37- Placental & Fetal Membranes Flashcards by Staci Thomas

What are the fetal membranes?

Chorion
Amnion
Umbilical Vesicle
Allantois

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Placenta is a fetomaternal organ with two components, which are…

Fetal Part = chorionic sac (outermost fetal membrane)

Maternal Part = derived from endometrium

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Exchanges of nutrients and oxygen occurs between maternal and fetal bloodstreams via the ________.

Placenta

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Vessels in the _______ _______ connect the placental circulation with the fetal circulation.

Umbilical Cord

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What type of potency is a zygote?

Totipotent

***Can give rise to any cell type!

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Expression of cell lineage specific factors begins in the blastocyst. The _________ will become the embryo and the _________ will become the extraembryonic tissue.

Embryoblast

Trophoblast

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Implantation occurs and embryoblast becomes a…

Bilaminar embryonic disc

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What do the extraembryonic structures include?

Amnion
Umbilical Vesicle
Connecting Stalk
Chorionic Sac

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This is the functional layer of the endometrium that separates from the remainder of the uterus after parturition (childbirth).

Decidua

***Pale-staining cells with glycogen and lipid accumulation!

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This part of the decidua is deep to the conceptus and forms the maternal part of the placenta.

Decidua Basalis

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This part of the decidua is superficial and overlies the conceptus.

Decidua Capsularis

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This part of the decidua consists of all its remaining parts.

Decidua Parietalis

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Cellular and vascular changes occur to the endometrium as the blastocyst implants. This is called the…

Decidual Reaction (Decidualization)

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This is completed the late 2nd week (about 10 days post-fertilization) and is when the blastocyst embeds in the endometrium.

Implantation

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In implantation, the trophoblast differentiates into what?

Cytotrophoblast (inner layer)

Syncytiotrophoblast (outer layer) – invades and displaces decidual cells of the endometrium

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_________ appear in syncytiotrophoblast layer and fill with blood and uterine secretions. Adjacent ones fuse to form networks.

Lacunae

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_______ _______ _______ is when oxygen and nutritive substances pass to the embryo via diffusion through lacunar networks.

Primordial Uteroplacental Circulation

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Put the following steps of implantation in order –

A. Blood-filled lacunae appear in the syncytiotrophoblast.

B. Primary chorionic villi develop.

C. Implantation of the blastocyst in the uterine endometrium begins at the end of 1st week, completed by end of 2nd week.

D. Lacunar networks form by fusion of adjacent lacunae.

E. Blastocyst adheres to the endometrial epithelium.

F. ZP degenerates due to enlarging the blastocyst and enzymatic lysis.

G. Syncytiotrophoblast erodes endometrial blood vessels, allowing maternal blood to seep in and out of lacunar networks, and establishing uteroplacental circulation.

H. Trophoblast differentiates into two layers, the syncytiotrophoblast and cytotrophoblast.

1) C.
2) F.
3) E.
4) H.
5) A.
6) D.
7) G.
8) B.

***Look at slides for exact days!

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This is the implantation of blastocyst outside the uterine cavity (2% of all pregnancies). Most occur in the oviduct, most frequently in the ampulla and isthmus. Signs can include abdominal pain, amenorrhea, vaginal bleeding, rupture of oviduct wall, and surgical removal of affected tubes/conceptus.

Ectopic Pregnancy

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T/F. Ectopic pregnancies produce a highly increased amount of hCG than a regular pregnancy.

False. Ectopic pregnancies produce hCG but at a slower rate than normal pregnancies.

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This type of mesoderm lines the trophoblast and covers the amnion.

Extraembryonic Somatic Mesoderm

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This type of mesoderm surrounds the umbilical vesicle.

Extraembryonic Splanchnic Mesoderm

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This is a fluid-filled cavity that surrounds the amnion and umbilical vesicle.

Extraembryonic Coelom

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What do the following collectively make?

- Extraembryonic Somatic Mesoderm
- Cytotrophoblasts
- Syncytiotrophoblasts

Chorionic Sac

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This is a thin, tough membrane that surrounds the embryo/fetus and amniotic fluid.

Amnion (Amniotic Sac)

________ separate from the epiblast and enclose the developing amniotic cavity.

Amnioblasts

Amnion will eventually obliterate chorionic cavity and form epithelial covering of the...

Umbilical Cord

This cushions the fetus, permits fetal movements, and regulates fetal body temperature. It's composed of organic compounds (proteins, carbs, fats, enzymes, hormones) and inorganic salts, ions, glycophospholipids, and steroid hormones.

Amniotic Fluid

Amniotic fluid is initially derived from maternal tissue and interstitial fluid. The _______ _______ ______ will excrete amniotic fluid (500 mL/day) at 11 weeks, as well as the ________ ________ and ________ ________ (300-400 mL). It is a dialysis-like exchange via the umbilical cord.

Fetal Urinary System Respiratory System GI Tract

This is the term for excessive amniotic fluid. It is due to a genetic defect, a fetal defect in the CNS, or blockage of the GI tube. Clinical signs include abdominal pain, significant swelling or bloating, and breathlessness.

Hydramnios

This is the term for insufficient amniotic fluid (< 400 mL). Problem with fetal development (renal agenesis, pulmonary hypoplasia). There is placental abnormality or maternal HBP. Decreased fluid does not create enough cushion to fetus and umbilical cord.

Oligohydramnios ***Remember, a normal amount of amniotic fluid at 37 weeks is 700-1000 mL!

The ________ ________ forms a capsule covering the surface of the chorionic sac.

Decidua Capsularis

As the embryo/fetus enlarges, the ________ ________ bulges into the uterine cavity.

Decidua Capsularis

The Decidua Capsularis degenerates and the ________ ________ fuses with the ________ ________ on the opposite wall, causing the obliteration of the uterine cavity.

Smooth Chorion | Decidua Parietalis

The Amniotic Sac grows faster than the Chorionic Sac. They fuse together to form the...

Amniochorionic Membrane

The Amniochorionic Membrane will fuse with the ________ ________ and adhere to the ________ ________.

Decidua Capsularis | Decidua Parietalis

What are the two components of the placenta?

Fetal Part | Maternal Part

This part of the placenta is the villous chorion that projects into the intervillous space containing maternal blood.

Fetal Part

This part of the placenta is the Decidua Basalis, which is the endometrium deep to the conceptus.

Maternal Part

Placental development involves 1) the formation of _______ _______ (from chorionic sac) and 2) proliferation of _________.

Chorionic Villi | Cytotrophoblasts

These are chorionic processes of cytotrophoblasts that grow into the syncytiotrophoblast layer, forming vascular, syncytial columns. Their appearance marks the 1st stage of placental development (end 2nd week).

Primary Chorionic Villi

Chorionic Villi will cover the Chorionic Sac until the 8th week. Villi associated with the Decidua Capsularis become compressed then degenerate, forming the...

Smooth Chorion

Villi associated with the ________ _______ rapidly increase. They branch profusely and form bushy area of the chorionic sac, called the ________ ________.

Decidua Basalis | Villous Chorion

Cytotrophoblasts of chorionic villi proliferate at chorionic plate. They extend through syncytiotrophoblasts to form the _________ _________. This surrounds the chorionic sac and attaches and erodes the Decidua Basalis. Creates the ________ ________.

Cytotrophoblastic Shell | Intervillous Space

________ ________ is derived from lacunae that developed in the invading syncytiotrophoblast during 2nd week.

Intervillous Space

Decidual erosion produces ________ ________, which divides the Villous Chorion into irregular convex areas, or ________.

Placental Septa | Cotyledons

The intervillous space of the placenta contains what?

Maternal blood (by 11-14 weeks)

_______ ______ (fetal) and _______ _______ (maternal) are now fused, and Chorionic Villi span the Intervillous Space and are exposed to maternal blood.

Villous Chorion | Decidua Basalis

These villi extends from the chorionic plate.

Main Stem Villi

These villi extend from a Main Stem Villus, and increase the surface area.

Branch Villi

These villi attach to the maternal tissues through the Cytotrophoblastic Shell.

Anchoring Villi

_________ contain 2+ Main Stem Villi and multiple Branch Villi.

Cotyledons

These villi are a cytotrophoblast core covered by syncytiotrophoblasts.

Primary Villi

These villi are when extra-embryonic mesoderm grows through primary villi (3rd weeks). There is an extraembryonic mesoderm core, cytotrophoblasts, and syncytiotrophoblasts.

Secondary Villi

These villi are when extra-embryonic mesoderm differentiates into capillary and blood cells. There is a capillaries and CT core (EEM), cytotrophoblast layer (middle), syncytiotrophoblast layer (outer).

Tertiary Villi

Secondary Villi (DO/DO NOT) have capillaries, but Tertiary Villi (DO/DO NOT).

Do Not | Do

________ Chorionic Villi are bathed in maternal blood and main site of exchange. They provide a large surface area for materials exchange across the placental membrane.

Branch

What things can cross the placenta?

``` Nutrients (water, glucose, electrolytes, AAs, vitamins) Hormones IgG Antibodies Waste Products Drugs (most cross) Infectious Agents ```

What things do NOT cross the placenta?

Protein Hormones Bacteria Drugs with amino acid-like structures

This is the attachment to placenta, usually near the center of the fetal surface.

Umbilical Cord

The ________ ________ is enveloped by the amnion as it enlarges, forming the Umbilical Cord.

Connecting Stalk

What is contained in the Umbilical Cord?

Two Umbilical Arteries (deoxygenated fetal blood) One Umbilical Vein (80% oxygenated fetal blood)

There can be an absence of the Umbilical Artery in 1 in 100 neonates. Commonly associated with chromosomal and fetal abnormalities. Agenesis or degeneration of one of the two Umbilical As. Detected before birth by __________.

Ultrasonography

This is an anomaly where the placenta implants in lower uterine segment or cervix. Often leads to serious 3rd-trimester bleeding and is the most common type of abnormal placentation. 20% of all cases of bleeding are due to this.

Placenta Previa

What are the types of placenta previa?

Total Placenta Previa Partial Placenta Previa Marginal Placenta Previa

This anomaly is the partial or complete absence of the decidua, making the villous chorion adhere directly to myometrium. There is failure of placental separation at birth. Can cause severe, possibly life-threatening postpartum bleeding.

Placenta Accrete/a

________ ________ is a replacement of normal villi by dilated or hydronic (edematous) translucent vesicles.

Hydatidiform Mole

This type of Hydatidiform Mole occurs when a portion of villi are edematous, and capillaries can be seen in the villi. Fetal tissue commonly found. A normal ovum is fertilized with two sperm. Results in triploid (69, XXY) or tetraploid (92, XXXY) karyotype.

Partial Mole

This type of Hydatidiform Mole occurs when all/most villi are enlarged, covered with trophoblast invasion. There is no fetal tissue. There is fertilization of an empty ovum by one or two sperm, making all DNA paternal. Frequent karyotypes are 46,XX or 46,XY.

Complete Mole

A _________ Complete Mole occurs when one sperm fertilizes an empty ovum, making the karyotype 46,XX.

Homozygous

A _________ Complete Mole occurs when two sperm fertilizes an empty ovum, making the karyotype 46,XX and 46,XY.

Heterozygous

This is when a Complete Mole penetrates or even perforates the uterine wall (15%). Diagnosed by persistent high blood levels of hCG. Trophoblast deeply invades the uterine wall and can cause hemorrhaging. Responsive to chemotherapy.

Invasive Mole

This is a highly invasive, metastatic tumor that arises from trophoblast cells. Observed in about 50% of patients with molar pregnancies. There is an increasing hCG titer with no uterine enlargement. Treatment with combined chemotherapy agents is usually curative.

Gestational Choriocarcinoma

Dizygotic, or (IDENTICAL/FRATERNAL) twins originate from two zygotes, which means they have separate implantations resulting in two chorions and two amnions. Their relationships depend on how the blastocysts implant.

Fraternal

Monozygotic twins originate from one zygote. Membranes in monozygotic twins are dependent upon timing of the division. The (EARLIER/LATER) the split, the more separate the membranes and placenta will be.

Earlier

If monozygotic twins are at the 2-8 cell stage at the time of cleavage (0-72 hours), what is the nature of the membranes?

Diamniotic | Dichorionic

If monozygotic twins are at the blastocyst stage at the time of cleavage (4-8 days), what is the nature of the membranes?

Diamniotic | Monochorionic

If monozygotic twins are at the implanted stage at the time of cleavage (9-12 days), what is the nature of the membranes?

Monoamniotic | Monochorionic

65% of monozygotic twins develop from one zygote by division of the _________ of the blastocyst.

Embryoblast

35% of monozygotic twins develop from one zygote. Separation of the blastomeres may occur anywhere from the 2-cell stage to the morula stage, producing two identical _________. Each embryo subsequently develops its own amniotic and chorionic sacs.

Blastocysts