i want 20 multiple choice questions with their mode answer below each question that covers different aspects of all of the following information: General EmbryologyObjectives
By the end of this lecture student should be able to:
-Explain the development of the fetus
(Development of the fetal membranes and
placenta).Contents
-The external appearance during the
embryonic & fetal periods.
-The amnion and the umbilical cord.The external
appearance during
the embryonic periodBy the end of the
4th week the main
external features:
Pharyngeal arches
The external appearance
SomitesThe external appearance
By the beginning of
the 5th week the
main external
features:
limb budsThe external appearance
-During the second
month, the external
appearance of the
embryo:
-Increase in
head size.
-Formation of
the limbs, face,
ears, nose, and
eyes.Development of the
fetus
(The external
appearance during the
fetal period)Development of the fetus
During the third
month, the face
becomes more
human looking.Development of the fetus
By the 12th week
external genitalia
develop and the sex
of the fetus can be
determined by
ultrasound.Development of the fetus
-During the fifth
months the fetus is
covered with fine hair,
called lanugo hair.
-Eyebrows and head
hair are also visible.Development of the fetus
-During the sixth
month, the skin of the
fetus is reddish and has
a wrinkled appearance
because of the lack of
underlying connective
tissue.Development of the fetus
-By the end of
intrauterine life,
the skin is covered
by a whitish fatty
substance (vernix
caseosa)
(Sebaceous glands
secretions).Fetal membranesFetal membranes
Amnion
Chorion
Umbilical cord
Connecting stalk
Allantois
Yolk sac
PlacentaThe amnionDay 8
Amnioblast
The amnion
Day 9
Amnioblast
Amniotic cavity
Amniotic cavityDay 11&12
The amnion
Amniotic cavity
Day 13
Definitive
yolk sac
Primitive
yolk sac
Chorionic cavity
Chorionic cavitySagittal section
The amnion
Amniotic
cavity
Cross sectionSagittal section
The amnion
Amniotic
cavity
Cross section
Amniotic
cavityThe amnion
1- Amniotic cavity
2- Amnion
3- Chorionic cavity
4- Chorion
5- Endometrium
(Decidua)
6- Uterine cavity
6
5
4 3
5
2 1The amnion
-By the end of the
third month
the amnion (2)
expands and it
adheres to the
chorion (4) ,
obliterating the
chorionic cavity(3) .
-The uterine cavity
(6) is also obliterated.
6
2
4 3The amnion
-By the end of the
third month
the amnion expands
and it adheres to the
chorion , obliterating
the chorionic cavity.
-The uterine cavity is
also obliterated.
Amniotic cavityThe amniotic fluid
-The amniotic fluid
is clear, watery fluid
fills the amniotic
cavity.
-It is Produced by:
.Amniotic cells.
.Fetal urine is
added daily to the
amniotic fluid in the
5th month.The amniotic fluid
Normal amount
of amniotic fluid
10
weeks
20
weeks
37
weeks
Polyhydramnios :
Excess amniotic fluid
(1,500 to 2,000 mL).
Oligohydramnios :
Decreased amount
(<400 mL)
30 mL
450 mL
800 – 1000 mLThe amniotic fluid
Function of the amnion
and amniotic fluid:
-Absorbs shocks.
-Prevents adherence of
the embryo to the
amnion.
-Allows for the fetal
movements.
-During childbirth, the
amniochorionic
membrane helps to
dilate the cervical canal.The umbilical cordThe umbilical cord
Umbilical cordDay 9
The umbilical cord
Day 11 & 12
Primitive
yolk sac
Primitive
yolk sac
Extraembryonic
mesodermDay 11 & 12
The umbilical cord
Connecting stalk
Day 13
Definitive
yolk sac
Primitive
yolk sac
Chorionic cavityThe umbilical cord
Connecting stalk
AllantoisDay 17
The umbilical cord
Connecting stalk
yolk sac
AllantoisDay 24
The umbilical cord
Allantois
yolk
sac
Vitelline duct
Connecting stalkDay 28
The umbilical cord
Allantois
Vitelline duct
yolk
sac
Connecting stalkThe umbilical cord
With the
embryonic
folding the
primitive
umbilical ring
is formed.The umbilical cord
By the 5th week of
development the
following structures
pass through the
umbilical ring:
2
1
1-Connecting stalk
containing the
allantois & the
umbilical vessels
(two arteries and
one vein).
2-Vitelline duct
(yolk stalk ) &
vitelline vessels.The umbilical cord
With rapid
enlargement of the
amniotic cavity
the amnion covers
the connecting stalk
and vitelline duct
and the primitive
umbilical cord is
formed.
Amnion
AmnionThe umbilical cord
With rapid
enlargement of the
amniotic cavity
the amnion covers
the connecting stalk
and vitelline duct
and the primitive
umbilical cord is
formed.
Amniotic
cavity
Amnion
AmnionThe umbilical cord
Due to the small
abdominal cavity of the
fetus, some of the
intestinal loops are
pushed into the umbilical
cord and form:
The physiological
umbilical hernia.The umbilical cord
By the end of the third
month:
The loops of the intestine
are withdrawn into the
body of the embryo.
The allantois , the vitelline
duct and its vessels are
obliterated.
The yolk sac shrinks and
gradually obliterated.The umbilical cord
All that remains in
the cord are the
umbilical vessels
surrounded by
Wharton jelly
(protective layer
for the blood
vessels).The umbilical cord
At birth the umbilical
cord is:
-1 to 2 cm in diameter
-50 to 60 cm long
-It is tortuous, causing
false knots.Umbilical cord abnormalities
-Short umbilical cord -Long umbilical cord -Single umbilical artery