Reproductive Cycles

 
The menstrual cycle of females is comprised of two main cycles; the ovarian cycle and the uterine cycle. These cycles are under the control of the hormones such as FSH, LH, estradiol and progesterone. .

Hormones

Hormones are tiny chemical messengers involved in sending information between various parts of the body. Hormones use the bloodstream as the highway along which they travel to reach different body parts.

Nearly all hormones are released in a pulsatile fashion in short bursts every 1-3 hours. As a result, bloodstream hormone levels can fluctuate over the course of days and weeks.

Estrogen and progesterone are the major female sex hormones, both produced by the ovaries. However, it is the follicle-stimulating hormone (FSH) and luteinizing hormone (LH) that play a role in the mother's ability to conceive. FSH stimulates the ovaries to produce follicles, while LH is critical for ovulation and the production of the corpus luteum. Ovulation is usually ushered in by a drastic peak in LH known as the LH surge.

Another key hormone involved in female reproduction is gonadotropin-releasing hormone (GnRH). Released by the hypothalamus in the brain, GnRH stimulates the pituitary to release FSH and LH. Finally, FSH and LH stimulate the production of sex hormones (testosterone and estrogen) in the testes of men and the ovaries of women, respectively.

The Ovarian Cycle

The ovarian cycle commands pelvic operations by also conducting the uterine cycle. The four major hormones involved in the ovarian cycle include FSH, LH, estrogen and progesterone. The ovarian cycle is divided into two main parts: the follicular phase and the luteal phase. The follicular phase lasts from the onset of bleeding until ovulation and it involves FSH and estrogen. The luteal phase extends from ovulation until bleeding begins again, involving LH and progesterone.

The Uterine Cycle

The uterine cycle is a 3 part cycle that mirrors the endocrine activity of the ovary. Its regulation is strongly determined by the ovarian cycle.

Menstrual Phase

The first part of the uterine cycle is the menstrual phase. The menstrual phase usually begins on the first day of bleeding and can last up to five days. The menstrual fluid excreted is composed of uterine lining, tissue fluid and blood. While it may seem like this phase is the most active phase of the mother's cycle, it is actually the phase in which her body returns to normal, baseline levels. Consequently, this is the most accurate time for hormone and ultrasound testing.

Proliferative Phase

Estrogen released from the follicle in the ovarian cycle allows for the multiplication of endometrial cells in the uterus. This phase of proliferation lasts until progesterone is released from the ovary. The wall of the uterus thickens and bleeding stops in preparation for egg implantation.

Secretory Phase

Progesterone secretion causes a switch from the proliferation of endometrial cells to the creation of a lush, nurturing environment in preparation for implantation. If pregnancy occurs, progesterone is continually released to maintain the hospitable lining. If there is no pregnancy, the levels of progesterone fall and endometrial cells degenerate, allowing for menstruation to take place.

Body Changes During Monthly Menstrual Cycle

The following is a brief overview of the physical changes occurring in the mother during the monthly menstrual cycle:

1. Rising levels of hormones, along with the LH surge, stimulates ovulation 14 days before the next period.

2. The lining of the uterus thickens as it prepares to create a nurturing environment for the egg.

3. The cervix increases its supply of mucus; the mucus also becomes more clear and slippery.

4. The ovary releases the egg and the egg proceeds on its path down the fallopian tube.

Typically, body temperature drops on the day of ovulation, followed by a rise of 0. 5-1. 0 degrees Fahrenheit, for a few days after ovulation.

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