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 one...

Plato Symposium


Campbell and Reece Chap. 46 (also 47)

Chambered nautilus
Helix - land snail
Hercules beetle
in Drosophila genetic crosses, males are sometimes identified by tarsal claw on front leg
African fighting fish Betta splendens- (spawning - external)
Frog - external
Human (cartoon)

Parthenogenesis - egg develops without being fertilized
pseudosex in parthenogenetic lizards
Hermaphrodite - each have both
sequential hermaphroditism sex reversal in fish


Testes - seminiferous tubules - FSH
Interstitial cells, testosterone - ICSH = LH
(histology picture)

Spermatogonia (mitosis and meiosis) - primary spermatocytes
- meiosis (both divisions) - spermatids (scrotum cooler)
Sperm (meioses throughout adult life) Seminiferous tubules
300 million/ ejaculation
Many attack one egg, only one fertilizes - fast (electrical) response
acrosome, nucleus, mitochondria (not go into egg), flagellum
Epididymis TRANSPARENCY 46.8 a and b (graphic)
Vas deferens - peristalsis -(vasectomy 100% effective- permanent long term effects unknown)

/Bulbourethral (Cowper's) gland (early overflow from sexual excitement)
/Seminal vesicle - fructose, amino acids, mucus, prostaglandins (uterine contractions)
/Prostate - alkaline (infection, cancer most men > 50)
Urethra (condom)
Capacitation of sperm

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
1998 Nobel Prize for Physiology and Medicine is for NO to: ROBERT F. FURCHGOTT, LOUIS J. IGNARRO and FERID MURAD
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


"eggs" ->
TRANSPARENCY (FIG. 46.13 a & b) 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
Summary: Many sperm attach, one penetrates
Final meiosis then
Division in Fallopian tubes
Hollow out - outer=placenta; inner=embryo

Fallopian tube (fimbria capture ovulated egg - Sperm meets, 2nd meiosis makes ootid 3 polar bodies discarded nucleii
ootid becomes ovum - fertilization
When sperm meets, quite complex
acrosomal and cortical reaction TRANSPARENCY Fig. 47.2
fast events to block polyspermy
(prim cyte - 2nd cyte - ootid - ovum - fertilization)
TRANSPARENCY (Fig. 46.9 a and b) (graphic)

cleavage divide but skip growth (G1 & G2 of cell cycle)

Blastocyst (trophoblast, blastocoel, inner cell mass)
(trophoblast - chorion - placenta)
(inner cell mass - embryo - fetus)
Inner cell mass
if divide, MZT (2 amnions, 1 chorion), 30% of twins
Tubal ligation (laparoscopy) 100% effective. Reverse?
Uterus - trophoblast implants becomes chorion -
(recall endometrium thick from estrogen and progesterone)
make HCG 2 wks - 4 mo (pregnancy test)
to maintain corpus luteum
(later placenta TRANSPARENCY Fig. 46.17)
IUD prevent implantation, irritate, after previous child, not for everybody legal question
Cervix (diaphragm, cervical caps, foam, spermicidal jelly)
External genitals = vulva (labia, clitoris)


Trophoblast - placenta - exchange
diseases like rubella
alcohol, drugs
Chorionic villus biopsy
Membranes - amnion - amniocentesis

Immunology - why not "paternal antigens"?
maybe antigens not expressed
maybe a suppressor cell that blocks interleukin-2
must have initial immune resp.; if antigens too close, infertility

2 sexes from 1 primordium
H-Y antigen = testes differentiating factor, then testosterone alters development, female pattern is the default pathway, clitoris is equivalent of penis

Trimesters embryo becomes fetus
Birth - heart shunts disappear

TRANSPARENCY (Fig. 46.20) delivery
TRANSPARENCY (Fig. 46.19) oxytocin, prostaglandins
formerly use sedatives, father in waiting room
classes, "natural" delivery
Mucus plug falls out ("water" [amnionic fluid] "break)
Labor room contractions oxytocin (pitocin drip)
Cervix effaces dilate 4-10 cm (labor) obstetrician palpates
Paracervical, Epidural, (Tranquillizers)
Delivery - push
face down normal, face up harder, breech difficult
Umbilicle cord


condom - good in that it prevents STD, brands- natural skin not effective for virus - synthetic ruber material is greatly weakened with any oil based lubricants
pills - good example for understanding hormonal control of cycle
--steroids build up endometrium and inhibit FSH & LH
diaphragm, caps
IUD - prevent implant, after child, irritate

The A word
Con- value of life and life begins at conception- Catholic
Pro - prevent quacks, rape, incest, danger to mother
Abortion laws
1970's most states prohibited except e.g. mother's health
(go to other countries or back alleys)
Roe vs. Wade -1973 Supreme Court, States can't prohibit 1st 3 mo if O.K. w/ MD
extreme controversy continues

Dave Barry Babies & other Hazards of sex, Rodale Press, Emmaus PA, 1984 - When I was a teenage male, it was very difficult to obtain condoms, because you had to buy them at the drugstore from the Condom Lady, who was about 65 and looked like your grandmother only more moral. She had a photographic memory so she knew exactly who you were, and as soon as you left the store, she would dial a special number that would connect her with a gigantic loudspeaker system so she could announce to your parents and your teachers and everybody in your church or synagogue and people on the street that you had just bought condoms. Now they sell condoms right out in the open on display racks, just like breath mints or something, and the Condom Lady has switched over to selling Penthouse magazine to middle-aged businessmen at the airport.

Seminiferous tubules
sperm and ovum
5 wk
tail early to 3 mo (and gills)
ontogeny recapitulates phylogeny
3 mo 3 inches 1 oz

Animal development

Chapter is descriptive (histology. Just like when I was in college)
Also convey search for general principles

All cells have all genes, only some genes are expressed in differentiated cell- first cell is pluripotent
certain mechanisms must limit the number of genes expressed

remember TRANSPARENCY Fig. 32.7
Protostome (molluscs, annelids, arthropods)- spiral cleavage
Deuterostome(lophophores, echinoderms, chordates)- radial cleavage
Folding -
Protostome - first is mouth
Deuterostome - first is anus

studies of amphioxis (lancet - look back to Chap. 34)
zygote->blastomeres->morula->blastula (with blastocoel)
->gastrulation->gastrula with blastopore and archenteron (deuterostome)

Gastrulation in frog TRANSPARENCY Fig. 47.10
Ectoderm - skin, nerves
Mesoderm - bones, muscle, organs
Endoderm - guts, lungs
TRANSPARENCY (Fig. 47.22) Spemann organizer - dorsal lip induces notocord and neural tube
transplant can make double embryo
Organogenesis in frog TRANSPARENCY Fig. 47.11
Neural tube

limb bud transplantation, zone of polarizing activity (ZPA)
indicates posterior positional information
has important molecules like sonic hedgehog (SHH), as does notocord
add an extra ZPA, get 2 posteriors
SHH can substiture
[also ZPA has morphogens like retinoic acid (which works like a steroid hormone)]

ultimately, exquisite, but general, cell to cell signalling yields final cellular identity
"American plan" - neighbors communicate and induce to determine
vs. the "European plan" - TRANSPARANCY 47.20b - lineage
very important in roundworm C. elegans
also there is programmed cell death - planned senescence - apoptosis

Fate maps - Vogt, embryo vital (nontoxic) dyes to see which cells become what

SLU's Biology Department has several faculty members who concentrate on developmental biology and embryology, including Dr. Schreiweis, Dr. Medoff and Dr. Coulter and there is an embryology course is on the web.

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this page was last updated 2/25/03