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Biology: The Unity and Diversity o...

15th Edition
Cecie Starr + 3 others
ISBN: 9781337408332

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BuyFindarrow_forward

Biology: The Unity and Diversity o...

15th Edition
Cecie Starr + 3 others
ISBN: 9781337408332
Textbook Problem
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The placenta consists of __________.

  1. a. embryonic tissue
  2. b. maternal tissue
  3. c. paternal tissue
  4. d. a combination of a and b

Summary Introduction

Concept introduction: The placenta is an exclusive feature of placental mammals. The placenta is an extra embryonic membrane along with allantois and chorion that helps to nourish the developing fetus by exchanging materials between the mother and the fetus.

Explanation

Reasons for the correct statement:

The sperm fertilizes the egg and then the zygote is formed. The zygote undergoes cleavage to form the blastocyst. The blastocyst is implanted in the uterus. The outermost cells of the blastocyst and the wall of the uterus help to give rise to a few extra embryonic membranes. The placenta consists of two layers. The outer layer is contributed by the outer layer of blastocysts and the inner layer is contributed by the maternal endometrium. Thus, both embryonic and maternal tissue gives rise to the placenta.

Option d. is given as “a combination of a and b”.

As both embryonic and maternal tissue give rise to placenta, option d. is correct.

Reasons for the incorrect statements:

Option a...

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