Question

Consider the following statements: Assertion (A): Placenta of human beings is described as haemochorial type. Reason (R): Chorionic villi of the foetus are dipped in the blood pools of uterine wall.

• A. Both (A) and (R) are correct, (R) is the correct explanation for (A)
• B. Both (A) and (R) are correct, (R) is not the correct explanation for (A)
• C. (A) is correct, but (R) is not correct
• D. (A) is not correct, but (R) is correct

Hint:

Human placenta = Haemochorial type Foetal chorionic villi are surrounded by maternal blood pools. This arrangement allows efficient exchange of oxygen, nutrients and wastes between mother and foetus.

Answer 1

The Correct Option is A

Concept: The human placenta is formed by interaction between maternal tissues and foetal chorionic villi. Classification of placenta depends on the relationship between maternal blood and foetal tissues.

Step 1: Understand haemochorial placenta. The term haemochorial means: \[ \text{Haemo} = \text{blood} \] \[ \text{Chorion} = \text{foetal membrane} \] In this type of placenta, chorionic villi are directly surrounded by maternal blood.

Step 2: Examine Assertion (A). Human placenta is classified as: \[ \boxed{\text{Haemochorial placenta}} \] Therefore Assertion is correct.

Step 3: Examine Reason (R). Maternal blood collects in spaces called blood pools. Foetal chorionic villi project into these pools. Thus, \[ \boxed{\text{Chorionic villi are bathed in maternal blood}} \] Hence Reason is also correct.

Step 4: Determine whether Reason explains Assertion. The placenta is called haemochorial precisely because chorionic villi are immersed in maternal blood spaces. Therefore Reason directly explains Assertion. \[ A=\text{True} \] \[ R=\text{True} \] \[ R \Rightarrow A \]

Step 5: Choose the correct option. \[ \boxed{\text{Option (A)}} \]