RAM DAYAL
Embryologist
What is Infertility? Inability to conceive a baby after one year of
unprotected intercourse.
Affects the reproductive organs of both men and women.
Infertility affects about 15% of couples in the United States.
InfertilityRequirements for a successful conception:
A healthy sperm and a healthy egg unite to form a zygote
Place for fertilization to occur (a fallopian tube)
Place for the fetus to grow (a uterus)
Causes of Infertility in Males Low sperm count
Low sperm motility
Impotence including erectile dysfunction
Aspermia
Other Causes of Infertility in Females
Secondary amenorrhea
Fallopian tube blockage
Other Factors Influence Fertility Personal habits
Environmental factors
Age associated with decreased fertility and increased risk of chromosomal abnormality
Sexually transmitted diseases
Social factors
Age and Infertility
Causes of Infertility in Women
Most Common Choices of Treatment In Vitro Fertilization
Artificial Insemination
Frozen Embryos
Gamete Intra Fallopian Transfer
Zygote Intra Fallopian Transfer
Methods of Assisted Reproduction In vitro fertilization (IVF) Gametes are collected and fertilized in a dish The resulting zygote is implanted in the uterus
Gamete intrafallopian transfer (GIFT) Gametes are collected and placed into a womans
oviduct
Intracytoplasmic sperm injection (ICSI) An egg is fertilized by microinjection of a single sperm
(for defects in sperm count or motility)
IVF (in vitro fertilization) is a method in
which egg cells are fertilized by sperm
cells outside the mothers womb (in vitro). The resulting embryos are then
transferred back into the uterus.
Oocyte at Ovulation 2 oocyte arrested in Metaphase II
Completion of Meiosis only if fertilization occurs
Follicular cells of corona radiata protect ovum as it breaks through ovary wall
Hormonaltreatment
Female
Harvest the ovum
Mix in a test tube
Natural ejaculation
Collect semen
Mature Ova
Motile sperms
Keep to develop embryo
Transfer to mother
Male
Basic Principle of IVF
Oocytes with granulosa cells
"Naked" Oocyte
Fertilization:the fusion of the sperm cell nucleus with the egg cell nucleus to produce a zygote (fertilized egg)
FertilizationTaking place in ??
Viability of gametes: Oocyte 12-24 h
Sperm 12-48 h
Acrosome contains hyaluronidase acrosomal reaction breaks down intercellular cement between adjacent follicle cells
Single sperm fuses with oocyte
amphimixis - fusion of sperm and oocyte pronuclei
Sperm parts
Acrosome
tail
Egg parts
Corona radiata
zona pellucida
Plasma membrane
Polyspermy prevented by a
change in the zone pellucida
membrane charge as one
sperm enters
The male and female pronuclei are indistinguishable from one another.
The second polar body can be seen (arrow).
The plasma membranes of the two pronuclei are dissolving and one diploid
nucleus will remain.
Fusion of the pronuclei:(in vitro)
Advanced Fertility Center of Chicago
http://www.advancedfertility.com/
Stage of fertilization: Membranes of the pronuclei break down,
chromosomes condense and arrange themselves for mitotic cell division
On membrane dissolution, there is 1 cell with 46 chromosomes = diploid (2N)
The first cleavage follows shortly, leaving 2 cells, each with 46 chromosomes.
Mitosis in the new zygote uses centrioles derived from the sperm. The oocyte has no centrioles.
Fertilization facts: Completed within 24 hours of ovulation
Approximately 400 to 600 MILLION sperms are deposited at cervical opening during ejaculation.
Some sperm are held up by the folds of the cervix and are gradually released into the cervical canal; this gradual release increases the chances of fertilization.
Most human sperms do not survive longer than 48 hours in the female genital tract.
Only about 200 sperms reach the fertilization site; most degenerate and are absorbed by the female genital tract.
The results of fertilization: Stimulates the secondary oocyte to complete meiosis.
Restores the normal diploid number of chromosomes (46).
Results in variation of human species as maternal and paternal chromosomes intermingle.
The embryo contains only maternal mitochondria because the sperm mitochondria are dispersed into the egg cytoplasm and discarded.
Determines the sex of the embryo. The sex chromosome (Y or X) carried by the successful
sperm determines embryonic sex.
Twins: still 1 sperm per egg Monozygotic (monoovular): A fertilized, single egg splits into two developing zygotes at
a very early stage.
Identical twins; same sex.
Dizygotic (polyovular): Result from the fertilization by two sperm of two separate
ova that have reached maturation at the same time.
Not identical twins; can be different sexes
Incidence increases with age of the mother
HIGH QUALITY THREE DAY OLD EMBRYO
Intrauterine Insemination (IUI)
In intrauterine insemination (IUI), donor sperm is placed into the uterus of an ovulating woman. The sperm swim up the oviduct and fertilize the egg.
Fertilization to implantation:
Know where this happens.
Gamete Intrafallopian Transfer (GIFT)
Fig. 16-9a, p. 360
Zygote Intrafallopian Transfer (ZIFT)
Fig. 16-9, p. 360
Implantation:
After 6 days the blastocyst
imbeds into the
endometrium. Usually on
the high back wall of the
uterus
How can fertilization go awry? Too many sperm = dispermy or triploidy
Leads to spontaneous abortion in most cases.
Infertility
Bad timing:
The sperm can only survive 48 hours within the female genital tract.
In vitro studies show the ovulated egg cannot be fertilized after 24 hours.
Triploidy (in vitro)
Advanced Fertility Center of Chicago
http://www.advancedfertility.com/
There are 3 pronuclei within this one zygote. In the laboratory, such embryos are discarded. In vivo, such embryos almost always abort spontaneously.
Use of ART Carries Risks to Parents and Children
Risks of ART
Threefold increase in ectopic pregnancies
Multiple births (35% in IVF)
Increased risk of low birth weight
Increased risk of transmitting genetic defects to male children (in ICSI)
Surrogacy is another form of ART
Fig. 16-10, p. 361
IVF has Resulted in the Birth of Millions of Children
Fig. 16-7, p. 359
Thank you