Human Development and Birth Chapter 18

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Human Development and Birth - Chapter 18
First step in human development is
__________________- process by which the gametes
recombine to form a _________________________. Fer
tilization accomplishes 2 things 1. provides
for recombination of _______________
______________________________(half from male
parent and half from the female parent) to
restore the diploid chromosome number 2.
triggers the process of _______________________
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Gametes

• Sperm is the male gamete.
• Consists of
• 1. Head piece
• _____________________ - contains enzymes for
  oocyte penetration
• ___________________ - contains 23 chromosomes
• 2. _______________________ _______________________
  __
• 3. ____________________

3
Gametes
________________________is female cell ready for
fertilization. Surrounded by 2 protective
layers 1. Cells of the ________________________
2. ______________________
4
Fertilization
Process begins when the male inserts his penis
into the female vagina and semen is ejaculated
into the vagina near the cervix.  - millions of
sperm begin their journey to the fallopian tube
to find a secondary oocyte  - sperm can live in
the female for a maximum of 72 hours, so they
must find a secondary oocyte during this time
period or they will die - by the time sperm
reach the single secondary oocyte, numbers have
declined to ____________________
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Fertilization
After ovulation, the secondary oocyte remains
alive in the fallopian tube for 12 to 24 hours.
The 72 hour life span of a sperm and the 12 to
24 hour life span of the secondary oocyte must
overlap. This is called the ______________________
_____________.
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How does fertilization occur?
Several sperm reach the secondary oocyte in the
fallopian tube and begin the process of
penetration through the 2 protective
layers. Enzymes from the ________________________
speed penetration.  
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When the first sperm penetrates through the 2
protective layers and reaches the cell membrane
of the secondary oocyte, the cell membrane
thickens. The thick cell membrane now prevents
all other sperm from entering. Why is this
important? _______________________________________
__________________________________________________
___________________  
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Sperm penetration now stimulates Meiosis II and
the secondary oocyte becomes the
_________________________containing a
_____________________________. Sperm cell now
loses its tail and becomes the head of the sperm
Head of the sperm unites with the female nucleus
to form the ___________________________. Zygote
now contains _________chromosomes - diploid
number.
Ovum
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Human Development
After fertilization, the zygote begins mitotic
division called __________________________,
eventually forming a ball of 32 cells called the
____________________________.  Smaller and
smaller cells formed from these divisions are
called _______________________________.
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Formation of the Blastocyst

• By about 5 days, the blastomeres separate to form
  the blastocyst
• outer cells the ______________________________
  ____- will form the _____________________________
• inner cells the ______________________________
  ___- will eventually form the ____________________
  ______
•   a cavity appears in the blastocyst called the
  _____________________________
•  

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• Inner cell mass consists of many
  ___________________________ that show the
  following characteristics
• Stem cells are the ancestors of all tissues and
  organs
• They can be grown in culture.
• They can be transplanted into a patient where
  they can grow into healthy adult cells.
• Transplanted stem cells show less rejection
  compared to other transplants.
•  

embryonic stem cells
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Source of these stem cells are from blastocysts
that are created in excess at fertilization
clinics. Thus, some believe that they should not
be used under any circumstances, not even to help
people with serious diseases. Research is needed
to figure out how a stem cell can be made to
differentiate into the type of cell we
want. These cells may someday be used to treat
people with Parkinsons disease, Alzheimers
disease, diabetes, leukemia, and spinal cord
injuries.    
Read more about stem cells on pages 94-95 of
your textbook.
embryonic stem cells
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Implantation
At day 6 after fertilization, implantation
occurs. At this point, the blastocyst moves
into the uterus and adheres to the
__________________________________(inner wall
that has been made ready by the action of
estrogen and progesterone from the ovary) A
woman is now considered to be ____________________
_____  
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Implantation
By day 14, the blastocyst is well implanted into
the uterine ________________________ The stem
cells of the inner cell mass begin to separate to
form the ____________________________
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Embryonic Development Weeks 3 to 8
About 3 weeks, the ___________________________form
s. Cells in the gastrula differentiate to form
the three primary germ layers -
__________________________ -
__________________________ -
__________________________  
 
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Gastrula stage in lab
Ectoderm Mesoderm Endoderm
Frog Sea Star
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Formation of the Placenta
In weeks 2-4, the trophoblast differentiates into
3 layers of the placenta. 1. outer
____________________ - attaches to the uterine
endometrium by fingerlike projections called the
chorionic villi   - through the chorionic villi,
gases, nutrients, and wastes are now exchanged
between the embryo and mother    
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Formation of the Placenta
 2. ______________________ - begins to
form blood cells and umbilical blood vessels
3.  inner layer becomes the ______________________
____ - a protective membrane around the embryo
which is filled with amniotic fluid      
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Formation of the Placenta

• With the formation of the placenta, the chorion
  also secretes a hormone called human chorionic
  gonadotropin (HCG)
• HCG acts on the corpus luteum in the ovary to
  stimulate the continued production of estrogen
  and progesterone by the corpus luteum
• - HCG is the hormone that is detected in a
  ____________________________ (some of it is
  present in ___________________)
•  
•  

 
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Formation of the Placenta

• HCG is produced for the first 3 months of the
  pregnancy to stimulate estrogen and progesterone
  secretion by the ______________________________
• In the second and third trimesters, the
  _________________________ produces estrogen and
  progesterone
• Estrogen and progesterone from these two sources
  keep the uterine endometrium intact during the 9
  months of human development.

 
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Neurula stage differentiation of the 3 germ
layers
From weeks 3 to 4, there is rapid growth and
development of the germ layers. The embryo at
this stage is called the _________________________
____ ___________________________forms the
epidermis and nervous system brain and spinal
cord are formed from neural groove, then neural
tube.
 
cross section

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Neurula stage differentiation of the 3 germ
layers

• _______________________________forms the
  circulatory system, urogenital system, muscles,
  bones, and connective tissues
• _________________________forms vertebral column
• _________________________ form muscles

 
cross section

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Neurula stage differentiation of the 3 germ
layers
________________________________forms the
digestive system, respiratory system, and
endocrine glands.

lumen of the digestive tract
 
cross section

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Embryo
At weeks 4-6, the embryo shows rapid development
but does not yet look like a human. Head with
___________________________ (pharyngeal arches)
appears. ______________________ begins to beat.
Muscles appear as _______________________ _______
_________________appear. A ___________________is
present.
 
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Embryo
At weeks 6-8, the eyes and ears become visible,
and the 4 limbs have fingers and toes. Skeleton
is cartilaginous. Heart and circulatory system
become
functional. If the embryo is _______, the testes
develop
and a burst of testosterone stimulates
male
characteristics. If the embryo is _______, the
absence of the
testosterone burst results in development
of the
ovaries.
 
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Fetal Development
By the end of 8 weeks, all the features of a
human being are present. The embryo is now
called a ____________________ - most organs begin
to function - the fetus is only about 1½ inches
long  
 
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First 8 weeks of Development
The first 8 weeks of human development is the
most sensitive period of development in which
external factors can cause birth defects. Smoking
causes 1. 2. 3. 4. 5. new finding
increased chances for chromosomal damage
resulting in childhood __________________    
 
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First 8 weeks of Development

• Alcohol causes fetal alcohol syndrome resulting
  in
• 1. _______________________________
• _______________________________(small brains
  resulting in mental deficiency)
• ______________________________
•  
•  

 
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First 8 weeks of Development
 
Will this mother have a healthy child?
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Fetus
In months 4, 5, and 6 - now called the
_____________________________________ - fetal
movements become obvious and the fetus grows to a
length of 12 inches and 1 to 2 pounds. The
____________________ develop and begin to produce
urine. Cartilaginous skeleton is replaced by
__________________ ______________________ begin

producing blood cells. Nervous system and
skeletal
muscles allow for fetal
_____________________
 
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Fetus

Its chances of survival outside the uterus are
low, as body _____________________________ cannot
be regulated and the _____________________________
_ and _________________ are barely functional.
 
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Fetus
The ______________________________ (months 7, 8,
9) is a period of growth and the fetus rapidly
gains weight, up to 7 pounds or more. Movements
of the fetus are increased. In the male, the
_______________________descend through the
_____________________________ into the
scotum. Digestive and respiratory systems become
fully functional.
 
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Birth takes place about about _______________
days after conception (calculated at 280 days
after the last menstrual period) The process
starts with _______________________ - rhythmic
contraction of the uterine muscles. Three
stages of labor 1. _______________________-
stretching and opening of the cervix. Dilation
is accompanied by the rupture of the
______________________ (water breaks). Uterine
contractions increase over time. Dilation often
lasts 6 to 12 hours.

 
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Birth

• Delivery of the baby, usually head first, follows
  dilation.
• This is a _____________________
• With its first breath, the three fetal shortcuts
  close off to restore a complete pulmonary
  circuit.
• They are
• ________________________
• ________________________
• ________________________
•  

 
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Birth
3. Delivery of the ________________________
(called afterbirth) occurs about 15 minutes after
birth of the baby. Uterus contracts to
constrict blood vessels so that blood loss is
minimal.  

 
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Birth

• If complications arise, a vaginal birth may not
  be possible
• _____________________________
• ______________________________
• ______________________________
• ______________________________
• A ___________________________ involves major
  surgery in which the abdominal wall and uterus
  are opened to allow for birth.
• _____ of US births
• trying to reduce these numbers

 
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Lacation
Final step in human development is
Lactation.  After birth, the anterior pituitary
gland secretes ______________________. This
hormone acts on the _______________________ to
stimulate _______________________    

 
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Lacation

   
The suckling response from the newborn stimulates
the release of _______________________which is
stored in the posterior pituitary. Oxytocin
stimulates muscle contraction in the mammary
gland resulting in the flow of milk called
______________ _______________________.  
 
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Lacation
As long as the baby is suckled, the mammary
glands will produce milk and allow for breast
feeding.   Should breast feeding stop, the
absence of the sucking response inhibits the
secretion of both ________________________________
______________, and milk production ceases.

   
 
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Twins
One out of 90 births results in
twins. __________________________ 2 secondary
oocytes are ovulated at the same time and are
fertilized by _______ sperm. Zygotes are
products of different sperm and oocytes.
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Twins
Identical twins A single sperm and secondary
oocyte are fertilized. In early cleavage, the
blastomeres separate into 2 groups but they share
same placenta. Because each is formed from the
same sperm and oocyte, they have identical
__________________________________________________
____________
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Twins
__________________________ A single sperm and
secondary oocyte are fertilized. In early
cleavage, the blastomeres separate into 2 groups
as in identical twins, but they do not separate
completely. Two individuals are formed but remain
attached. Surgery may or may not be possible to
separate them.
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Diagnosing Fetal Defects
Chorionic villi sampling examining cells of the
chorion for chromosomal or chemical
analysis. When done?
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Diagnosing Fetal Defects
Amniocentesis amniotic fluid containing skin
cells is examined for chromosomal
abnormalities. When done? About _________fetal
defects can be diagnosed with amniocentesis.
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Diagnosing Fetal Defects
_________________________ gives a moving
picture of the fetus in the uterus. Can see the
embryo as early as ___________________ Can
identify the sex of the fetus. Measurements of
the fetus can be used to determine the due date
more precisely.
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Healthy Mother and Child
With good prenatal care and avoidance of smoking
and alcohol, a healthy child will make its way
into the world. Well review human development
by looking at a movie on the Miracle of Life.