Book - Uterine and tubal gestation (1903) 2-2
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Bandler SW. Uterine and tubal gestation. (1903) William Wood & Company, New York.
|zygote, morula, and blastocyst stages with implantation occurring in week 2.|
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Part II. The Essentials of Tubal Gestation
Chapter II. Varying Views Concerning the Histology of Tubal Gestation
In the uterus the ovum descends by a centrifugal process into a well-developed decidua, which is gradually divided into a superficial compact layer and a deeper spongy glandular layer. Concerning the existence of a tubal decidua, however, opinions differ. Webster's view that a compacta and spongiosa are formed receives no support. Wyder found, in one case, decidua in the periphery of the region occupied by the ovum. Mandl describes decidua cells in the placental area, while Veit found decidua cells not only at the placental site but at a distance from it on the opposite wall. In his eight closely examined cases Prochownik describes decidua cells and in one a well-developed decidua. Abel found a well-marked decidua about an ovum, especially in the region of the placenta. His statement is positive, since he compared it microscopically with the decidua cast out from the uterus.
On the other hand, Aschoff found none at the placental site. Kiihne describes only a pseudo-decidua consisting of fibrin, connective tissue, and invading ectoderm cells. Though slight decidual changes may occur at the placental area, the cells which have been previously described as decidual are considered by him to be the cells of Langhans, and the same vieiv is shared by Aschoff and Ulesko-Stroganoiva. In most cases fibrin masses, blood, villi, and cells which at least look like decidua cells, but which many consider to be trophoblast cells, are to be found. It is a fact, however, that at the area of greatest pressure the socalled decidua is often thinned to a decided extent.
Veit in turn considers the so-called cells of Langhans to be, in the peripheral areas, decidual cells. Though he finds cells of the layer of Langhans in the maternal vessels, yet they are not connected with like cells about the vessels. There is an absence of like cells between the vessels and the serotinal surface. While granting that the resemblance is great, he considers those interstitial cells present in the peripheral areas about the ovum to be decidual, and concludes that the connective tissue in the circumference of the intervillous space in tubal gestation undergoes decidual change, only that this layer is very much thinner than in the uterus.
Embedding of the Ovum, and the Reflexa or Capsularis
A considerable difference of opinion exists as regards the reflexa. Wyder found none in his case and the ovum was only loosely attached. Abel found no capsularis and most of the villi were free and only few were adherent. "Werth described sections of a tube in which the ovum had settled at the height of a tubal fold. Werth described, in another case, a capside containing muscle fibres passing out at the base from the muscular fibres of the tube wall. The external covering of the capsule consisted of epithelium. According to Kreisch, the capside may consist of united folds. He described the presence of a reflexa in three cases, however, which was not composed of tubal folds. In a specimen examined eight days after conception a reflexa was found by him. The formation of a pseudo-reflexa readily takes place if the ovum is embedded in a thick system of folds. Others believe that in many cases a capsule consisting of longitudinal muscle fibres and mucosa, with no epithelium on the inner side, is of frequent occurrence.
Asehoff and Fiith make it evident that the ovum makes its way down into the mucosa, as is the case in the uterus, and that it extends even further deeply into the muscular wall. It is then covered laterally by the inner layers of the muscularis and by the mucosa, which are pushed over it, forming a capsularis and bounding the intervillous space. In several closely examined cases the ovum has been found almost under the entire thickness of the tubal wall, lying directly on the vessels of the ligamentum latum. Muscle fibres are absent, however, at the summit of this resulting capsule. In another case the ovum was nearly extratubal, lying between the muscularis of the tube and the muscle fibres of the ligamentum latum. The ovum was, of course, separated from the lumen by the mucosa and by muscle fibres. At the apex of this capsularis there was considerable thinning, but the epithelium upon the mucosa was intact. Such a development would explain the so-called pseudo-intraligamentous cases of Kiistner. The capsule has been found in some cases to be lined with the cells of Langhans.
If the capsule be composed of folds, according to Kreisch, they may be so firmly united that an intervillous space may exist. In Abel's case the space between the chorion frondosum and the decidua was larger than at any other point; adherent villi extended into the decidua, bnt most of the villi were found free in the space. The vessels of the decidua opened directly into these intervillous spaces, which contained blood. According to Aschoff, the centrifugal descent of the ovum makes the existence of an intervillous space easy. Veit, in a well-preserved non-interrupted case, found a well-developed intervillous space in which Mood circulated, and traced a vein containing villi into this common intervillous space. Ktihne, on the other hand, considers the invasion of the blood vessels by the villi to be pathological, and does not consider the existence of an intervillous space probable, because in eight cases he found no reflexa. Since Von Both collected 84 cases of ectopic gestation with viable fetus, an intervillous space must have been present.
Abel, as stated before, finds a decidua vera in the peripheral areas of the ovum ; the villi, however, he found to extend only up to the muscle. Leopold and others, on the contrary, find the villi extending deeply into the muscular ivall of the tube. The villi are covered with two layers. At their ends are pillarlike groups of cells growing into the wall, between the muscle fibres, and representing extensions of the trophoblast. The cells of Langhans growing into the muscle and uniting with it form the so-called Saugeplatle. It is with this layer that the villi unite through the cell groups found at the ends. These complexes of cells of Langhans and syncytium speak for the fetal nature of the latter, and the pillar-like groups are simply groups of trophoblast not yet reached by the mesoderm.
Abel found most of the villi free and only some adherent to the decidua. As they did not enter into the muscle, the connection was not a close one. Wyder removed an ovulum in its entirety from a tube and later examination showed no villi extending through the decidua to the muscle. Kuhne, Ulesko-Stroganowa, and others find that the cells of Langhans extend actively into the submucous tissue and into the muscle bundles, and believe that these are the cells which are often mistaken for decidual cells. It is upon them, as upon the compacta of the uterus, that the villi grow. At the same time, they may extend entirely up to the serosa of the tube.
As just mentioned, the villi may extend up to the serosa, and perforations of the wall covered by thrombi have been frequently found. Kuhne describes cells which have entered the serotinai veins. In the vessel spaces under the pseudo-decidua he finds free cells whose character proves them to be pseudo-decidual elements. He considers these cells to have entered through the vessel walls. Mandl found decidual cells in the vessels and believes that they have passed out of the surrounding tissue into the lumen. Other cells in the same location he views as proliferated endothelium. Cornil found syncytial elements in the vessels and considers them decidual cells which have entered through the vessel walls. Other investigators hold that the cells of Langhans grow directly into the submucous tissue and into the muscle bundles, and that these cells may penetrate the vessels and open them as in the uterine compacta. They describe the villi as following the course of these cells of Langhans into the muscularis, up to the serosa and through the serosa, which latter perforations are usually covered by thrombi. Aschoff, Ulesko-Stroganowa, Leopold, and others have described villi as perforating the vessel walls.
By Veit a quite different theory is given, however, to explain the presence of fetal cells and villi in the muscular wall of the tube. In discussing the relation of the ovum to the uterus, Heinz considers that the fetal tissues grow into the maternal structures and says that the maternal glands, vessel ivalls, and tissues are eaten up by the villi. Cornil considers that the ovum in an extrauterine gestation not only does the same, but follows a course resembling that of a uterine chorioma. AVhile Veit may grant the correctness of such a view in pathological conditions, he does not believe it justifiable to consider it the usual course.
In the case of a normal uterine gestation, villi do not project into the arterial openings of the intervillous space. They do, however, project normally, not only in the border sinuses but at all the serotinal points, into the veins alone. The villi are of normal structure and often so numerous that they occlude the vein lumina. They are frequently very long and follow the course of the veins to a considerable distance. In the uterus, villi are thus found in direct contact with the uterine muscle, or, better, in the veins of the uterine muscle. The same is true in tubal gestation. Whether this occurs in all cases or not cannot be positively stated (Veit).
Veit believes that cells in the periphery of the ovum enter at an early period into the peripheral veins. In normal gestation the uterus grows as much as the ovum needs, and the ovum as much as the uterus permits. Later, as soon as the ovum in the uterus has attained a certain size and the edge of the placenta extends laterally, another process is added to that of general growth. This process is brought about by the villi which project into the serotinal veins. If a villus enters a vein it generally remains in contact with the periphery of the ovum and grows further in its length as well as in its circumference. In its growth it dilates the lumen of the vein so decidedly that its serotinal portion is everted and taken up into the general intervillous space. On either side endothelium then extends for a short distance upon the serotinal surface. In the uterus, normally, only cells of the ovum or of the villi are loosened and pass on into the veins, but the villi themselves, as a rule, remain in contact with the ovum. In uterine gestation the entire endometrium becomes deciduous, and, therefore, decidua cells are found in the periphery of these vessels which contain villi. In the peripheral region of the well-preserved tubal sac Veit found free villi in a vein. Series sections showed this vein to enter into the intervillous space. Therefore the villi were no longer connected with the ovum. This occurrence, whereby syncytium and villi, loosened from all connection with the ovum, are found in the veins, is given by Veit the name deportation.
Veit, then, explains the descriptions of Aschoff, Fiith, Cornil, and Ulesko-Stroganowa, who find a destruction of the tube wall and an invasion of vessels by the villi, on the theory of deportation through the veins.
Veit does not believe that the fetal cells possess the power of wandering, because he finds the cells of Langhans in a vessel but no such cells about it. Therefore, in his opinion, the cells have not perforated the vessel because none are present in the connective tissue. Veit, however, forgets that, in addition to deportation, a wandering of cells and a perforation of the vessels does occur.
Veit denies that the cells of the ovum wander into the connective tissue. We know that cell groups go gradually over into the cells of Langhans on the villi, while on the other side they are either separated from the decidua by fibrin, or else the cells pass gradually into the decidua with such a resemblance to the latter cells that it is difficult to differentiate them.
Veit does not believe that the cells of Langhans in the periphery of the tube look different from those which are near the villi. He found at the area of the tubal vera a few changed connective-tissue cells and considers them to be a beginning stage of a decidua vera. In the periphery he saw cells about the vessels differing somewhat in appearance and stain from the cells of Langhans, and, since they are like the above-mentioned vera cells, he considers them decidual. In this connection he overlooks the power of the trophoblast.
Where the cell groups enter the decidua he sees a certain form of cells. At other points where, in series, sections, no villi enter the serotina he finds the same cells. Therefore either the cells of Langhans can wander in all directions or else a decidual change is present, and he believes the latter to be the case and states that a decidua exists, but much less than in the uterus.
In the uterus there takes place a centrifugal descent of the ovum on a spot free of epithelium. The compact layer of the decidua forms the enveloping zone. There is an early connection between the maternal Mood and the fetal cells in the form of a trophoblast which is a product of the ectoderm. The trophoblast, at points, extends far into the compacta and the cells have a decided power of wandering. The trophoblast is changed to syncytium through the corrosive action of the blood. The opening of the maternal vessels occurs even before villi are formed, and at this and at all subsequent stages fetal cells enter the maternal circulation. The primary enveloping zone becomes the subsequent intervillous space. Neither the uterine epithelium nor the maternal endothelium play any part in the formation of the syncytium. No reflexa is formed, but through the descent of the ovum a capsularis results. The ovum, through its trophoblast cells and villi, invades and destroys the maternal decidua. The fibrin layer of Nitabuch and the thickness of the decidua prevent the extension of the villi too deeply into the wall.
In the tube we find no division into two layers, as is the normal in the uterus. In fact, no decidua is formed. There is an absence of the thin-walled decidual vessels, and the muscularis, if at all, is only slightly hypertrophied. We are only anticipating the results of our investigations when we say that, with the exception of the absence of the decidua and an enveloping zona composed of compacta, the processes of gestation in the tube are the same as those in the uterus, modified only, as we ivoidd naturally expect, by the absence of the decidua and the thinness of the tube wall.
The varying differences of opinion are due to five causes :
- Ova of different states of preservation have given, quite naturally, different pictures.
- Ova of very different ages have been described and compared without taking this fact into consideration.
- As in the uterus, but even more so, the differentiation between fetal and maternal cells has been almost overlooked, so that trophoblast cells have been viewed as decidual. The ability of the fetal cells to wander, to invade the tube wall, and to perforate the vessels has been granted by only a few investigators.
- The fact that there are several forms which the ovum follows in its embedding in the tube has almost entirely escaped attention.
- "While Veit's deportation is an accepted fact, he leaves out of consideration the processes of "cell wandering" and "vessel invasion."
How nearly and how closely in all important details the histology of tubal gestation may resemble the course of uterine gestation, will be seen in the following pages.
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Reference: Bandler SW. Uterine and tubal gestation. (1903) William Wood & Company, New York.
Cite this page: Hill, M.A. (2020, October 25) Embryology Book - Uterine and tubal gestation (1903) 2-2. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Book_-_Uterine_and_tubal_gestation_(1903)_2-2
- © Dr Mark Hill 2020, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G