(11) Placental Development

The placenta can carry how many mLs of maternal blood at one time?

150 mL

Hydatidiform Mole (What might cause this?)

2 sperm can fertilize an egg with no nucleus; Sperm can fertilize egg with no nucleus then undergo DNA duplication to become diploid.

By the end of Week _____, the ____ villi will cover the entire chorion.

4; tertiary

Decidua Capsilaris

A thin layer of endometrium on the abembryonic pole

Hydatidiform Mole (What is it?)

An abnormality where the conceptus consists only of extraembryonic tissues, but the embryo itself is missing. Usually aborts early.

Allantois

An outgrowth of the yolk sac; grows into the connecting stalk to form the umbilicus that surrounds the blood vessels

If a woman has low progesterone levels, what can happen?

As a result, a woman can have a spontaneous miscarriage.

If a vaginal delivery is attempted with Placenta Previa, what may happen?

As the baby tries to push out, the placenta will rupture because the placenta is covering the opening of the cervix.

What are some other things that may pass through the placenta?

Bacteria, Antibodies, Viruses

Placental Abruption (Treatments)

Bed Rest; Transfusions [if the mom is anemic], early delivery of the fetus

What is the main role of the placenta?

Bring maternal blood supply into close contact with the embryonic blood: nutrient & gas exchange

What are some placental rituals/trends/fads?

Burying the placenta; placentophagy

Why might the fetus try to increase the mom's blood pressure/blood volume?

By increasing the mother's blood supply and/or blood volume, more blood will go to the placenta [and eventually to the fetus].

What are the two components of the placenta?

Chorion and Decidua

Once the blastocyst makes contact with the uterine wall, the contacted endometrial cells differentiate into ____.

Decidual cells

By what method of transport can nutrients and waste products by crossed over the placenta?

Diffusion

Most hydatidiform moles are (haploid/diploid).

Diploid

How/when can the mother get blood from the fetus if their circulatory systems are not directly connected?

During delivery, fetal blood can leak into the mother's circulation.

Sinusoids

Enlarged Blood-filled Spaces

Tertiary Stem Villus

Extraembryonic mesoderm develops into blood vessels that connect to the embryonic circulation

Secondary Stem Villus

Extraembryonic mesoderm proliferates and then penetrates into the center of the villus

T/F: The Chorion Laeve is associated with the Chorion Frondosum

False

T/F: Hemolytic Disease of the Newborn affects all the babies of one mother.

False. All babies that are Rh- and the first baby that is Rh+ are safe from this.

T/F: There is no way to prevent HDN.

False. An Rh- mom of an Rh+ fetus should be given an antibody to Rh at the time of delivery. (Rhogam) This removes the fetal RBCs and prevents mom from making her own antibodies.

True/False: The Chorion is derived from the epiblast.

False. It is derived from the trophoblast.

True or False: There is direct communication (i.e. mixing) between the mother's blood and fetus' blood.

False. There is the endothelium of the villous capillaries, the connective tissue of villus, a layer of cytotrophoblast, a layer of syncytiotrophoblast

True/False: Mammalian eggs carry a large yolk.

False. These eggs do not carry large stores of yolk.

How many layers of tissue separate the fetal and maternal blood?

Four layers

Erythroblastosis fetalis can also be known as...

Hemolytic Disease of the Newborn (HDN)

How is the time of implantation related to placenta previa?

In a normal pregnancy, the embryo should implant in the upper part of the uterus, but in this case, the embryo may have implanted in a lower part.

Why might an individual have pre-existing scarring of the uterus?

Infection, Surgery, STDs

What is the role of the Progesterone & Estrogen secreted by the placenta?

Maintains pregnancy; Prog - maintaining the endometrial wall; Est - secondary role in maintaining uterine structure

Erythroblastosis fetalis (What is it?)

Maternal Antibodies attack fetal red blood cells

What crosses into the fetal circulation that can then persist for several months after birth?

Maternal antibodies

Preeclampsia (Why is placentation poor to begin with?)

Maternal immune defects may have seen the placenta as foreign and NOT helped it invade the uterine wall.

Primary Stem Villus

Outgrowth of cytotrophoblast

What are some of the nutrients than can cross from mom to baby?

Oxygen, Water, Carbohydrates, Amino Acids, Lipids, Electrolytes

Most hydatidiform moles contain only (maternal/paternal) chromosomes.

Paternal

Placental Abruption (What is it?)

Premature separation of the placenta from the uterine wall.

What growth factors and hormones are secreted by the placenta? (List the names.)

Progestrogene & Estrogen, Human Chorionic gonadotropin (HCG), Placental Lactogens; Prostaglandins

The lacunae are originally open spaces but are filled with blood to form the ____.

Sinusoids

Which pole begins to bulge into the uterine cavity as the embryo grows?

The abembryonic pole

Which pole is the side opposite of the embryo?

The abembryonic pole is the side opposite of this.

If a mother who has made antibodies against Rh then has a second Rh+ baby, what happens? What may this eventually result in?

The antibodies in mom's immune system will attack the fetus. This can result in anemia, brain damage, fetal death, [and hydrops fetalis]

Why is it important that the maternal antibodies can cross over to the fetus?

The baby will need these to fight off infections in the early part of their life before they can make antibodies of their own.

When the decidua basalis & capsularis and the Chorion Laeve & Frondosum have developed, is the chorionic cavity large or small in size?

The chorionic cavity is small at this time.

What was secreting Progesterone before the placenta took over this role?

The corpus luteum secreted this before the placenta took over this role.

Decidua Basalis

The decidua underlying the embryonic pole; This will eventually form the placenta

Implantation occurs at which pole of the blastocyst?

The embryonic pole is where this occurs.

Decidual Reaction

The endometrial cells contacting the blastocyst differentiate into decidual cells. What is this called?

Which cells become the decidual cells?

The endometrial cells touching the embryo become these cells.

______ and _______ secrete growth factors that support the embryo.

The endometrial glands and the decidual cells secrete these in order to support the embryo.

What are the 4 layers of tissue that separate the fetal and maternal blood?

The endothelium of the villus capilaries, the connective tissue of the villus, a layer of cytotrophoblast, and a layer of syncytiotrophoblast

What differentiates to eventually become the blood vessels of the umbilical cord?

The extraembryonic mesoderm of the the connecting stalk differentiates to become this.

Preeclampsia (What is it?)

The mother's blood pressure spikes dramatically, and protein is found in the urine.

Chorion Laeve

The part of the chorion that no longer has villi

Smooth Chorion

The part of the chorion that no longer has villi

Chorion Frondosum

The part of the chorion that still has villi; associated with the decidua basalis

Placenta Previa (What is it?)

The placenta lies over the opening of the cervix

The contacting trophoblast cells proliferate to form the _______.

The syncytiotrophoblast form from these cells.

By day 8 of development, what is happening to the embryo?

The syncytiotrophoblast is proliferating (cell connections have been broken down) and getting closer to uterine glands and maternal capillary

What happens to the villi on the abembryonic side of the chorion and why?

The villi on this pole disappear because there is no point in growing the placenta in a place where it is not needed.

As the embryo grows, what is eventually used up & degenerated/disappears?

The yolk sac

If the placenta is not delivered completely after the baby is delivered, what can go wrong?

There may be increased chances of infection.

What are placental lactogens, and what is their role as they secreted by the placenta?

These are protein hormones important for the growth of the fetus.

What are Rh factors?

These are proteins on the surface of RBCs in some people.

Trophoblastic Lacunae

These are vacuoles that appear within the syncytiotrophoblast.

The trophoblastic lacunae appear within the ______.

This appears within the syncytiotrophoblast.

What happens to the endometrial wall after implantation occurs?

This becomes highly vascularized after implantation occurs.

In preeclampsia, the placenta becomes ______ as the fetus grows.

This becomes hypoxic in preeclampsia.

Erythroblastosis fetalis (Treatments?)

This can be treated in utero with transfusions through the umbilical cord. This would increase the oxygen carrying capacity.

Placenta Previa (What kind of problems can arise?)

This can cause severe bleeding during vaginal delivery; C-section is recommended

Preeclampsia can lead to...?

This can lead to stroke, kidney failure in the mom, fetal distress/death

What kind of blood does the umbilical vein carry: oxygenated vs. deoxygenated?

This carries oxygenated blood from the placenta to the embryo.

Preeclampsia (During what trimester does this usually take place?)

This condition usually takes place during the third trimester.

Placental Abruption (How frequently does it occur?)

This happens approx 1 in 100 pregnancies.

Placenta Previa (How frequently does it occur?)

This happens approx 1 in 200 pregnancies.

By what day of development is the embryo completely in the uterine wall?

This happens by Day 9 of development.

The human blastocyst implants at which day/week of development?

This happens by the end of the first week of development. (approx Day 6 according to previous lectures)

Why does the endometrial wall have to become highly vascularized after implantation occurs?

This has to occur so that there will be a great blood supply to feed the growing embryo.

Choriocarcinoma

This is a malignant tumor (very rare) that was formed from a hydatidiform mole. This is a fast growing and invasive cancer; cure rate is high.

Preeclampsia is due to...?

This is due to underdevelopment of the placenta: when the villi do not penetrate deeply enough into the endometrium.

What is the role of the Prostaglandins secreted by the placenta?

This is required for the onset of labor.

Preeclampsia (Treatments?)

This is treated with antihypertensives, bed rest, and early delivery of the baby.

Hydrops Fetalis

This is when the fetus develops heart failure due to severe anemia.

Hydatidiform Mole: If not detected early, can be diagnosed by ______.

This may be diagnosed by very high levels of hCG.

Placenta Previa may result from...?

This may result from pre-existing scarring of the uterus.

How frequently is the maternal blood exchanged through the placenta?

This occurs 3-4 times per minute.

Preeclampsia (How frequently does it occur?)

This occurs in about 2-3% of pregnancies.

What does the cytotrophoblast secrete and why?

This secretes enzymes that break down the connections between the endometrial cells. This is done so that the syncytiotrophoblast can proliferate.

What happens to the cytotrophoblast by day 12/13?

This starts making finger-like extensions.

Why might one participate in placentophagy?

To recover nutrients; to deter predators; possible contains hormones that stimulate uterine recovery and milk production

T/F: Rh+ people have the Rh factor on their RBCs.

True

T/F: The Decidua Basalis will eventually form the placenta

True

T/F: The umbilical artery carries deoxygenated blood.

True. The umbilical artery carries the deoxygenated blood from the embryo to the placenta.

T/F: The Endometrial glands start to enlarge when the human blastocyst is implanted in the uterus.

True. These glands start to enlarge when the human blastocyst is implanted in the uterus.

T/F: The Chorion is the embryonic portion of the placenta.

True. This is the embryonic portion of the placenta.

What are some of the waste products that go from the baby to the mother?

Urea, Uric Acid, Bilirubin, Carbon Dioxide

When the placenta become hypoxic in preeclampsia, what happens?

When this happens, factors are secreted into the maternal blood that will cause endothelial changes in the mother. This will lead to an increased bp in mom.

Chorion

embryonic portion of the placenta; derived from the trophoblast

Decidua

maternal portion of the placenta; derived from the endometrium

________ proliferates and surrounds the embryo.

syncytiotrophoblast

Occasionally, hydatidiform moles form _______.

tumors that are usually benign

The allantois grows into the connecting stalk to form the ________.

umbilicus