According to the embryologist when an embryo is termed as Fetus
**Core Concept**
The development of an embryo into a fetus is a critical period in human embryology, marking significant morphological and physiological changes. This transition is characterized by the formation of major organs and tissues, which prepares the embryo for life outside the womb. The embryological distinction between an embryo and a fetus is essential for understanding fetal development and prenatal care.
**Why the Correct Answer is Right**
The embryo is considered a fetus when it reaches a gestational age of approximately 8 weeks, marking the end of the embryonic period and the beginning of the fetal period. During this time, the embryo undergoes rapid growth and differentiation, with the formation of vital organs such as the heart, lungs, and kidneys. The development of the nervous system, including the brain and spinal cord, also progresses significantly during this period.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the embryonic period is typically defined as the first 8 weeks of gestation, after which the embryo is considered a fetus.
* **Option B:** There is no specific gestational age or developmental milestone that marks the transition from an embryo to a fetus at 16 weeks.
* **Option C:** The development of limbs and digits is an important aspect of embryonic development, but it does not mark the transition to a fetus.
* **Option D:** The formation of the placenta and umbilical cord is essential for fetal development, but it is not the defining characteristic of a fetus.
**Clinical Pearl / High-Yield Fact**
The embryonic period is a critical time for organogenesis, during which the major organs and tissues form. Understanding the timeline and milestones of embryonic development is essential for diagnosing and managing congenital anomalies.
**Correct Answer:** C.