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Questions and Answers
What is the average volume of semen in normal ejaculation?
Which of these terms describes the stage from fertilization to implantation?
The age of viability is generally accepted as 28 weeks.
False
What are the two types of cells that the blastocyst consists of?
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The first trimester of pregnancy lasts from ______ to ______ weeks.
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How long is an ovum capable of fertilization?
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What is the term for the embryo from implantation to 5-8 weeks?
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Match the following stages of development with their descriptions:
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What is hyaluronidase and its function?
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Study Notes
Stages of Fetal Development
- Pre-embryonic stage lasts the first 2 weeks from fertilization.
- Embryonic stage covers weeks 3 through 8.
- Fetal stage spans from week 8 until birth.
Terms of Fetal Growth
- Zygote: The term for the fertilized egg from fertilization to implantation.
- Embryo: The developing organism from implantation to 5-8 weeks.
- Fetus: Refers to the developing organism from 5-8 weeks until term.
- Conceptus: Encompasses the developing embryo and placental structures throughout pregnancy.
- Age of Viability: Generally accepted as 24 weeks; fetus can survive outside the womb if weighing more than 500-600 grams.
Fertilization Journey
- Begins in the fallopian tube, where the zygote travels and develops into a morula and then a blastocyst over about 5-6 days.
- Morula: Solid ball of cells formed 3-4 days post-fertilization.
- Blastocyst: Formed 4-5 days after fertilization, consisting of an inner cell mass (embryoblast) and an outer layer (trophoblast).
Fertilization and Sperm Details
- Normal ejaculation delivers about 2.5 mL of semen, containing 20-200 million sperm per milliliter.
- Average sperm count per ejaculation is approximately 400 million.
- Sperm require approximately 6 days in the female reproductive tract for successful fertilization.
- Ovum is viable for only 24 to 48 hours post-ovulation.
Cell Division and Implantation
- After fertilization, the first cleavage (cell division) occurs within 24 hours, continuing approximately every 22 hours.
- Implantation occurs about 8-10 days after fertilization, primarily high in the uterus, where the blastocyst contacts the uterine endometrium.
- The trophoblast cells nourish and protect the embryo while the embryoblast will develop into the fetal tissue.
Nutrient Transfer Post-Implantation
- By the 3rd week, maternal nutrients such as glucose, amino acids, and minerals are transported through the chorionic villi into the developing embryo’s circulation.
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Description
Explore the stages of fetal development in Chapter 9. This quiz covers vital concepts, including pre-embryonic and embryonic stages, along with reproductive details like semen composition. Perfect for students looking to reinforce their understanding of early human development.
