Question

Which of the following animals show menstrual cycle?
A) Gorillas and chimpanzees
B) Monkeys and humans
C) Orangutans and monkeys
D) All of these

Answer 1

Hint: Menstruation cycle occurs in all primates. In these organisms, the lining of endometrium is lost every month when an egg misses fertilization. It is lost through the vagina.

Complete answer:
Menstruation cycle is the same in all mammals to some extent. It involves the thickening of the endometrium thus preparing it for the embryo implantation. But this endometrial lining is shed in case if the egg is not fertilized. Menstruation cycle takes place in all primates, a group consisting of apes, monkeys and human beings. In gibbons and chimpanzees, the menstrual bleeding can be detected easily whereas in orangutans and gorillas bleeding is quite less and therefore the menstruation is visible only on closer inspection.
Gorillas, chimpanzees, monkeys, orangutans and humans are all primates and therefore they all show menstruation cycle.

So, the correct answer is option “D”.

Note: In the majority of mammals, the lining of the endometrium is extremely thin and therefore it is completely reabsorbed into the body. This process is referred to as covert menstruation. However, in other mammals, like human beings, there is formation of thick endometrial lining and therefore a part of it is lost from the body through the vagina when an egg remains unfertilized after ovulation. This is known as overt menstruation. This occurs in human beings and in the majority of Asiatic and African monkeys, along with 50 other species. Overt menstruation is found only in a few species of the monkey. Non-primates like African elephant shrews, few species of bat and tupaia also menstruate in this way only.