Transcript Reproduction and Development - Lincoln

Reproduction and
Development
How do organisms reproduce?
Asexually
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Budding
Binary fission
Sexually
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External fertilization
Internal fertilization
What does it mean to reproduce
asexually?
Sexual reproduction
Sex cells are called ________.
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The male gamete is a __________.
The female gamete is an _____ or ____.
In humans, each gamete has ___ chromosomes.
Two gametes fuse to form a ______.
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A human zygote has ___ chromosomes from
each gamete, giving a total of ____
chromosomes.
Reproductive anatomy of the female
What do all of these things do?
A woman’s eggs (ova) are made in the
_______.
An egg (ovum) matures in a _______.
The egg is released during _________.
When the egg is released, it travels to the
uterus via the ________ (also called the
fallopian tube).
The uterus is lined by a thick, muscular wall
called the ____________.
What else?
A fertilized egg is a ______.
After the zygote begins to divide, but before it
develops body structures (9 weeks), it is called an
_______.
From 9 weeks until birth ( a time period called
gestation) it is called a _____.
If the zygote implants someplace other than the
main part of the uterus, it is called an
_________________ and is very dangerous. Most
of these pregnancies are terminated.
How is all of this connected to the
outside world?
External structures: protection and
making the environment receptive
The ______ is the narrow tube connecting the
uterus to the body’s exterior. It is also the
“repository for sperm during copulation.”
The labia are folds of skin which protect the
vaginal opening.
The stimulation of the clitoris results in sexual
arousal. This causes increased blood supply
and lubrication production by the walls of the
vagina and Bertholin’s gland.
Male Reproductive Anatomy
(aka foreskin)
What do all of these things do?
A man’s gametes (sperm) are made in the ______.
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The testes are kept a few degrees cooler than core body
temperature (about 35 instead of 37ºC) due to their
location in the scrotum -- this is key for proper sperm
formation!
Developing and mature sperm are stored in the
__________.
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Sperm are released from here during ejaculation, when
semen is expelled from the penis.
When the sperm leave the epididymis, they travel
to the _______ via the ____________ (and the short
ejaculatory duct).
The urethra also carries urine from the urinary
bladder.
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true in male human only -- urethra is not a reproductive
structure in female.
What else?
The seminal vesicles, the prostate gland, and
the bulbourethral gland, secrete fluids into the
urethra that make up the fluid portion of semen
(95%). The rest (5%) is made up of 200-500
million sperm (per ejaculation).
The urethra passes through the penis, which
consists mostly of erectile tissue that can fill with
blood and cause an erection during sexual
arousal.
Self test - Female System
1. Where are eggs located before ovulation? ________
2. What is the structure in which an egg matures before
ovulation? ____________
3. What happens in ovulation?
__________________________________________
4. When does a female begin to ovulate? ___________
5. How often does she ovulate? ______________
6. Where does fertilization of an egg occur? _________
7. How many days after ovulation is an egg still viable?
_____________
8. How many days does it take for an egg to reach the
uterus? ____________
Self test - Male System
1.
2.
3.
4.
5.
6.
Where are sperm first formed? _____________
Where are sperm stored within the male reproductive
system? __________________
What are the last three tubes through which sperm pass in
order to exit the body? ___________________________
________________________________________
What are the components of semen? What is it made of?
___________________________________________
What is the role of the seminal vesicle, prostate gland, and
bulbourethral gland? What to they contribute to the
makeup of semen? ____________________________
About how many days after ejaculation can a sperm
survive within the female reproductive system? _________
How does it all work?
Hormones, hormones, hormones!
Males and females are born with all their reproductive
structures in place, but they don’t start making sex cells
(gametes) until ___________________.
During puberty, hormone levels increase in the body and
the reproductive system _______ to become fully
functional.
Which hormones get things going during puberty?
To start, a part of the brain, the hypothalamus, signals
another part of the brain, the pituitary, to release two
important hormones:
• follicle-stimulating hormone (_____)
• luteinizing hormone (___)
These happens in both males and females. What happens
next, however, is different in the two sexes.
Hormonal Control of the Testes
What’s next? In males:
LH from pituitary signals testes
to produce ___________.
FSH and testosterone both
stimulate sperm production in
testes.
Starting during puberty, testes
produce hundreds of millions of
sperm a day.
What else does testosterone do?
Causes secondary sex
characteristics:
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hypothalamus
BRAIN
pituitary
TESTIS
Sperm Formation in Testes
In humans,
And in the Female…
Before puberty, the “pre-eggs” are in the ovary, stored
within sacs called ________.
What happens during & after puberty, when the pituitary
begins to produce FSH and LH?
In females, FSH and LH stimulate ovaries to eventually
produce two other important hormones: ________ and
____________.
Estrogen is primarily responsible for female secondary
sex characteristics such as:
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Estrogen & progesterone also work with FSH and LH to
produce mature ova (eggs) from the ovaries. This is a bit
more complicated than sperm production, however…
Egg Formation in the Ovary
Every month, one follicle in an ovary is activated by rising levels of
FSH to develop and produce a mature egg or ovum. While the egg
is maturing, the follicle produces the hormone estrogen.
Once the egg reaches maturity, it is released from the follicle into
one of the fallopian tubes. This release of the egg from the ovary is
called _________.
Pre-Egg
After the egg is
released, the empty
follicle is known as
the _____________.
This structure plays
an important role
after ovulation by
producing the
hormones estrogen
and progesterone.
Let’s look at why…
Mature
Egg
What’s going on in the uterus while the
egg is maturing in the ovary??
Monthly changes also occur within the uterus. The
sequence of events that includes the development
and release of an egg for fertilization and the
preparation of the uterus to receive a fertilized egg
is called the _____________.
There are four parts to the menstrual cycle:
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Follicular Phase
Ovulation
Luteal Phase
Menstruation
The Menstrual Cycle
Follicular Phase (about 10 days)
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Begins when estrogen levels in blood are low
Pituitary releases FSH and LH. FSH stimulates a follicle
in the ovary to start maturing
Follicle begins to produce estrogen
Estrogen causes lining of uterus to thicken in preparation
for receiving a fertilized egg
Ovulation
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Shortest phase in cycle;
Due to increasing levels of estrogen, pituitary suddenly
produces extra large amount of FSH and LH especially
LH especially causes mature follicle to rupture/burst,
releasing the mature egg into the oviduct
More Menstrual Cycle
Luteal Phase
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Begins after release of egg
Follicle turns yellow and is known as Corpus Luteum
Corpus Luteum releases estrogen and hormone
progesterone also; these hormones inhibit production of
FSH & LH and thus inhibit the development of another
follicle
Estrogen & progesterone also allow further development
of lining of uterus, in preparation for fert. egg implantation
Chance of fertilization of egg greatest the 2 days after
ovulation (10-14 days after end of last menstrual cycle)
If fertilization occurs, zygote implants in lining of uterus
Uterus & embryo release hormones that keep corpus luteum
functioning for several weeks, so lining nourishes developing
embryo until placenta forms
Even More Menstrual Cycle
Menstruation (3-7 days)
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If no fertilization, egg passes through uterus without
implanting
Corpus luteum begins to disintergrate, less hormone
produced
When level of estrogen (& progesterone) in blood drops
enough, lining of uterus detaches and is shed, along with
unfertilized egg
New cycle begins on first day of menstruation
Recap: Menstrual Cycle Hormones
Hormones control everything!
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FSH & LH made by the Pituitary.
Estrogen made by the Ovarian follicle and the
Corpus Luteum.
Progesterone made by the Corpus Luteum.
The ovary and the uterus, side by side
The Menstrual Cycle is controlled by
Hormones: FSH, LH, Estrogen, Progesterone
Yes. Sex can be dangerous, so if you do
ALWAYS USE A CONDOM!!
So what happens if sperm meets
egg?
An enzyme-filled sac
called an acrosome lies
just inside the tip of the
sperm’s head.
These enzymes can
penetrate the jelly coat of
the egg.
When this happens, the
sperm membrane fuses
with the egg’s membrane
and the sperm nucleus is
released into the egg.
Now what?
The fertilized egg (the
zygote) is now a cell with
46 chromosomes.
It will begin to divide (by
mitosis) to eventually
produce all of the cells of
the body.
Early, rapid cell divisions
are called cleavage.
The hollow ball of cells
with a fluid-filled hollow
center develops. This ball
is called a blastula.
Gastrulation
Now we go from a
hollow ball of cells
to a three-layered
stage called the
gastrula.
The three cell layers in the gastrula are
embryonic tissues that will develop into all
the parts of the adult animal
Ectoderm  forms nervous system & skin
Endoderm  forms innermost lining of our
digestive, respiratory, & urogenital systems, liver,
pancreas, thyroid, & thymus
Mesoderm  forms all other organs and tissues
(kidney, heart, muscles, dermis)
Next step: Embryo develops
notochord and neural tube
Notochord supports developing
tissues and eventually helps form
backbone.
Neural tube forms brain and spinal
cord (the nervous system).
Let’s follow the development of a human…
From fertilization…
To implantation…
Extra-embryonic membranes support the
embryo during development
• the amnion: forms
fluid-filled cavity which
protects embryo
• the “yolk” sac: no yolk
in human but produces
first blood and germ cells
• the chorion: forms
embryo’s part of
placenta
• the allantois: forms
part of umbilical cord
and part of embryo
urinary bladder
Evolutionary note: These four
membranes are found in all mammal,
bird, & reptile embryos.
Parturition
Hormonal induction of labor