Folding of the Embryo. Figures or photographs used in this presentation are originally reproduced from Langman’s Medical Embryology by T. W. Sadler, 10th Edition, Lippincott Williams & Wilkins, for teaching purpose only. Folding Of Embryo.
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Folding of the Embryo
Figures or photographs used in this presentation are originally
reproduced from Langman’s Medical Embryology by T. W. Sadler,
10th Edition, Lippincott Williams & Wilkins, for teaching purpose only.
- Folding means conversion of the flat trilaminar embryonic disc into a cylindrical embryo (Fig. 46).
Time: Folding of the embryo begins by the end of the 3rd week. It is completed by the 4th week.
Folding of the embryo is due to rapid growth of the embryo specially the nervous system.
The head folds first then the tail . At the same time, side to side folding occurs.
1- Embryo change into cylinderical embryo.
2-Transposition between septum transversum and cardiogenic plate( S.T lies cranial then ventral and lastly caudal).
3- Yolk sac reduced in size ÷d into:
a- intraembryonic ( gut).
b- extraembryonic ( atrophies).
c- yolk stalk (degenerates).
4- Allantois& connecting stalk become dorsal then caudal then ventral.
5- formation of umbilical cord.
6- The oral membrane was cranially ventral.
7- The cloacal membrane and allantois was caudal ventral.
Prof. Dr. wafaaabdelrahman