3: Gametogenesis and Hormones in Reproduction and Development Flashcards
(152 cards)
1
Q
development of gametes
A
Gametogenesis
2
Q
Gametogenesis usually not completed until the organism has become
A
physically mature
3
Q
Gametogenesis completed in the sexually mature adult, begins at _ times during development, depending on the species
A
different
4
Q
Gametogenesis divided into four phases
A
a.) the extraembryonic origin of the germ cells and their migration into the gonads,
b.) an increase in the number of germ cells by mitosis,
c.) a reduction in chromosomal number by meiosis, and
d.) structural and functional maturation of the eggs and spermatozoa
5
Q
The first phase of gametogenesis is _ in males and females, whereas distinct differences exist between the male and female patterns in the last three phases.
A
identical
6
Q
process of sperm cell production
A
Spermatogenesis
7
Q
Spermatogenesis _ process in the adult male
A
prolific and continuous
8
Q
Spermatogenesis occurs in the paired male gonads, or testes, specifically in the _
A
seminiferous
tubules
9
Q
each ejaculation of a human male contains _ sperm cells, and males can ejaculate daily with little loss of fertilizing capacity
A
100 to 650 million
10
Q
Primordial germ cells of the embryonic testes differentiate into
A
spermatogonia
11
Q
diploid cells that are the precursors of sperm
A
spermatogonia
12
Q
are undifferentiated cells located near the outer wall of the
seminiferous tubules
A
Spermatogonia
13
Q
Spermatogonia undergo repeated _ to produce more spermatogonia.
A
mitosis
14
Q
In a mature male, about 3 million spermatogonia per day differentiate into _
A
primary spermatocytes.
15
Q
diploid or haploid?
Each primary spermatocyte undergoes first meiotic division producing _
A
haploid secondary spermatocytes.
16
Q
how many are they?
In the second meiotic division, each secondary spermatocyte gives rise to _
A
two haploid spermatids.
17
Q
_ are produced from the original primary spermatocyte.
A
Four spermatids
18
Q
Spermatids then differentiate into a mature sperm cell or _.
A
spermatozoa
19
Q
The differentiation of the spermatids into sperm cells is called _
A
spermiogenesis
20
Q
corresponds to the final part of spermatogenesis and comprises the following individual processes that partially proceed at the same time.
A
spermiogenesis
21
Q
Spermatogenesis involves association of the developing sperm with _ which transfer nutrients to the spermatozoa
A
large Sertoli cells
22
Q
The release of a sperm cell from its connection to a Sertoli cell is known as
.
A
spermiation
23
Q
During spermatogenesis, the developing sperm are gradually pushed toward the _, flow toward _ and make their way to the _ where they acquire motility.
A
center or lumen of seminiferous tubules
ducts of the testes
epididymis
24
Q
This process from spermatogonia to motile sperm, takes _ in the human male to complete.
A
64 days
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Sperm cells **mature at a rate** of _ per day.
300 million
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Once ejaculated, they will probably **not survive** more than _ **within the female** reproductive tract.
48 hours
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The approximate _ cycle of the spermatogenesis can be subdivided into four phases that last differing lengths of time
64-day
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# process-> days-> product
The Temporal Course of Spermatogenesis
1. Mitosis of the spermatogonia - 16 days:primary spermatocytes
2. First meiosis - 24 days: secondary spermatocytes
3. Second meiosis - few hours: spermatids
4. Spermiogenesis - 24 days: sperm cells
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# parts of sperm
Each mature sperm consists of a
head, midpiece, and flagellum (tail)
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The head consists of the nucleus and the nuclear material DNA and a cap called **acrosome** that produces enzymes _ that aid sperm cell to penetrate the secondary oocyte.
hyaluronidase and proteinases
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Numerous mitochondria, located in the _ of the sperm (provides the energy (ATP) for locomotion)
midpiece
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A tail, the flagellum has a typical eukaryotic arrangement of _ propels the sperm along its way.
9+2
microtubules
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sperm head may appear _ in bull and man, _ in rat, while _ in birds
ovoid
triangular and with a hook
slender and with pointed tips
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“discards cytoplasm and growing tails”
Spermiogenesis
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Stages of Spermiogenesis
1. Formation of the Acrosomal Cap
2.Condensation of the Nucleus
3.Development of the Flagellum
4.Sheath Arrangement of the Mitochondria
5.Cytoplasm Reduction
6.The mature sperm cell is approximately 60 µm long and completely enveloped by the plasma membrane
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# Formation of the Acrosomal Cap
The development of the **acrosomal cap** is due to the coalescence of the _ which pinch off from it and forms a membranous structure called **acrosome**
vesicles of the Golgi apparatus
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# Formation of the Acrosomal Cap
Acrosome contains enzymes that play important role in the penetration through the _ (part) of the oocyte.
zona pellucida
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# Formation of the Acrosomal Cap
The acrosome corresponds functionally to a **lysosome** and thus contains **lysosomal enzymes** (_ among others).
hyaluronidase
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# Condensation of the Nucleus
The _ makes it condensed, thus, reducing its size and decreasing the concentration of its chromatin
loss of fluid in the nucleus
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# Condensation of the Nucleus
The acrosome lies over the _ of the nucleus
tip
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# Condensation of the Nucleus
_ form the sperm cell's head that is bound to the mid-piece by a short neck.
Nucleus and acrosome
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Involves the generation of the sperm cell tail.
Development of the Flagellum
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# Development of the Flagellum
At the opposite pole of the spermatids, a _ becomes the root of the growth of a group of **microtubules**.
pair of centrioles
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# Development of the Flagellum
The posterior centriole which moves away from the anterior one forms the shape of a _ surrounding the flagellum.
ring
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# Development of the Flagellum
This organelle supports the developing flagellum which extends into the lumen of the tubule.
mitochondrion
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# Sheath Arrangement of the Mitochondria
The cell’s mitochondria aggregate around the base of the flagellum forming a _ configuration
spiral
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# Cytoplasm Reduction
As the event continues, the _ disintegrates, leaving the spermatozoon **stripped of all nonessential parts**.
residual part of the cytoplasm
## Footnote
All unnecessary cytoplasm is eliminated during the process.
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development of ova (mature, unfertilized egg) from oogonia
Oogenesis
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Oogenesis involves _ and occurs in the ovaries (the female gonad)
meiosis
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# 1
The process begins when oogonia undergo _ to produce a **fixed number** of daughter cells during embryonic stage of development
mitotic division
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# 1
Before
birth, hundreds of thousands of _ are present in the ovaries
oogonia
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# 2
_ arises from the primordial germ cell dividing by meiosis in the ovary into oocyte.
Oogonium
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# 2
**All** of the female’s gametes originate during _.
embryonic development
## Footnote
**No new oogonia are formed after birth.**
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# 3
During **prenatal development**, the oogonia increase in size and become _
primary oocyte
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# 4
By the time of birth, they are in the _. At this stage, they enter a resting phase that last throughout childhood and into the adult life
prophase of the first meiotic division
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# 4
A primary oocyte and the cluster of cells surrounding it together make up a _
follicle
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# 4
when?
With the onset of puberty a few follicles develop _ in response to FSH secreted by the anterior pituitary gland.
each month
## Footnote
As the follicle grows, the primary oocyte completes its first meiotic division.
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# 5
?
The two cells produce are different in size. The smaller one, the first polar body.
What divides that eventually disintegrate?
forming two polar bodies
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# 6
The larger cell, the **secondary oocyte,** proceeds to the ***second meiotic division*** but remains in _ until it is fertilized.
metaphase
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# 6
product?
When meiosis does not continue, the second meiotic division gives rise to a
_
single ovum and a second polar body
## Footnote
The polar bodies are small and apparently serve to dispose of unneeded chromosomes with minimal amount of cytoplasm
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products?
Series of events if meiosis did not continue.
1. Oogonia (diploid)
2. Primary oocyte (diploid)
3. Secondary oocyte + 1st Polar body (both haploid)
4. Ovum + 2nd Polar body (both haploid)
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o Each primary spermatocyte gives rise to _ sperms.
o Each primary oocyte generates _ ovum.
## Footnote
In the male, large number of sperms are necessary to ensure fertilization.
four
only one
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As follicle develops, it becomes separated from its **surrounding follicle cells by a thick membrane**, the
zona pellucida.
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o As the follicle develops, follicle cells secrete fluids, which collect in the space between them.
o The **follicle secretes** _, female sex hormones.
estrogens
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As a **follicle matures**, it moves closer to the _ of the ovary, eventually resembling **fluid-filled bulge** on the ovarian surface.
surface
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# how many
Typically, _ follicle matures each month.
only one
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Several others (follicle) may develop for about a _ and then disintegrate.
week
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At ovulation, the secondary oocyte is ejected through the wall of the ovary and into the pelvic cavity.
The **portion of the follicle that remains** in the ovary develops into the _ wherein it **secretes estrogens and progesterone**.
corpus luteum (temporary endocrine gland)
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It undergoes or it does not?
Once the secondary oocyte exits the ovary, it begins to travel down the uterine (fallopian tube).
o If it does not encounter spermatozoa, it _
o If the secondary oocyte comes in contact with spermatozoa, fertilization begins, and the **secondary oocyte** undergoes its _to form an **ovum** and another **polar body.**
* never undergoes the second meiotic division.
* second meiotic division
## Footnote
1. The second meiotic division only occurs when fertilization happens.
2. Polar bodies are small and die quickly, just the ovum survives.
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# where
each primary oocyte develops within a
follicle
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in response to FSH, (follicle stimulating hormone) several follicles grow, but _ usually matures
only one
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in the process known as _ , the **follicle ruptures** releasing a secondary oocyte
ovulation
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the remaining follicular tissue develops into _ , which
disintegrates **if fertilization does not occur**
corpus luteum
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# every
meiosis or mitosis every?
During puberty, a single primary oocyte usually complete
_.
meiosis I each month
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describe the division?
The meiotic divisions in oogenesis involve _ cytokinesis
unequal
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cyclic, physiologic **changes in the levels of hormones** that cause the release of an egg from the ovary and thickening of the lining of the uterus
(endometrium) in preparation of receiving and nourishing a fertilized egg
Menstrual Cycle
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Menstrual cycle recurs approximately every _ from puberty to menopause
four week or 28 days
## Footnote
occurs in female of reproductive age
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2 Kinds of Menstrual Cycle
1. Overt menstruation
2. Covert menstruation
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where there is **blood flow from the vagina** occurs primarily in humans and close evolutionary relatives such as
chimpanzees
Overt menstruation
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where there is **no blood flow**, the
**endometrium is completely resorbed** by the animal at the end of its reproductive cycle; occurs in females of other species of placental
mammals that have **estrous cycle**
Covert menstruation
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# what cycle is?
under the **control of the hormone system** and is necessary **for reproduction**
mestrual cycle
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Menstrual Cycle divided into 3 phases:
o Menstruation
o Follicular phase
o Luteal phase
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defines the transition **from the follicular** phase **to the luteal** phase
Ovulation
## Footnote
Counted from the first day of menstrual flow, the length of each phase varies from woman to woman and cycle to cycle.
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The average Menstrual cycle length is _
28 days or 4 weeks
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**MC stimulated** by gradually increasing amounts of _ in the follicular phase, the lining of the uterus _
estrogens
thickens
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Follicles in the ovary begin to develop under the influence of a complex interplay of hormones, and after several days, one or occasionally two become dominant, **(non-dominant follicle undergoes** _).
atrophy and die
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The **dominant follicle releases an ovum**, or egg in an event called _
ovulation
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After ovulation, the remains of the **dominant follicle** in the ovary become the **corpus luteum**; this so called *yellow body* has a primary function of **producing** large amounts of _
progesterone.
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Under the influence of _ , the **endometrium** (uterine lining) changes and **thickens** in preparation for possible implantation of an embryo to establish pregnancy
progesterone
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If implantation does not occur within approximately _ , the **corpus luteum will disintegrate** and die, causing sharp drops in levels of both progesterone and estrogens
two weeks
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Drop in the level of hormone concentration, causes the uterus to shed its lining in a process termed as _.
menstruation
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also comprises the recurring physiologic changes that are induced by reproductive hormones in most mammalian placental females; humans undergo a menstrual cycle instead
estrous cycle
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**Estrous cycles start after puberty** in sexually mature females and are **interrupted by** _
anestrous phases
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Typically, **estrous** cycles continue **until** _
death
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# Estrous Cycle
Some animals may display **bloody vaginal discharge**, often mistaken for menstruation also called “_.”
period
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Mammals share the same reproductive system, including the:
1. regulatory hypothalamic system that releases _ in pulses,
2. the pituitary that secretes_ , and
3. the ovary itself releases _.
However, species vary significantly in the detailed functioning.
* gonadotropin releasing hormone
* follicle stimulating hormone and luteinizing hormone
* sex hormones; estrogens and progesterone
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One difference is that animals that have estrous cycle (what happens) _ the endometrium **if conception does not occur** during that cycle
reabsorb
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Animals that have menstrual cycles shed the endometrium through _ instead.
menstruation
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o In species with **estrous** cycles, **females** are generally **sexually active** only during the _ of their cycle.
o This is also referred to as being **“in heat.”**
estrous phase
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females of species with **menstrual** cycles can be **sexually active** at _ in their cycle, even when they are not about to ovulate.
any time
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A woman’s **first menstruation** is termed _ , and is one of the **later stages of puberty** in girls
menarche
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o The average age of menarche in humans is _ , but is still normal anywhere between ages **8 and 16**.
o Factors such as **heredity, diet and overall health** can accelerate or delay menarche.
12 years old
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The **cessation of menstrual** cycles at the end of the woman’s reproductive life is termed _
menopause
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o The average age of menopause in women is _ , with anywhere between **40 and 58** being common.
o Menopause **before age 35** is considered _.
51 years
premature
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The **changes** associated with the **menstrual cycle** are brought about by _ at different times of the month.
fluctuations in hormone levels
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menstrual cycle can be divided into the following parts:
1.) ovarian cycle; and
2.) uterine cycle
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▪ involves changes in the ovaries.
OVARIAN CYCLE
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OVARIAN CYCLE divided in 3 phases:
1. Follicular phase
2. Ovulation
3. Luteal phase
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# what phase of ovarian cycle?
the time from the **first day of menstruation** until ovulation when a mature **egg is released from the ovary**
Follicular phase
## Footnote
because growth and maturation of the egg is taking place inside the **follicle**, a small sac where the egg matures
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occurs around day 14 of the cycle, in response to a **surge of luteinizing hormone (LH)** that occurs **just before the egg is released** from the ovary.
Ovulation
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- is the time from when the **egg is released** (ovulation) until the **first day of menstruation**
Luteal phase
## Footnote
corpus luteum (Latin: yellow body) - structure that grows in the ovary where a mature egg was released at ovulation
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involves changes in the uterus
UTERINE CYCLE
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UTERINE CYCLE divided into 2 phases
1. Proliferative phase
2. Secretory phase
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is the time **after menstruation** and up to ovulation.
Proliferative phase
## Footnote
When menstruation is over, the endometrium grows and thickens during this period to prepare for implantation of an embryo (fertilized egg).
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is the time after ovulation and **before** the start of a **woman’s period.**
Secretory phase
## Footnote
Glands within the endometrium secrete proteins in preparation for a fertilized egg to implant. If implantation does not occur, the endometrium begins to break down and the glands stop secreting hormones. The result is shedding of the uterine lining (endometrium) called menstruation
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what control the menstrual cycle.
Female hormones
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two
During each cycle, the brain’s _ send hormone signals back and forth with the ovaries.
o These signals get the ovaries and uterus ready for pregnancy.
hypothalamus and pituitary gland
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_ build up the lining of the uterus.
Estrogens
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_ **increase after an ovary releases an egg** at ovulation in the middle of the cycle
Progesterone
## Footnote
This helps the estrogens keep the lining thick and ready for a fertilized egg.
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**chemical substances** formed in tissues organs **carried by the blood**
hormones
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stimulates or inhibits the growth or function of another part of the body
hormones
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5 Hormones in Reproduction and Development
1. Gonadotropin-releasing hormone (GnRH)
2. Follicle-stimulating hormone
3. Luteinizing hormone
4. Estrogens
5. Progesterone
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produced by the hypothalamus
Gonadotropin-releasing hormone (GnRH)
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hormone that stimulates the release of follicle-stimulating hormone (**FSH**) and luteinizing hormone (**LH**) **from the pituitary** gland
Gonadotropin-releasing hormone (GnRH)
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2 hormones produced by the anterior pituitary gland
Follicle-stimulating hormone
Luteinizing hormone
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**stimulates the growth of follicles** in the ovaries which secrete estrogens
Follicle-stimulating hormone
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**works with the FSH** to cause ovulation and later the release of estrogens and progesterone.
Luteinizing hormone
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hormones secreted by the ovarian follicles and corpus luteum
Estrogens
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stimulates **thickening of the uterine wall**, maturation of an egg, and development of the female sex characteristics
Estrogens
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also provides feedbacks to inhibit FSH secretion and increase LH secretion.
Estrogens
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hormones secreted by the corpus luteum
Progesterone
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stimulates thickening of the uterine wall and **formation of mammary ducts**
Progesterone
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Estrogen stimulates the thickening of the uterine lining and exerts a _ on GnRH secretion by the hypothalamus
negative feedback inhibition
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A rapid rise in **estrogen** concentration **peaks** on day _ as the dominant follicle enlarges
12
135
The anterior pituitary produces a sharp **increase in LH** and a smaller increase in FSH that peak on day _.
13
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_ , hormone-like substances involved in pain and
inflammation, trigger uterine muscle contractions.
Prostaglandins
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the absence of menstruation
Amenorrhea
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is the **failure of a woman to begin menstruation**, and is caused by endocrine disorders or abnormal reproductive development
Primary amenorrhea
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is the **absence of one or more menstrual** periods without pregnancy. This may result from excessive physical exertion or excessive weight loss.
Secondary amenorrhea
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painful menstruation that prevents a woman from doing her normal activity for one or more days during her menses. **Uterine contractions** are thought to be responsible for pain
Dysmenorrhea
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direct cause of dysmenorrhea
prostaglandins
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Increased _ levels – substances involved in inflammation also may be a contributing **factor of dysmenorrhea**
leukotriene
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a painful condition, the type of tissue that lines the uterus becomes implanted **outside the uterus**, most commonly in the fallopian tube, ovaries, or the tissue lining the pelvis
Endometriosis
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a condition that occurs when the tissue that lines the uterus begin to grow **within the muscular walls of the uterus.**
Adenomyosis
145
infection of the female reproductive organs caused by **sexually transmitted bacteria.**
Pelvic inflammatory disease (PID)
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a small, plastic, **T-shaped birth control device** inserted into the uterus may cause increased cramping, particularly during the first few months after insertion
Use of an intrauterine device (IUD)
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are **non-cancerous tumors** and growth that protrude from the lining of the uterus
Uterine fibroids and uterine polyps
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in females is inability to conceive
Infertility
149
3 causes of Infertility in females
1. tubal obstruction,
2. ovarian disease,
3. lack of maintenance of the uterine lining
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Cancer of the female reproductive system most often occurs as (type)
breast cancer
or cervical cancer
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is a slow-growing cancer caused by **human papillomavirus** infections of sexual partners and associated with multiple sex partners
Cervical cancer
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Cervical cancer can usually be detected early by a
Pap smear
## Footnote
Annual examinations are recommended for women over 30 years of age
