Fertilization and Development

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Fertilization and Development
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• The process of a sperm joining an egg is called
  fertilization.
• Steps in fertilization
• Sperm to penetrates egg using enzymes to break
  through eggs protective layer.
• Once inside the egg, the nuclear membrane of both
  the sperm and egg rupture and the genetic
  material of the egg and sperm are combined.

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The new cell created by fertilization is called a
zygote. Fertilization is the joining of two sex
cells (haploid) to create a new individual which
is a genetic combination of both parents
(diploid). Once the zygote is formed it begins
to grow in cell number through the process of
Mitosis
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In a fertilized egg or zygote this mitotic
division is called cleavage
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As the zygote moves through the fallopian tube it
continues to divide and grow into a ball of
cells known as the morula made up of
approximately 50 cells.
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As the Morula moves into the uterus from the
fallopian tube it becomes a hollow structure
known as a blastocyst
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The blastocyst secretes an enzyme and breaks
through the uterus wall in a process known as
implantation Implantation
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The cluster of cells known as the blastocyst
divides into 3 layers in a process of
gastrulation These layers will become all of the
organs and tissues of the embryo.
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The outer layer of the blastocyst forms a
membrane that protects and nourishes the
developing embryo. The embryo is known as the
amniotic sac.
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By the 3rd week of pregnancy the placenta begins
to form in the uterus. The placenta is the
connection between the mother and the embryo
which provides a supply of oxygen and nutrients,
while keeping the mother and embryos blood
supplies separate.
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Section 39-4
Nutrients and oxygen are exchanged through
diffusion. The placenta is the embryos organ of
respiration, nourishment, and excretion
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Almost everything the mother takes into her body
passes through the placenta into the embryo
including drugs, alcohol and some diseases.
Alcohol, drugs and disease can affect the
development of the embryo.
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After 3 months the umbilical cord becomes the
connection between the embryo and the placenta.
Once this occurs the embryo is known as a fetus.
The average fetus is now 8cm and capable of some
movement.
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Tissues continue to differentiate (become
specialized for individual jobs) throughout
development
Development images Heart Growth
After 9 months a fetus has undergone enough
development to survive without connection to the
mothers body and birth takes place.
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Premature babies (born prior to 8 months of
development) are able to survive outside of the
mother with life-support equipment. Incomplete
organ development in premature babies requires
that machines complete some body system tasks.
Example Lungs are not fully developed until
late in pregnancy. Premature babies usually have
breathing difficulty
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Childbirth takes place about 9 months after
fertilization. The processes of childbirth is
controlled by the endocrine system. The hormone
oxytocin affects involuntary muscles in the
uterine wall. These contractions are known as
labor.
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Development continues after birth. Infancy (4
weeks after birth to 2 years) is a time of rapid
development and growth in the nervous, muscular
and skeletal system. Development of teeth.
Childhood (2 years to puberty) social skills
and reasoning are developing. Permanent teeth
develop, bones lengthen. Adolescence (puberty to
adulthood) surge of hormones completes
development of reproductive system. Skeletal
system fully develops.