Book - Uterine and tubal gestation (1903) 1-14
Embryology - 25 Apr 2024    Expand to Translate
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Bandler SW. Uterine and tubal gestation. (1903) William Wood & Company, New York.
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Part I. The Essentials of Uterine Gestation
Chapter XIV. Gross Anatomy of the Placenta
The placenta is a thickly spongy, fairly circular mass measuring 15-20 centimetres in diameter and about 3-4 centimetres in thickness. The surface toward the embryo has attached to it the cord and is covered, or rather lined, with the amnion.
Placenta is the finally developed membrana chorii of the chorion frondosum with its myriads of chorionic villi. Instead of each villus being connected with the membrana chorii, we have connected with the latter large stems on which are numberless branches and sub-branches covered with chorionic villi.
The outer surface of the placenta is divided by furrows into areas or islands called cotyledones. A cotyledo consists of a stem passing out from the membrana chorii. From it pass villi and large branches covered with villi, and from these still smaller branches with villi. The uterine placental area has been invaded by trophoblast cells and villi during a period of nine months, so that compacta and almost all of the spongiosa have been "eaten up." If, from a certain area, we remove compacta and spongiosa, we pass from the region of capillaries toward the region of vessels situated in the muscularis. The uterus, however, has grown actively in the first three months. The vessels of such an area have hypertrophied during this time proportionately with the enlargement and hypertrophy of all the uterine structures. In the next six months the uterus enlarges passively and a further influence is exerted on the openings of the vessels on the uterine surface — i.e.] they are stretched and opened in trumpet fashion. As a result, we find on the uterine placental surface larger and smaller sinuses lined more or less with endothelium, which endothelium may extend in trumpet fashion to various degrees.
Except at the margin, practically no glands are found beneath the decidual projections. The remnant of decidua covering the uterine placental area is very thin and is so infiltrated with fetal trophoblast cells as to be practically fetal in character. The same is true of the decidual projections.
The sinuses are situated in hollows or depressions, for the uterine surface is very irregular. As a result of irregular invasion by trophoblast cells and villi, and as a result of the deeper invasion by the "adherent villi," the uterine surface shows irregular decidual projections. Between these projections and at their base are the "sinuses." Numberless individual villi are loosely attached to the tips and sides of the projections. Masses of villi fill up the hollows or bays. To the bottom of these bays are attached the adherent villi — i.e., the large stems which pass off from the membrana chorii.
The attachment of stems between decidual projections, and the extension of decidual projections between masses of villi, serve to divide off the uterine surface and the placenta into compartments. These compartments are filled solidly with villi. As a result the blood coining from the uterine arteries is limited more or less to the compartment into which it enters. We have the socalled intervillous spaces. The entire placental structure is not washed or infiltrated by all the maternal blood making exit from the uterine placental surface, but by the blood of its compartment.
No space separates external placental surface from uterine surface. The masses of villi composing the placenta have the most external groups close to the openings of the maternal sinuses. Villi and masses of villi extend into the uterine veins. This arrangement, whereby maternal blood passes out between the densely grouped villi and back again through the venous sinuses of compartments, gives the greatest and most plentiful opportunity of surrounding the myriads of villi with maternal blood. The fetal vessels passing through the cord, through the membrana chorii, through the villous stems, through the villous branches into every villus, give a tremendous opportunity for exchange between maternal blood and fetal blood through the syncytium.
The placenta is thus well attached to the uterine wall. In addition the reflexa is attached to the vera at all parts of its periphery. In addition the liquor amnii presses placenta and reflexa closely against serotinal area and vera.
At the edge of the placenta the amnion which lines it passes on and lines the membrana chorii which has not formed placenta, the chorion lasve.
From the edge of the placenta on, the membrana chorii or chorion lgeve is attached by means of the reflexa to the decidua vera.
At the edge of the placenta the attachment of reflexa and vera is not very close. This area represents the point of junction of vera, serotina, and reflexa. After union of base of reflexa to vera at this point, the edge of the placenta may extend on upon the reflexa, now united to vera. Beyond this point the attachment of chorion to vera per the reflexa is the same as at other points. The uterine wall at the edge of the placenta has at all times the best-preserved growth of glands, for here the attachment of reflexa and vera is last completed and the pressure is least.
There remains of the decidua only a thin layer at best. In some areas the villi are practically on the muscularis. At other points spongiosa is preserved, but the glands have lost their epithelia and look like vessel sinuses. At other points compacta and spongiosa are fairly well preserved. The invasion of the decidua is very irregular in character (Fig. 43). Generally speaking, little decidua separates the villi from the muscularis. The layer of Nitabuch said to separate fetal and maternal structures, and probably derived from fetal ectoderm, is varying in amount and regularity.
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Reference: Bandler SW. Uterine and tubal gestation. (1903) William Wood & Company, New York.
Cite this page: Hill, M.A. (2024, April 25) Embryology Book - Uterine and tubal gestation (1903) 1-14. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Book_-_Uterine_and_tubal_gestation_(1903)_1-14
- © Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G
