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Development
Learning objectives
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Ovulation and fertilization
Implantation
Embryonic and fetal development
Labor and birth
Postnatal development
Ovulation
Spikes in FSH and LH stimulate
ovulation of a secondary oocyte
Secondary oocytes do not complete
meiosis until fertilization
Ovulation of a secondary oocyte
Egg and sperm
Secondary oocyte has a layer
of follicular cells and the
protective zona pellucida
Acrosome of sperm contain
enzymes for passing the
corona radiata and zona
pellucida
The acrosome on sperm requires
about 7 hrs for activation
• Enzymes from the
acrosome
– Disrupt the attachments
between cells of the
corona radiata and the
zona pellucida
– Allows the sperm to
reach the oocyte
Modern IVF techniques create
significant ethical questions
• Combined with PCR,
pre-implantation
genetic diagnosis is
possible for 8-cell
embryos
• A single cell can be
sampled
• What can be learned
about an embryo from
looking at its DNA?
• The union of the sperm and the egg that
results in a cell with 46 chromosomes is called
a(n):
A) embryo.
B) zygote.
C) fetus.
D) trophoblast.
Fertilization until first cleavage
Identical and fraternal twins
Gastrulation allows formation of
differential tissues from the inner cell mass
Gastrulation- forming of a
gastrula- a primitive gut
Ectoderm, endoderm, and
mesoderm are formed
Ectoderm, endoderm and mesoderm
give rise do different tissues
• The inner cell mass of the
blastocyst undergoes
gastrulation, forming
ectoderm, endoderm and
mesoderm, which will
ultimately give rise to all the
tissues of the body
• When two secondary oocytes are released
from the ovaries and are fertilized by different
sperm cells, this is called:
• A) fraternal twins.
• B) identical twins.
• C) conjoined twins.
• D) clones.
Implantation
The embryo release human
chorionic gonadotropin
Alerts the mother’s body to its
presence, thereby sustaining the
corpus luteum throughout pregnancy
The outermost layer of blastocyst cells give rise
to the extraembryonic membranes- amniotic
sac, umbilical cord and chorionic villi of the
placenta
The placenta is the interface between
fetal and maternal circulation
• allows the transfer of
oxygen and nutrients
from the mother’s
blood to the fetus
• Prevents the mixing of
fetal and maternal
blood, allowing for
differences in blood
type between mother
and child
Sexual development
• Male and female
reproductive structures
are formed from the
same tissue
• Differentiated by the
presence of absence of
the SRY gene region of
the Y chromosome
• A male has a genetic disease coded for on his
Y chromosome. Which parent passed on this
trait?
• A) The mom
• B) The dad
• C) Either the mom or dad
• D) Neither parent: it is a spontaneous
mutation
Because organs such as the lungs are not used in
utero, fetal circulation is arranged differently
from the circulatory pathway of adults
Fetal development is most susceptible
to birth-defect causing environmental
insults between weeks 3 and 16
Growth of the fetus is allometric, and
continues to be allometric until
development is complete at adulthood
Labor is the painful process of birthing
a baby, and consists of dilation,
expulsion, and placental stages
Lactation cannot begin until a baby is
delivered
• Colostrum and milk
both contain antibodies
which protect a baby
against disease during
its infancy
• Which of the following functions to maintain
the corpus luteum and to stimulate it to
continue to produce the hormone
progesterone?
• A) Human chorionic gonadotropin
• B) Progesterone
• C) Estrogen
• D) Testosterone