Page 95 - 86 human physiology part-2

Chapter 16

occur, the embryo produces Human Chorionic Gonadotropin (HCG), which maintains the corpus
luteum and causes it to continue producing progesterone until the placenta can take over production of
progesterone. Hence, progesterone is "pro gestational" and maintains the uterine lining during all of
pregnancy. If fertilization and implantation do not occur the corpus luteum degenerates into a corpus
albicans, and progesterone levels fall. This fall in progesterone levels cause the endometrium lining to
break down and sluff off through the vagina. This is called menstruation, which marks the low point for
estrogen activity and is the starting point of a new cycle.

Common usage refers to menstruation and menses as a period. This bleeding serves as a sign that a
woman has not become pregnant. However, this cannot be taken as certainty, as sometimes there is
some bleeding in early pregnancy. During the reproductive years, failure to menstruate may provide the
first indication to a woman that she may have become pregnant.

Menstruation forms a normal part of a natural cyclic process occurring in healthy women between
puberty and the end of the reproductive years. The onset of menstruation, known as menarche, occurs
at an average age of 12, but is normal anywhere between 8 and 16. Factors such as heredity, diet, and
overall health can accelerate or delay the onset of menarche.

Signs of ovulation

The female body produces outward signs that can be easily recognized at the time of ovulation.
The two main signs are thinning of the cervical mucus and a slight change in body temperature.

Thinning of the Cervical Mucus

After menstruation and right before ovulation, a woman will experience an increase of cervical
mucus. At first, it will be thick and yellowish in color and will not be very plentiful. Leading up to
ovulation, it will become thinner and clearer. On or around the day of ovulation, the cervical mucus
will be very thin, clear and stretchy. It can be compared to the consistency of egg whites.

Temperature Change

A woman can also tell the time of ovulation by taking her basal body temperature daily. This is a
temperature taken with a very sensitive thermometer first thing in the morning before the woman gets
out of bed. The temperature is then tracked to show changes. In the uterine cycle, a normal temperature
will be around 97.0 – 98.0. The day of ovulation the temperature spikes down, usually into the 96.0 –
97.0 range and then the next morning it will spike up to normal of around 98.6 and stay in that range
until menstruation begins.

Both of these methods are used for conception and contraception. They are more efficient in
conception due to the fact that sperm can live for two to three days inside of the fallopian tubes. A
woman could be off by a couple of days in her calculations and still become pregnant.

Menopause is the physiological cessation of menstrual cycles associated with advancing age.
Menopause is sometimes referred to as "the change of life" or climacteric. Menopause occurs as the
ovaries stop producing estrogen, causing the reproductive system to gradually shut down. As the body
adapts to the changing levels of natural hormones, vasomotor symptoms such as hot flashes and
palpitations, psychological symptoms such as increased depression, anxiety, irritability, mood swings
and lack of concentration, and atrophic symptoms such as vaginal dryness and urgency of urination

310 | Human Physiology