Maternity Nursing: Antepartum Q 19

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The developing cells are called a fetus from the:

  

     A. Time the fetal heart is heard

     B. Eighth week to the time of birth.

     C. Implantation of the fertilized ovum.

     D. End of the send week to the onset of labor.

    

    

Correct Answer: B. Eighth week to the time of birth.

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In the first 7-14 days, the ovum is known as a blastocyst; it is called an embryo until the eighth week; the developing cells are then called a fetus until birth.

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Option A: The ectoderm forms the epidermis, nails, hair, peripheral nervous system, brain, and spinal cord. The mesoderm forms the muscle, bone, connective tissue, notochord, kidney, gonads, and circulatory system. The endoderm forms the epithelial lining of the digestive tract, stomach, colon, liver, bladder, and pancreas.

Option C: Once fertilization takes place, there are quick changes at the cellular level of the zygote. The zygote is a single cell, and it undergoes mitosis to create many cells. Once the zygote has reached the thirty-two cell stage, it becomes morula. Day four begins blastulation and cavities begin to form by first forming a hollow ball. Some studies suggest that the timing of this process may affect implantation.

Option D: At sixteen weeks the primitive streak forms. The primitive streak establishes the midline of the body. The next stage in development is neurulation. At this time the notochord induces the ectoderm to form the neural plate which eventually forms the neural tube. The neural tube will become the brain and spinal cord.

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