Observe sections of the human brainstem and combine them with observations of a model of the nucleus accumbens and a model of the nerve conduction pathways to understand the internal structure of the brainstem, to grasp the location of its major nuclei and fiber bundles, and to develop a three-dimensional concept of the structure as seen in a plane.
Operation method
Observation experiment on the internal structure of the brainstem
Materials and Instruments
Brain stem specimen Nucleus model Nerve conduction pathway model Human brain stem slice Move When observing the sections, it is important to follow a certain procedure, first of all, to find out through which part of the brainstem each section is cut, to identify the morphology around the section with reference to the brainstem specimen and model, and then to consider what important structures should be present in this section, so as to search for and identify the main nuclei of the nerves as well as the location of the upper and lower fiber bundles passing through this section, and to consider the connections between them. Think at all times while observing to establish a three-dimensional concept of the internal structure of the brainstem. 1. The trigeminal pontine nucleus is located on the lateral side of the pontine reticular formation. 3. Hypothalamic nucleus A neural nucleus located in the hypothalamus into which some of the fibers of the lateral thalamic system enter. 6. dorsal cover cross Located on the dorsal side of the cover, it is formed by the crossing of fibers from the spinal cord of the parietal. 8. The reticulum is located mainly on the lateral and dorsal sides of the red nucleus. For more product details, please visit Aladdin Scientific website.
Solid microscope Microscope
The section is stained by the Weigert method, with nerve fibers stained blue by hematoxylin and nuclei stained red by erythrosin. When observing the section, the entire morphology of the section is visualized with the naked eye, and then the locations of the nuclei and fiber bundles are identified with a solid microscope. The position of each fiber bundle was identified according to the direction of the fibers, the thickness of the diameter, and the coloration of the myelin sheath. After observing the location of the nucleus, the nerve cells inside the nucleus were observed with a low-power microscope.
Observe the following sections and fill in the words for each figure (refer to the relevant atlas of human anatomy)
I. Internal structure of the medulla oblongata
It is divided into upper and lower parts. In the lower part, the central canal is located in the center and is structurally similar to the spinal cord. However, after the emergence of the cones crossing and the medial thalamus crossing in this part, the gray matter of the medulla oblongata does not appear in the shape of "H" in the transverse section like that of the spinal cord gray matter, but it is divided into various neuronal nuclei. In the upper part, the central canal enlarges into the fourth ventricle. The central gray matter becomes the nuclei at the base of the fourth ventricle.
(i) Cross section of the flat cones
Identify the following major structures (Fig. 5):
1. cone crossings are made by crossing cone bundle fibers.
2. thin bundles, wedge bundles A continuation of the homonymous bundles of the spinal cord.
3. the nuclei of the thin and wedge bundles are just visible in this section. They are located on the deep surface of the thin and wedge fascicular nodes.
4. central gray matter The gray matter surrounding the central canal.
5. reticulum Interwoven gray and white matter on either side of the central gray matter.
6. anterior and posterior cerebellar fascicles of the spinal cord Located in the superficial layers of the lateral medulla oblongata, the two fascicles are not clearly demarcated on section.
7. trigeminal spinal tract and trigeminal spinal tract nucleus Lateral to the cuneate fasciculus, there is the trigeminal spinal tract, which is medial to the semilunar trigeminal spinal tract nucleus.
(ii) Cross section of the Hirakuchi system 
1. cones Aggregates of descending cone bundles, located on both sides of the anterior median fissure.
2. thin bundles, wedge bundles Two bundles of fibers have been reduced.
3. thin bundle nuclei, wedge bundle nuclei In this section the two nuclei have increased in size.
4. thalamocortical crossings are formed when the fibers emanating from the nuclei of the thin fasciculus and the cuneate fasciculus cross each other around the outer edge of the central gray matter to the opposite side.
The crossed fibers are called the medial thalamic tract and travel upward immediately on either side of the midline.
5. trigeminal spinal tract and trigeminal spinal tract nucleus Lateral to the cuneate fasciculus.
6. hypoglossal nucleus In this section, only a small nucleus is visible on either side of the central canal, from which the hypoglossal nerve root emanates obliquely outward.
7. reticular formation Located ventral to the central gray matter.
(iii) Section of the middle of the flat olive
Identify the following major structures (Fig. 7): 
2. inferior olivary nucleus A deep, wrinkled pouch-like nucleus of the olive.
3. The central canal has opened into the fourth ventricle.
4. hypoglossal nucleus On either side of the midline at the base of the fourth ventricle. The hypoglossal nerve root is obliquely forward and outward.
5. dorsal vagal nucleus Dorsolateral to the nucleus of the hypoglossal nerve.
6. solitary fasciculus and solitary fasciculus nucleus Located ventral to the dorsal nucleus of the vagus nerve.
7. vestibular nuclei Located lateral to the upper two pairs of nuclei.
8. medial longitudinal fasciculus A longitudinal bundle of fibers located deep to the nucleus of the hypoglossal nerve, immediately on either side of the median sulcus.
9. medial thalamic tract Located dorsal to the pyramidal tract against the midline.
l0. subcerebellar peduncle A thick fiber bundle dorsolateral to the spinal tract of the trigeminal nerve.
(iv) Section of the superior part of the flat olive
Identify the following major structures (Fig. 8):
2. The vestibular nucleus is immediately below the floor of the fourth ventricle and lies dorsal to the medial aspect of the inferior cerebellar peduncle.
3. The nucleus of the pallidum is located anteriorly and posteriorly to the lateral aspect of the inferior cerebellar peduncle.
4. the vestibulocochlear nerve is located in the lateral aspect of the inferior cerebellar peduncle and is connected to the nucleus of the cochlear nerve and the nucleus of the vestibulocochlear nerve.
5. nucleus of suspicion Located in the reticular formation.
Internal structure of the pons
(i) Section of the lower part of the pontine pons
In the transverse section of the lower part of the pontine bridge (through the spreading and facial nerve roots) (Fig. 9), the pontine bridge can be divided into the dorsal part of the perineurium and the ventral part of the basal part of the pontine bridge. The two divisions are bounded by a transverse syrinx, which is crossed by a longitudinal medial thalamic tract in the transverse fibers of the syrinx.
1. The dorsal part of the pons is the floor of the fourth ventricle.
(2) The nucleus of the facial nerve is located in the reticular formation ventral to the nucleus of the spreading nerve. The facial nerve root encircles the nucleus of the spreading nerve and then emanates from the ventral part of the cerebral bridge.
(3) Medial longitudinal fasciculus On the ventral surface of the central gray matter on either side of the median suture of the pallidum.
(4) Oblique and medial thalamic tracts Located between the perineurium and the basal part.
(5) Lateral mound system The fibers of the rhomboid fold upward across the midline, which is the lateral mound system.
(2) Base
(1) Conus tract and corticobulbar tract Both are longitudinal bundles of fibers within the basal part of the brain.
(2) Transverse pontine fibers are fibers that run transversely within the basement.
(3) Nucleus accumbens is a mass of gray matter between the longitudinal and transverse fibers.
(4) Middle cerebellar peduncle The transverse fibers cross to the dorsal side of the opposite side and converge to form the middle cerebellar peduncle.
(ii) Section of the middle part of the pontine pons
In the section of the middle part of the pontine bridge (through the trigeminal nerve root), in addition to the above structures, the following structures can be observed (Fig. 10) 
2. trigeminal motor nucleus Located medial to the former.
3. trigeminal root Located at the junction of the basal base and the middle cerebellar peduncle.
4. supracerebellar peduncle Located on either side above the fourth ventricle and consists of bundles of fibers from the cerebellum to the midbrain.
III. Internal structure of the midbrain
(i) Section of the flat inferior colliculus
Identify the following major structures (Fig. 11):
1. Midbrain aqueduct The fourth ventricle to the midbrain narrows into the midbrain aqueduct, which is surrounded by a very thick periaqueductal gray matter, with the central gray matter dorsal to the parietal and ventral to the cerebral peduncle.
2. hypothalamus A pair of small elevations on the dorsal side.
4. buccal nucleus Located ventral to the central gray matter near the midline.
5. synovial nerve root On some sections, synovial nerve fibers are seen to travel dorsally around the central gray matter. Below the inferior colliculus, the left and right roots cross and exit the brain after crossing.
6. medial longitudinal fasciculus Nested with the nucleus of the synovial nerve.
7. superior cerebellar peduncle crossing Ventral to the medial longitudinal fasciculus.
8. cerebral peduncle Located ventral to the section and divided into two parts, the dorsal part being the pallium and the ventral part being the human cerebral peduncle bounded by the substantia nigra.
9. substantia nigra A semilunar-shaped neuronal nucleus containing melanin.
10. cerebral peduncle The foot of the brain consists of longitudinal bundles of fibers descending from the cortex, and from the outside inward are the parieto-occipital facial pontine tracts, the pyramidal tracts, and the frontal pontine tracts.
11. medial thalamic system Located dorsal to the substantia nigra.
(ii) Section of the level superior colliculus
Identify the following major structures (Fig. 12):
1. superior colliculus A pair of small elevations on the dorsal side. The cells within the superior colliculus are arranged in layers and are the gray matter layer of the superior colliculus.
2. the nucleus of the actinic nucleus and the paranucleus of the actinic nucleus are located in the ventral part of the central gray matter.
3. oculomotor nerve roots are fibers emanating from the nucleus and paranucleus of the oculomotor nerve, which course ventrally and exit the brain through the pedunculopontine fossa.
4. red nuclei are a pair of rounded nuclei located in the perisylvian fossa.
5. the ventral cross of the pallidum is located on the ventral side of the pallidum and consists of fibers from the spinal cord bundle of the red nucleus crossing over the pallidum.
7. medial thalamic system Located lateral to the red nucleus and dorsal to the substantia nigra.
9. The substantia nigra and cerebral peduncle are identical to the inferior colliculus plane.