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What is considered a type of placenta previa where the placenta does not reach the internal os?
At what point does the second meiotic division of the secondary oocyte complete?
Which hormone is primarily used for the detection of pregnancy?
Which stage is primarily associated with implantation?
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Which hormone governs the preovulatory phase of the ovarian cycle?
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What process involves the removal of the cholesterol coat covering the acrosome?
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What is a result of fertilization?
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Which of the following structures is derived from the ectoderm?
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Where does fertilization typically occur in the female reproductive system?
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Which of these structures is mesodermal in origin?
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Identify the structure that is an endodermal derivative.
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The process responsible for the formation of the three germ layers is known as what?
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Which area of the embryo is considered bilaminar?
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What is the fetal part of the placenta formed by?
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Which component forms the placental barrier in early pregnancy?
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What separates the maternal surface of the placenta into numerous cotyledons?
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What is the typical weight of a full term placenta?
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Which type of placenta is characterized by its disc shape?
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Which of the following describes a low lying placenta previa?
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What is indicative of a placenta previa?
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Which anomaly involves the placenta growing into the myometrium?
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How many cotyledons can the maternal surface of a full term placenta be divided into?
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In which condition does an accessory lobe of placenta form?
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Which statement is true regarding the fetal surface of a full term placenta?
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What complication can arise from a very long umbilical cord?
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What is a common issue associated with a very short umbilical cord?
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Which type of umbilical cord attachment is characterized by the cord ending in the membranes surrounding the placenta?
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What distinguishes true knots from false knots in umbilical cords?
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What percentage of twins are dizygotic?
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Which type of twins results from the splitting of a single original embryo?
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Which type of conjoined twins involves fusion between two heads?
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What distinguishes dizygotic twins in terms of their traits?
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What is the primary purpose of amniocentesis during pregnancy?
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What specific condition does an increased level of alpha-fetoprotein (AFP) in maternal serum primarily indicate?
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At what gestational age is chorionic villus sampling (CVS) preferred?
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Which structure represents the fetal part of the placenta?
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What is a common cause of oligohydramnios during pregnancy?
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Which of the following is an indication for amniocentesis?
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Which maternal structure is primarily involved in forming the maternal part of the placenta?
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What is a condition associated with polyhydramnios during pregnancy?
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Study Notes
Abnormal Sites of Implantation
- Ectopic pregnancy: implantation occurs outside the uterus.
- Uterine tube (tubal pregnancy): most common.
- Abdominal cavity: rare.
- Ovary (ovarian pregnancy): very rare.
- Placenta previa: placenta develops in the lower segment of the uterus near the internal os.
Types of Placenta Previa
- Low-lying placenta previa: placenta is in the lower part of the uterus but doesn't reach the internal os.
- Marginal placenta previa: placenta's edge reaches the margin of the internal os.
- Partial placenta previa: placenta partially covers the internal os.
- Complete placenta previa: placenta completely covers the internal os.
Normal Fertilization
- Occurs in the ampulla of the uterine tube.
Second Meiotic Division of Secondary Oocyte
- Completes at fertilization.
Implantation Stage
- Blastocyst stage is crucial for implantation.
Result of Fertilization
- Restoration of the diploid number of chromosomes.
Acrosomal Reaction
- Removal of the cholesterol coat and glycoprotein coat covering the acrosome.
Pregnancy Detection Hormone
- Human Chorionic Gonadotrophin (hCG) is used for pregnancy detection.
Preovulatory Phase of Ovarian Cycle
- Influenced by follicle-stimulating hormone (FSH).
Postovulatory Phase of Ovarian Cycle
- Influenced by progesterone.
Embryonic Folding & Its Effects
- Primitive gut: forms foregut, midgut, and hindgut.
- Definitive yolk sac: smaller than the primitive yolk sac.
- Yolk sac stalk: connects the yolk sac to the embryo.
Ectodermal Derivatives
- Epidermis
Endodermal Derivatives
- Urinary bladder
Mesodermal Derivatives
- Dermis
Gastrulation
- Process of forming the three germ layers (ectoderm, mesoderm, endoderm).
Bilaminar Areas of the Embryo
- Buccopharyngeal membrane
- Septum transversum
- Cardiac area
Placenta Components
- Fetal part: formed by the chorion frondosum.
- Maternal part: formed by the decidua basalis.
Chorion Parts
- Chorion frondosum: forms the fetal part of the placenta.
- Chorion laeve: villi degenerate.
Decidua
- Decidua basalis: lies over the chorionic frondosum.
- Decidua capsularis: covers the chorion laeve.
- Decidua parietalis: lines the remaining part of the uterine cavity.
Internal Structure of Placenta
- Chorionic villi: filled with fetal blood.
- Intervillous spaces: filled with maternal blood.
- Placental septa: divide the maternal surface into 15-20 cotyledons.
Placental Barrier
- Early pregnancy: formed by the endothelium of fetal vessels and extra-embryonic mesoderm.
- Late pregnancy: formed by the endothelium of fetal vessels, cytotrophoblast, and syncytiotrophoblast.
Full-Term Placenta
-
Disc-shaped:
- Diameter: 15-25 cm
- Thickness: 3 cm
- Weight: 500 g.
Full Term Placenta Surfaces
- Fetal surface: formed by the chorion frondosum.
- Maternal surface: formed by the decidua basalis.
Placental Anomalies
-
Shape anomalies:
- Diffuse placenta (placenta membranacea): all fetal membranes remain covered by chorionic villi.
- Accessory placenta (succenturiate placenta): a main placenta with a small accessory lobe.
- Bidiscoidal placenta: two disc-like equal parts.
-
Invasion anomalies:
- Placenta accreta: placenta grows superficially into the myometrium.
- Placenta increta: placenta grows into the myometrium.
- Placenta percreta: placenta invades the myometrium and perimetrium.
-
Attachment anomalies:
- Placenta previa: placenta develops in the lower segment of the uterus near the internal os.
-
Chord anomalies:
- Very long umbilical cord: may wind around the fetus's neck and cause death.
- Very short umbilical cord: may cause premature separation of the placenta.
-
Umbilical cord anomalies:
- Eccentric attachment.
- Marginal attachment (battledore placenta).
- Velamentous attachment: cord ends in the membranes surrounding the placenta.
- False knots: caused by excessive tortuosity of umbilical vessels.
- True knots: rare but dangerous; they obstruct blood flow in umbilical vessels, leading to fetal death.
- Single umbilical artery: one umbilical artery instead of two.
Twins
-
Dizygotic (fraternal):
- Incidence: 70% of twins.
- Mechanism: two ova released simultaneously.
- Characteristics: 2 placentae, 2 chorionic cavities, 2 amniotic cavities.
- Sex: can be the same or different.
-
Monozygotic (identical):
- Incidence: 30% of twins.
- Mechanism: splitting of a single embryo.
- Characteristics: can share no, some, or all their fetal membranes.
- Sex: always the same sex.
Siamese (Conjoined) Twins
- Fused monozygotic twins due to incomplete separation of the embryonic disc.
- Types:
- Craniopagus: fusion of two heads.
- Thoracopagus: fusion at the thoracic region.
- Pygopagus: fusion at the pelvic region.
Prenatal Diagnosis Techniques
-
Non-invasive:
- Maternal serum screening: measures levels of alfa-fetoprotein (AFP), unconjugated estriol (uE3), and hCG.
- Ultrasound.
-
Invasive:
- Amniocentesis: sampling amniotic fluid; preferred after 16 weeks gestation.
- Chorionic villus sampling (CVS): sampling chorionic villi; preferred at 10 weeks gestation.
Maternal Serum Screening
-
AFP:
- Increased: neural tube defects.
- Decreased: Down syndrome.
-
uE3:
- Increased: throughout pregnancy.
- Decreased: Down syndrome.
-
hCG:
- Increased: Down syndrome.
- Decreased: Down syndrome.
Invasive Tests
-
Amniocentesis:
- Withdrawal of amniotic fluid for analysis of bilirubin levels, AFP, and fetal cells.
-
Chorionic villus sampling (CVS):
- Sampling of chorionic villi for DNA analysis and chromosomal abnormality detection.
Fetal Part of Placenta
- Chorion frondosum
Maternal Part of Placenta
- Decidua basalis
Polyhydramnios Causes
- Diabetic mother
- Fetus with renal agenesia
- Fetus with obstructive uropathy
Oligohydramnios Causes
- Fetus with esophageal atresia
- Fetus with renal agenesia
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Description
Test your knowledge on abnormal sites of implantation, including ectopic pregnancy and types of placenta previa. This quiz will cover essential concepts such as normal fertilization and the implantation stage critical for human development.
