Final answer:
It is false that a zygote has a fully functioning nervous system by 8 weeks into the pregnancy; rather, this is the period where basic nervous system structures like the neural tube are developing but are not yet fully functioning. The correct answer to the question is false.
Step-by-step explanation:
The correct answer to the question is false. A zygote does not have a fully functioning nervous system by 8 weeks into the pregnancy. The development of the nervous system begins during the embryonic stage, which spans from weeks 3 to 8 after fertilization. Within this period, three germ layers form, and it's from the ectoderm that the nervous system begins to develop. By the 3rd week, the process of neurulation starts, leading to the creation of the neural tube, which eventually becomes the brain and spinal cord. The early nervous system is a simple structure that gradually develops into more intricate brain and spinal cord structures. At about 25 days, the anterior end of the neural tube starts differentiating into the brain, and the posterior becomes the spinal cord. However, it is only after the 8th week when the embryonic stage transitions to the fetal stage that more rapid growth and refinement of the nervous system, among other organs, occurs.
True or False: The nervous system develops from the same germ layer as skin cells do. True, as both the nervous system and skin cells (epidermis) derive from the ectodermal germ layer.
Stages of Prenatal Development
- Zygote: This is the stage following conception when the egg and sperm unite, and cell division begins.
- Embryo: After the zygote divides and implants in the uterus lining, the embryonic stage starts, spanning from approximately 3 to 8 weeks, and is characterized by organ formation, including the initial development of the nervous system.
- Fetus: Starting from week 9, the fetal stage continues until birth. During this time, the body, brain, and organ systems mature and grow, preparing for life outside the womb.
The correct order of prenatal development is the zygote, embryo, and fetus. The correct answer to the question is false.