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=Part I. The Essentials of Uterine Gestation=
==Chapter VI. The Trophoblast of the Human Ovum==
===The Early Development of the Ectodermal Extra-Embryonal Area===
Trophoblast. — The outer layer of the ovum consists of trophoblast. It is a product of the ectoderm and from it develop the future syncytium and, according to most authors, the cells of Langhans. The "trophoblast," according to Hubrecht, "is the epiblast of the blastocyst, as far as it has a direct nutritive significance as indicated by proliferating processes, by immediate contact with maternal tissues, maternal blood, or secreted material." It consists of small and large cells of various forms. Shortly after the ovum descends into the mucosa a connection between the trophoblast and the maternal blood takes place. As all the capillaries near the trophoblast consist of endothelium and evidence many blood sinuses, the trophoblast is infiltrated with blood lacunas which are separated from each other by these trophoblast cell groups. As a result of the growth of these cells, of congestion and of pressure, the blood takes its exit from the capillaries and bathes the cells. The lacunas, then, represent a united system fed by peripheral capillaries and are separated externally from the decidua by a thin layer of ectodermal trophoblast cells, but the trophoblast at various points may extend much further into the compacta.
Fig. 20. — Low-power drawing of the trophoblast, enveloping zone, etc., of an ovum three days old. in transverse section. (Peters.) Sy., syncytium; F.P., plug of fibrin at the summit of the capsularis ; Bl.L., blood lacunae; Tr., trophoblast ; M., mesoderm ; Cap., capillaries ; CI., glands ; E.Z., enveloping zone ; E.F., embryo formation ; Comp., compacta ; U.E., uterine epithelium ; GL, gland.
The ectoblast cells are of varying form: 1. Cubical, with large, strongly stained round or oval nucleus containing granules and nucleolus. 2. These become changed. The nucleus becomes pale and swollen. Vacuoles appear in the cells and strongly stained fragments of the nucleus are evident. The cells are irregular in form. 3. The nuclei are larger, especially in the external layers, and more swollen. The chromatin network is irregular and dark lumps appear in the nucleus. The nuclei are of various forms, oval, spindle-shaped, and contain vacuoles. 4. Swollen groups of nuclei in degeneration are found. These nuclei contain one or more nucleoli. 5. The protoplasm of these cells unites, forming protoplasmic masses in the shape of bands or irregular groups with extensions.
Fig. 21. — Section through the central portion of the trophoblast layer. The trophoblast {Tr.) is covered with syncytium {Sy.) at all points in contact ivith the blood lacunae (Bl.L.). Ekt., ectoderm. (Peters.)
From the simple cubical cells of the central layer of the trophoblast we find, in going toward the periphery, gradual changes from 1 to 5. The trophoblast cells grow through direct cell division. These changes represent the results of the corrosive action of the Mood on these cells, whereby the future syncytium is formed. The syncytium then lines the lacunas (Fig. 22) . The endothelium of the lacunae and of the capillaries degenerates wherever it is not lined by syncytium. The syncytium is found also under the endothelium of the most peripheral trophoblast masses, and proves that the endothelium plays no part in tlie formation of the syncytium.
Fig. 22. — A capillary (Cap.) in the serotinal portion of the trophoblast infiltrated with blood lacunae (Bl.L.). The peripheral wall of the capillary is preserved and forms the serotinal wall of the intervillous space at this point. The capillary at many points communicates with the lacunas (Bl.L.). In the capillary is a large mass of syncytium (Sy.) containing changed trophoblast nuclei (a) and red blood cells (6). At c changes in the trophoblast nuclei are evident. (Peters.) Tr., trophoblast; EM., ectoderm; M., mesoderm; CO., central cavity of ovum ; p. En., peripheral endothelium.
It is to be noted that the opening of the maternal vessels occurs at this early stage, before villi are formed. The endothelium of the capillaries degenerates and the blood makes its exit from the capillaries. It ought to coagulate, but does not. It circulates against the fetal cells, which have the power to prevent coagulation, and yet the blood exerts a deleterious influence on these cells. Thus the resulting syncytium lines the lacunae, prevents coagulation in this primary intervillous space and later about the villi, separating the blood at all times from the cells of the chorionic centre. Free syncytial cells are present, even in the vessels of the periphery in the compacta. At later periods they are found free in the veins and arteries. It is thus seen that the cells of the trophoblast of the ovum enter the veins at an early period.
The Primary Intervillous Space is intravascular and is bounded by maternal and fetal structures. That the developed intervillous space contains free blood has been granted by Virchow, Kolliker, Langhans, Waldeyer, etc. The drawings of Peters indicate a slowing and probable stagnation of the blood current. The maternal endothelium on the side toward the compacta is at first intact and forms the serotinal wall of the space (Fig. 22). In it are found isolated cells and groups of trophoblast. Trophoblast cells are also present on the serotinal wall, so that this wall consists of trophoblast, maternal endothelium, and decidual tissue. Later the endothelium of the serotinal side is found only in the areas corresponding to the openings of the maternal vessels. Where the trophoblast cells extend into the enveloping zone in the form of bands, uniting with each other in a network, it is often difficult to distinguish between maternal and fetal cells. Merttens says the same. Thus the earliest ectoderm cells enter actively into the maternal tissues.
Fig. 23. — Change of trophoblast to syncytium (Sij.) The syncytially changed trophoblast is infiltrated with numerous vacuoles (vac), c, red blood cells of the capillary in which this syncytial mass was floating attached by a pedicle (p). (Peters.)
The primary intervillous space is formed through the gradual consumption of the trophoblast. Through its growth more and more layers of the compacta are included in the enveloping zone, until the corrosive action of the blood has furnished the villous mantle of the ovum. 1. The trophoblast is reduced to a single layer. 2. The union of the lacunas at first separated by large trophoblast cell masses takes place. The origin and growth of the intervillous space thus goes hand in hand with the various steps leading to the formation of villi. In the ovum of Peters no villi are yet present. The inner surface of the trophoblast shows irregular, finger-like depressions into which mesoderm is beginning to enter. The lacunas have enlarged and the cell masses between them have become smaller. Through the entrance of the growing mesoderm into these divided cell masses, which are finally reduced by the blood to the syncytial layer, villi are formed and the primary intervillous space becomes larger. The primary enveloping zone becomes the subsequent intervillous space.
Fig. 24. — Schematic representation of the earliest stage of the development of the placenta. (Peters.) M., mesoderm; Tr., trophoblast; Bl.L., blood lacunae; Sy., syncytium ; En., endothelium ; Cap., capillary ; E.Z., enveloping zone ; Sp., spongiosa.
The maternal endothelium breaks down and is found floating in the lacunas. It is never seen in a proliferating stage. Syncytium is found under it. It is impossible for the endothelium to fill out all the spaces of the trophoblast, and, if it did do so, we ought to see it somewhere in the process of growth. On the contrary, it is always seen to degenerate. Therefore the syncytium does not originate from maternal endothelium.
The syncytium is found over the surface of the ovum, in the trophoblast, in the lacunae, toward the enveloping zone, and also in the periphery of the ectodermal trophoblast. At the summit of the ovum syncytium is also present. In numerous points the direct transition from trophoblast cells to syncytium is distinctly seen. Therefore it does not originate from the uterine epithelium.
The glands in the decidua about the ovum become filled with blood. They are pushed aside by the growing ovum and are broken into by the trophoblast and syncytium. Their epithelium degenerates and disappears. The uterine epithelium plays no part in the formation of the syncytium.
The syncytium consists of a shining, granular protoplasm containing numerous nuclei. The nuclei are round, oval, or flattened. There are also vacuoles in the protoplasm, which make the latter appear like septa in which are flat and half-moonshaped nuclei (Fig. 23).
Van Siegenbeck finds syncytial giant cells especially near the union between maternal and fetal tissues, in and about the lacuna?, between the ectoblast and the compacta, covering the free compacta, about the maternal capillaries, and even more externally in the vessels. He finds a gradual transition from trophoblast to syncytium. In one place he observed a syncytial giant cell between the mesoblast, and the ectoblast of the fetal sac, which he considers as a proof of the ability of these cells to wander into surrounding tissues.
The processes, so far, are well represented in the schematic drawing, Fig. 24.
Merttens found in the particles obtained by curetting sixteen days after the last menstruation a few sections of an ovum with the enveloping decidua. He describes (1) the chorion and the villi ; on the latter are cell groups, and between them are found spaces constituting the intervillous space; (2) the spongiosa, containing numerous glands, and (3) the compacta, a pale zone lying between 1 and 2, and containing large pale cells between which are numerous darkly-stained nuclei.
In the compacta he finds large cells and large spaces. Between the large cells syncytial masses are irregularly distributed. The cell spaces are round, long, or irregular, and often empty into the intervillous space. They contain blood and are all lined with syncytial masses, which at some points are very thin, and at other points quite thick. Where these spaces empty into the intervillous space the syncytial masses continue into the syncytium of the villi. Merttens does not know whether these spaces are glands, vessels, or lymph spaces. They are possibly, however, the lacunae ~of Hubrecht and Peters.
The epithelia of the glands are like beaker cells, and on their free tips is a half -moon of glycogen. The glands evidence papillary projections (compare Fig. 14ft). Merttens believes that the syncytium results through a change of the surface and gland epithelium ( ?). In his Fig. 8 Merttens represents, in the upper portion, the epithelium of such a gland, and the lower half represents syncytial masses. He believes that the latter results from these epithelial cells, which lose their cylindrical form and unite. From his description and his drawings it is neither clear nor probable that the epithelium goes over into these syncytial masses. Besides, this area is taken from decidua particles not connected with the ovum, and at no point can he find the epithelium of the glands contributing in any way to the syncytium of the chorion.
On the contrary, this ovum is at the stage where the trophoblast is almost consumed by the growth of the intervillous space, and the cell groups at the end of the villi, which Merttens calls points of union between the villi and the decidua, are really the remains of the trophoblast (Fig. 31).




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Bandler SW. Uterine and tubal gestation. (1903) William Wood & Company, New York.

Uterine and Tubal Gestation (1903): Part I. The Essentials of Uterine Gestation I. The Processes Antedating Uterine Gestation | II. The Embedding of the Ovum in the Guinea-Pig | III. The Embedding of the Human Ovum | IV. The Early Development of the Human Ovum | V. The Trophoblast in the Ova of Animals | VI. The Trophoblast of the Human Ovum | VII. The Further Development of the Human Ovum | VIII. The Chorionic Villi | IX. The Membrana Chorii | X. The Blood-Forming Function of the Trophoblast | XI. The Further Development of the Uterine Placenta | XII. The Placenta | XIII. The Umbilical Vessels and Cord | XIV. Gross Anatomy of the Placenta Part II. The Essentials of Tubal Gestation I. Processes Antedating Gestation in the Tube | II. Varying Views Concerning the Histology of Tubal Gestation | III. Embedding of the Ovum and the Development of Extra-Embryonal structures | Part III. Ovarian and Placental Secretion
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This early historic 1903 textbook by Samuel Wyllis Bandler (1869-1932) described the understanding of human normal and abnormal implantation at that time. Some of these historic theories described in this textbook have now proved inaccurate or incorrect. Note that all early human developmental stages were still described as the "ovum", today this would be described as the zygote, morula, and blastocyst stages with implantation occurring in week 2.


PDF | Internet Archive

Also by this author: The Endocrines (1921)

Modern Notes: implantation | placenta | ectopic pregnancy | Week 2 | blastocyst

Search PubMed: embryo implantation

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Part I. The Essentials of Uterine Gestation

Chapter VI. The Trophoblast of the Human Ovum

The Early Development of the Ectodermal Extra-Embryonal Area

Trophoblast. — The outer layer of the ovum consists of trophoblast. It is a product of the ectoderm and from it develop the future syncytium and, according to most authors, the cells of Langhans. The "trophoblast," according to Hubrecht, "is the epiblast of the blastocyst, as far as it has a direct nutritive significance as indicated by proliferating processes, by immediate contact with maternal tissues, maternal blood, or secreted material." It consists of small and large cells of various forms. Shortly after the ovum descends into the mucosa a connection between the trophoblast and the maternal blood takes place. As all the capillaries near the trophoblast consist of endothelium and evidence many blood sinuses, the trophoblast is infiltrated with blood lacunas which are separated from each other by these trophoblast cell groups. As a result of the growth of these cells, of congestion and of pressure, the blood takes its exit from the capillaries and bathes the cells. The lacunas, then, represent a united system fed by peripheral capillaries and are separated externally from the decidua by a thin layer of ectodermal trophoblast cells, but the trophoblast at various points may extend much further into the compacta.




Fig. 20. — Low-power drawing of the trophoblast, enveloping zone, etc., of an ovum three days old. in transverse section. (Peters.) Sy., syncytium; F.P., plug of fibrin at the summit of the capsularis ; Bl.L., blood lacunae; Tr., trophoblast ; M., mesoderm ; Cap., capillaries ; CI., glands ; E.Z., enveloping zone ; E.F., embryo formation ; Comp., compacta ; U.E., uterine epithelium ; GL, gland.


The ectoblast cells are of varying form: 1. Cubical, with large, strongly stained round or oval nucleus containing granules and nucleolus. 2. These become changed. The nucleus becomes pale and swollen. Vacuoles appear in the cells and strongly stained fragments of the nucleus are evident. The cells are irregular in form. 3. The nuclei are larger, especially in the external layers, and more swollen. The chromatin network is irregular and dark lumps appear in the nucleus. The nuclei are of various forms, oval, spindle-shaped, and contain vacuoles. 4. Swollen groups of nuclei in degeneration are found. These nuclei contain one or more nucleoli. 5. The protoplasm of these cells unites, forming protoplasmic masses in the shape of bands or irregular groups with extensions.


Fig. 21. — Section through the central portion of the trophoblast layer. The trophoblast {Tr.) is covered with syncytium {Sy.) at all points in contact ivith the blood lacunae (Bl.L.). Ekt., ectoderm. (Peters.)



From the simple cubical cells of the central layer of the trophoblast we find, in going toward the periphery, gradual changes from 1 to 5. The trophoblast cells grow through direct cell division. These changes represent the results of the corrosive action of the Mood on these cells, whereby the future syncytium is formed. The syncytium then lines the lacunas (Fig. 22) . The endothelium of the lacunae and of the capillaries degenerates wherever it is not lined by syncytium. The syncytium is found also under the endothelium of the most peripheral trophoblast masses, and proves that the endothelium plays no part in tlie formation of the syncytium.



Fig. 22. — A capillary (Cap.) in the serotinal portion of the trophoblast infiltrated with blood lacunae (Bl.L.). The peripheral wall of the capillary is preserved and forms the serotinal wall of the intervillous space at this point. The capillary at many points communicates with the lacunas (Bl.L.). In the capillary is a large mass of syncytium (Sy.) containing changed trophoblast nuclei (a) and red blood cells (6). At c changes in the trophoblast nuclei are evident. (Peters.) Tr., trophoblast; EM., ectoderm; M., mesoderm; CO., central cavity of ovum ; p. En., peripheral endothelium.



It is to be noted that the opening of the maternal vessels occurs at this early stage, before villi are formed. The endothelium of the capillaries degenerates and the blood makes its exit from the capillaries. It ought to coagulate, but does not. It circulates against the fetal cells, which have the power to prevent coagulation, and yet the blood exerts a deleterious influence on these cells. Thus the resulting syncytium lines the lacunae, prevents coagulation in this primary intervillous space and later about the villi, separating the blood at all times from the cells of the chorionic centre. Free syncytial cells are present, even in the vessels of the periphery in the compacta. At later periods they are found free in the veins and arteries. It is thus seen that the cells of the trophoblast of the ovum enter the veins at an early period.

The Primary Intervillous Space is intravascular and is bounded by maternal and fetal structures. That the developed intervillous space contains free blood has been granted by Virchow, Kolliker, Langhans, Waldeyer, etc. The drawings of Peters indicate a slowing and probable stagnation of the blood current. The maternal endothelium on the side toward the compacta is at first intact and forms the serotinal wall of the space (Fig. 22). In it are found isolated cells and groups of trophoblast. Trophoblast cells are also present on the serotinal wall, so that this wall consists of trophoblast, maternal endothelium, and decidual tissue. Later the endothelium of the serotinal side is found only in the areas corresponding to the openings of the maternal vessels. Where the trophoblast cells extend into the enveloping zone in the form of bands, uniting with each other in a network, it is often difficult to distinguish between maternal and fetal cells. Merttens says the same. Thus the earliest ectoderm cells enter actively into the maternal tissues.



Fig. 23. — Change of trophoblast to syncytium (Sij.) The syncytially changed trophoblast is infiltrated with numerous vacuoles (vac), c, red blood cells of the capillary in which this syncytial mass was floating attached by a pedicle (p). (Peters.)


The primary intervillous space is formed through the gradual consumption of the trophoblast. Through its growth more and more layers of the compacta are included in the enveloping zone, until the corrosive action of the blood has furnished the villous mantle of the ovum. 1. The trophoblast is reduced to a single layer. 2. The union of the lacunas at first separated by large trophoblast cell masses takes place. The origin and growth of the intervillous space thus goes hand in hand with the various steps leading to the formation of villi. In the ovum of Peters no villi are yet present. The inner surface of the trophoblast shows irregular, finger-like depressions into which mesoderm is beginning to enter. The lacunas have enlarged and the cell masses between them have become smaller. Through the entrance of the growing mesoderm into these divided cell masses, which are finally reduced by the blood to the syncytial layer, villi are formed and the primary intervillous space becomes larger. The primary enveloping zone becomes the subsequent intervillous space.


Fig. 24. — Schematic representation of the earliest stage of the development of the placenta. (Peters.) M., mesoderm; Tr., trophoblast; Bl.L., blood lacunae; Sy., syncytium ; En., endothelium ; Cap., capillary ; E.Z., enveloping zone ; Sp., spongiosa.


The maternal endothelium breaks down and is found floating in the lacunas. It is never seen in a proliferating stage. Syncytium is found under it. It is impossible for the endothelium to fill out all the spaces of the trophoblast, and, if it did do so, we ought to see it somewhere in the process of growth. On the contrary, it is always seen to degenerate. Therefore the syncytium does not originate from maternal endothelium.


The syncytium is found over the surface of the ovum, in the trophoblast, in the lacunae, toward the enveloping zone, and also in the periphery of the ectodermal trophoblast. At the summit of the ovum syncytium is also present. In numerous points the direct transition from trophoblast cells to syncytium is distinctly seen. Therefore it does not originate from the uterine epithelium.

The glands in the decidua about the ovum become filled with blood. They are pushed aside by the growing ovum and are broken into by the trophoblast and syncytium. Their epithelium degenerates and disappears. The uterine epithelium plays no part in the formation of the syncytium.

The syncytium consists of a shining, granular protoplasm containing numerous nuclei. The nuclei are round, oval, or flattened. There are also vacuoles in the protoplasm, which make the latter appear like septa in which are flat and half-moonshaped nuclei (Fig. 23).

Van Siegenbeck finds syncytial giant cells especially near the union between maternal and fetal tissues, in and about the lacuna?, between the ectoblast and the compacta, covering the free compacta, about the maternal capillaries, and even more externally in the vessels. He finds a gradual transition from trophoblast to syncytium. In one place he observed a syncytial giant cell between the mesoblast, and the ectoblast of the fetal sac, which he considers as a proof of the ability of these cells to wander into surrounding tissues.

The processes, so far, are well represented in the schematic drawing, Fig. 24.

Merttens found in the particles obtained by curetting sixteen days after the last menstruation a few sections of an ovum with the enveloping decidua. He describes (1) the chorion and the villi ; on the latter are cell groups, and between them are found spaces constituting the intervillous space; (2) the spongiosa, containing numerous glands, and (3) the compacta, a pale zone lying between 1 and 2, and containing large pale cells between which are numerous darkly-stained nuclei.

In the compacta he finds large cells and large spaces. Between the large cells syncytial masses are irregularly distributed. The cell spaces are round, long, or irregular, and often empty into the intervillous space. They contain blood and are all lined with syncytial masses, which at some points are very thin, and at other points quite thick. Where these spaces empty into the intervillous space the syncytial masses continue into the syncytium of the villi. Merttens does not know whether these spaces are glands, vessels, or lymph spaces. They are possibly, however, the lacunae ~of Hubrecht and Peters.

The epithelia of the glands are like beaker cells, and on their free tips is a half -moon of glycogen. The glands evidence papillary projections (compare Fig. 14ft). Merttens believes that the syncytium results through a change of the surface and gland epithelium ( ?). In his Fig. 8 Merttens represents, in the upper portion, the epithelium of such a gland, and the lower half represents syncytial masses. He believes that the latter results from these epithelial cells, which lose their cylindrical form and unite. From his description and his drawings it is neither clear nor probable that the epithelium goes over into these syncytial masses. Besides, this area is taken from decidua particles not connected with the ovum, and at no point can he find the epithelium of the glands contributing in any way to the syncytium of the chorion.

On the contrary, this ovum is at the stage where the trophoblast is almost consumed by the growth of the intervillous space, and the cell groups at the end of the villi, which Merttens calls points of union between the villi and the decidua, are really the remains of the trophoblast (Fig. 31).




Historic Disclaimer - information about historic embryology pages 
Mark Hill.jpg
Pages where the terms "Historic" (textbooks, papers, people, recommendations) appear on this site, and sections within pages where this disclaimer appears, indicate that the content and scientific understanding are specific to the time of publication. This means that while some scientific descriptions are still accurate, the terminology and interpretation of the developmental mechanisms reflect the understanding at the time of original publication and those of the preceding periods, these terms, interpretations and recommendations may not reflect our current scientific understanding.     (More? Embryology History | Historic Embryology Papers)
Uterine and Tubal Gestation (1903): Part I. The Essentials of Uterine Gestation I. The Processes Antedating Uterine Gestation | II. The Embedding of the Ovum in the Guinea-Pig | III. The Embedding of the Human Ovum | IV. The Early Development of the Human Ovum | V. The Trophoblast in the Ova of Animals | VI. The Trophoblast of the Human Ovum | VII. The Further Development of the Human Ovum | VIII. The Chorionic Villi | IX. The Membrana Chorii | X. The Blood-Forming Function of the Trophoblast | XI. The Further Development of the Uterine Placenta | XII. The Placenta | XIII. The Umbilical Vessels and Cord | XIV. Gross Anatomy of the Placenta Part II. The Essentials of Tubal Gestation I. Processes Antedating Gestation in the Tube | II. Varying Views Concerning the Histology of Tubal Gestation | III. Embedding of the Ovum and the Development of Extra-Embryonal structures | Part III. Ovarian and Placental Secretion


Reference: Bandler SW. Uterine and tubal gestation. (1903) William Wood & Company, New York.


Cite this page: Hill, M.A. (2024, March 29) Embryology Book - Uterine and tubal gestation (1903) 1-6. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Book_-_Uterine_and_tubal_gestation_(1903)_1-6

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