Menstrual Cycle Quiz

The corpus luteum produces progesterone which causes the endometrium to become receptive to implantation of a blastocyst and prevents menstruation occurring.

The secretory phase of the menstrual cycle begins after ovulation when the ruptured graafian follicle develops into the corpus luteum. The corpus luteum produces progesterone which causes the endometrium to begin secreting various substances which make the uterus more receptive to implantation of a fertilised ovum.

The most fertile period of the menstrual cycle is from 5 days before ovulation to 1-2 days after. Couples often use this knowledge to increase their chances of conception.

It is not uncommon for women to miss a period, however, it doesn't necessarily mean a woman is pregnant. It can be due to a large number of other factors such as hormonal imbalances, stress, diet, age and contraception.

An increase in a woman's basal body temperature occurs due to the LH surge. As a result, the rise in body temperature indicates that ovulation is likely to occur in the next 24-48 hours. The cervical mucus also becomes thinner around the time of ovulation to allow easier passage of sperm.

The LH surge usually occurs on day 12. This occurs due to oestrogen levels reaching a peak level which stimulates large amounts of LH production. The high LH level causes the membrane of the Graafian follicle to become thin. As a result, 24-48 hours after the LH surge ovulation usually occurs due to the rupture of the Graafian follicle.

In the follicular phase oestrogen functions to increase the probability of successful fertilisation. As a result, it causes the mucus of the cervix to become much thinner allowing easier passage of sperm. It also causes thickening of the endometrium to increase chances of successful implantation of a blastocyst.

The menstrual phase occurs at the very beginning of the uterine cycle. It only occurs if no ovum is fertilised. The process begins with the breakdown of the corpus luteum which therefore ceases to produce progesterone. The loss of progesterone causes vasoconstriction of the spiral arteries supplying the functional layer of the endometrium. As a result, it becomes necrotic and is then lost through the vagina causing the 3-5 days of bleeding.

The corpus luteum is the primary source of progesterone at the start of pregnancy, however, the corpus luteum breaks down eventually. So from the 8th week of pregnancy, the main source of progesterone is the placenta.

The proliferative phase begins immediately after the menstrual phase and involves increased levels of oestrogen driving repair and growth of the functional endometrial layer.

Progesterone is involved in many different processes during the menstrual cycle. It causes the endometrium to become more receptive to implantation of a fertilised ovum. It also inhibits the production of LH and FSH via negative feedback.