Placenta & Fetal Membranes

Describe Gestational changes in the decidua?

Formation of the smooth chorion (laeve) and villous chorion (frondosum) Fusion of decidua capsularis with decidua parietalis results in Lack of blood supply, which causes decidua capsularis to degenerate Smooth chorion then fuses with the decidua parietalis which results in the Obliteration of uterine cavity.

What is the amnion formed from?

Formed from epiblast in week 2, from ectoderm. Has a amniotic cavity and fluid

Describe development in week 2?

Generally, the cells of epiblast move up and around to create the amniotic cavity, which is between epiblast and amniotic membrane. The hypoblast moves down and around to create the primary. Then secondary yolk sacs forms. Extraembryonic mesoderm also around and helps form placenta.

Placenta previa

Implantation too close to the cervix. Marginal Placental Previa = Very close to internal os of the cervix. Partial Placental Previa = Part of the placenta covering the internal os Total (Central) Placental Previa = Placenta covers entire internal os Remember Antepartum bleeding (bleeding before childbirth) should prompt sonographic evaluation BEFORE digital (using finger) vaginal exam (b/c if it is a total (central) placental prevue, you could rupture the placenta.

Where does fertilization normally occur?

In the Ampulla.

Placental septum

Indentation between the endometrium in between the different layers of the cytotrophoblastic shell Holds placenta together so its harder to tear All together forms the Cotyledon

Structures that gives rise to tissue of the embryo itself are known as?

Intraembryonic

What is the composition of amniotic fluid? composition, and fucntions?

Ions, glycophospholipids, steroid hormones, particulates, cross placenta

List the Layers of the decidua and what is it?

It is the endometrium of Uterus and is the maternal contribution to the placenta. 1. Decidua Basalis = deep to the conceptus 2. Decidua Capsularis = Superficial part of the decidua overlying the conceptus 3. Decidua Parietalis = the remaining parts of the decidua

What is Oligohydramnios and what causes it?

Low volume of amniotic fluid caused by renal agenesis.

What is a Choriocarcinoma (malignant tumor)?

Malignant tumor which develops from hydatidiform mole

Placenta: maternal vs fetal side

Maternal side: have Cotyledon = different areas supplied by 1-2 main chorion villius. Fetal side: have attacahement of umbilical cord and the amion. Translucent layer

Describe the Late placenta histologically? (late 3rd trimester)

Note: DC of the decidua basalis are polygonal, rounded. filled with lipids and glycoproteins. IS = interstitial space or lacuna where moms blood vessels are. TV = Tertiary villi specifical an anchoring villi SK = Synctial knots ME = mesoderm

Mature placenta schematic

Note: on right sows smooth corion and amion on left show s them fused as the amniochorionic membrane. Note Cytotrophoblastic shell: interphase between fetus and mom. Anchoring and stem villi and branch.

List Things that cross the placenta?

Nutrients = Water, Glucose and electrolytes, Amino acids, Vitamins Hormones = Testosterone, Progestins, Thyroxin, Triiodothyronine Antibodies = IgG Waste products = Urea, Uric Acid, Conjugated bilirubin Drugs = Most drugs cross the placenta, Alcohol, Cocaine and heroine, Labor management drugs Infectious agents = Cytomegalovirus, Rubella, Coxsackieviruses, Variola, Measles, Herpes, Treponema pallidum (syphilis), Toxoplasma gondii, Listeria monocytogenes

What is Placenta accreta, increta, percreta?

Placenta accreta = Abnormal adherence of chorionic villi to myometrium Placenta increta = Chorionic villi penetrate into the myometrium Placenta percreta = Chorionic villi penetrate through the myometrium to uterine serosa or adjacent organs Go in order of severity

Umbilical arteries are O2 _________ and umbilical veins are O2 _____.

Poor, rich

What is the Decidua reaction and what week does this occur?

Series of changes of endometrium in Week 2 that provide nutrients and provides an Immunologically privileged site. Specifically, As syncytiotrophoblast invade and lyse the endometrial cells that were filled with glycogen and lipids release then to nourish the embryo.

Which cells are responsible for implantation and the initial signal of pregnancy?

Syncytiotrophoblasts which release HCG (Human chorionic gonadotropin), which is the initial signal of pregnancy.

What are the Chorionic villi?

They are important for gas/waste exchange w/ the circulation.

What is Amniotic band syndrome?

Trauma or avascularization can cause parts of the amnion to slough off and wrap around the fetus.

What is early pregnancy factor? What secretes it?

Trophoblasts secrete early pregnancy factor which is a immunosuppressive protein that are important so that the "foreign embryo" is not rejected.

List Umbilical cord complications?

True umbilical cord knot The absence of umbilical artery • May be associated with chromosomal and fetal abnormalities • 15%-20% incidence of cardiovascular defects

List the 3 layers of the chorion?

1. Extraembryonic Somatopleure 2. Cytotrophoblasts 3. Syncytiotrophoblasts.

The Hypoblast gives rise to what structures?

1. Primary and secondary yolk sac (ubilical vesicle) 2. Extraembryoinic mesoderm, becomes placenta

List the Early placenta layers (before wk 20)?

1. Syncytiotrophoblast 2. Cytotrophoblast 3. Villi Connective Tissue (mesoderm) 4. Endothelium of fetal capillaries. Substances passing through branched villi nee to pass through all these structures.

List the Late placental layers (after 20 wks)?

1. Syncytiotrophoblast 2. Vasculosyncytial placenta membrane 3. Endothelium of fetal capillaries Cytotrophoblast has disintegrated.

List Things that do not cross the placenta?

1. hormones: protein hormones like insulin or pituitary hormones 2. Antibodies: IgD, IgM, IgE 3. Drugs: with structural similairties to aminoacids like methyldop and heparin - most drugs will cross tho. 4. Infectious agents - bacteria in general

What are the derivatives of the Extraembryonic mesoderm?

1.) Connecting stalk at the embryonic pole (extraembryonic somatic mesoderm) 2.) Primitive blood (extraembryonic splanchnic mesoderm) 3.) Chorion is a layer of the placenta (extraembryonic somatic mesoderm, cytotrophoblast & syncytiotrophoblast)

List abnormal types of implantation?

1.) Ectopic pregnancy (can occasionally happen in the abdomen) - tubal pregnancy is also an example. 2.) Placenta previa = Implantation too close to the cervix.

Fertilization usually occurs in which of the following locations? A. Ampulla (distal two-thirds) of the uterine tube B. Isthmus (proximal third) of the uterine tube C. Ovary D. Upper portion of the uterus E. Lower portion of the uterus

A. Ampulla (distal two-thirds) of the uterine tube

The placenta arises, in part, from which of the following layers of the uterus? A. Endometrium B. Myometrium C. Parametrium D. Perimetrium

A. Endometrium

All of the following statements are true concerning the umbilical cord except: A. Umbilical vein carries deoxygenated blood B. There are two umbilical arteries C. The cord has mucous connective tissue rich in sulfated proteoglycans D. Inserts on the chorionic plate side of the placenta E. Umbilical arteries are afferent to placenta

A. Umbilical vein carries deoxygenated blood

What are Hydatidylform Moles and describe the types?

Abnormal trophoblast proliferation, which leads to excessive amounts of hCG produced. TWO types: Complete - Results from fertilization of an empty oocyte followed by duplication of the sperm or fertilization of an oocyte by two sperm Partial - Fertilization of a normal oocyte by two sperm

What structures does the epiblast give rise to in week 2?

Amnion & amniotic cavity

The intervillous spaces contain: A. Fetal blood B. Maternal blood C. A mixture of maternal and fetal blood D. Blood with high CO2 E. Blood with low oxygen content

B. Maternal blood

Ectopic pregnancy is most commonly found in the: A. Abdominal cavity B. Proximal uterine tube C. Lower uterine segment D. Cervix E. Mesenteries

B. Proximal uterine tube

Implantation begins at what day?

Begins at day 6 and continues through week 2

AT the end of week 1 what do we have?

Blastocyst which consists of an inner cell mass = embryo proper and Trophoblast (placenta).

What does the Connecting stalk become?

Connects the secondary yolk sac to the trophoblast and eventually becomes the umbilical cord Remember it is Not necessarily a fixed position and can move.

Trophoblast cells give rise to ________.

Cytotrophoblast cells (Stem cell layer, mitotically active) which then differentiates into Syncytiotrophoblast which erodes into the endometrium via Proteolytic enzymes and releases chorionic gonadotropin (hCG), which is responsible for implantation and the initial signal of pregnancy.

The Late placenta lacks what layer of cells?

Cytotrophoblasts

What is the treatment for hydatidylform Moles?

D&C (Dilation and curettage) -> scraping out the tissue from the uterus. Detection at week 3.

Which embryonic structure is involved in the initial formation of the umbilical cord? A. Extraembryonic coelom B. Amnion C. Chorion D. Connecting stalk E. Vitelline duct

D. Connecting stalk

Tertiary chorionic villi have all of the following morphological characteristics except: A. Continuous layer of cytotrophoblastic cells B. Continuous syncytiotrophoblast C. Connective tissue core D. Decidual cells E. Fetal blood vessels

D. Decidual cells

In the human placenta, maternal and fetal blood streams are: A. Confluent B. Separated by syncytiotrophoblast only C. Separated by fetal endothelium only D. Separated by fetal endothelium and syncytiotrophoblast E. Separated by maternal endothelium only

D. Separated by fetal endothelium and syncytiotrophoblast

Which of the following cells secrete human chorionic gonadotropin (hCG) to maintain pregnancy? A. Embryoblasts B. Epiblasts C. Hypoblasts D. Syncytiotrophoblasts E. Cytotrophoblasts

D. Syncytiotrophoblasts

Describe the Primary chorionic villi?

Days 13-14 Components = Cytotrophoblast and Syncytiotrophoblast. Trophoblast lacunae (filled with maternal blood from spiral arteries)

Describe Secondary chorionic villi?

Days 15-18 Components = Extraembryonic mesoderm, Cytotrophoblast, and Syncytiotrophoblast Intervillous space (lacuna) Cytotrophoblastic shell is the interphase between between fetal and moms placenta/

Describe Teriary chorionic villi?

Days 19-21 Components = Villous capillaries, Extraembryonic mesoderm, Cytotrophoblast, Syncytiotrophoblast. Intervillous space (lacuna) - Stem villi, Anchoring villi, and Branching villi

Developmental adnexa in twins

Dizygotic: two different eggs fert by two diff sperm. - fraternal twins. Monozygoitic: Identical: - Split at the 2,4,8 cell stage area. -2cell stage split: not developed trophblast yet so they split and form two different trophoblasts, so 2 chorion and 2 placenta. Also 2 amnion. (25%) -7 day split (ICM formed) so trophoblasts already formed. Only 1 chorion and one placenta, however amnion formed so if ICM split will have 2 amnion. (75%) - Week 2 split with an amnion already. Embryo splits, 1 amnion, 1 chorion, 1 placenta (Rare) Cannot look at layers around twins and tell if they are identical bc they split at different times.

All of the following structures are present in secondary chorionic villi EXCEPT A. Cytotrophoblast B. Syncytiotrophoblast C. Fetal connective tissue D. Mesoderm E. Fetal blood vessels

E. Fetal blood vessels

Which of the following statements is most accurate for dizygotic twins? A. Usually the same sex B. Are genetically identical C. Are usually phenotypically identical D. Can share one placenta E. Normally have two amniotic sacs

E. Normally have two amniotic sacs

Which tissue is most directly responsible for degradation of endometrial epithelium during implantation? A. Uterine stroma B. Uterine endometrial epithelium C. Epiblast D. Cytotrophoblast E. Syncytiotrophoblast

E. Syncytiotrophoblast

Describe the Early placenta histologically (2 weeks) and midterm Placenta?

Early Placenta = on left 9: Syncytiotrophoblast 8: cytotrophoblast 7: Villi CT aka mesoderm (this is a secondary villus here) Midterm = on right 12 is the start of a knot 13> some cytotrophoblast cells. 14. Placental macrophages = Hofbauer cells

What does the epiblast eventually give rise to?

Ectoderm

In week 2, what two structures does the inner cell mass give rise to?

Epiblast and hypoblast Bilaminar Disc = two layers of the embryo

Hypoblast gives rise to structures that are? When does it exist?

Extraembryonic Only during week two, then they disintegrate

Amnion is an example of what type of structure (extraembryonic or intraembryonic)?

Extraembryonic - Doesn't give rise to tissue of embryo itself

Describe the Extraembryonic mesoderm in week two that helps to form the placenta?

Extraembryonic Coelom: hollow cavity outside of the embryo Extraembryonic Somatic Mesoderm: lining the trophoblast and covering the amnion Extraembryonic Splanchnic Mesoderm: lining the yolk sac (umbilical vesicle)

In the week 2 stage of embryonic development, what are the cells that line the cytotrophoblast and cover the amnion

Extraembryonic Somatic Mesoderm

In the week 2 stage of embryonic development, what are the cells that line the secondary yolk sac?

Extraembryonic splanchnic mesoderm

Describe the development of the Placenta

Fetal Part (Chorionic Sac and Amnion) Maternal Part (Decidua Basalis and Decidua Capsularis)

What is Hemolytic disease of the newborn?

Fetal RBCs destroyed by maternal IgG (RH + baby and RH - Mother) Clinical presentation = mild to severe • Mild: hyperbilirubinemia in first 24 hours of life, symptomatic anemia (eg, lethargy or tachycardia) but without signs of circulatory collapse • Severe: Hydrops fetalis; skin edema, pleural or pericardial effusion, or ascites

What is the most common place for Abnormal implantation?

Uterine tubes.

LIst Clinical Features of Hydatidylform Moles?

Vaginal bleeding, pelvic pressure pain, enlarged uterus, and hyperemesis gravidarum (morning sickness)

Chorionic villia will cover the entire chorionic sac until when?

beginning of the 8th week

What is the function of aniotic fluid?

cushions against injury, maintains temp, ease of movement, diagnostic info

What happens to the Syncytiotrophoblasts in week 2.

fragments eroded into the uterine lining. THey migrate upwards into the endometrial layer

What is Polyhydramnios and what causes it?

high amniotic fluid volume Caused by anencephaly, esophageal atresia, maternal diabetes, multifetal gestations, hypoplastic lungs

Umbilical cord comes from what?

• Amnion • Extraembryonic mesoderm • Umbilical arteries • Umbilical vein • Allantois • Vitello-intestinal duct • Extraembryonic coelom (chorionic cavity)

Describe the Allantois?

• Posterior midline • Diverticulum from wall of yolk sac • Endoderm • Template for umbilical arteries & vein • Becomes urachus

List the 3 sources of amniotic fluid?

1. Cells of amion 2. Maternal blood 3. Fetal urine