Final answer:
The biosynthesis of progesterone in pre-pregnant females occurs primarily in the ovaries, specifically by the corpus luteum during the luteal phase of the menstrual cycle.
Step-by-step explanation:
Biosynthesis of progesterone in pre-pregnant females predominantly takes place in the ovaries. Specifically, progesterone is produced by the corpus luteum, which is a temporary endocrine structure in the ovaries that forms after an egg has been released from the follicle during ovulation. The corpus luteum secretes progesterone during the luteal phase of the menstrual cycle to thicken the endometrial lining, preparing the uterus for potential pregnancy. In instances where pregnancy does not occur, the corpus luteum degenerates, leading to a decrease in progesterone, which initiates the next menstrual cycle.
If pregnancy occurs, progesterone production continues to play a vital role in maintaining the pregnancy. Initially, the corpus luteum is responsible for producing progesterone, but as the pregnancy advances, particularly starting at weeks 12-17 from the last menstrual period (LMP), the placenta gradually takes over the role of progesterone synthesis, becoming the primary endocrine organ during pregnancy.
Answer Choices
- A. Ovaries
- B. Adrenal glands
- C. Placenta
- D. Uterus
In the context of the question, the correct answer is: A. Ovaries.