10 Questions
What is the function of zona pellucida in fertilization?
Protects the zygote from maternal cellular defenses
What is the initial site of fertilization in mammals?
The upper region of the oviduct
Where does implantation occur in the female reproductive system?
Uterine wall
What facilitates the movement of the developing embryo within the uterine tube?
Combination of ciliary and muscular action
What is the role of fertilization in providing nutrients to the conceptus?
Uptake of nutrients by embryo itself
Describe the process of fertilization in mammals.
Fertilization occurs when sperm enters the uterus and travels through the reproductive tract until reaching the oviduct. An egg, released from the ovary, travels into the same oviduct and allows for penetration and fertilization by the sperm.
Explain the role of zona pellucida in fertilization.
Zona pellucida protects the zygote from maternal cellular defenses and is immunologically inert as it does not express major histocompatibility complex antigens.
What happens during implantation in the female reproductive system?
As the embryo is enclosed within an intact zona pellucida, implantation cannot occur until it moves through the uterine tube. Upon reaching the uterus, the blastocyst hatches from the zona pellucida and remains free for a short period in the uterine lumen.
How does the developing embryo move within the uterine tube?
The developing embryo, suspended in fluid within the tube, is moved by a combination of ciliary and muscular action and takes up to three days to reach the uterus in most mammals.
What are the nutritive requirements of the conceptus during fertilization?
The secretions of the maternal reproductive tract supply the necessary nutrients for the conceptus.
Study Notes
Fertilization in Mammals
- Fertilization occurs in the ampulla of the uterine tube, where sperm meet the egg.
- The zona pellucida, a glycoprotein layer surrounding the egg, plays a crucial role in fertilization by:
- Preventing polyspermy (multiple sperm penetration)
- Facilitating species-specific sperm recognition and binding
- Guiding the sperm to the egg's plasma membrane
- During fertilization, the sperm penetrates the zona pellucida, then the plasma membrane, and fuses with the egg's nucleus.
Implantation and Embryo Development
- Implantation occurs in the uterus, where the blastocyst embeds into the uterine lining (endometrium) approximately 6-7 days after fertilization.
- The developing embryo moves within the uterine tube due to the muscular contractions of the tube and the cilia-lined epithelium.
- During this time, the conceptus (fertilized egg) receives nutrients from the uterine fluids, which provide energy and support for early development.
Nutritive Requirements
- The conceptus relies on the uterine environment for nutrition, receiving essential nutrients, such as glucose, amino acids, and lipids, from the uterine fluids.
- The zona pellucida does not provide nutrients to the conceptus; instead, it facilitates fertilization and protects the embryo during early development.
Test your knowledge about fertilization, implantation, and placenta formation. This quiz covers the process of fertilization, implantation, and the development of the placenta in the reproductive system.
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