Animal Reproduction and development
From speech of Aristophanes:
...The sexes were not as they are now...the primeval man...had four hands
and four feet, one head with two faces...Terrible was their might and strength...and
they made an attack upon the gods...Zeus...said: "Methinks I have a
plan which will humble their pride and improve their manners; men will continue
to exist, but I will cut them in two...After the division of the two parts
of man, each desiring his other half, came together, and throwing their
arms about one another, entwined in mutual embraces, longing to grow into
Love (sweet Chloe) is a god, a young Youth, and very fair, and wing'd to
flye... His power's so vaste, that that of Jove is not so great... For there
is no med'cine for Love, neither meat, nor drink, nor any Charm, but only
Kissing, and Embracing, and lying naked together.
-Daphnis & Chloe By Longus Translated out of Greek by George Thornley
Fox Chapter 20
Meiosis and sperm
Spermatogonia (mitosis and meiosis) - primary spermatocytes
- meiosis (both divisions) - spermatids (scrotum cooler)
Sperm (meioses throughout adult life) Seminiferous tubules
300 million/ ejaculation
Testes - seminiferous tubules make sperm, stimulated by FSH, inhibin for
Interstitial (Leydig) cells produce testosterone, stimulated by LH (ICSH),
Low mag section of testis, higher mag showing seminiferous tubule and interstitial
Testes in short
day hamsters are smaller than in long day hamsters
An even higher magnification showing Sertoli cell that supports spermiogenesis,
(Here is a picture
from our histology course)
Bulbourethral (Cowper's) gland (early overflow from sexual excitement)
Seminal vesicle - fructose, amino acids, mucus, prostaglandins (uterine
Prostate - alkaline (infection, cancer most men > 50)
Capacitation of sperm
Vas deferens - peristalsis -(vasectomy 100% effective- permanent long term
Urethra (of course, it is output here for which condom is a form of contraception)
The prostate story.
MBGarnick, The great prostate cancer debate, Scientific American Feb 2012,
Monitoring is used more, surgery is used less
Cancer in men >50, diagnosed by paplation
PSA=prostate specific antigen, 1 is low, 5 is high, but not specific to
cancer, might be high after having sex
Several "remedies" including selenium
Surgery and radiation, etc.
Slowly developing cancer
Complications - incontinence (for #1, even #2), possibly impotence (ED)
For ED, Viagra, Levitra, Cialis
Many sperm attack one egg, only one fertilizes - fast (electrical) response
acrosome, nucleus, mitochondria (not go into egg), flagellum
Parasympathetic arterioles (unique, usu only symp.) - erection (sleep)
ACh - NO - smooth muscle dilate- viagra blocks breakdown enzyme
NO synthase in cavernous artery and corpus cavernosum
Robert F. Furchgott, Louis J. Ignarro, Ferid Murad Nobel
1998 "for their discoveries concerning nitric oxide as a signalling
molecule in the cardiovascular system"
Sympathetic - ejaculation inhib erection
Here is a picture
from our histology course showing the spongy tissue of the corpus cavernosum
which becomes engorged with blood to mediate erection.
rodents racoons walruses - bone
Sympathetic - ejaculation inhib erection
Here is the typical text book diagram depicting the menstrual (ovarian)
cycle (covered earlier)
For convenience, I used the term "eggs" earlier, now I get more
Meiosis, ovary, steroids
I showed this to you before
primary oocyte in early follicle
secondary oocyte in mature follicle
Here's how that relates to meiosis
Primary oocyte (2-4 million at birth, 1st meiotic prophase)
(400,000 at puberty, only 400 used)
(no oogonia after 3 mo)
Secondary oocyte + polar body
(Graffian follicle finish 1st meiosis) ovulation
if 2 ovulations - DZT - 2 amnions, 2 chorions
twins 1.2% of births, of these 70% "fraternal"
DZT run in family
Uterus, fertilization, and early development
I showed this to you before
anatomy of ovary, and relation of ovulation to fimbriae of uterine (Fallopian)
Tubal ligation (laparoscopy) 100% effective. Reverse?
Cervix (diaphragm, cervical caps, foam, spermicidal jelly)
Fallopian tube (fimbria capture ovulated egg - Sperm meets, 2nd meiosis
makes ootid 3 polar bodies discarded nucleii
Division in Fallopian tubes
Blastocyst (trophoblast, blastocoel, inner cell mass)
(trophoblast - >chorion -> placenta)
(inner cell mass -> embryo -> fetus)
IUD prevent implantation, irritate, after previous child, not for everybody
if inner cell mass divides, Monozygotic (identical) twins MZT (2 amnions,
1 chorion), 30% of twins
Shows trophoblast, implantation and a little development
While I have this up, I will talk about "stem cell research"
This relates to cloning.
(Not cloning as in cloning a gene, but cloning an organism)
1950's work on amphibians - Since all nuclei should have all the genes,
any nucleus should work to make whole organism, taken out of, for instance,
an intestine cell. But not all cells work, so put the nucleus into an egg
where it is certain that the nucleus already there has been destroyed.
work to make sheep Dolly. Nuclear transfer by removal of egg nucleus followed
by fusion with cell with diploid nucleus. Need to implant into a surogate
Cloning has been extremely controversial, and human "reproductive cloning"
is banned. Some scientists hoping to advance medical treatments would like
to distinguish "theraputic cloning" from cloning to produce a
person genetically identical with the donor. Some think the issue would
be simplified by use of the term "nuclear transplantation."
Stem cell research
Because cells lose their pluripotency, researchers have focussed on their
discovery that embryonic stem cells are better at differentiating into cells
that can repair cell damaged areas such as in the case of spinal cord injury;
the issue is very controversial because it may encourage practitioners to
create and destroy human embryos for no other purpose than to harvest stem
cells. Of note, there may be "left-overs" (it is hard to find
a diplomatic euphemism) from in vitro fertilization after a couple has had
all the children they want (that might go to "waste"). For this
reason, for humans, only the use of some 60 cell lines that are already
in culture was dictated in the US by President Bush.
Several colleagues and I were collaborating
to cure blindness in a mouse mutant with cells that started as embryonic
and were induced to become precursors of nerve cells; identified by green
fluorescent protein, here
is a cell that has been put into the retina and is beginning to show a neuron-like
SSHall, Diseases in a dish, Scientific American, March 2011, 40-45. Take
skin of elderly person who has ALS in the family, make stem cells, turn
them to neurons, watch ALS develop, test drugs
1998 James Thompson (University of Wisconsin - Madison)
2001 (Aug) George W Bush restrictions
Harvard, Columbia, Stanford - labs with private funding
2002 TMJessell, HWichterle et al (Columbia) how to get embryonic stem cells
to be motor neurons
2006 SYamanaka (Kyoto) how to get stem cells from skin2009 Obama relax restrictions
2010 court banned NIH support
Cursory overview of development
trophoblast implants becomes chorion -
Chorionic villus biopsy - early genetic testing
Amniocentesis-later genetic screening
placenta - exchange, diseases like rubella, alcohol, drugs
make HCG 2 wks - 4 mo (pregnancy test)
to maintain corpus luteum
(not graphic, 20.6 is the graphic version)
2 sexes from 1 primordium
H-Y antigen = testes differentiating factor
then testosterone alters development
MIF (Mullerian inhibiting factor) contributes to development of male "plumbing"
female pattern is the default pathway, clitoris is equivalent of penis
Before he recently retired, Prof Aldridge
taught several courses and did research on reproduction. Prof Ogilvie
teaches developmental biology.
Exam questions from 2004 - 2011 relating to this outline
A blood test to assay for (name the substance in words) is commonly used
to determine the likelihood of prostate cancer.
prostate specific antigen
In the ovary, if the corpus luteum becomes the corpus albicans, what does
didn't get pregnant, no gonadotropins
After the zygote is first formed, but before implantation, some rudimentary
development occurs. Answer either (1) What is the term used for these cell
divisions? or (2) Where do they take place?
cleavage, uterine (fallopian) tube
Why did they need a surrogate mother when they cloned Dolly?
after nuclear transfer in vitro and early development, they neded a uterus
to implant into
In early development, what happens to the Mesonephric duct in the absence
it degenerates instead of becoming the epididymis, vas deferens, etc
Testes, prostate, bulbourethral gland (Cowper's gland). What gland that
is missing from that list contributes to semen?
I said "The likelihood of having two sperm cells with the same combination
of genes you got from your mother vs. your father in your whole life is
infinitesimal." State how this diversity is achieved,
not only is there a random selection of which centromere is chosen (that
comes to 2 to the 23 possibilities) but crossing over (recombination) exchanges
genes along the chromosome
Answer one of the following. (1) What is the status of the "egg,"
in terms of progress through the entire process of meiosis, at the time
of ovulation? or (2) What is the status of the "egg," in terms
of progress through the entire process of meiosis, at the time the sperm
is about to penetrate?
same answer for both. Through with meiosis I but not II (arrested at metaphase)
After implantation,...(answer ONE of the following) a peptide ( name
that peptide) sees to it that a steroid ( where is the steroid from?)
maintains the endometrium.
HCG, corpus luteum
"The IUD does not prevent fertilization!" Elaborate.
after fertilization and early development, it prevents implantation.
In 2006, while George W. Bush was President, the famous actor Michael J.
Fox, who has Parkinson's disease, came to Missouri to support McCaskill,
the democrat running for senate. Answer either (1) Why would he have been
so interested (in embryonic stem cell research)? or (2) Why has interest
in the issue of embryonic stem cell research decreased so much since then?
such stem cells might eventually be used in treatments to replace the degenerated
neurons but now embryos might not be needed since skin cells can be made
into pluripotent stem cells
About the time chorionic villi are present, what had been the inner cell
mass has further developed, and one portion is now called the embryo. Answer
either (1) Why might it be useful to biopsy the chorionic villi? or (2)
In addition to the endoderm and the mesoderm, what is the third layer in
that early embryo?
to test for chromosomal or genetic disorders, ectoderm
What happens if there is no Mullerian inhibiting factor?
uterus and uterine tubes are formed
Spermatids become spermatozoa. State one of the things that occurs during
Cells become separated, cytoplasm is sloughed off and flagella are added
How is sperm moved along the length of the ductus (vas) deferens?
Peristalsis by smooth muscle
In addition to sperm from the testes, several glandular secretions contribute
to semen. Name one of the glands.
Prostate, seminal vesicle and bulbourethral (Cowpers) gland
Simultaneous with menstruation, what happens to the corpus luteum?
It regresses (becomes corpus albicans)
"It is the conventional wisdom that men are more likely to have erections
when they are asleep." Explain why this is the case in physiological
High parasympathetic output
In your textbook's diagram of the seminiferous tubule, cells called "spermatogonia"
were shown. No analogous "oogonia" were shown in the diagrams
of the ovary. Why not?
There are no oogonia after 3 months of age
At what stage in the process of meiosis is the egg at the time of ovulation?
It is a secondary oocyte and has not completed the second meiotic division
"Then it implants into the endometrium." EITHER (1) name or (2)
describe what it is that implants.
Blastocyst, ball of cells with inner cell mass, trophoblast and blastocyst
What capability did embryonic stem cells possess that other cells lacked?
Pluripotent or totipotent, can become any type of cells
Explain why it is safe to assume that cells from the amniotic fluid do not
come from the mother.
Amnion is on one side, embryo then fetus, on the other and everything is
surrounded by chorion, all derived from zygote
Under the influence of a gene on the Y chromosome, "indifferent gonads"
turn into a structure that produces Mullerian Inhibiting Factor (MIF) plus
the testes also produce testosterone
Answer EITHER: "Viagra inhibits the enzyme (what enzyme?) that breaks
down (what?) as a medication for erectile dysfunction."
How much before or after the sperm meets the egg is meiosis completed for
Pretty much simultaneous (just a moment before) fertilization
What would have happened to a person who did not have Mullerian Inhibiting
Primordial "plumbing" would become uterus and uterine tubules
How many oogonia does a woman have at puberty?
A ball consisting of trophoblast plus what other clump of cells becomes
implanted in the endometrium?
inner cell mass
When is meiosis completed in the "egg?"
when sperm meets egg
A low PSA reading is around 1 while a high PSA is 5. What does PSA stand
prostate specific antigen
Where is the acrosome?
tip of spermatozoan
Why might a physician want to test a sample of amnionic fluid?
to test prenatally for gene or chromosomal defects
Semen has components from seminiferous tubules, seminal vesicles, bulbourethral
(Cowper's) gland, and what other gland?
The trophoblast becomes the chorion, and the chorion, in turn, becomes what?
What divides to make monozygotic (identical) twins?
inner cell mass
Where does fertilization take place?
way up in uterine (Fallopian) tube
What becomes of the mitochondria of the spermatozoan during fertilization?
they do not go into the egg
Incontinence is a common consequence of what surgery?
What is the result of ligating and snipping the vas deferens?
man is no longer fertile
Where is the "egg" when meiosis is complete?
when the sperm fuses
What divides to make identical twins?
inner cell mass
Genetically, how are fully differented adult cells different from pluripotent
They both have the same genes, though only a limited subset are being expressed
in the former
One diploid primary oocyte undergoes two meitic divisions. How many cells
that can be fertilized result?
What part of the blastocyst will eventually (much later) become the placenta?
How can a physician test for defects earlier than amniocentesis?
chorionic villus biopsy
What happens if neither MIF (Mullerian inhibition factor) nor testosterone
primordia of sex structures adopt female development
The PSA (prostate specific antigen) test is used to diagnose a predisposition
for what disorder?
Why is development of uterus and clitoris considered the default pathway?
testes-determining factor (TDF), Mulleriasn-inhibiting factor and testosterone
actively cause indifferent gonad primordia to select the male pattern
Spermatogonia undergo meiosis to make sperm. In what way is this process
different for formation of oocytes in the adult human?
There come to be no oogonia in women, thus the entire meiosis does no occur
throughout life, way fewer gametes are formed, 4 sperm vs 1 oocyte and polar
bodies, sperm constant oocyte meiosis regulated when sperm meets egg
Name one of the glands that adds to sperm to make semen.
bulbourethral (Cowper's), seminal vesicle, prostate
Nitric oxide activates an enzyme that makes cGMP. (Maybe you did not know
this.) Why might some people take a drug to inhibit the enzyme that breaks
for erectile dysfunction
Why is the IUD (intrauterine device) particularly controversial?
prevents implantation, not fertilization
Say where (or when) the second meiotic division occurs for the oocyte
uterine tubule, when sperm meets egg
What technique provides earlier information on genetic or chromosomal abnormalities
chorionic villus biopsy
What specific body of cells divides to make monozygotic (identical) twins
(and also is a source of embryonic stem cells)?
inner cell mass
What is the "egg" called officially at the time of ovulation,
and what stage of meiosis or mitosis is it at at that time?
secondary oocyte, before meiosis II is complete
Tell me about oogonia in the human female between the first menstrual period
there are none
Why do proponents think that embryonic stem cells might be useful to treat
such cells are pleuripotent
An embryonic structure becomes the penis if testosterone is present. What
does it become without testosterone?
Tell me about spermatogonia in the adult male.
diploid, replace themselves by mitoses, give rise to diploid primary spermatocytes
Ligation and cutting of what tube is a common elective surgery for men to
Why might an elderly man decide not to have surgery after first being diagnosed
with prostate cancer?
it progresses slowly, surgery has side effects
Ovulation comes after a striking surge in what gonadotropin from where?
LH from anterior pituitary
Where (anatomically) does fertilization take place in the human.
in the uterine (fallopian) tube
How do dizygotic (fraternal) twins come about?
Birth control prevents fertilization. Why is the intrauterine device qualitatively
prevents implantation meaning that fertilization (and many cell divisions)
have already taken place
In cloning (Dolly, for example) what do you put into the surrogate mother
blastocyst to uterus
"Spermatogenesis: the formation of spermatozoa, including meiosis"
(from the glossary in your book). How is spermiogenesis distinguished from
spermiogenesis is just the stripping of the cytoplasm of spermatids and
the streamlining of spermatozoa
For purposes of family planning, some men elect to have a straightforward
surgery that results in sterilization. What is done?
vasectomy = ligate and sever the vas deferens
Why might an elderly man decide not to have surgery for prostate cancer?
it is a slowly developing cancer, and possible side effects of impotence
and incontinence detract from the quality of life
As the sperm cell is about to fertilize the "egg," how far along
in its meiotic divisions is the egg?
arrested at metaphase II (i.e. meiosis I is complete, but not II)
When are primary oocytes formed from oogonia in the human female?
With the intrauterine device, which irritates the uterus, the likelihood
of an ectopic pregnancy is increased. How does ectopic differ from normal?
way up in uterine (fallopian) tube (instead of uterus)
What is the specific source of embryonic stem cells?
inner cell mass
What is the difference between identical vs fraternal twins in how they
two ovulations both fertilized fraternal, inner cell mass divides identical
Why do researchers have high hopes for the use of embryonic stem cells for
eventual therapies for disorders like retinal degeneration and Parkinson's
they are pluriotent, amazingly form into needed cells if placed where they
Why should cells in the amniotic fluid give us information about genetic
(and chromosomal) abnormalities of the fetus (and not the mother)?
the amnion (and of course the fetus) are of zygotic (as opposed to maternal)
origin, so the fluid is surrounded only by cells from the fertilized egg
Under the influence of Mullerian inhibition factor (MIF) and (what else?)
male development is initiated instead of the female default pathway.
How do the mitochondria in the sperm cell contribute to the DNA in the zygote?
They do not
Two meiotic divisions in the female result in only one "egg."
What did the other nuclei produced by meiosis become?
In cloning Dolly, an egg was obtained, its nucleus was removed, a somatic
cell nucleus was put in, and cell divisions create an embryo (a hollow ball
of cells) in vitro. What did they have to do after that so that a
sheep was born?
Implant into a surrogate mother
Why would the intrauterine device (IUD) be considered to be particularly
Well, even blocking fertilization might be controversial, but blocking implantation
is a really early abortion
Why does in vitro fertilization come up in discussions of the benefits
and controversities of stem cell research?
One possible source of embryonic stem cells would be "left overs"
once a couple has decided they have had enough children
How is it that a doctor can check for an enlarged prostate?
the latest in digital technology (there is no polite way to describe it
but it involves a finger in a rubber glove)
Under what circumstances would a corpus albicans be formed?
without implantation, the corpus luteum regresses to the corpus albicans
In cloning Dolly, what did they need to do after they had a blastocyst?
implant it into a surrogate mother
Despite controversy, why would "left-overs" of in vitro
fertilization have been perceived as particularly useful for theraputic
embryonic stem cells are pluripotent
Starting with a secondary spermatocyte (2n), two meiotic divisions gives
4 haploid (n) spermatids. Answer either (1) What happens to make those into
spermatozoa? Or (2) What nearby supportive cell can assist in that process?
cyroplasm sloughed (and flagella added), Sertoli cell
Why does it make sense that surgical removal of a cancerous prostate might
lead to incontinence (poor bladder control)?
the urethra passes through the prostate
Other than the seminiferous tubules and the prostate, name a gland that
contributes to semen.
bulbourethral (Coper's), seminal vesicle
A sperm cell is about to meet a secondary oocyte (but they have not yet
joined). Where, in the process of meiosis, is the egg?
before second meiotic division is completed
Where (anatomically) do cleavage divisions take place?
in the uterine (fallopian) tube
Why would using the "left-overs" of in vitro fertilization
be particularly controversial for theraputic purposes?
the stem cells harvested are embryonic
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