91影视

Menstruation is a monthly cycle in females during which the endometrial lining of the uterus peels off. This process occurs in females who have not conceived, and pregnancy has not taken place. During menstruation, blood and endometrial tissues make their way out of the body through the vagina.

All mammals do not have a menstrual cycle; some of them exhibit an estrous cycle. This is covert of the menstrual cycle exhibited in some mammals when they are in heat or are sexually receptive. When they mate during this period, these organisms conceive.

Thus, all mammals do not have a menstrual cycle.

Therefore, the given statement is false.

In menstrual cycles, the endometrial lining is shed, and it comes out through the vagina. However, during the estrous cycle, the endometrial lining is shed, but it is so minimal that they get reabsorbed by the uterus.

Thus, the endometrial lining is removed during the menstrual cycle, but in the estrous cycle, it is reabsorbed.

Therefore, the given statement is true.

Estrous cycles do not occur every month like menstrual cycles. The reoccurrence of the estrous cycle varies in different mammals. In some mammals, the estrous cycles occur thrice a year, while in others, it occurs twice or only once.

Thus, the estrous cycle does not occur as frequently as menstrual cycles.

Therefore, the given statement is false.

In estrous cycles, the endometrial lining thickens several days before ovulation can occur. The thickening reaches the highest peak six hours before ovulation can occur. Once ovulation has taken place, the endometrial tissue gradually thins down.

Thus, the endometrium thickens before ovulation occurs in the estrous cycle.

Therefore, the given statement is false.