Placenta

Question 1

Maternal side of the placenta

Answer 1

Decidua basalis

Question 2

Formation of the amniotic cavity

Answer 2

Forms around the cells of the epiblast around Day 9; cells of the hypoblast will migrate around the cytotrophoblast to form the exocoelomic membrane and cavity

*Exocoelomic cavity= primitive yolk sac

Question 3

Formation of the chorionic cavity

Answer 3

Extraembryonic mesoderm splits into 2 layers; creates the extraembryonic cavity divided in the middle by the body stalk

*Body stalk= primitive umbilical cord

Question 4

Formation of Villi

Answer 4

Primary villus pushes into into the decidua

Secondary villus forms w/ the invasion of the mesoderm

Tertiary villus formed w/ formation of blood vessels in the mesoderm

Question 5

Chorion frondosum

Answer 5

Part of the anterior fetus whose intestinal villi project to form part of the placentaa

Question 6

Chroion levae

Answer 6

Posterior part of fetus w/ relatively smooth decidua capsularis

*After growth, will fuse w/ the decidua parietalis on the opposite side of the uterus and eliminate the chorionic cavity

Question 7

Placenta Exchange Barrier

Answer 7

1. Synctium
2. Cytotrophoblast
3. CT
4. Endothelium
   * After 4 months, only made up of Synctium and Endothelium

Question 8

Vitelline Vessels

Answer 8

Develop in the mesoderm of the yolk sac; become the embryonic supply to the gut

Question 9

Umbilical Artery

Answer 9

Develops in developing mesoderm of the body stalk; connects directly to the descending Aorta

Question 10

Ductus venosus

Answer 10

Connects the umbilical vein to the IVC right before the heart; allows blood to travel to the heart w/o passing thru the hepatic circulation

*Shunting more prominent in early pregnancy; closure occurs w/in minutes as birth due to the cessation of placental blood flow

Question 11

Foramen Ovale

Answer 11

Transports 27% of the CCO directly from the RA to the LA

• Final LA % of CCO= 34%
• Closes @ birth as LA pressure exceeds RA pressure

Question 12

Ductus arteriosus

Answer 12

Directs blood from the pulmonary artery to the descending aorta; only 7% of the 66% of CCO from the RV gets directed to the fetal lungs due to the increased pressure

*Initial closure occurs 18 hrs post-delivery due to decreased PGE2 and decreased PVR
Anatomical occlusion occurs over the next few days as fibrous and endothelial tissue proliferate

Question 13

Cardiopulmonary Adjustments @ birth

Answer 13

• Closure of fetal shunts
• Gas exchange changes from the placenta to the lungs
• Increase in LV output
• Increase SVR
• Decreased Pulmonary resistance

Question 14

Patent Ductus Arteriosus

Answer 14

Failure of the ductus arteriosus to close resulting in overload of the left heart => Left heart failure

*Right heart is fine unless pulmonary vascular disease develops

Question 15

Blastocyst formation

Answer 15

Fluid accumulates on one side of the morula leading to the formation of the blastocoel; other side has inner cell mass

Question 16

Formation of placenta

Answer 16

Occurs when cells of the cytotrophoblast ex and over the Synctium and make contact w/ the endometrium

Question 17

Blood from fetal LV

Answer 17

Primarily flows to the head and upper limbs

Question 18

Normal closure of the ductus arteriosus is due to…

Answer 18

Increased pO2

Decreased prostaglandin synthesis

Decreased PVR