2. AMNION
-It is a membrane that enclose amniotic cavity.
-Formation:
-It is formed at the 8th
day as a small cavity in
epiblast cells with formation of amnioblasts.
-So, floor of the cavity is epiblast while the
roof is formed from amnioblasts.
-By the 12th
day it becomes separated from
cytotrophoblasts by primary mesoderm
(Extraembryonic).
-Amnio-ectodermal junction is at the margin
of oval embryonic disc at the 3rd
week.Dr. Sherif Fahmy
3. -During 4th
week, expansion of amniotic cavity
leads to folding of the embryonic disc and amnio-
ectodermal junction will be present at primitive
umbilical ring.
-At 3rd
month amnion comes in contact with
chorion to form amnio-chorionic membrane with
obliteration of chorionic cavity.
-By the end of 3rd
month, uterine cavity is
obliterated due to expansion of amniotic cavity.
-Finally, the amniotic cavity surrounds the fetus
and forms a tubular sheath around the umbilical
cord.
Dr. Sherif Fahmy
4. 8th
day of pregnancy
Dr. Sherif Fahmy
Endometrium
CytotrophoblastAmnioblast
Amniotic cavity
Epiblast Hypoblast
Dr. Sherif Fahmy
5. 9th
& 10th
days
Dr. Sherif Fahmy
Cyto-
trophoblast
Amnioblast
Amniotic
cavity
Epiblast
Hypoblast
Dr. Sherif Fahmy
15. Amniotic fluid
- Normal volume is 1000 – 1500 cc clear
watery fluid at full term.
- Source: 1st
from amnioblast then from
kidney.
- If the volume is less than 500 cc it is
called oligohydramnios.
-If the volume is more than 2000 cc is
called polyhydramnios. Dr. Sherif Fahmy
16. Functions of amniotic fluid:
1- At early pregnancy:
1- Acts as water cushion that absorbs external
shocks.
2- Acts as heat insulator.
3- Prevents adhesion of embryo to wall of uterus.
4- Prevents adhesion of fetal parts.
2- At late pregnancy:
1- A space for accumulated urine.
2- Allows fetal movements to help body muscles
to develop.
3- Help suckling training and development of gut
muscles. Dr. Sherif Fahmy
17. 3- During labor:
1- Protects against uterine contractions.
2- Formation of bag of water that gradually
dilate the cervix.
3- Sterile amniotic washes vagina before
passage of baby.
4- Rupture of amniotic sac is a sign of start
of delivery.
Dr. Sherif Fahmy
18. Abnormalities of amniotic fluid:
1- Polyhydramnios.
Causes:
1- No cause (35 %).
2- Maternal diabetes.
3- Congenital malformation e.g.
anencephaly and esophageal atresia.
2- Oligohydramnios.
Cause:
-Renal agenesis.
Dr. Sherif Fahmy
20. Morphology of Umbilical Cord
It is the connection between placenta and
fetus.
• Length: 50 – 60 cm
• Diameter: 2 cm.
• Shape: Tortous, showing false notes.
• Contents: 2 umbilical arteries, one umbilical vein
embedded in wharton’s jelly and surrounded by
amniotic membrane.
• Attachments: It is attached to fetal surface of placenta
near its center, the other attachment is to ventral
aspect of fetal abdominal wall.
• Functions:
– It contains umbilical vessels that connect the fetus to the
placenta.
23. Development of the Cord
1- Primitive umbilical ring.
2- Primitive umbilical cord.
3- Definitive umbilical cord.
24. Primitive Umbilical Ring
Expansion of amniotic cavity, leads to folding with
ventral shifting of amnio-ectodermal junction and
formation of primitive umbilical ring.
Contents:
Connecting stalk containing allantois and
umbilical vessels.
Vitelline duct and vitelline vessels.
Connection between intra-embryonic and extra-
embryonic coelom.
25. Expansion of amniotic cavity, leads to
elongation of umbilical cord.
Contents:
1- Yolk sac and vitelline duct.
2- Connecting stalk with remnant of
allantois.
3- Umbilical and vitelline vessels.
4- Intestinal loop in its proximal part.
Primitive umbilical cord
26. Return of intestinal loop to abdominal
cavity at 3rd
month.
Obliteration of extra-embryonic part of
vitelline vessels and one umbilical vein
with persistence of other vein and 2
umbilical arteries.
Degeneration of vitelline duct and
allantois
Transformation of mesoderm of
connecting stalk into wharton’s jelly.
Definitive Umbilical Cord
38. • Abnormalities of Umbilical Cord
• 1- Short cord: leads to premature separation
of placenta.
• 2- Long cord: It may encircle neck of fetus and
may form true knots.
• 3- Congenital umbilical hernia
(omphalocele): the cord contains coils of
intestine.
• 4- Presence of one umbilical artery.
• 5- Abnormal attachment of the cord:
–Marginal attachment (battledore)
–Through membranes (velamentous).