Reproductive System
6.6.1 Draw and label diagrams of the adult male and female reproductive systems.
6.6.2 Outline the role of hormones in the menstrual cycle, including FSH (follicle stimulating hormone), LH
(luteinizing hormone), estrogen and progesterone.
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Menstrual Cycle:
o Prepares the ovaries for ovulation and the uterus for implantaion
o Lasts approximately 28 days…time between the females release of the egg from the ovaries
(known as ovulation).
o Egg must be released to the endometrium (the inner lining of the uterus.)
o The endometrium is highly vascularized which allows implantation if egg is fertilized
o If egg is not fertilized, endometrium breaks down, which leads to menstrual bleeding
o Menstruation is a sign that pregnancy has not occurred
Role of Hormones
o Hypothalamus is the control center for the menstrual cycle.
o Gonadotrophin Releasing Hormone (GnRH)
 Causes pituitary gland to secrete follicle stimulating hormone (FSH) and Leutinizing
Hormone (LH) to be released into the blood stream and target the ovary .
o Follicle Stimulating hormone (FSH)
 Stimulates the development of a primary follicles, which surround the oocyte (egg)
providing protection and nutrients.
 Develops the oocyte in the follicle and Produces follicular fluids.
 Increases the number of follicular cells which in turn produce estrogen, which
causes vascularization of endometrium.
o Luteinizing Hormone (LH):
 High LH is associated with a resumption of meiosis in the oocyte. Meiosis has been
arrested in Prophase I since the embryonic stage. Only at the point of fertilization
does meiosis complete.
 Surges in mid cycle (12 days) to bring about ovulation, or release of oocyte
(surrounded by follicles) from ovary.
 Some follicle cells remain in the ovaries and develop into the corpus luteum. These
cells also release progesterone, which maintains the thickened vascularized
endometrium
o Estrogen - causes vascularization of endometrium
o Progesterone - prevents break down of endometrium and implantation can still occur
o High levels of Estrogen and Progesterone are negative feedback signals w/ hypothalamus, as
it will not produce GnRH, which in turn will not allow FSH and LH to affect ovaries
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Assuming no pregnancy, corpus luteum breaks down, progesterone and estrogen levels
decline, endometrium breaks down causing menstruation
Drop in estrogen and progesterone levels signals the hypothalamus to release GnRH and
another menstrual cycle begins
6.6.3 Annotate a graph showing hormone levels in the menstrual cycle, illustrating the relationship between
changes in hormone levels and ovulation, menstruation and thickening of the endometrium.
6.6.4 List three roles of testosterone in males.
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Week 7 of embryonic development, testosterone initiates the development of male genitalia.
Around mid-teens, testosterone initiates the development of secondary sexual characteristics
a. increase in muscle mass
b. increase in the length of the long bones (height)
c. increase in the length of the vocal cords (voice deepens)
d. spermatogenesis
e. growth of the penis and testis
Post puberty testosterone maintains the production of sperm cells and the male sex drive.
6.6.5 Outline the process of in vitro fertilization (IVF).
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Problems with Fertilization
o Low sperm counts
o Males w/ impotence (failure to achieve/maintain an erection)
o Females who cannot ovulate normally
o Females with blocked fallopian tubes
In-vitro Fertilization (IVF)
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Woman injected with FSH for about 10 days, causing production of many follicles, and
allows for several eggs to be harvested
Man donates his sperm into an external container
Fertilization occurs in separate culture dishes and observations reveal which ova are
fertilized and appear normal and healthy
2-3 healthy embryos inserted into woman’s uterus for implantation
6.6.6 Discuss the ethical issues associated with IVF.
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Pro IVF
Enables couples to have children
Embryos not healthy can be eliminated
to increase chance of implantation
Genetic screening is possible to
eliminate chance of passing on some
genetic diseases
IVF tech can advance and lead to
further benefits of reproduction
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Anti IVF
Embryos not implanted are frozen or
destroyed
Legal issues concerning frozen
embryos when couples split
Genetic screening could lead to society
choosing desirable traits
Bypasses natures way of decreasing
genetic frequency of
reproductive/genetic problems
Multiple births and problems
associated with multiple births are
more likely with IVF than natural
conception
11.4.1 Annotate a light micrograph of testes to show the location of interstitial cells (leydig cells), germinal
epithelium cells, developing spermatozoa, and Sertoli cells
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Leydig Cells: Produce testosterone and
other hormones
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Spermatogonia: Germinal Epithelium Cells
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Spermatozoa: sperm cells
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Sertoli Cells: provide nutrients to
Spermatozoa during sperm differentiation
11.4.2 Outline the process involved in spermatogenesis within the testes, including mitosis, cell growth,
meiosis, and cell differentiation
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Spermatogenesis: the production of sperm cells, which occurs within the testes
Testes located outside the body to provide cooler temps for spermatogenesis
Occurs within seminiferous tubules
Spermatogonia: diploid germinal epithelial cells that will undergo mitosis (to produce more
Spermatogonia) or they will undergo meiosis (to produce 4 haploid Spermatozoa, aka sperm cells)
Process
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Spermatogonia cells contain 23 pairs of chromosome (46 total) – undergo normal parts of
cell cycle (G1, S, G2)
o Meiosis occurs after DNA replication to cut number of chromosomes in half (23 total
chromosomes), making spermatozoa (1 spermatogonia  4 spermatozoa)
o Spermatozoa must differentiate into fully functioning sperm cell (spermatozoon) inside
seminiferous tubule, attached to Sertoli cells for nutrients
 Flagellum for motility
 Acrosome contains enzyme necessary for fertilization
o As sperm cells develop, they move closer to lumen of seminiferous tubule
o Once development is completed, they detach from Sertoli cells and carried to epididymis
where it is stored
Sperm cell production starts at puberty and continues throughout life, producing millions of sperm
cells a day
11.4.3 State the role of LH, FSH, and testosterone in spermatogenesis
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Leutinizing Hormone (LH) stimulates Leydig Cells to produce testosterone
Follicle Stimulating Hormone (FSH) and testosterone stimulate meiotic divisions of spermatogonia
into spermatozoa
11.4.6 Draw and label the structure of a mature sperm
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Flagella provides motility for swimming
Mitochondria provides ATP for energy for swimming
Head contains haploid nucleus with half number of chromosomes
Acrosome contains hydrolytic enzymes to help with fertilization process
Small size allows them to swim great distances
11.4.7 Outline the role of the epididymis, seminal vesicle, and prostate gland in the production of semen
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Semen: Fluid that is ejaculated during intercourse, contains sperm cells and fluids that assist in
reproduction
Epididymis: Stores sperm cells allowing them to gain motility
Vas Deferens: sperm moves from epididymis to urethra through vas deferens
Seminal Vesicles: Add large volume of fluid (70%) that contains high concentration of fructose,
needed to provide energy to sperm cells to swim to ovum
Prostate Gland: Adds more fluid (30%) that contains alkaline and helps sperm cells survive
environment in female vagina
Urethra: excretory tube, site of ejaculation
11.4.4 Annotate a diagram of the ovary to show the location and function of germinal epithelium, primary
follicles, mature follicle, and secondary oocyte
11.4.5 Outline the processes involved in oogenesis within the ovary, including mitosis, cell growth, two
divisions of meiosis, unequal division of cytoplasm, and degeneration of polar bodies
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Oogenesis: the production of ovum (egg cells) through meiosis
Produces four haploid cells, however, only one becomes an egg cell
o 3 are too small to produce zygote upon fertilization and become polar bodies (containers for
divided chromosomes after meiosis)
o 1 is very large and becomes egg cell
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Oogenesis Before Birth
o During fetal development, oogonia cells (diploid) undergo mitosis, increasing number of
cells in ovary
o Oogonia cells grow into larger cells called primary oocytes (diploid), which will undergo
initial steps of meiosis (through prophase 1, then pauses)
o Follicle cells undergo mitosis and a single layer surrounds primary oocytes, forming primary
follicle
o Females born with half a million primary follicles
Oogenesis & Menstrual Cycle
o Each menstrual cycle, primary follicle finishes meiosis I and forms 1 secondary oocyte and
polar bodies
o Follicle cells begin dividing and forming 2 rings with a fluid filled cavity around secondary
oocyte
o Secondary Oocyte begins Meiosis II, but again is paused during prophase forming Graafian
Follicle
o Secondary Oocyte and its inner follicle ring are released during ovulation and only completes
Meiosis if fertilized by sperm cell
o * Be able to relate these steps to what happens in menstrual cycle and hormones that are
used.
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11.4.6 Draw and label the structure of a mature egg
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Largest cell in body by volume
Unequal distribution of cytoplasm ensured on cell has all nutrients,
cytoplasm, and organelles necessary for a new life.
Haploid nucleus/nucleolus
Nutrients are referred to as yolk
Follicle cells, protect and nourish egg
Cortical granules ensure only one sperm cell can fertilize egg
Zona pellucida (layer of glycoproteins) becomes impermeable to other sperm cells upon fertilization
11.4.8 Compare the process of spermatogenesis and oogenesis, including the number of gametes and the
timing of the formation and release of gametes
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11.4.9 Describe the process of fertilization, including acrosome reaction, penetration of the egg membrane
by a sperm, and the cortical reaction
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The union of haploid male and female gametes to form a diploid zygote
Typically occurs in the Fallopian Tube
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Takes many sperm cells to accomplish fertilization, however only one can fuse its membrane with the
egg cell to create a zygote
Many sperm cells are needed to penetrate the follicle cell layer.
Several Sperm cells gain access to zona pellucida and release hydrolytic enzymes, enabling the cells
to penetrate the zone and reach plasma membrane
One sperm cell reaches the plasma membrane of secondary oocyte
Plasma membranes fuse together and initiates the cortical reaction:
o Cortical granules fuse with cell membrane and release enzymes, making the zona pellucida
impermeable to other sperm cells
o Takes place immediately after first sperm cell fuses with egg cell and ensures only one sperm
cell fertilizes egg
Egg now completes meiosis II as haploid nucleus from sperm cell enters the egg
Resulting in a diploid zygote
11.4.11 Outline early embryo development up to the implantation of the blastocyst
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Fertilization triggers mitotic division in zygote, which takes roughly 5 days to reach uterus
Embryo consists of about 100 cells by time implantation occurs (7 days after fertilization), which
appear as a ball of cells, called a blastocyst
Blastocysts consist of:
o Trophoblast – surrounding layers of cells that will help form fetal portion of placenta
o Inner Cell Mass – interior cells located towards one end of blastocyst that will become body
of embryo
o Fluid filled cavity
11.4.10 Outline the role of HCG in early pregnancy
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Human Chorionic Gonadotrophin (HCG): hormone secreted by embryo that signals to corpus luteum,
causing it to maintain secretions of estrogen and progesterone
Maintains endometrium, which will form placenta after implantation
11.4.12 Explain how the structure and functions of the placenta, including its hormonal role in secretion of
estrogen and progesterone, maintain pregnancy
11.4.14 State that materials are exchanged between the maternal and fetal blood in the placenta
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Forms from trophoblast layer of blastocyst, and the endometrium of mother
Two fetal blood vessels within umbilical cord carry fetal blood to placenta and exchanges materials
with mother, which are brought back using a separate fetal blood vessel
o Embryo passes CO2, urea, water, and hormones to mother
o Mother passes O2, nutrients, water, hormones, vitamins/minerals, alcohol/drugs (if taken),
and viruses (if infected)
At no point does blood mix, only materials are exchanged
Placenta will also act as an endocrine organ during pregnancy, secreting estrogen and progesterone
Functions to maintain vascularized endometrium and provide rich blood supply to embryo
11.4.13 State that the fetus is supported and protected by the amniotic sac and amniotic fluid
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Amniotic sac surround embryo as it continues to grow and develop
Amniotic Fluid inside sac functions to:
o Cushion embryo from blunt force applied to mother’s abdomen
o Provide environment for movement allowing exercise, muscular and skeletal development
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Thermal stability (mainly water, so has excellent temperature stability)
General support so that the embryo does not experience any excess pressure
11.4.15 Outline the process of birth and its hormonal control, including the changes in progesterone and
oxytocin levels and positive feedback.
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Physiological events preparing for birth are called parturition
Progesterone levels decrease, and the hormone oxytocin is secreted from posterior pituitary gland
Initial low levels of oxytocin are associated with first contractions of uterus
Each uterine contraction signals to posterior lobe of pituitary to produce more oxytocin
Higher levels of oxytocin cause more intense and frequent contractions
This is a positive feedback mechanism and will continue and only stops when birth occurs and uterus no
longer has something to contract on.
Major Events @ Childbirth
o Major Hormone Change (discussed above)
o Dilation/Opening of Cervix to 10 cm
o Baby positioned head first, face down
o Shoulders typically widest part to pass through birth canal
o Afterbirth is name of expelled placenta
o Lactation (breast milk production) begins soon after birth.