3: Gametogenesis and Hormones in Reproduction and Development Flashcards
development of gametes
Gametogenesis
Gametogenesis usually not completed until the organism has become
physically mature
Gametogenesis completed in the sexually mature adult, begins at _ times during development, depending on the species
different
Gametogenesis divided into four phases
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
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.
identical
process of sperm cell production
Spermatogenesis
Spermatogenesis _ process in the adult male
prolific and continuous
Spermatogenesis occurs in the paired male gonads, or testes, specifically in the _
seminiferous
tubules
each ejaculation of a human male contains _ sperm cells, and males can ejaculate daily with little loss of fertilizing capacity
100 to 650 million
Primordial germ cells of the embryonic testes differentiate into
spermatogonia
diploid cells that are the precursors of sperm
spermatogonia
are undifferentiated cells located near the outer wall of the
seminiferous tubules
Spermatogonia
Spermatogonia undergo repeated _ to produce more spermatogonia.
mitosis
In a mature male, about 3 million spermatogonia per day differentiate into _
primary spermatocytes.
diploid or haploid?
Each primary spermatocyte undergoes first meiotic division producing _
haploid secondary spermatocytes.
how many are they?
In the second meiotic division, each secondary spermatocyte gives rise to _
two haploid spermatids.
_ are produced from the original primary spermatocyte.
Four spermatids
Spermatids then differentiate into a mature sperm cell or _.
spermatozoa
The differentiation of the spermatids into sperm cells is called _
spermiogenesis
corresponds to the final part of spermatogenesis and comprises the following individual processes that partially proceed at the same time.
spermiogenesis
Spermatogenesis involves association of the developing sperm with _ which transfer nutrients to the spermatozoa
large Sertoli cells
The release of a sperm cell from its connection to a Sertoli cell is known as
.
spermiation
During spermatogenesis, the developing sperm are gradually pushed toward the _, flow toward _ and make their way to the _ where they acquire motility.
center or lumen of seminiferous tubules
ducts of the testes
epididymis
This process from spermatogonia to motile sperm, takes _ in the human male to complete.
64 days
Sperm cells mature at a rate of _ per day.
300 million
Once ejaculated, they will probably not survive more than _ within the female reproductive tract.
48 hours
The approximate _ cycle of the spermatogenesis can be subdivided into four phases that last differing lengths of time
64-day
process-> days-> product
The Temporal Course of Spermatogenesis
- Mitosis of the spermatogonia - 16 days:primary spermatocytes
- First meiosis - 24 days: secondary spermatocytes
- Second meiosis - few hours: spermatids
- Spermiogenesis - 24 days: sperm cells
parts of sperm
Each mature sperm consists of a
head, midpiece, and flagellum (tail)
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
Numerous mitochondria, located in the _ of the sperm (provides the energy (ATP) for locomotion)
midpiece
A tail, the flagellum has a typical eukaryotic arrangement of _ propels the sperm along its way.
9+2
microtubules
sperm head may appear _ in bull and man, _ in rat, while _ in birds
ovoid
triangular and with a hook
slender and with pointed tips
“discards cytoplasm and growing tails”
Spermiogenesis
Stages of Spermiogenesis
- 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
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
Formation of the Acrosomal Cap
Acrosome contains enzymes that play important role in the penetration through the _ (part) of the oocyte.
zona pellucida
Formation of the Acrosomal Cap
The acrosome corresponds functionally to a lysosome and thus contains lysosomal enzymes (_ among others).
hyaluronidase
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
Condensation of the Nucleus
The acrosome lies over the _ of the nucleus
tip
Condensation of the Nucleus
_ form the sperm cell’s head that is bound to the mid-piece by a short neck.
Nucleus and acrosome
Involves the generation of the sperm cell tail.
Development of the Flagellum
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
Development of the Flagellum
The posterior centriole which moves away from the anterior one forms the shape of a _ surrounding the flagellum.
ring
Development of the Flagellum
This organelle supports the developing flagellum which extends into the lumen of the tubule.
mitochondrion
Sheath Arrangement of the Mitochondria
The cell’s mitochondria aggregate around the base of the flagellum forming a _ configuration
spiral
Cytoplasm Reduction
As the event continues, the _ disintegrates, leaving the spermatozoon stripped of all nonessential parts.
residual part of the cytoplasm
All unnecessary cytoplasm is eliminated during the process.
development of ova (mature, unfertilized egg) from oogonia
Oogenesis
Oogenesis involves _ and occurs in the ovaries (the female gonad)
meiosis
1
The process begins when oogonia undergo _ to produce a fixed number of daughter cells during embryonic stage of development
mitotic division
1
Before
birth, hundreds of thousands of _ are present in the ovaries
oogonia
2
_ arises from the primordial germ cell dividing by meiosis in the ovary into oocyte.
Oogonium
2
All of the female’s gametes originate during _.
embryonic development
No new oogonia are formed after birth.
3
During prenatal development, the oogonia increase in size and become _
primary oocyte
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
4
A primary oocyte and the cluster of cells surrounding it together make up a _
follicle
4
when?
With the onset of puberty a few follicles develop _ in response to FSH secreted by the anterior pituitary gland.
each month
As the follicle grows, the primary oocyte completes its first meiotic division.
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
6
The larger cell, the secondary oocyte, proceeds to the second meiotic division but remains in _ until it is fertilized.
metaphase
6
product?
When meiosis does not continue, the second meiotic division gives rise to a
_
single ovum and a second polar body
The polar bodies are small and apparently serve to dispose of unneeded chromosomes with minimal amount of cytoplasm
products?
Series of events if meiosis did not continue.
- Oogonia (diploid)
- Primary oocyte (diploid)
- Secondary oocyte + 1st Polar body (both haploid)
- Ovum + 2nd Polar body (both haploid)
o Each primary spermatocyte gives rise to _ sperms.
o Each primary oocyte generates _ ovum.
In the male, large number of sperms are necessary to ensure fertilization.
four
only one
As follicle develops, it becomes separated from its surrounding follicle cells by a thick membrane, the
zona pellucida.
o As the follicle develops, follicle cells secrete fluids, which collect in the space between them.
o The follicle secretes _, female sex hormones.
estrogens
As a follicle matures, it moves closer to the _ of the ovary, eventually resembling fluid-filled bulge on the ovarian surface.
surface
how many
Typically, _ follicle matures each month.
only one
Several others (follicle) may develop for about a _ and then disintegrate.
week
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)
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
- The second meiotic division only occurs when fertilization happens.
- Polar bodies are small and die quickly, just the ovum survives.
where
each primary oocyte develops within a
follicle
in response to FSH, (follicle stimulating hormone) several follicles grow, but _ usually matures
only one
in the process known as _ , the follicle ruptures releasing a secondary oocyte
ovulation
the remaining follicular tissue develops into _ , which
disintegrates if fertilization does not occur
corpus luteum
every
meiosis or mitosis every?
During puberty, a single primary oocyte usually complete
_.
meiosis I each month
describe the division?
The meiotic divisions in oogenesis involve _ cytokinesis
unequal
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
Menstrual cycle recurs approximately every _ from puberty to menopause
four week or 28 days
occurs in female of reproductive age
2 Kinds of Menstrual Cycle
- Overt menstruation
- Covert menstruation
where there is blood flow from the vagina occurs primarily in humans and close evolutionary relatives such as
chimpanzees
Overt menstruation
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
what cycle is?
under the control of the hormone system and is necessary for reproduction
mestrual cycle
Menstrual Cycle divided into 3 phases:
o Menstruation
o Follicular phase
o Luteal phase
defines the transition from the follicular phase to the luteal phase
Ovulation
Counted from the first day of menstrual flow, the length of each phase varies from woman to woman and cycle to cycle.
The average Menstrual cycle length is _
28 days or 4 weeks
MC stimulated by gradually increasing amounts of _ in the follicular phase, the lining of the uterus _
estrogens
thickens
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
The dominant follicle releases an ovum, or egg in an event called _
ovulation
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.
Under the influence of _ , the endometrium (uterine lining) changes and thickens in preparation for possible implantation of an embryo to establish pregnancy
progesterone
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
Drop in the level of hormone concentration, causes the uterus to shed its lining in a process termed as _.
menstruation
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
Estrous cycles start after puberty in sexually mature females and are interrupted by _
anestrous phases
Typically, estrous cycles continue until _
death
Estrous Cycle
Some animals may display bloody vaginal discharge, often mistaken for menstruation also called “_.”
period
Mammals share the same reproductive system, including the:
- regulatory hypothalamic system that releases _ in pulses,
- the pituitary that secretes_ , and
- 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
One difference is that animals that have estrous cycle (what happens) _ the endometrium if conception does not occur during that cycle
reabsorb
Animals that have menstrual cycles shed the endometrium through _ instead.
menstruation
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
females of species with menstrual cycles can be sexually active at _ in their cycle, even when they are not about to ovulate.
any time
A woman’s first menstruation is termed _ , and is one of the later stages of puberty in girls
menarche
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
The cessation of menstrual cycles at the end of the woman’s reproductive life is termed _
menopause
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
The changes associated with the menstrual cycle are brought about by _ at different times of the month.
fluctuations in hormone levels
menstrual cycle can be divided into the following parts:
1.) ovarian cycle; and
2.) uterine cycle
▪ involves changes in the ovaries.
OVARIAN CYCLE
OVARIAN CYCLE divided in 3 phases:
- Follicular phase
- Ovulation
- Luteal phase
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
because growth and maturation of the egg is taking place inside the follicle, a small sac where the egg matures
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
- is the time from when the egg is released (ovulation) until the first day of menstruation
Luteal phase
corpus luteum (Latin: yellow body) - structure that grows in the ovary where a mature egg was released at ovulation
involves changes in the uterus
UTERINE CYCLE
UTERINE CYCLE divided into 2 phases
- Proliferative phase
- Secretory phase
is the time after menstruation and up to ovulation.
Proliferative phase
When menstruation is over, the endometrium grows and thickens during this period to prepare for implantation of an embryo (fertilized egg).
is the time after ovulation and before the start of a woman’s period.
Secretory phase
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
what control the menstrual cycle.
Female hormones
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
_ build up the lining of the uterus.
Estrogens
_ increase after an ovary releases an egg at ovulation in the middle of the cycle
Progesterone
This helps the estrogens keep the lining thick and ready for a fertilized egg.
chemical substances formed in tissues organs carried by the blood
hormones
stimulates or inhibits the growth or function of another part of the body
hormones
5 Hormones in Reproduction and Development
- Gonadotropin-releasing hormone (GnRH)
- Follicle-stimulating hormone
- Luteinizing hormone
- Estrogens
- Progesterone
produced by the hypothalamus
Gonadotropin-releasing hormone (GnRH)
hormone that stimulates the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the pituitary gland
Gonadotropin-releasing hormone (GnRH)
2 hormones produced by the anterior pituitary gland
Follicle-stimulating hormone
Luteinizing hormone
stimulates the growth of follicles in the ovaries which secrete estrogens
Follicle-stimulating hormone
works with the FSH to cause ovulation and later the release of estrogens and progesterone.
Luteinizing hormone
hormones secreted by the ovarian follicles and corpus luteum
Estrogens
stimulates thickening of the uterine wall, maturation of an egg, and development of the female sex characteristics
Estrogens
also provides feedbacks to inhibit FSH secretion and increase LH secretion.
Estrogens
hormones secreted by the corpus luteum
Progesterone
stimulates thickening of the uterine wall and formation of mammary ducts
Progesterone
Estrogen stimulates the thickening of the uterine lining and exerts a _ on GnRH secretion by the hypothalamus
negative feedback inhibition
A rapid rise in estrogen concentration peaks on day _ as the dominant follicle enlarges
12
The anterior pituitary produces a sharp increase in LH and a smaller increase in FSH that peak on day _.
13
_ , hormone-like substances involved in pain and
inflammation, trigger uterine muscle contractions.
Prostaglandins
the absence of menstruation
Amenorrhea
is the failure of a woman to begin menstruation, and is caused by endocrine disorders or abnormal reproductive development
Primary amenorrhea
is the absence of one or more menstrual periods without pregnancy. This may result from excessive physical exertion or excessive weight loss.
Secondary amenorrhea
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
direct cause of dysmenorrhea
prostaglandins
Increased _ levels – substances involved in inflammation also may be a contributing factor of dysmenorrhea
leukotriene
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
a condition that occurs when the tissue that lines the uterus begin to grow within the muscular walls of the uterus.
Adenomyosis
infection of the female reproductive organs caused by sexually transmitted bacteria.
Pelvic inflammatory disease (PID)
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)
are non-cancerous tumors and growth that protrude from the lining of the uterus
Uterine fibroids and uterine polyps
in females is inability to conceive
Infertility
3 causes of Infertility in females
- tubal obstruction,
- ovarian disease,
- lack of maintenance of the uterine lining
Cancer of the female reproductive system most often occurs as (type)
breast cancer
or cervical cancer
is a slow-growing cancer caused by human papillomavirus infections of sexual partners and associated with multiple sex partners
Cervical cancer
Cervical cancer can usually be detected early by a
Pap smear
Annual examinations are recommended for women over 30 years of age
