebellum into several lobes. Among these lobes, the choroid is the most isolated. The pomphium is adjacent to the middle cerebellar peduncle, and is connected to the cerebellar peduncle by a pair of pomphial peduncles, constituting the pomphial peduncle lobe. The first deeper fissure above the cerebellum is the protocerebellum.
The cerebellar peduncle connects the cerebellum to the rest of the brain through three pairs of peduncles. Cerebellar foot is the thickest, located in the most lateral, is from the bridge of the brain from the bridge of the nucleus pulposus fibers, and the bridge is connected; cerebellar foot is located in the bridge of the dorsal medial near the middle, mainly by the cerebellar nucleus of the fibers issued by the midbrain is connected; cerebellar foot is located in the middle cerebellar foot of the medial side of the two boundaries are not clear, by the spinal cord, medulla oblongata into the cerebellum from the fibers of the cerebellum.
(ii) Internal structure of the cerebellum
Taking a sagittal cut specimen from the middle of the brain for observation, it can be seen that the cerebellar cortex is located on the surface, and the white matter (cerebellar medulla) is located on the deep surface. When a horizontal section of the cerebellum is taken and stained, the white matter is seen to contain gray matter nuclei called the cerebellar nuclei. The cerebellar nuclei consist of four pairs of nuclei, and the largest of these is observed as the dentate nucleus, which is located in the white matter of the cerebellar hemispheres.
(I) Microstructure of the cerebellar cortex
Take transverse sections (Weigert's stain or silver stain) of cerebellar lobes from human or cats and observe the layering of nerve cells in the cerebellar cortex.
1. Naked eye observation The surface of the cerebellar cortex can be seen to have uneven grooves and lobules. Note the distinction between cortex and medulla.
2. Low magnification observation Observe from the cortical surface inward.
(1) The molecular layer is a thicker layer on the surface, which is reddish in Weigert's stained section, lighter in staining and with fewer cellular components.
(2) Pearly cell layer is located in the middle layer of the cerebellar cortex. Pear-shaped cells were arranged in a row in this layer, and the cytosol was in the shape of a pear, with one or two dendrites at the top extending into the molecular layer. In Golgi silver-stained sections, the dendrites and axons of the pyriform cells can be clearly shown, and the dendrites can be seen to branch repeatedly to form a huge fan, and most of the axons are cut off, and can only be seen close to a small section of the cell body.
(3) The granular layer is a layer on the deep surface of the cortex. It is mainly composed of granular cells, with small, rounded and densely arranged cytosol. It is clearer in silver-stained sections.
The deep part of the granular layer is the cerebellar medulla, which is composed of nerve fibers. On Weigert-stained sections, the nerve fibers stain dark blue. On silver-stained sections, the nerve fibers are dark brown.
Gross anatomy of the telencephalon
The telencephalon includes the left and right cerebral hemispheres, the two hemispheres are separated by a longitudinal fissure - the longitudinal fissure of the brain, and there are transverse fibers at the bottom of the fissure, called the corpus callosum, which connects the two hemispheres.
(I) Shape of the cerebral hemispheres
Specimens and models of the cerebral hemispheres were taken for observation. On the surface of the cerebral hemispheres, there are many grooves of different depths, and the elevation between the grooves is called the gyrus, and there are three main grooves in each hemisphere:
The lateral sulcus is the most obvious sulcus on the dorsal and lateral surfaces of the hemispheres, running obliquely from anterior to posterior.
The central sulcus originates slightly behind the midpoint of the upper edge of the hemisphere, curves forward and downward, and its lower end is close to the lateral sulcus.
The parieto-occipital sulcus is located on the posterior part of the medial surface of the hemisphere, and runs from anterior to posterior to superior, and turns slightly to the dorsal surface of the hemisphere.
(ii) Lobes of the cerebral hemispheres
Specimens and models of the cerebral hemispheres were taken for observation. The lateral sulcus, central sulcus and parieto-occipital sulcus divide each hemisphere into the following five lobes:
1. frontal lobe Located anterior to the central sulcus.
2. the parietal lobe is located between the posterior part of the central sulcus and the parieto-occipital sulcus.
3. the occipital lobe is the smaller part of the parieto-occipital sulcus posteriorly.
4. temporal lobe Located just below the lateral sulcus.
5. insula is deep inside the lateral sulcus
(iii) The dorsolateral sulcus of the cerebral hemispheres
Take specimens of cerebral hemisphere and insula for observation.
1. Frontal lobe Identify the following sulci:
(1) The precentral sulcus the sulcus anterior to and parallel to the central sulcus.
(2) The precentral gyrus lies between the central sulcus and the precentral sulcus.
(3) Superior and inferior frontal sulci The superior and inferior sulci that come out horizontally forward from the precentral sulcus.
(4) Supra-frontal gyrus The gyrus located above the supra-frontal sulcus.
(5) Middle frontal gyrus The gyrus located between the superior and inferior frontal sulci.
(6) The inferior frontal gyrus is located below the inferior frontal sulcus.
2. parietal lobe Identify the gyrus below the inferior sulcus:
(l) Postcentral sulcus The sulcus posterior to and parallel to the central sulcus.
(2) Postcentral gyrus The gyrus between the central sulcus and the postcentral sulcus.
(3) Intraparietal gully A gully that travels in an anterior-posterior direction behind the post-central gully.
(4) Parietal lobule The part of the gyrus located above the intraparietal sulcus.
(5) Inferior parietal lobule The part located below the intraparietal sulcus, which is subdivided into the supramarginal gyrus that surrounds the lateral sulcus anteriorly and the angular gyrus that surrounds the end of the superior temporal sulcus posteriorly.
3. temporal lobe Identify the following sulcus:
(1) Supratemporal sulcus, inferotemporal sulcus Below the lateral sulcus, two sulci parallel to it are present.
(2) Superior temporal gyrus The gyrus between the lateral sulcus and the superior temporal sulcus.
(3) Middle temporal gyrus and inferior temporal gyrus are located above and below the inferior temporal sulcus respectively.
(4) The transverse temporal gyrus is hidden in the lateral sulcus and is a short transverse gyrus above the superior temporal gyrus.
4. Occipital lobe The sulcus is irregular and not constant.
5. insula A specimen of the frontal, parietal, and temporal lobes, which were partially removed from the insula, reveals a slightly triangular shaped insula, which is also covered with sulci.
(iv) The sulcus of the medial aspect of the cerebral hemisphere.
Take a median sagittal cut specimen and a model of the brain for observation.
1. The sulcus of the corpus callosum Circumferential to the dorsal surface of the corpus callosum and continues around the back of the corpus callosum, moving forward to the sulcus of the hippocampus.
2. the cingulate sulcus is located above and parallel to the former. This sulcus is located about the posterior part of the corpus callosum and turns dorsally into what is called the marginal branch.
3. cingulate gyrus Located between the sulcus of the corpus callosum and the sulcus of the cingulate gyrus, it encircles the gyrus above the corpus callosum.
4. paracentral lobule The paracentral lobule is a migratory area on the medial surface of the anterior and posterior central gyrus.
5. talonavicular sulcus At the lower end of the parieto-occipital sulcus, it is bowed backward toward the posterior end of the occipital lobe.
6. cuneate lobe Located between the parieto-occipital sulcus and the talar sulcus, belonging to the occipital lobe.
7. lingual gyrus An anteriorly narrow and posteriorly wide gyrus located below the talar sulcus.
8. parahippocampal gyrus Anterior portion of the lingual gyrus from the caudal end of the corpus callosum to the anterior portion of the gyrus.
9. parahippocampal hook The anterior part of the parahippocampal gyrus that curves into a hook.
10. hippocampus The inferior portion of the medial temporal lobe curls into the inferior horn of the lateral ventricle via the hippocampal sulcus in a bow-shaped elevation.
The dentate gyrus is located in the medial hippocampus and is a long, jagged strip of gray matter. The hippocampus and dentate gyrus are more easily visualized with anatomical specimens showing the hippocampus in the inferior horn of the lateral ventricle.
(v) Floor of the cerebral hemispheres
Mainly the olfactory brain. The following structures are mainly observed with cerebral hemisphere specimens and models:
1. olfactory bundle A ciliated bundle, the olfactory bundle, can be seen traveling anteriorly and posteriorly on the bottom surface of the frontal lobe.
2. the olfactory bulb is the enlarged anterior portion of the olfactory bundle where the olfactory nerve terminates.
3. the olfactory triangle is the posteriorly enlarged part of the olfactory bundle.
(vi) Internal structure of the brain
1. Basal nucleus First, use a model of the nucleus accumbens or the basal nucleus to understand the interrelationship between the caudate nucleus, the nucleus pulposus and the dorsal thalamus. Then take anatomical specimens of the caudate nucleus and stained specimens of horizontal sections of the brain for observation.
(1) The caudate nucleus is an elongated curved gray mass, divided into head, body and tail. The head is enlarged, and its dorsal surface protrudes into the anterior horn of the lateral ventricle. The body is slightly thin, extending backward along the dorsolateral margin of the dorsal thalamus and residing in the central part of the lateral ventricle. The tail is elongated, turning ventrally from the posterior end of the dorsal thalamus to fold along the top of the inferior horn of the lateral ventricle, and connecting to the amygdala (amygdala) at the end.
On stained specimens of horizontal sections of the cerebral hemispheres, the caudate nucleus is cut into two sections, one anterior, larger, section of the head, and one posterior, smaller, section of the tail.
(2) Nucleus accumbens is a mass of gray matter located on the lateral side of the internal capsule (see posterior), the anterior and inferior part of the nucleus is connected to the head of the caudate nucleus, and the rest of the nucleus is separated from the caudate nucleus and the dorsal thalamus by means of the internal capsule. In a stained specimen of a horizontal cross-section of the cerebral hemisphere, the nucleus accumbens is triangular in shape, and the nucleus is separated by the white matter plate into three parts, the outer one is the shell, and the total remaining two are the pale self-sphere.
(3) The nucleus pallidus is a thin layer of gray matter between the insula and the nucleus pulposus.
2. White matter of the cerebral hemispheres The following major projection fibers and connective fibers were observed in a sagittal section of the median cerebrum and a stained section of the cerebrum at the level of the cerebral bulb.
(1) Projectile fibers are the upper and lower fibers that connect the cerebral cortex with the brainstem and spinal cord.
The internal capsule is located in the dorsal thalamus, between the caudate nucleus and the nucleus pulposus, and in the horizontal section of the brain stained specimens, the shape of the internal capsule can be seen as an outwardly open obtuse angle, which is divided into three parts: the front half is shorter, called the anterior limb of the internal capsule, which is located between the caudate nucleus and the nucleus pulposus; the back half is longer, called the posterior limb of the internal capsule, which is located between the nucleus pulposus and the dorsal thalamus; and the obtuse angle where the two intersect is called the knee of the internal capsule.
(2) Connexion fibers are the fibers connecting the left and right cerebral hemispheres: they include the corpus callosum, the anterior commissure and the fornix.
The corpus callosum is located at the base of the longitudinal fissure. In the median sagittal specimen of the brain, the corpus callosum is seen as a very thick, hook-shaped fiber bundle plate at the head end.
On a median sagittal specimen of the brain, a small circular section of white matter is seen below the septum pellucidum, i.e., the section of the anterior commissure.
(3) The fornix and fornix conjunction The fornix starts from the medial side of the hippocampus. It first leaves the hippocampus backward and attaches itself to the underside of the corpus callosum in a bow shape, and then it moves forward to the right and left sides, and some of its fibers cross over to the opposite side to form the fornix conjunction, which connects the hippocampus on both sides. Beyond the fornix, two bundles of fibers advance in parallel on either side of the midline to form the body of the fornix. The body of the fornix then moves forward and separates right and left to become the column of the fornix, which moves forward and down and finally ends in the papillary body. In the median sagittal specimen of the brain, a bow-shaped bundle of white fibers is seen below the corpus callosum, which is the column of the fornix, and since it is partially obscured by the hypothalamus, its direct connection with the papillary body cannot be seen. The membrane between the fornix column and the anterior portion of the corpus callosum is a pellucid septum, separating the two lateral ventricles.
Fourth, the microstructure of the cerebral cortex
Sections (silver-stained) of the central anterior gyrus of the human or cat cerebral cortex were taken for observation to learn about cortical stratification and structure.
(I) Naked eye observation
The darker stained surface is the cortex, and the lighter stained deeper part is the medulla.
(B) Low magnification observation
The neocortex of the brain can be divided into six layers from the surface to the inside according to the morphology, size and sparseness of the arrangement of the cells, but the layers are migrating with each other without obvious demarcation.
1. molecular layer in the shallowest layer of the cortex, thin, light staining, for a small number of nerve cells and many parallel to the surface of the nerve fibers, nerve cells are small and few.
The outer granular layer is small and dense, stained darker, containing a large number of small pyramidal cells and astrocytes.
3. outer pyramidal layer Containing medium and small pyramidal cells, the shallower part of this layer is small pyramidal cells, and the deeper the layer, the larger the cell body.
The inner granular layer is similar to the second layer of cells, with denser cells, mostly astrocytes. If the section is taken from the precentral gyrus, this layer is not obvious.
5. The inner cone layer contains large and medium-sized cone cells with axons traveling toward the medulla. One type of giant pyramidal cell, the Betz cell, can also be seen in sections from the precentral gyrus.
6. polymorphic layer with cells of different shapes, containing spindle cells and astrocytes, sparsely arranged.
The deep cortex is medullary, lightly stained, and composed of nerve fibers and glial cells.
V. Cerebral ventricles
Observed with ventricular specimens and median sagittal cut specimens of the brain.
1. The lateral ventricles, one on the left and one on the right, are located in the two cerebral hemispheres.
The third ventricle is the sagittal fissure between the dorsal thalamus and hypothalamus on both sides. It communicates with the lateral ventricles upward through the interventricular foramen and with the fourth ventricle downward through the middle cerebral aqueduct.
3. The fourth ventricle is located between the pons, medulla oblongata, and cerebellum, and communicates with the subarachnoid space through the median foramen of the fourth ventricle and the lateral foramen of the fourth ventricle on both sides. The fourth ventricle communicates downward with the medulla oblongata and the central canal of the spinal cord.
After studying and observing the structures of the various parts of the brain, it is then comprehensively reviewed with a specimen of the entire brain in profile and a specimen of the brain in median sagittal section in order to get a complete picture of the interrelationships between the various parts of the brain.
VI. Periaqueductal membrane of the brain
Observed with the meningeal specimen, the meninges are divided from outside to inside:
1. Dura mater is the tough outer layer of the membrane. The protrusion of the dura mater between the two hemispheres of the brain is called the cerebral falx. The protrusion between the occipital lobe of the brain and the cerebellum is called the cerebellar vermis. In some parts, the two layers of the dura mater separate to form a cavity containing venous blood called the dural sinus.
2. Arachnoid membrane of the brain Thin and transparent membrane, connected with the soft meninges by many small fiber bundles, the cavity between them is the arachnoid space, which is continuous with the subarachnoid space of the spinal cord.
In some parts of the cranial cavity, the cerebral arachnoid membrane protrudes toward the dura mater to form a small bulge called the arachnoid granule, the cerebrospinal fluid is infiltrated into the dural sinus through this structure and flows into the veins.
3. Soft meninges are thin and rich in blood vessels, close to the surface of the brain, and deep into the sulcus, in a certain part of the ventricular wall, the soft meninges and its blood vessels and the ventricles of the ventricle of the ventricular epithelium together protruding into the ventricles, forming the choroid plexus. It is the principal structure for the production of cerebrospinal fluid.