In a cross section of a vertebrate embryo that has just completed neurulation, which is the correct order of structures and tissues encountered, starting at the dorsal surface and moving inward along the midline?
A) Epidermis, notochord, neural tube, gut
B) Epidermis, neural tube, notochord, gut
C) Epidermis, vertebral column, gut, neural tube
D) Epidermis, neural tube, vertebral column, gut
E) Epidermis, vertebral column, neural tube, gut

Question

Quizplus · Accepted Answer

Starting at the dorsal surface and moving inward along the midline, the correct order of structures and tissues encountered in a vertebrate embryo that has just completed neurulation is the epidermis, neural tube, notochord, and gut. The neural tube, the precursor to the central nervous system, forms first, followed by the notochord, which helps to pattern the developing embryo. The gut forms later as an outpocketing of the endodermal layer. The epidermis, the outermost layer of the embryo, is formed from the ectoderm and does not play a role in neurulation, but is included in the sequence to show the direction of movement. Vertebrae, which form around the notochord, are not mentioned in the correct order of structures and tissues.

In a Cross Section of a Vertebrate Embryo That Has