Ovulation is the process by which the graafian follicle in the ovary ruptures and, the ovum is released into the abdominal cavity. Ovulation occurs on the 14th day of menstrual cycle in a normal cycle of 28 days.
The ovum, which is released into the abdominal cavity, enters the fallopian tube through the fimbriated end of the tube. Usually, only one ovum is released from any one of the ovaries. LH is responsible for ovulation.
Process Of Ovulation
Prior to ovulation, large amount of LH is secreted (lureal surge). This causes changes in the graafian follicle leading to ovulation.
Stages of ovulation:
- Graafian follicle moves towards the periphery of ovary
- New blood vessels are formed in the ovary by actions of LH and progesterone
- These blood vessels protrude into the wall of the follicle
- This increases the blood flow to the follicle
- Now, prostaglandin is released from the granulosa cells of the follicle
- It causes leakage of plasma into the follicle
- Just before ovulation the follicle swells and protrudes against the capsule of the ovary. This protrusion is called stigma
- Then, progesterone activates the proteolytic enzymes present in the cells of theca interna
- These enzymes weaken the follicular capsule and cause degeneration of the stigma
- After about 30 minutes, fluid begins to ooze from the follicle through the stigma
- It decreases the size of the follicle causing rupture of stigma
- Now, ovum is released from the follicle along with plenty of small granulosa cells into the abdominal cavity.
Determination Of Ovulation Time
Usually, ovulation occurs on the 14th day of menstrual cycle if the cycle occurs in 28 days period. There are various methods to determine the ovulation time.
In human beings, usually indirect methods are adopted such as:
- By determining basal body temperature
- By determining hormonal excretion in urine
- By determining hormonal level in plasma
- By using ultrasound scanning>
By Determining Basal Body Temperature
The body temperature is measured for few days during the mid period of menstrual cycle. Temperature is measured in the morning by placing the thermometer in rectum or vagina. There is a slight fall in the basal temperature just prior to ovulation. And, the temperature increases slightly after ovulation. The alteration in the temperature is very mild and it is about ± 0.3 to 0.5°C.
By Determining Excretion Of Hormonal End Products In Urine
At the time of ovulation there is an increase in the urinary excretion of end products from:
- Estrogen metabolism like estrone, estriol and 17-beta estradiol
- Progesterone metabolism like pregnanediol also increases after ovulation.
By Determining Hormonal Level In Plasma
Plasma level of FSH, LH, estrogen and progesterone is measured. The hormonal level is altered at the time of ovulation and after ovulation.
At the time of ovulation:
- Decrease in FSH level
- Increase in LH level
- Increase in estrogen level.
Increase in progesterone level.
By Using Ultrasound Scanning
The process of ovulation can be observed in ultrasound scanning.
Significance Of Determining Ovulation Time
Family planning by rhythm method may be well adopted by determination of ovulation time.