Which statement about embryonic gut formation is true?

Which statement about embryonic gut formation is true?

• A. The gut tube remains open throughout gestation
• B. The gut tube closes at cranial and caudal ends by distinct membranes
• C. Only endoderm contributes to the gut wall
• D. The hindgut forms first

Answer: (B)

In embryology, the gut tube starts as an endoderm-lined tube that is closed at both its cranial and caudal ends by separate membranes—the oropharyngeal (buccopharyngeal) membrane at the head end and the cloacal membrane at the tail end. These membranes mark where ectoderm and endoderm meet without intervening mesoderm, and they rupture later to form the mouth and the anus, respectively. The gut wall itself arises from both endoderm and surrounding mesoderm, with mesoderm contributing the muscular and connective tissue layers, so it isn’t composed only of endoderm. Development proceeds cranial to caudal, so the foregut forms before the hindgut. Because of these points, the true statement is that the gut tube closes at the cranial and caudal ends by distinct membranes.

In embryology, the gut tube starts as an endoderm-lined tube that is closed at both its cranial and caudal ends by separate membranes—the oropharyngeal (buccopharyngeal) membrane at the head end and the cloacal membrane at the tail end. These membranes mark where ectoderm and endoderm meet without intervening mesoderm, and they rupture later to form the mouth and the anus, respectively. The gut wall itself arises from both endoderm and surrounding mesoderm, with mesoderm contributing the muscular and connective tissue layers, so it isn’t composed only of endoderm. Development proceeds cranial to caudal, so the foregut forms before the hindgut. Because of these points, the true statement is that the gut tube closes at the cranial and caudal ends by distinct membranes.