Biology, Grade 12 SBI4U
Female Reproductive System
Specific Expectations
 E2.1 Use appropriate terminology related to
homeostasis, including, but not limited to:
insulin, testosterone, estrogen, nephron,
dialysis, pituitary, synapse, and acetylcholine.
 E3.2 Explain how reproductive hormones act in
human feedback mechanisms to maintain
homeostasis (e.g., the actions of male and female
reproductive hormones on their respective body
systems).
Agenda
 The Female Reproductive System
 Puberty
 Sex Hormones
 Negative Feedback Loop
 The Menstrual Cycle (Ovarian/Uterine)
 Rhythm Method
 Menopause
 Amenorrhea
Introduction
 The human reproductive system involves separate male
and female reproductive systems. In many ways, the female
system is more complicated than that of the male.
 Gonads are organs such as the testes (male), which
produce sperm, and ovaries (females) that produce
eggs(ova). These reproductive cells are known as gametes.
Uterus and Vagina
 The uterus is a muscular
organ that holds and
nurtures a developing
fetus
 Size/shape of a pear
(when not pregnant)
 The lining of the uterus
is known as the
endometrium
 The upper end of the
uterus connects to the
fallopian tubes and the
lower end connects to the
cervix.
Ovaries
 The two ovaries are
involved in Oogenesis,
which is the production
of ova/egg cells.
In general, ovaries switch,
producing one egg per
ovary each month
Ovaries
 Each ovary contains specialized
structures called follicles.
 Follicles contain 2 types of
cells:
1.
Egg Cells
2. Follicular Cells
Each month 1 follicle releases
1 ovum into a fallopian tube
(ovulation)
Any remaining follicles
deteriorate and are reabsorbed
within the ovary.
http://www.youtube.com/watch?v=nLmg4wSHdxQ
Puberty
 Puberty occurs around ages 9-13 in females, and 10-13
in males where the reproductive system starts to
develop maturely.
Puberty and Sex Hormones
 How does it begin?
 Puberty begins when GnRH is released from the hypothalamus and
acts on the anterior pituitary causing secretion of the following protein
hormones:
1. Follicle Stimulating Hormone (FSH)
2. Luteinizing Hormone (LH)
 FSH and LH stimulate the ovaries to secrete the steroid hormone:
1. Estrogen - activates the development of most secondary sex
characteristics.
Menstrual Cycle
 Begins in girls at 12-13 years of age
 Lasts about 28 days (may vary:20-45)
 Two separate cycles controlled by ovarian hormones
(mainly estrogen and progesterone) and pituitary
hormones (mainly FSH and LH)
1)Ovarian Cycle- Occurs in the ovaries
2)Uterine Cycle- Occurs in the uterus
Ovarian Cycle
http://www.youtube.com/watch?v=I0RsB1dj55o
1) Each follicle in the ovary contains an immature single
ovum
2) In one ovarian cycle, one follicle in the ovary matures and
releases a single ovum.
3) Once ovum is released, the existing follicle develops into a
yellowish gland structure known as the corpus luteum,
which then degenerates if fertilization does not occur
 Repeats every month
Uterine Cycle
http://www.youtube.com/watch?v=WGJsrGmWeKE&feature=related
Essentially, after the end of menstruation, the endometrium begins to
grow and thicken in cells, blood vessels, and glands.
Menstrual Cycle: Ovarian + Uterine
Cycles
Negative Feedback Mechanism
Menstruation Summary
Days
Ovary
Uterus
Hormones
1-5
Menstruation
(Menstrual Flow)
Shedding of the
endometrium
-No particular
hormonal surges
6-13
Follicles develop in
ovaries
Endometrium is
restored
-Estrogen rises to
maximum
-FSH rises a bit
Egg bursts from the
ovary and follicular cells
differentiate into the
corpus luteum
Endometrium
gradually thickening
-Estrogen drops
sharply
-LH surges
Corpus Luteum is
maintained and slowly
degenerates if
fertilization does not
occur
Endometrium
Estrogen/Progesterone
thickens to maximum rises then falls if
fertilization does not
occur
-FSH/LH inhibited
14
15-28
Rhythm Method
 The rhythm method, also called the calendar method is a form of
natural family planning.
How it works:
 You track your menstrual history to predict when you'll ovulate. This
will help to determine when you're most likely to conceive.
 Similarly, if you're hoping to avoid pregnancy, you can use the rhythm
method to determine which days to avoid unprotected sex.
 Using the rhythm method for birth control requires careful record
keeping and diligence. If you don't want to conceive, you and your
partner must avoid having sex or use other forms of contraception
Menopause
 Number of functional follicles begins to decline with age which
leads to a gradual decline in estrogen and progesterone in the
blood.
As these hormone levels drop, the menstrual cycle becomes
irregular and then stops which is known as menopause around
the age of 50 years.
Can have a wide range of effects of women
-hot flashes
-loss of bone mass
-increase risk of heart disease, breast cancer and uterine cancer
 Hormone replacement therapy may be considered.
Amenorrhea
 The term used to describe "absence of periods“.
 There are two types of amenorrhea:
1. Primary amenorrhea is when a young woman has not
had her first period by the age of 16.
2. Secondary amenorrhea is when a woman who has had
normal menstrual cycles stops having her monthly periods
for three or more months.
Causes of Amenorrhea
Possible causes of primary amenorrhea include:
 Failure of the ovaries
 Poorly formed reproductive organs
Common causes of secondary amenorrhea include:
 Pregnancy
 Stopping the use of birth control
 Stress/depression
 Poor nutrition
 Extreme weight loss/sudden weight gain
 Over-exercising