Download fetal stage.

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4
Pregnancy
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Conception
• Cell is the smallest unit of life that is
able to reproduce itself
• Sperm is the male germ cell
• Ovum is the female germ cell
• Conception occurs when ovum and
sperm combine
• Zygote is a single cell formed at
conception
– also called a fertilized egg
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continued
Conception
• Fallopian tubes
extend from the
sides of the uterus
– where the ovum is
fertilized
• Uterus is the organ
in which the baby
develops
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Genetic Factors and the Unborn
Baby
• Genetic factors are traits passed
through the genes
– affect all stages of growth and
development
• Genome is a genetic blueprint that
guides growth and development
during pregnancy
– gives cells instructions for family-like
traits that will unfold throughout life
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continued
Genetic Factors and the Unborn
Baby
• Nucleus is the
center of the cell
• Genetic code is a
set of instructions
for development
• DNA store the
genetic code
• Chromosomes
carry the DNA
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Objective
• Describe how a person inherits traits
through genes.
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Chromosomes and Genes
• Chromosomes
– each person has 46, pairs of 23
– half from sperm, half from egg
– contains 20,000 genes
• Genes
– each human cell contains about 1 million
genes
– a gene, or group of genes, decides a trait
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Dominant and Recessive Traits
• Dominant traits always show in a
person even if only one gene of the
pair is inherited for that trait
• Recessive traits typically do not
show in a person unless both genes
for the trait are inherited
– one from each parent
– person who inherits only one recessive
gene for a trait becomes a carrier of
that trait
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Sex Chromosomes
• Sex chromosomes determine genetic
sex of baby
– XX female
• ovum always carries only X chromosomes
– XY male
• sperm can carry either X or Y chromosome
• boys’ sex-linked traits are determined only
by their mothers
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Multiple Pregnancy
• Multiple pregnancy
occurs when two or
more babies develop
in the same pregnancy
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continued
Multiple Pregnancy
• Fraternal children develop from two
or more ova
– most common
– each baby has own chorion
• Identical children develop from same
ova and sperm
• Mixed types of pregnancy must include
fraternal and identical babies
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What Do You Think?
How can parents help identical twins
maintain separate identities while still
nurturing a close sibling relationship?
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Stages in Prenatal Development
• Prenatal development takes place
between conception and birth
– germinal stage
– embryonic stage
– fetal stage
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Germinal Stage
• Germinal stage is the first stage of
development
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continued
Germinal Stage
• Amnion is a fluid-filled sac that
surrounds the baby in the uterus
• Placenta is an organ filled with
blood vessels that nourish the baby
in the uterus
• Umbilical cord is a cord that
connects the baby to the placenta
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Embryonic Stage
• Embryonic stage is the second stage
of development, lasts about six weeks
– most crucial to development
– baby is called an embryo
– development of most body systems
– heart begins to beat
– cartilage is present before bones form
– substances pass from mother’s placenta
through the umbilical cord
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Fetal Stage
• Fetal stage is the third
stage of pregnancy,
lasts from about nine
weeks after conception
until birth
– bone starts to replace
cartilage
– baby is known as a fetus
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continued
Fetal Stage
• During the fetal stage,
– all parts of the body mature
– overall size increases quickly
– hear heartbeat in the third month
– quickening begins between the fourth
and fifth months
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continued
Fetal Stage
• Age of viability is the age at which a
baby could survive if born, 28 weeks
– still need extensive medical care
– better chance of survival each week the
baby is not born
• During last two months of pregnancy,
– inner layer of lungs produces substance
that allows for breathing air
– receives immunities from mother in the
ninth month
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What Do You Think?
• Pregnancies that end before 20 weeks
are considered a miscarriage, resulting
in no record of the life, such as a birth
or death certificate.
• How do you think this impacts a
parent after the loss of a wanted
pregnancy?
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Glossary of Key Terms
• age of viability. Age at which most
babies could survive if they were born
(28th week of pregnancy).
• amnion. Fluid-filled sac that surrounds
the baby in the uterus.
• cartilage. Soft, elastic, flexible tissue
that provides structure for the body.
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Glossary of Key Terms
• cell. Smallest unit of life that is able to
reproduce itself.
• chorion. Membrane that surrounds the
baby in the uterus.
• chromosomes. Threadlike structures
that carry genes in living cells.
• conception. Union of the ovum and
sperm cells.
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Glossary of Key Terms
• dominant traits. Traits that always
show in a person even if only one gene
of the pair is inherited for that trait.
• embryo. Medical term used to describe
the unborn baby in the embryonic stage
of development (week 3 through 8 of
pregnancy).
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Glossary of Key Terms
• embryonic stage. Second stage of
prenatal development, lasting about
six weeks.
• fallopian tubes. Two hollow tubes
that connect to the uterus and have
fingerlike projections that reach
toward each ovary.
• fetal stage. Third stage of pregnancy,
lasting from about nine weeks after
conception until birth.
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Glossary of Key Terms
• fetus. Medical term used to describe
the unborn baby in the fetal stage of
development (week 9 until the end of
pregnancy).
• fraternal. Term used to describe
children from multiple pregnancies who
develop from two or more fertilized ova
and differ in genetic makeup.
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Glossary of Key Terms
• genetic factors. Traits that are passed
through the genes.
• germinal stage. First stage of prenatal
development, lasting about two weeks
after conception.
• identical. Term used to describe
children from multiple pregnancies who
develop from one fertilized ovum and
have the same genetic makeup.
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Glossary of Key Terms
• multiple pregnancy. Pregnancy in
which two or more babies develop.
• ovum. Female sex cell; also called egg.
• placenta. Organ filled with blood
vessels that nourish baby in the uterus.
• prenatal development. Development
that takes place between conception
and birth.
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Glossary of Key Terms
• quickening. Movements of the fetus
that can be felt by the mother.
• recessive traits. Traits that typically
do not show in a person unless both
genes for the trait are inherited.
• sperm. Male sex cell.
• umbilical cord. Cord that connects the
baby to the placenta.
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Glossary of Key Terms
• uterus. Organ in which the baby
develops and is protected until birth.
• zygote. Single cell formed at
conception; also called fertilized egg.
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