Paper - The gall bladder and the extrahepatic biliary passages in late embryonic and early fetal life

Henry Lee And Bela Halpert

Laboratory of Pathology and Department of Surgery, Yale University School of Medicine, New Haven, Connecticut

FOUR. PLATES (SEVEN FIGURES)

The early stages of the development of the biliary system have frequently been investigated, but little information is available on the human gall bladder and the biliary passages in late embryonic and early fetal life(1,2). Adequate material for such studies is, of course, diﬂicult to obtain. It was our good fortune to secure some preparations suitable to furnish information on some points of particular interest regarding the structural evolution of the gall bladder and the extrahepatic biliary passages. The data obtained are presented in this preliminary report.

MATERIAL

There were at our disposal: 1) Serial sections of the entire biliary system of two embryos, 25 and 40 mm. long, and, 2) serial sections of eight gall bladders of embryos and fetuses ranging from 80 to 370 mm. in length. Most of the sections were stained with hematoxylin eosin, and some by the method of van Gieson.

A. The gall bladder

The endodermal portion of the gall bladder in both the 25- and 40-mm. embryos is represented by a single layer of columnar epithelial cells which line the lumen, the mes0dermal portion comprising the rest of the wall (fig. 1).

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THE ANATOMIGAL RECORD, VOL. 54, NO. 1 30 HENRY LEE AND B}i1LA HALPERT

The mucosal surface is smooth and devoid of elevations a11d indentations. The cells of the endodermal epithelial lining appear uniform in size and staining reaction. Only here and there are seen cells in a state of mitotic division. The cell nuclei are large and contain granules which are deeply stained and evenly distributed. The location of the nuclei is, with slight variations, in the midportion of the cell. The cytoplasm is stained lightly except for a narrow strip of the free margin. However, the intensely stained border of the gall-bladder epithelium is not a true cuticula. This becomes evident by a comparison with the cuticular margin of the intestinal epithelium. At this stage of development the mesodermal portion of the gall bladder shows only a slight indication of differentiation. Although the tunica muscularis cannot be recognized as such, a zona muscularis may be tentatively separated from the zona subepithelialis and the zona perimuscularis. In the zona subepithelialis, which is a narrow band encircling the epithelial lining, the cell nuclei are round and very numerous. In the zona muscularis, from which the muscular coat is going to develop, the nuclei are oval and less numerous. Young muscle cells and capillaries in process of formation may be recognized in this layer. Up to the periphery of this zone, the gall—bladder wall is alike on both its peritoneal and liver surfaces. The next zone, the zona perimuscularis, is broader toward the liver, attaining a width almost equal to that of the zona subepithelialis and zona muscularis combined. Here the cell nuclei are round, sparse, and evenly distributed. An occasional vessel is seen in process of formation. Along the line of attachment to the liver a collection of round nuclei is noted. On the peritoneal aspect of the viscus the perimuscular layer is a barely perceptible, narrow zone between the muscularis and the peritoneal serosa. A comparison with the intestine reveals the remarkable fact that the differentiation here has progressed much farther than in the gall bladder. The mucosa of the intestinal wall is thrown into folds, the lamina propria mucosae is distinct, a zona muscularis mucosae is indicated, and the tunica muscularis contains muscle cells already arranged into an inner circular and an outer longitudinal layer.

The gall bladder of both the 80- and 95-mm. embryos shows distinctly the differentiation into layers (ﬁg. 2). In the mucosa the formation of folds has begun; alveolar indentations and corresponding rounded elevations give a pattern to its surface. This is particularly marked in the neck where the lumen is minute and is composed of from two to six communicating epithelial—lined indentations. The tunica propria mncosa.e is a thin layer of connective tissue with numerous blood capillaries. On this layer rests the epithelial lining. The subepithelial layer is surrounded by the tunica muscu— laris which is a well-deﬁned layer composed of smooth-muscle cells embedded in a connective-tissue stroma. This tunic is rather complete, there being no interruption of its continuity by penetrating epithelial indentations of the mucosa. The perimuscular layer is slightly denser in its portion adjacent to the muscular coat. This denser zone contains the coarse ramiﬁcations (plexus perimuscularis) of the large blood Ves— sels. The width of the perimuscular layer almost equals that of the mucosa and muscularis combined. A structural difference in the portion attached to the liver and that covered by peritoneum is not apparent.

The gall bladders of the 115-, 120-, and 130—mm. fetuses show further progression in the differentiation of their struc— tures (ﬁg. 3). The surface pattern of the mucosa is rich in elevations and indentations. In the neck an occasional acinar outpouching of the lumen appears external to the muscular coat. The cytoplasm of the lining cells of these outpouchings are stained lightly and their nuclei placed at the base of the cells. Evidently they represent glands which, at this site, make their ﬁrst appearance in this period of development. Another structure, the ‘true Luschka ducts,’ remnants of the liver primordium, are ﬁrst seen in sections of the 130—mm. fetus. They appear as groups of deeply stained cuboidal cells situated in the periphery of the perimuscular layer on both the liver and the peritoneal sides of the viscus.

The gall bladders of the 200-, 280-, and 370-mm. fetuses are miniatures of that of the newborn (ﬁgs. 4. to 6). Rapid advance in the development of the mucosal pattern is a prominent feature of this stage. The folds of Heister and the curves of the neck now assume deﬁnite forms (ﬁg. 4). The active proliferation of the lining epithelium is rather conspicuous in sections from the gall bladder of a 370-mm. fetus (ﬁg. 5). The arrangement of the muscular tunic into an incomplete inner longitudinal and outer rather oblique layer is seen. The distribution of the vascular supply is strikingly brought out in the injected specimen of a 280—mm. fetus (ﬁg. 6). The coarse ramiﬁcations (plexus perimuscularis) of the large vessels are located in the dense zone of the perimuscular layer, in that adjacent to the muscular coat. Surrounding the muscular coat are six to twelve small arteries, placed equidistant from one another, with their concomitant veins. Branches of these vessels communicate through the muscular layer with the rich capillary bed (plexus subepithe— lialis) distributed beneath the lining epithelium.

B. The hepatocystic and the choledochoduodenal junctions

The endodermal portion of the extrahepatic biliary ducts in both the 25- and 40~mm. embryos is represented by a tube lined with a single row of columnar epithelial cells. The mesodermal portion is wholly undifferentiated. The lumen of the cystic duct merges gradually with that of the common hepatic duct (ﬁg. 7). The course of the ductus choledochus can be easily followed in serial sections and its gradual penetration together with the pancreatic duct on the dorsomedial side of the duodenum observed (ﬁg. 1). At this stage of development the differentiation of muscular tissue in the gall bladder has not occurred, and, as just mentioned, the mesodermal portion of the ductus choledochus is wholly undifferentiated. The duodenal musculature, on the other hand, has already a quite well-developed inner circular and outer longitudinal layer. Thus, it seems reasonable to assume that any muscle tissue present at the choledochoduodenal junction at this stage of development would be of duodenal origin.

In the 200—mm. fetus, the ductus choledochus is quite well formed (ﬁg. 4). Its lumen is lined by a single row of high columnar epithelial cells. There are numerous outpouchings of the mucosa. The deeper portions of some of these outpouchings are lined by low columnar cells which have a lightly staining cytoplasm and a nucleus close to the base. The

mesodermal portion of the duct is composed of young connective tissue.

SUMMARY

The evolution of the gall bladder was followed in ten human embryos and fetuses, ranging from 25 to 370 mm.; and the extrahepatic biliary passages in serial sections of two of the embryos and one of the fetuses.

In the 25- and 40—mm. embryos the endodermal portion of the gall bladder is represented by a single layer of columnar epithelial cells which li11e the lumen. In the mesodermal portion, comprising the rest of the wall, the zona muscularis is barely indicated, while the tunica muscularis of the intestine is already Well deﬁned. In the 80- and 95—mm. embryos the wall of the gall bladder is differentiated into layers. In the 115-, 120-, and 130-mm. fetuses the surface pattern of the gall—bladder mucosa is rich in elevations and indentations. The glands in the neck appear and the ‘true Luschka ducts’ are ﬁrst seen. In the 200-, 280-, and 370-mm. fetuses the gall bladder is a miniature of that of the newborn; the curves of the neck and the folds of Heister appear.

The endodermal portion of the extrahepatic biliary ducts in both the 25- and 40-mm. embryos is represented by a tube, lined with a single row of columnar epithelial cells; the mesodermal portion is Wholly undifferentiated. In the 200—mm. fetus the endodermal portion of the ductus choledochus is well formed, the lining epithelium showing numerous outpouchings and glandular structures; the mesodermal portion is composed of young connective tissue.

LITERATURE CITED

1 M5LLENDORFF, v. W. 1932 Handbuch der microscopischen Auatomie des Menschen, Bd. 5. Julius Springer, Berlin.

2 HALPER/1‘, BELA 1927 Morphological studies on the gall bladder, I and II. Bull. Johns Hopkins Hospital, vol. 40, p. 390, and vol. 41, p. 77. PLATES

35 PLATE 1 EXPLANATION or FIGURES

1 Gall bladder and duodenum of a 40-mm. human embryo; cross section at the level of the umbilicus. The cells of the endodermal epithelial lining appear uniform in size and staining reaction. The mesodermal portion of the gall bladder shows only a slight indication of differentiation into layers. The passage through the duodenal wall of the ductus choledochus and the ductus pancreaticus is seen. Photomicrograph, X 50.

2 Gall bladder of an 80-mm. human embryo; cross sections from the corpus (0.) and from the neck (b). The alveolar indentations and corresponding round elevations give a pattern to the mucosal surface. This is particularly marked in the neck, where the stellate lumen is composed of several communicating epithelial-lined indentations. The muscular coat is a well-defined layer of smooth-muscle cells embedded in a connective-tissue stroma. Photomicrographs, X 60.

36 EVOLUTION OF GALL BLADDER AND BILE DUCTS PLATE 1 HENRY LEE AND BIELA HALPERT

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THE ANATOMICAL 320031», VOL. 54. N0- 1 PLATE 2

EXPLANATION OF FIGURE

3 Gall bladder of 3. 130—mm. fetus; cross sections from the corpus (a) and from the neck (b). The surface pattern of the mucosa is rich in elevations and iudeiitatious. Two groups of deeply stained cuboidal cells situated in the periphery of the perimuseular layer are remnants of the liver primordiuni. These ‘true Luschka. ducts’ make their ﬁrst appearance at this stage of development (a). Some of the acinar outpmicliings of the lumen of the neck appear external to the muscular coat and are lined by low columnar cells stained lightly and having their nuclei in the base of the cells (12). Photomicrographs, X 100.

38 mm

EXPLANATION OF‘ FIGURE

4 Gall bladder of a 200-mm. fetus in longitudinal section. The folds of Heister and the curves of the neck assume deﬁnite forms. The viscus is the miniature of that of the newborn (a). The ductus choledochus is quite well formed. The mucosa shows numerous outpouehings. The mesoderma] portion of the duct is composed of young connective tissue (b). Photornicrographs, (a),

X 12; (1)), X 120.

40 EVOLUTION OF GALL BLADDER AND BILE DUCTS HENRY LEE AND BELA HALPERT

PLATE 3 PLATE 4 EXPLANATION or FIGURES

5 Gall bladder of a 370-nnn. fetus in longitudinal section. The active proliferation of the lining epithelium is rather conspicuous. Photomicrograph, X 120.

6 Gall lolad<ler of a 280—mm. fetus in cross section. The coarse ramiﬁcations (plexus perimuseularis) of the large vessels are located in the dense zo11e of the perimuseular layer, in that adjacent to the muscular coat. Branches of these vessels communicate through the muscular layer with the rich capillary bed (plexus subepithelialis) distributed beneath the lining epithelium. Photomier0graph, X 60.

7 The hepatoc-ystic junction of the 40mm. human embryo. The lumen of the cystic duct merges gradually with that of the common hepatic duct. The endodermal portion of both duets is represented by a tube lined with a single row of columnar epithelial cells. The mosodermal portion is wholly undifferentiated. Photomicrograph, X 120.

Cite this page: Hill, M.A. (2024, April 26) Embryology Paper - The gall bladder and the extrahepatic biliary passages in late embryonic and early fetal life. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Paper_-_The_gall_bladder_and_the_extrahepatic_biliary_passages_in_late_embryonic_and_early_fetal_life

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