becomes what? a) Lining of digestive and respiratory tracts liver, pancreas b) Enidermis CNS, sense organs, neural crest e) Skeleton muscles, blood yessels, heart,gonads (organ that makes gametes) d) Both a and Part II. Short answers and discussions (2 marks each) 1. A hollow ball of cells formed when a zygote undergoes a series of divisions is known as a 2. What are the endoerine functions of the placenta? 3. What two tissue types form the placenta? 4. What is the function of the yolk sac? (3 marks) 8. Which is the extraembryonic membrane whose function is to store nitrogen wastes of the embryo? 6. What is the cell division process directly related to the embryonic growth? 7. Participation of more than one spermatozoon in fertilization is called 8. Extra sperm which succeed in passing through the zona pellucida into the perivitelline space are called __ 9. How the transport of ovum in the oviduct is facilitated? (3 marks) 10. Explain the mechanisms underlying the blocks to polyspermy?

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becomes what? a) Lining of digestive and respiratory tracts liver, pancreas b) Enidermis CNS, sense organs, neural crest e) Skeleton muscles, blood yessels, heart,gonads (organ that makes gametes) d) Both a and Part II. Short answers and discussions (2 marks each) 1. A hollow ball of cells formed when a zygote undergoes a series of divisions is known as a 2. What are the endoerine functions of the placenta? 3. What two tissue types form the placenta? 4. What is the function of the yolk sac? (3 marks) 8. Which is the extraembryonic membrane whose function is to store nitrogen wastes of the embryo? 6. What is the cell division process directly related to the embryonic growth? 7. Participation of more than one spermatozoon in fertilization is called 8. Extra sperm which succeed in passing through the zona pellucida into the perivitelline space are called __ 9. How the transport of ovum in the oviduct is facilitated? (3 marks) 10. Explain the mechanisms underlying the blocks to polyspermy?

Answer 1

Part I: Multiple Choice Questions1. The correct answer is d a and b. The lining of digestive and respiratory tracts, liver, pancreas, and the endodermis CNS, sense organs, neural crest are all formed from the endoderm layer during embryonic development.Part II: Short Answers and Discussions1. A hollow ball of cells formed when a zygote undergoes a series of divisions is known as a **blastocyst**.2.ocrine functions of the placenta include the production of hormones such as human chorionic gonadotropin (hCG), progesterone, and estrogen. These hormones help maintain the pregnancy, support fetal development, and prepare the mother's body for childbirth.3. The two tissue types that form the placenta are the **chorion** and the **decidua basalis**. The chorion is the outermost layer of the placenta, and the decidua basalis is the innermost layer of the endometrium (uterine lining) that interacts with the chorion.4. The function of the yolk sac is to provide nutrients and oxygen to the developing embryo before the placenta takes over this role. It also plays a role in the formation of blood cells and the development of the circulatory system.5. The extraembryonic membrane whose function is to store nitrogen wastes of the embryo is the **allantois**.6. The cell division process directly related to the embryonic growth is **mitosis**.7. The participation of more than one spermatozoon in fertilization is called **polyspermy**.8. Extra sperm that succeed in passing through the zona pellucida into the perivitelline space are called **polyspermy-inducing sperm**.9. The transport of the ovum in the oviduct is facilitated by the **ciliary action** and **muscular contractions** of the oviduct walls. The cilia create a current that helps move the ovum, while the muscular contractions help propel it towards the uterus.10. The mechanisms underlying the blocks to polyspermy include the **zona reaction** and the **fast block to polyspermy**. The zona reaction involves changes in the zona pellucida that prevent additional sperm from binding and penetrating the egg. The fast block to polyspermy involves the depolarization of the egg membrane, which prevents further sperm from entering the egg.

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