Hello, Thanks for posting your query.
Firstly I would like to mention about the structures of a female reproductive system, they are from bottom to top, vagina, cervix, uterus, tubes and ovaries.
Inwardly, the cervix is lined by a layer of cells among which are mucous secreting glands. These glands secrete mucous and they let the mucus into the cervical canal which gradually leaks out of vagina along with the vaginal secretions. This cervical mucous consists of fructose which attracts sperms, it is alkaline with a pH of 7.8. It helps in alkalinizing the vaginal acidity during menstruation.
Cervical mucous periodically changes its consistency and amount under the influence of the cyclical hormonal changes. It also varies among women, in quantity based on timing.
There is influence of two hormones specifically, estrogen and progesterone. During ovulation there are high levels of estrogen, due to which the cervical mucus changes its physical characters like- it becomes thin and profuse- that the patient may notice a clear discharge. This mucous has a property of great elasticity and can stretch even up to 10 cm. This process is called spinnbarkeit or thread test for ovulation.
On the other hand, in the post ovulatory phase under the influence of progesterone the cervical mucous becomes more viscous and it loses the property of stretching and breaks easily. The properties of cervical mucus, change from individual to individual, and within the same individual during different phases of development.
The amount of cervical mucous increases during puberty, during ovulation, during pregnancy and in some women pre-menstrually.
Also, there are variations if there is any medical condition associated with the cervix, in sexually transmitted diseases.
Hope this helps.