Choose the true statements about chorionic villi! A. Secondary chorionic villi form when blood capillaries differentiate; B. Primary chorionic villi consist only of syncytiotrophob... Choose the true statements about chorionic villi! A. Secondary chorionic villi form when blood capillaries differentiate; B. Primary chorionic villi consist only of syncytiotrophoblast; C. Secondary villi are visible on the 75th day. D. Secondary chorionic villi contain extraembryonic mesoderm;
Understand the Problem
The question is asking to identify which statements regarding chorionic villi are true or false. This involves understanding the structure and development of chorionic villi during pregnancy.
Answer
Secondary chorionic villi contain extraembryonic mesoderm.
The true statement is: Secondary chorionic villi contain extraembryonic mesoderm.
Answer for screen readers
The true statement is: Secondary chorionic villi contain extraembryonic mesoderm.
More Information
Secondary chorionic villi develop when mesenchymal cells invade the primary villi, introducing extraembryonic mesoderm. Primary chorionic villi consist of a layer of cytotrophoblast cells covered by syncytiotrophoblast, contrary to the claim that they consist only of syncytiotrophoblast. The development of secondary villi and their visibility do not coincide with the 75th day but occur earlier in pregnancy.
Tips
A common mistake is confusing the different stages of villi development and their structures at those stages.
Sources
- Placenta and Extraembryonic Membranes - University of Michigan - med.umich.edu
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