Which of the following structures helps to organize the embryo around a central axis?

• A. Somites.
• B. Neural plate.
• C. Notochord.
• D. Allantois.

Answer: (C)

Verified step by step guidance

1. Begin by understanding the role of the notochord in embryonic development. The notochord is a flexible, rod-shaped structure that forms in the embryo and serves as a primary skeletal element.
2. Recognize that the notochord is crucial for the organization of the embryo. It provides signals that help in the development of the surrounding tissues, including the neural tube and somites.
3. Consider the location and function of the notochord. It is positioned along the central axis of the embryo, which is essential for the proper alignment and segmentation of the body plan.
4. Compare the notochord with other structures mentioned: somites, neural plate, and allantois. Somites are segmented blocks of mesoderm that develop into skeletal muscle, vertebrae, and dermis. The neural plate is a thickened region of ectoderm that gives rise to the nervous system. The allantois is involved in early fluid exchange between the embryo and the yolk sac.
5. Conclude that the notochord is the structure that helps organize the embryo around a central axis, providing the necessary signals for the development of the axial skeleton and influencing the patterning of surrounding tissues.