Talk:1987 Developmental Stages In Human Embryos - Stage 5

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Table 5-1. Significant Dimensions (in mm) of Carnegie Specimens of Stage 5

Stage Serial No. Chorion Chorionic cavity Trophoblast Embryonic disc Amniotic cavity Primary umbilical vesicle Reference
5a 8225 0.33 x 0.306 x 0.12 0.228 x 0.20 x 0.03 0.006 - 0.086 0.09 x 0.078 x 0.036 0.06 x 0.054 x 0.006 0.08 x 0.023 Hertig and Rock (1945b)
5a 8020 0.45 x 0.30 x 0.125 0.288 x 0.186 x 0.044 0.003 - 0.09 0.126 x 0.092 x 0.044 0.025 x 0.024 x 0.003 0.043 x 0.06 Hertig and Rock (1945a)
5a 8155 0.306 x 0.210 x 0.15 0.168 x 0.082 x 0.066 0.003 - 0.08 0.09 x 0.05 x 0.03 0.048 x 0.032 x 0.02 absent Hertig and Rock (1949)
5b 8215 0.525 x 0.498 x 0.207 0.228 x 0.21 x 0.10 0.013 - 0.16 0.084 x 0.052 x 0.05 0.05 x 0.048 x 0.022 0.246 x 0.168 x 0.124 Hertig and Rock (1945c)


5b 5b 5b 5c 5c 5c 5c 5c

8171 8004 9350 7699 7950 7700 8558 8330

0.422 x 0.404 x 0.256 0.582 x 0.45 x 0.31 0.599 x 0.58 x 0.36 1.026 x 0.713 x 0.515 0.75 x 0.45 0.948 x 0.835 x 0.54 0.96 x 0.52 0.85 x 0.65

0.164 x 0.138 x 0.08 0312 x 0.185 x 0.12 0.3 x 0.1 x 0.1 0.48 x 0.336 x 0.276 0.40 x 0.26 0.55 x 0.498 x 0.425 0.58 x 0.36 0.46 x 0.40

0.04 - 0.13 0.035 - 0.175 0.064 - 0.153 0.04 - 0.15 0.0125 - 0.185 0.02 - 0.28 0.10 - 0.24

0.114 x 0.088 x 0.046 0.132 x 0.10 x 0.046 0.132 x 0.09 x 0.05 0.138 x 0.138 x 0.089 0.16 x 0.07 0.204 x 0.165 x 0.045 0.22 x 0.08 0.216 x 0.063

0.04 x 0.036 x 0.024 0.078 x 0.066 x 0.012 0.108 x 0.099 x 0.024 0.02 x 0.014 0.174 x 0.14 x 0.0125 0.216 x 0.036 0.16 x 0.05

0.33 x 0.19 0.474 x 0.4l x 0.29 0.49 x 0.30 0.35 x 0.31

Hertig and Rock (1949) Hertig and Rock (1945a) Heuser (1956) Hertig and Rock (1941) Hertig, Rock, and Adams (1956) Hertig and Rock (1941) Hertig, Rock, and Adams (1956) Hertig, Rock, and Adams (1956)

Table 5-1. Significant Dimensions (in mm) of Carnegie Specimens of Stage 5

Stage 5a 5a 5a 5b 5b 5b 5b 5c 5c 5c 5c 5c

Serial No. 8225 8020 8155 8215 8171 8004 9350 7699 7950 7700 8558 8330

Chorion 0.33 x 0.306 x 0.12 0.45 x 0.30 x 0.125 0.306 x 0.210 x 0.15 0.525 x 0.498 x 0.207 0.422 x 0.404 x 0.256 0.582 x 0.45 x 0.31 0.599 x 0.58 x 0.36 1.026 x 0.713 x 0.515 0.75 x 0.45 0.948 x 0.835 x 0.54 0.96 x 0.52 0.85 x 0.65

Chorionic cavity 0.228 x 0.20 x 0.03 0.288 x 0.186 x 0.044 0.168 x 0.082 x 0.066 0.228 x 0.21 x 0.10 0.164 x 0.138 x 0.08 0312 x 0.185 x 0.12 0.3 x 0.1 x 0.1 0.48 x 0.336 x 0.276 0.40 x 0.26 0.55 x 0.498 x 0.425 0.58 x 0.36 0.46 x 0.40

Trophoblast 0.006 - 0.086 0.003 - 0.09 0.003 - 0.08 0.013 - 0.16 0.04 - 0.13 0.035 - 0.175 0.064 - 0.153 0.04 - 0.15 0.0125 - 0.185 0.02 - 0.28 0.10 - 0.24

Embryonic disc 0.09 x 0.078 x 0.036 0.126 x 0.092 x 0.044 0.09 x 0.05 x 0.03 0.084 x 0.052 x 0.05 0.114 x 0.088 x 0.046 0.132 x 0.10 x 0.046 0.132 x 0.09 x 0.05 0.138 x 0.138 x 0.089 0.16 x 0.07 0.204 x 0.165 x 0.045 0.22 x 0.08 0.216 x 0.063

Amniotic cavity 0.06 x 0.054 x 0.006 0.025 x 0.024 x 0.003 0.048 x 0.032 x 0.02 0.05 x 0.048 x 0.022 0.04 x 0.036 x 0.024 0.078 x 0.066 x 0.012 0.108 x 0.099 x 0.024 0.02 x 0.014 0.174 x 0.14 x 0.0125 0.216 x 0.036 0.16 x 0.05

Primary umbilical vesicle 0.08 x 0.023 0.043 x 0.06 absent 0.246 x 0.168 x 0.124 0.33 x 0.19 0.474 x 0.4l x 0.29 0.49 x 0.30 0.35 x 0.31

Reference Hertig and Rock (1945b) Hertig and Rock (1945a) Hertig and Rock (1949) Hertig and Rock (1945c) Hertig and Rock (1949) Hertig and Rock (1945a) Heuser (1956) Hertig and Rock (1941) Hertig, Rock, and Adams (1956) Hertig and Rock (1941) Hertig, Rock, and Adams (1956) Hertig, Rock, and Adams (1956)

Figures

Fig. 5-1. Drawings of the embryo from stage 2 to stage 5c to show implantation. The drawings, which are all at the same scale of magnification, are based on human specimens, with the exception of stage 4, for which a macaque blastocyst was used. B.C., blastocystic cavity. Asterisk, primary umbilical vesicle.


Fig. 5-2. Diagram to illustrate the presumed mode of development of monozygotic twins in the human. Based partly on Corner (1955). There exist “three critical stages at which the division of the embryo to form monozygotic twins may occur” (Bulmer, 1970). At stage 2, before the differentiation of the trophoblast, separation of the blastomeres would result in twins with separate choria and amnia. At stage 3 (and presumably at stage 4) before differentiation of the amnion, duplication of the inner cell mass would result in twins with a common chorion but separate amnia. At stage 5, duplication of the embryonic disc would result in twins with a common chorion and amnion. Deceptive fusion of the membranes may occur subsequently in certain instances but “the placenta and membranes, if subjected to skilled examination, including microscopic study of the chorionamniotic walls when necessary, will generally yield a correct impression of the type of twinning” (Corner, 1955; see also Allen and Turner, 1971). Partial instead of complete embryonic separation would result in conjoined twins of the various types classified by Wilder (1904).


Fig. 5-3. Surface view of the implantation site of No. 8020, stage 5a, photographed under liquid. The dark ring indicates the chorionic cavity. The opaque area within the ring represents the embryonic mass; that outside of the ring represents the trophoblast. The mouths of the endometrial glands appear as dark spots.

Fig. 5-4. General view of the tissues at and near the implantation site (No. 8020, stage 5a). The endometrium is edematous. Section 6-5-9.


Fig. 5-5. Section through the middle of No. 8020, stage 5a. The amniotic cavity and the bilaminar embryonic disc can be seen. The transition from the thin abembryonic trophoblast to the thick, solid layer at the embryonic pole is evident. Large multinucleated masses of syncytiotrophoblast project into the endometrial stroma. A dilated endometrial gland is cut through at the left-hand side of the photomicrograph. Section 6-5-9.


Fig. 5-6. Section approximately through the middle of No. 8155, stage 5a. The amniotic cavity (“trophoepiblastic cavity?“) and the bilaminar embryonic disc can be seen, although an amnion as such is not yet distinct. The thick, solid trophoblast at the embryonic pole is mainly syncytiotrophoblast. The endometrial stroma is edematous. Section 4-4-8.


Fig. 5-7. Surface view of the implantation site of No. 8004, stage 5b, photographed under liquid. The dark area in the middle represents the abembryonic wall of the specimen.

Fig. 5-8. General view of the tissues at and near the implantation site (No. 8004, stage 5b). The endometrium is “predecidual.” Section 11-4-4.

Fig. 5-9. Section through the middle of No. 8004, stage 5b. Some epithelial regeneration of the endometrium has taken place over the specimen. The large mass of syncytiotrophoblast shows intercommunicating lacunae. The chorionic cavity is surrounded by a thin layer of cytotrophoblast. The amniotic cavity and the bilaminar embryonic disc can be seen. Section 11-4-5.

Fig. 5-10. Surface view of the implantation site of No. 7700, stage 5c.

Fig. 5-11. Side view of the implantation site of No. 7700, stage 5c.


Fig. 5-12. View of the implantation site of No. 7700, stage 5c, as seen in the cleared celloidin block. The irregular, dark ring is caused by maternal blood within the trophoblastic lacunae, and is a characteristic feature of subdivision 5c, as it has been defined by Hertig, Rock, and Adams (1956).


Fig. 5-13. Section through the middle of No. 7700, stage 5c. The space outlined by the internal surface of the chorion now appears distended again. However, a gradient of differentiating trophoblast from abembryonic to embryonic pole is still evident. Intercommunicating lacunae are visible in the syncytiotrophoblast. The primary umbilical vesicle, surrounded by a meshwork, can be seen. The endometrial stroma is edematous and deciduas is developing. Section 6-1-5.


Fig. 5-14. The bilaminar embryonic disc of No. 7700, stage 5c. The amnion overlying the disc does not seem to be complete. The epiblast is a pseudostratified columnar epithelium. The surrounding cytotrophoblast is evident, and lacunae can be seen in the syncytiotrophoblast. Cytotrophoblastic clumps may be regarded as an indication of the future chorionic villi. Section 6-1-5.