Question

ASSERTION: The endometrium undergoes cyclical changes during the menstrual cycle.
REASON: The myometrium exhibits strong contractions during the delivery of the baby.
(a) Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
(b) Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
(c) Assertion is correct but Reason is incorrect
(d) Both Assertion and Reason are incorrect

Answer 1

Myometrium is the middle layer of the uterine wall, while the endometrium is the inner epithelial layer. So, the assertion and the reason given in the above-mentioned question are true but we mainly have to find that the reason is the explanation of the assertion, which seems to be false.

Complete answer:
The reason:‘The myometrium exhibits strong contractions during the delivery of the baby.’ is not the correct explanation of the assertion. The wall of the uterus consists of three layers of tissue. The external thin membranous perimetrium, a middle thick layer of smooth muscle, myometrium, and an inner glandular layer called endometrium that lines the uterine cavity. The endometrium undergoes cyclical changes during the method of the cycle whereas the myometrium exhibits strong contractions during the delivery process of the baby. Thus, both the statements are correct but they do not work as explanations for one another.

Additional Information:
- The myometrium forms the middle layer of the uterine wall, which mainly consists of uterine smooth muscle cells which are also known as uterine myocytes, but it also forms the supporting stromal and vascular tissue. Its main function is to induce uterine contractions.
- The endometrium is the inner lining of the uterus and it has two layers- a basal layer and a functional layer.
- Each month, the functional layer thickens and renews itself, preparing for pregnancy then if pregnancy doesn't occur, it is shed during menstruation in humans and some other mammals, such as apes, monkeys, some species of bat.
- The endometrium is reabsorbed in the estrous cycle in most of the other mammals.
- If pregnancy occurs or conception takes place, the embryo gets implants into the endometrium.
- The glands and blood vessels in the endometrium further increase in size and number during pregnancy.
- At the time of pregnancy the vascular spaces fuse and become interconnected resulting in the formation of the placenta, which supplies oxygen and nutrition to the embryo and fetus.

So, the correct answer is, ‘Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion’.

Note:
- The molecular structure of the smooth muscle of myometrium is very similar to that of smooth muscle found in other parts of the body, having myosin and actin as the predominant proteins.
- In uterine smooth muscle, there is approximately 6-fold more actin as compared to myosin.
- During the menstrual cycle a shift in the myosin expression of the uterine smooth muscle may be responsible for changes in the directions of uterine contractions.