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SOME MORPHOLOGICAL PECULIARITIES OF VERTEBRAL COLUMN IN EMBRYOLOGICAL AND EARLY PREFETAL PERIOD OF HUMAN ONTOGENESIS
Marchuk O.
Department of Traumatology and Orthopedics of Bukovinian State Medical University, Chernivtsi, Ukraine, PhD, assistant
Marchuk Yu.
Department of Clinical Immunology, Allergology and Endocrinology of Bukovinian State Medical University, Chernivtsi, Ukraine, PhD, Associate Professor
Andriychuk D.
Department of Pediatrics and Medical Genetics of Bukovinian State Medical University, Chernivtsi, Ukraine, PhD, Associate Professor
ABSTRACT
Background: Knowledge of the development of the vertebral column is a morphological basis to determine abnormalities in the formation and development of the axial skeleton and represents a timely opportunity to correct them. In recent years, considerable attention is paid to the study of combine pathology of vertebral column with some somatic conditions.
Material and methods: The study was carried out on 16 series of histological sections of the specimens of human embryos and prefetuses measuring from 5.0 - 40.0 mm of parietococcygeal length (PCL), by means of the methods of microscopy and morphometry.
Results: Anlage of the vertebral bodies and the intervertebral discs are determined in embryos of length 5.0 mm. In the embryos of 7-8 mm, traced out to be more clear boundaries between the anlages of the vertebral bodies and intervertebral discs. In the subsequent development, there is some differentiation in the development of the cervical, thoracic, lumbar and sacral vertebrae. In early prefetal period, the number of vertebrae and intervertebral discs corresponds to the definitive age.
Conclusions: 1. In the embryonic period in the places of anlage of the vertebral bodies and intervertebral discs occurs pronounced condensation of mesenchymal cells, which is represented by a homogeneous mass, and anlage of intervertebral discs become more intensive condensation. 2. At the beginning of prefetal period marked of contrast morphometric thickness, width and shape of the vertebral bodies and intervertebral disks in different parts of the vertebral column, and begins the formation of vertebral arch.
Keywords: embryo, prefetus, vertebra, human.
Topicality. Knowledge of the peculiarities the spinal column development is a morphological basis for identifying the deviations in the formation of the axial skeleton. It also provides the possibility of their timely correction [1, p. 17; 2. p. 127]. In recent years, considerable attention has been paid to the study of the combined pathology of the spinal column with some somatic diseases [3, p. 515]. The paper presents some interesting data on the relationship between morphogenesis of the cervical spine and morphogenesis of the bones of the facial skull [4, p. 448; 5, p. 428; 6, p. 399].
Material and methods. The research has been carried out on 16 embryos and pre-fetuses of 5.0 - 40.0
mm parietococcygeal length (PCL), by microscopy and morphometry. Material for histological examination was prepared in the following way: fresh preparations of human embryos and pre-fetuses have been fixed in a 6-8% solution of neutral formalin for 2 weeks. After fixation, the object was washed in running water for 12 days, and then immersed into 35% ethyl alcohol for a day, after which it was totally stained with hematoxylin and eosin for 1-3 days (depending on the size of the object). Dehydration of the preparations was carried out by processing them in ethyl alcohol of increasing concentration (from 30% to absolute), and then the prepa-
rations were embedded in paraffin. A series of histolog-ical sections were made from paraffin blocks in one of the three planes of the body of the embryo and prefetus - sagittal, frontal, and horizontal.
Results and discussion. In embryos of 5.0 - 6.0 mm, the PCL of the anlages of the vertebral bodies is represented by a homogeneous mass of mesenchymal cells, the nuclei of which are predominantly spherical. The buds of the intervertebral discs are also formed by mesenchymal cells, which are located more compactly.
The height of the anlages of the vertebral bodies ranges from 15.0 to 17.0 ^m, the width varies from 21.0 to 22.0 ^m. The height of the intervertebral discs is 11.012.0 microns, the width is in the range of 20.0-24.0 microns. It is important that in the center of the intervertebral discs of the cervical and sacral parts of the spinal column, insignificant loosened areas (cavities) surrounded by a dense layer of mesenchymal cells are distinctly seen (Fig. 1).
Figure 1. Sagittal section of the embryo 6.0 mm PCL. Stained with hematoxylin and eosin. Microprep. Ob. 8, ok 7: 1- anlages of the vertebral bodies; 2 - anlages of intervertebral discs; 3 - loosened areas within the intervertebral discs
The anlages of the vertebral bodies in embryos of 7.0-8.0 mm PCL are segmental in nature, their number reaches 28, the mesenchyme is presented in the form of isolated islands of different size and shape. Between the anlages of the vertebral bodies, thin plates of a denser mesenchyme are traced, which, in the further development of the embryo, are transformed into intervertebral discs.
Behind the anlages of the vertebral bodies is a spinal canal filled with an anlage of the spinal cord. The height of the anlages of the vertebral bodies in the studied embryos is 16.0-17.0 ^m, the width is 24.0-26.0 ^m, while the thickness of the intervertebral plate is 7.0-8.0 ^m. The diameter of the spinal canal in the thoracic region is 18.0-20.0 microns, and in the lumbar one - 26.0-28.0 microns. Externally, along the anlage of the entire spine, there is a dense layer of mesenchymal cells, the thickness of which is not the same both in front and behind: in front it is much thinner and is 10.012.0 microns, whereas in the back - 30.0-34.0 microns.
In embryos 12.0-13.0 mm of PCL, the anlages of most of the vertebral bodies acquire an oval shape, only in the cervical spine they are of an approximate spherical shape. A difference in the height of the anlages of spherical and oval bodies was also found. Thus, the height of the filling of spherical bodies is 40.0-41.0 ^m, and the height of the oval-shaped filling reaches 34.035.0 ^m. There is also a difference in the thickness of
the intervertebral disc inlays: for example, the thickness of the outer part of the inlays is 16.0-18.0 microns, and the thickness of the inner part (central) is 10.0-12.0 microns. It was traced that the anlages of the bodies of the lower sacral and coccygeal vertebrae have a spherical shape, and the thickness of the tabs of the intervertebral discs prevails the thickness of the tabs of the vertebral bodies and is 22.0-24.0 microns, and the thickness of the anlages of the vertebral bodies is 16.0-18.0 microns (Fig. 2).
In pre-fetuses 15.0-17.0 ^m TCD, the height of the vertebral bodies reaches 50.0-55.0 ^m, the thickness of the intervertebral discs is 10.0-14.0 ^m, and in the central part of the disc, its thickness is less and is only 5.06.0 microns. In the central part of the discs of the adjacent vertebral bodies, mainly in the thoracic and lumbar regions, there are small cavities filled with the remnants of the dorsal chord. Ribs are connected to the bodies of the thoracic vertebrae. In the place of their junction, a rarefaction of the mesenchyme is traced, but the articular cavity is not yet determined. The vertebral bodies are represented by a homogeneous mass of mesenchy-mal cells, the nuclei of which are predominantly round in shape. It is essential that in the intervertebral foramina, there are spinal nodes with sizes of 20.0-30.0 microns. They are much larger in the cervical and lumbar areas.
Figure 2. Sagittal section of the embryo 13.0 mm PCL. Stained with hematoxylin and eosin. Microprep. Ob. 8, ok 7: 1- anlages of the vertebral bodies; 2 - anlages of intervertebral discs; 3 - anlage of the esophagus; 4 - anlage of the liver; 5 - anlage of the mesonephros
In prefetus 19.0-20.0 ^m, the PCL of the vertebral body of the thoracic and lumbar areas is of an approximate rectangular shape. Their height is 25.0-27.0 microns, width is 900.0-950.0 microns. Intervertebral discs are represented by a clear plate of mesenchymal cells with a thickness of 20.0-22.0 microns in the central part, and 24.0-26.0 microns in the peripheral part. The spinal nodes are predominantly oval in shape, formed throughout the spinal cord (Fig. 3).
The bodies of the cervical vertebrae are oval in shape, their thickness reaches 60.0-62.0 microns, width
- 100.0-106.0 microns. At the junction with the transverse process, there is a slight narrowing, the transverse opening of the process is spherical, displaced in the ventral direction. The vertebral artery is defined within the holes. The arches of the vertebrae are formed, at the place of their connection with the vertebral body a thin dense layer of the mesenchyme is determined. The deep muscles of the neck are tightly attached to the anterior surface of the vertebrae. The spinal cord is located in the spinal canal, in which both gray and white matter can be traced, as well as the central canal.
Figure 3. Frontal cut of the pre-fetus 20.0 mm PCL. Stained with hematoxylin and eosin. Microprep. Ob. 8, ok 7: 1- vertebral bodies; 2 - intervertebral discs; 3 - ribs; 4 - cavity within the thoracic vertebrae; 5 - spinal nodes
The nerve processes (future plates of the vertebrae) are short, barely bifurcated; there are also transverse processes. The nerve processes are connected by densely spaced collagen fibers, the innermost of which form a kind of thin membrane. It is interesting that there exists some difference in the intensity of growth of the nerve processes of the thoracic vertebrae. The identity in many respects of the development of the lumbar vertebrae compared with the thoracic vertebrae was traced. However, the transverse process of the lumbar vertebra corresponds to the costal element, and the present transverse process (future additional) is reduced to an insignificant size and is located between the costal and articular processes. The mastoid process at the studied stage of intrauterine development is not determined. The anterior longitudinal ligament is presented in the form of a loose cord of connective tissue.
In pre-fetuses of 30.0-40.0 mm PCL, there are 35 vertebrae, the bodies of which are represented by a homogeneous mass of cells, the nuclei of which are of almost the same size, located chaotically against the
background of transparent protoplasm of cells. The intervertebral discs are more intensely colored. The height of the vertebral bodies in the cervical spine ranges from 100.0 to 120.0 microns, in the thoracic region it is 130.0-140.0 microns, in the lumbar and upper sacral, it reaches 160.0-170.0 microns. The thickness of the central part of the intervertebral discs is 18.0-20.0 microns, and the peripheral part of all discs is thickened and ranges from 26.0-32.0 microns. The spinal nodes are predominantly spherical in shape, observed along the entire spinal cord. The nodes are surrounded by a thin mesenchymal capsule 5.0-6.0 ^m thick (Fig. 4).
In the intervertebral discs of the thoracic vertebrae, an oval cavity with a width of 20.0-22.0 microns is determined. Both the anterior and posterior longitudinal connections are traced along the entire spinal column.
Moreover, the anterior longitudinal ligament is tightly connected both with the vertebral bodies and with the intervertebral discs, and the posterior longitudinal ligament is connected only with the intervertebral discs.
Figure 4. Sagittal section of the pre-fetus 40.0 mm PCL. Stained withhematoxylin and eosin. Microprep. Ob. 8, ok 7: 1- vertebral bodies; 2 - intervertebral discs; 3 - spinal nodes; 4 - spinous processes; 5 - anterior longitudinal
ligament
Conclusions:
1. In the embryonic period, in the places of the an-lages of the vertebral bodies and intervertebral discs, there is a pronounced thickening of the mesenchymal cells, which is represented by a homogeneous mass, and more intensive thickening is observed in the an-lages of the intervertebral discs. The anlages of the vertebral bodies and intervertebral discs are segmental in nature.
2. At the beginning of the pre-fetal period, there is a morphometric difference in the thickness, width and shape of the vertebral bodies and intervertebral discs in different parts of the spinal column, and also in this period of development, the formation of vertebral arches begins.
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