Your Menstrual Cycle(s): The ovarian cycle and the Uterine cycle

Within the menstrual cycle, there are two different cycles happening in sync. The ovarian cycle and the Uterine cycle. 

The cycle that most of us refer to is the Ovarian cycle (follicular, ovulation and luteal phase), describing the process of egg development and release. 

The Uterine cycle describes the build up and shedding of the lining of your uterus, it happens alongside the ovarian cycle and can often be incorporated into Ovarian cycle descriptions. 

Menstruation and Proliferation happening during the follicular phase, and then the secretory phase coinciding with the Luteal phase.

SO what's happening where? 

 

OVARIAN CYCLE - (OVARIES)

Follicular phase: The follicular phase begins from the start of the period until ovulation and can last from 7 to 21 days.

The pituitary gland (a small area at the base of the brain that makes hormones) produces a hormone called Follicle Stimulating Hormone (FSH). In this stage, FSH causes the maturation of an egg in the ovary. First the ovaries create follicles which contain an immature egg.

These growing follicles produce oestrogen, prompting the thickening of your uterine lining in preparation for a possible pregnancy.

Eventually, one dominant follicle will emerge as the frontrunner.

Ovulation: Around the middle of your menstrual cycle, typically 14 days before your next period, you enter the ovulatory phase.

A surge in Luteinising Hormone (LH) leads to the release of a mature egg from the dominant follicle, a process known as ovulation.

Ovulation takes place 28 to 36 hours after the onset of the Luteinising Hormone (LH) surge and 10 to 12 hours after LH reaches its peak.

The egg then travels down the fallopian tube where it may meet sperm and fertilisation can occur.

Luteal Phase: The luteal phase typically lasts 10 to 16 days, from ovulation until the start of the next period.

The empty follicle transforms into a structure called the corpus luteum.

If fertilisation does not occur, the corpus luteum will then degenerate leading to a subsequent drop in progesterone.

This hormonal shift triggers the start of a new menstrual cycle as your uterine lining begins to shed once more, initiating the menstrual phase.

UTERINE CYCLE - (THE UTERUS) 

Menstruation: Physically, the main sign is vaginal bleeding – your period – that usually lasts around 2 to 7 days.

Day 1 of your cycle is the first day of your period, meaning the first day of full flow.

This bleeding happens because your body is shedding the lining of your uterus (called the endometrium) from the previous cycle.

Levels of oestrogen and progesterone are typically at their lowest. This causes the top layers of the lining to release and leave the body.

Proliferative Phase: The proliferative phase lasts from the end of the period until ovulation. 

Proliferation is the quick growth of cells and tissue. The uterus builds up a thick inner lining so a potential fertilised egg can implant and grow. 

Oestrogen typically rises during this phase. This signals the uterine lining to grow.

Secretory Phase: The secretory phase is the final phase of the uterine cycle, and it corresponds to the luteal phase of the ovarian cycle.

It's called the secretory phase because the cells of the lining of the uterus release – or secrete – many types of chemicals.

During this phase, due to raised progesterone levels, the endometrium thickens further and becomes mature, thanks to the formation of glands and vessels within it.

It prepares to receive a fertilised egg.

If fertilisation does not happen, the corpus luteum no longer produces progesterone. With the drop in hormones, the endometrium lining breaks down. This 'shedding' starts a new period.

 

Sometimes it is a lot to take in isn't it.....Which makes it even more incredible to think our bodies are just doing this!