Spinal cord specimens, models, and transverse sections are viewed to understand the gross anatomy and microscopic configuration of the spinal cord.
Observation of brain f specimens and models to understand the external morphology of the brainstem and the location of cerebral nerves entering and exiting the brainstem
Operation method
Observational experiments on the structure of the spinal cord and the shape of the brainstem
Materials and Instruments
Spinal cord specimen Brain stem specimen Move I. Gross anatomy of the spinal cord For more product details, please visit Aladdin Scientific website.
Probe, dissecting disk, microscope.
Observe the following structures in a specimen in which the spinal cord is exposed by sawing through the human spinal canal and in a model of the human spinal cord:
(i) Location of the spinal cord
The spinal cord is located in the vertebral canal and is continuous with the medulla oblongata through the foramen magnum of the occipital bone at the upper end, and at the lower end with the spinal cord cone finally at the lower edge of the first lumbar vertebra.
(ii) Shape of the spinal cord
The spinal cord is a slightly flattened cylindrical shape, with two enlarged parts, the upper one is called cervical enlargement, which is located in the range of the 4th cervical vertebrae to the 2nd thoracic vertebrae; the lower one is called lumbar enlargement, which is gradually enlarged from the 10th thoracic vertebrae, and is thickest in the 12th thoracic vertebrae, and then gradually narrowed down to become the spinal cord cone. From the spinal cord cone a thin filament, called the terminal filament, extends downward, ending at the dorsal surface of the coccyx. The surface of the spinal cord has the following parallel longitudinal grooves:
1. anterior median fissure The deeper fissure in the middle of the front of the spinal cord.
The posterior median sulcus is the shallower sulcus in the middle of the back of the spinal cord.
3. anterolateral sulci A pair of sulci on either side of the front of the spinal cord.
4. posterior lateral sulci A pair of sulci on either side of the posterior aspect of the spinal cord.
5. Posterior median sulcus A shallow sulcus between the cervical and upper thoracic medulla, the posterior lateral sulcus and the posterior median sulcus. These grooves are more easily visualized on transverse sections of the spinal cord. Over the entire length of the anterolateral sulcus a series of root filaments emanate, many of which combine to form the anterior root. There are also a series of root filaments throughout the length of the posterior lateral sulcus, many of which combine to form the posterior root. The anterior and posterior roots of each segment converge at the intervertebral foramen to form the spinal nerve. Before the confluence, there is an expansion of the posterior roots into a spinal ganglion. The spinal cord can be divided into 31 segments, i.e. cervical (1-8), thoracic (1-12), lumbar (1-5), sacral (1-5) and caudal (1-3). However, the segments of the spinal cord are not obvious on the specimen, and only the spinal nerve roots are used as the surface markers of the spinal cord segments, i.e., the segment of the spinal cord connected to the root filaments of each pair of spinal nerves is a segment of the spinal cord.
The upper spinal nerve roots enter and exit the spinal cord more or less at right angles to the sides and immediately enter their corresponding intervertebral foramina. The nerve roots in the middle part of the spinal cord travel gradually and obliquely downward to their corresponding intervertebral foramina. The lower nerve roots are more oblique, and the lumbar, sacral, and caudal spinal nerve roots, which travel almost vertically downward in the putamen before exiting the corresponding intervertebral foramen, gather in bundles around the terminal filaments and are called cauda equina.
(iii) Perineurium of the spinal cord
The spinal cord is surrounded by a connective tissue periosteum, called the spinal membrane, the spinal membrane is divided into from the outside to the inside:
The dura mater is the outermost layer and is thick. The narrow cavity between the dura mater and the periosteum on the inner surface of the spinal canal, called the epidural space, contains blood vessels and fatty tissues, etc., and there are spinal nerve roots through.
2. The arachnoid membrane of the spinal cord is the membrane between the dura mater and the soft spinal membrane. Between it and the soft spinal membrane, there are many small fiber bundles connected to each other, and the space between them, called the subarachnoid space, contains cerebrospinal fluid. At the end of the spinal cord, the subarachnoid space expands into the terminal pool, where there is no spinal cord and only the cauda equina is immersed in cerebrospinal fluid.
3. Soft spinal membrane The innermost layer, close to the surface of the spinal cord.
Internal structure of the spinal cord
A transverse section (Weigert's stain or silver stain) of cat or human spinal cord (cervical or thoracic) is taken for observation.
(i) Naked eye observation
The "H''-shaped area around the central canal of the spinal cord is gray matter, and the peripheral part of the gray matter is white matter.
(ii) Low magnification observation
1. Surface sulcus Observe the anterior median sulcus, posterior median sulcus, anterior and posterior lateral sulcus and posterior median sulcus.
2. The gray matter is located in the center of the spinal cord and is "H" shaped.
(1) Anterior horn The enlarged anterior portion of the gray matter containing the motor neuron population.
(2) Posterior horn The posterior part of the gray matter is narrow. At the tip of the posterior horn, there is an inverted "V" shaped lightly colored structure called the colloid stroma, which consists of small neurons.
(3) Reticulum A structure of interwoven gray and white matter on the outer side between the anterior and posterior horns.
(4) Central canal It is a round hole in the center of the gray matter. The gray matter in front of and behind the central canal is gray matter contiguous .
(5) Intermediate zone The middle zone is the migrating part between the anterior and posterior horns. In the transverse section of the thoracic medulla, you can still see the outwardly protruding lateral horns of the intermediate zone. It contains small and medium-sized nerve cells, which belong to sympathetic preganglionic neurons.
3. White matter surrounds the gray matter and is mainly composed of myelinated fibers. The white matter is divided into three cords by the longitudinal sulcus of the spinal cord: the anterior cord between the anterior median fissure and the anterior lateral sulcus; the posterior cord between the posterior median sulcus and the posterior lateral sulcus; and the lateral cord between the anterior and posterior lateral sulcus. The superior and inferior fibrous bundles (conduction bundles) in the white matter are not easily recognized in sections, and only in transverse sections of the cervical and upper thoracic medulla , the posterior cord is seen to be divided into a medial thin bundle and a lateral wedge bundle by the posterior median sulcus. Anterior to the gray matter connectivity are transverse fibers connecting the white matter on both sides, called the anterior white matter connectivity. Intrinsic bundles are bundles of fibers immediately adjacent to the edge of the gray matter and are found within all three cords of the white matter.