Which membrane closes the gut tube at the cranial end?

Which membrane closes the gut tube at the cranial end?

• A. Oropharyngeal membrane
• B. Cloacal membrane
• C. Notochord
• D. Pericardial membrane

Answer: (A)

The cranial end of the gut tube is closed by the oropharyngeal (buccopharyngeal) membrane. This transient membrane forms where the foregut meets the stomodeum, created by the fusion of ectoderm and endoderm with no intervening mesoderm. It temporarily seals the gut opening to the amniotic cavity and later breaks down to establish the mouth, around the fourth week. The cloacal membrane closes the caudal end, not the cranial end; the notochord is a midline signaling structure, not a membrane that seals the gut; and the pericardial membrane relates to the heart area, not gut closure.

The cranial end of the gut tube is closed by the oropharyngeal (buccopharyngeal) membrane. This transient membrane forms where the foregut meets the stomodeum, created by the fusion of ectoderm and endoderm with no intervening mesoderm. It temporarily seals the gut opening to the amniotic cavity and later breaks down to establish the mouth, around the fourth week. The cloacal membrane closes the caudal end, not the cranial end; the notochord is a midline signaling structure, not a membrane that seals the gut; and the pericardial membrane relates to the heart area, not gut closure.