Placentation — MCQs
At what stage of pregnancy do tertiary chorionic villi develop?
Which immunoglobulin provides natural passive immunity to a newborn through the placenta?
Which structure do cytotrophoblasts invade during implantation?
At 30 days of intrauterine life, what is the expected developmental milestone?
The morula stage consists of how many cells?
Which of the following statements about placental hormones is true?
All are true about uteroplacental circulation except:
Which of the following statements about the placenta is correct?
A 30-year-old G2P1 is undergoing an elective repeat caesarean section at term. The infant is delivered without any difficulties, but the placenta cannot be removed easily because a clear plane between the placenta and uterine wall cannot be identified. The placenta is removed in pieces. This is followed by uterine atony and haemorrhage. All of the following are true regarding the condition except:
Which is correct about the diagram shown?
Placentation Indian Medical PG Practice Questions and MCQs
Question 1: At what stage of pregnancy do tertiary chorionic villi develop?
- A. Day 28
- B. Day 25
- C. Day 15
- D. Day 17 (Correct Answer)
Explanation: **Day 17** - By **Day 17** of gestation, the **chorionic villi** have developed into their **tertiary form**, characterized by the presence of **fetal capillaries** within their mesenchymal core [1]. - This stage marks the establishment of a functional **feto-maternal exchange system** for nutrients, gases, and waste products. *Day 28* - By **Day 28**, the tertiary chorionic villi are already well-established and undergoing further **maturation** and **branching**, not just initial development. - This period is more indicative of the continued growth and specialization of the **placenta**. *Day 25* - While significant development is occurring around **Day 25**, the **tertiary villi** are generally considered to be fully formed a few days earlier. - At this point, the villi are actively engaged in early **nutrient exchange**, building on the structural foundation laid earlier. *Day 15* - At **Day 15**, the chorionic villi are typically in the **primary** or early **secondary stage** of development [1]. - **Primary villi** consist of a cytotrophoblast core covered by syncytiotrophoblast, and **secondary villi** introduce a mesenchymal core, but not yet fetal capillaries [1].
Question 2: Which immunoglobulin provides natural passive immunity to a newborn through the placenta?
- A. IgA
- B. IgG (Correct Answer)
- C. IgE
- D. IgD
Explanation: ***IgG*** - **IgG** is the only immunoglobulin that can cross the **placenta**, providing the fetus with **passive immunity** from the mother's antibodies. - This maternal IgG protects the newborn from various infections during the first few months of life until its own immune system matures. *IgA* - **IgA** is primarily found in **mucosal secretions**, such as breast milk, saliva, tears, and gastrointestinal fluids. - While important for newborn immunity via **breastfeeding**, it does not cross the placenta. *IgE* - **IgE** is mainly involved in **allergic reactions** and defense against **parasitic infections**. - It does not cross the placenta to provide passive immunity to the fetus. *IgD* - **IgD** is primarily found on the surface of **B lymphocytes** and is involved in B-cell activation. - Its function is not related to passive fetal immunity through the placenta.
Question 3: Which structure do cytotrophoblasts invade during implantation?
- A. Decidua capsularis
- B. Decidua vera
- C. Decidua basalis (Correct Answer)
- D. Decidua parietalis
Explanation: ***Decidua basalis*** - The **cytotrophoblasts** invade the maternal **decidua basalis**, which is the portion of the **endometrium** directly underlying the implanted embryo, forming the maternal component of the **placenta**. - This invasion is crucial for establishing the **placenta** and allowing for nutrient and waste exchange between the mother and the fetus. *Decidua parietalis* - The **decidua parietalis** is the portion of the **endometrium** lining the rest of the **uterine cavity**, not directly involved in the immediate implantation site. - It plays a role later in pregnancy, fusing with the **decidua capsularis** as the **embryo** grows. *Decidua capsularis* - The **decidua capsularis** is the portion of the endometrium that overlies the implanted embryo, separating it from the uterine lumen. - It does not undergo invasion by the **cytotrophoblasts** in the same way the **decidua basalis** does. *Decidua vera* - The **decidua vera** is another term for the **decidua parietalis**, referring to the endometrial lining of the uterine cavity that is not involved in the implantation site. - It is not directly invaded by **cytotrophoblasts** during implantation.
Question 4: At 30 days of intrauterine life, what is the expected developmental milestone?
- A. Optic vesicle appears (Correct Answer)
- B. Heart starts beating
- C. Cerebellum develops
- D. Pinna appears
Explanation: Optic vesicle appears - The **optic vesicle** is an outpocketing from the diencephalon that appears around **day 22-28** of development. - At approximately **30 days** (end of 4th week/early 5th week), the optic vesicle is actively present and beginning to invaginate to form the optic cup. - Among the given options, this represents the developmental structure most characteristically associated with the **late 4th week/30-day timeframe** in embryology milestones. *Heart starts beating* - The primitive heart tube begins to beat around **day 22-23** of gestation. - By 30 days, the heart has already been beating for over a week, making this an earlier milestone rather than one expected "at" 30 days. *Cerebellum develops* - The cerebellum develops later, primarily during the **second and third months** (weeks 8-12) of gestation as the metencephalon differentiates. - Major cerebellar development occurs well after 30 days. *Pinna appears* - The external ear (pinna) begins forming around the **sixth week** (~42 days) from six auricular hillocks.
Question 5: The morula stage consists of how many cells?
- A. 4 to 8 cell stage
- B. 28 to 32 cell stage (Correct Answer)
- C. 12 to 16 cell stage
- D. 50 to 60 cell stage
Explanation: 28 to 32 cell stage - The morula is a solid ball of cells formed through **compaction** around **day 3-4 after fertilization**, typically consisting of **16-32 blastomeres** (most commonly 28-32 cells) [1]. - This stage represents a **compacted mass** where individual cell boundaries become less distinct, forming a solid cluster before blastocyst formation [1]. - The term "morula" (Latin for "mulberry") reflects its characteristic appearance at this cell count [1]. *12 to 16 cell stage* - This represents the **early/transitional morula stage** where compaction is just beginning [1]. - While sometimes included in broader definitions, the **classic morula** is defined at higher cell counts (16-32 cells) [1]. - Most embryology textbooks specify morula formation at 16+ cells [1]. *4 to 8 cell stage* - This is an **early cleavage stage** occurring around **day 2-3 after fertilization** [1]. - Cells (blastomeres) are still distinct and **loosely arranged**, without the compaction characteristic of morula. - This precedes morula formation by approximately 1 day. *50 to 60 cell stage* - At this cell count, the embryo has progressed to the **blastocyst stage** (around day 5) [1]. - The blastocyst features **cell differentiation** into inner cell mass and trophoblast, with a **fluid-filled blastocoel cavity**. - The solid, compacted structure of the morula is no longer present.
Question 6: Which of the following statements about placental hormones is true?
- A. hCS plays a role in maternal glucose metabolism. (Correct Answer)
- B. hCG levels remain consistently high throughout pregnancy.
- C. The luteal-placental shift occurs around 10-12 weeks of gestation.
- D. Progesterone production requires fetal adrenal precursors.
Explanation: **Correct: *hCS plays a role in maternal glucose metabolism.*** - **Human chorionic somatomammotropin (hCS)**, also known as placental lactogen, has **anti-insulin effects** that reduce maternal glucose utilization. - This action diverts glucose to the fetus, helping to meet the growing **fetal energy demands**. *Incorrect: hCG levels remain consistently high throughout pregnancy.* - **hCG (human chorionic gonadotropin)** levels peak in the first trimester (around 8-10 weeks) and then **decline and plateau** at much lower levels for the remainder of the pregnancy. - Its primary role is to maintain the **corpus luteum** during early pregnancy. *Incorrect: The luteal-placental shift occurs around 10-12 weeks of gestation.* - The **luteal-placental shift**, where the placenta takes over progesterone production from the corpus luteum, occurs around **7-9 weeks of gestation**. - By 10-12 weeks, the placenta is already the primary producer of progesterone. *Incorrect: Progesterone production requires fetal adrenal precursors.* - **Progesterone** is synthesized by the placenta from **maternal cholesterol** without requiring fetal steroid precursors. - **Estrogen**, particularly **estriol**, on the other hand, relies on **fetal adrenal androgens** as precursors.
Question 7: All are true about uteroplacental circulation except:
- A. The villi depend on the maternal blood for their nutrition
- B. Blood in the intervillous space is completely replaced 3-4 times per minute
- C. A mature placenta has 150 ml of blood in the villi system and 350 ml of blood in the intervillous space (Correct Answer)
- D. Intervillous blood flow at term is 500-600 ml per minute
Explanation: ***A mature placenta has 150 ml of blood in the villi system and 350 ml of blood in the intervillous space*** - This statement is incorrect because a **mature placenta** typically holds approximately **350 ml of blood** in the **villi system** and **150 ml of blood** in the **intervillous space**, which is the reverse of what is stated. - The villi system contains the fetal blood, which has a larger volume within the placental unit. *Blood in the intervillous space is completely replaced 3-4 times per minute* - This is a correct statement regarding uteroplacental circulation, as the **high turnover rate** ensures efficient **nutrient and gas exchange** between mother and fetus. - The rapid replacement prevents stagnant blood and facilitates continuous delivery of essential substances. *The villi depend on the maternal blood for their nutrition* - This statement is true because the **chorionic villi**, which are the functional units of the placenta, are bathed in **maternal blood** within the intervillous space. - The placental tissue itself receives its **nutrients and oxygen** directly from this maternal blood supply. *Intervillous blood flow at term is 500-600 ml per minute* - This is an accurate physiological fact. At term, the **maternal blood flow** through the intervillous space is indeed substantial, typically ranging from **500 to 700 ml per minute**, ensuring adequate perfusion for the growing fetus. - This significant blood flow is crucial for meeting the high metabolic demands of the fetus.
Question 8: Which of the following statements about the placenta is correct?
- A. The placenta produces estrogen. (Correct Answer)
- B. The placenta has 2 arteries and 1 vein.
- C. The placental artery carries deoxygenated blood from the fetus to the placenta.
- D. Wharton's jelly is found in the umbilical cord.
Explanation: ***The placenta produces estrogen.*** - The **placenta** is an important endocrine organ, producing various hormones including **estrogen** (specifically estriol) and progesterone. - These hormones are crucial for maintaining the pregnancy and supporting fetal development. *The placental artery carries deoxygenated blood from the fetus to the placenta.* - This statement is incorrect as the **umbilical arteries** (not placental arteries) carry **deoxygenated blood and waste products** from the fetus to the placenta. - The **umbilical vein** carries **oxygenated blood and nutrients** from the placenta to the fetus. *The placenta has 2 arteries and 1 vein.* - This describes the typical composition of the **umbilical cord**, not the placenta itself. - The **placenta** is a distinct organ that connects the mother and fetus, facilitating nutrient and gas exchange. *Wharton's jelly is found in the umbilical cord.* - This statement is correct, but the question asks about the **placenta**, not the umbilical cord. - **Wharton's jelly** is a gelatinous substance that protects and supports the blood vessels within the umbilical cord.
Question 9: A 30-year-old G2P1 is undergoing an elective repeat caesarean section at term. The infant is delivered without any difficulties, but the placenta cannot be removed easily because a clear plane between the placenta and uterine wall cannot be identified. The placenta is removed in pieces. This is followed by uterine atony and haemorrhage. All of the following are true regarding the condition except:
- A. May require obstetric hysterectomy
- B. Absence of Nitabuch's membrane
- C. Previous LSCS is a predisposing factor
- D. If placenta invades muscle and reaches serosa it is known as placenta increta (Correct Answer)
Explanation: ***If placenta invades muscle and reaches serosa it is known as placenta increta*** - **Placenta increta** refers to the invasion of the **myometrium (muscle)** only, not reaching the serosa. - When the placenta invades through the myometrium and reaches the **uterine serosa or beyond**, it is termed **placenta percreta**. *May require obstetric hysterectomy* - The inability to establish a clear plane between the placenta and uterine wall, coupled with a **postpartum hemorrhage**, is highly suggestive of **placenta accreta spectrum (PAS) disorders**. - **Obstetric hysterectomy** is often necessary in cases of PAS disorders to manage uncontrolled hemorrhage and save the mother's life. *Absence of Nitabuch's membrane* - The **pathophysiology of placenta accreta** involves the abnormal adherence of the placenta due to a defect in the decidua basalis. - This defect is characterized by the **partial or complete absence of Nitabuch's membrane**, which normally lies between the decidua and myometrium, preventing trophoblast invasion. *Previous LSCS is a predisposing factor* - A **previous lower segment cesarean section (LSCS)** is a significant risk factor for placenta accreta. - The uterine scar tissue from a prior LSCS provides a less resistant area for trophoblast invasion into the myometrium.
Question 10: Which is correct about the diagram shown?
- A. A= Allantois, B= Connecting stalk, C= Yolk Sac, D= Chorion with villi (Correct Answer)
- B. A= Amnion, B= Connecting stalk, C= Yolk Sac, D= Intraembryonic mesoderm
- C. A= Amnion, B= Connecting stalk, C= Yolk Sac, D= Extraembryonic Celom
- D. A= Amnion, B= Connecting stalk, C= Allantois, D= Chorion with villi
Explanation: ***A= Allantois, B= Connecting stalk, C= Yolk Sac, D= Chorion with villi*** - The image depicts a human embryo during early development. **A** points to the **allantois**, an embryonic outgrowth that contributes to the umbilical cord and bladder. - **B** indicates the **connecting stalk**, which later develops into the umbilical cord. **C** is the **yolk sac**, important for early hematopoiesis and nutrient transfer. **D** identifies the **chorion with villi**, which are essential for nutrient exchange and gas waste elimination between the mother and the fetus. *A= Amnion, B= Connecting stalk, C= Yolk Sac, D= Intraembryonic mesoderm* - **A** is incorrectly identified as **amnion**; the allantois is the structure shown as an outpouching from the developing hindgut, while the amnion would usually surround the entire embryo. - **D** is incorrectly identified as **intraembryonic mesoderm**, which is a germ layer within the embryo itself, not the outermost layer with villi. *A= Amnion, B= Connecting stalk, C= Yolk Sac, D= Extraembryonic Celom* - **A** is incorrectly identified as **amnion**. The amniotic cavity is the fluid-filled sac surrounding the embryo, but the structure pointed to by 'A' is the allantois, an extension from the hindgut. - **D** is incorrectly identified as **extraembryonic coelom**. The extraembryonic coelom is the space between the chorion and the amnion/yolk sac, while D clearly points to the chorionic villi. *A= Amnion, B= Connecting stalk, C= Allantois, D= Chorion with villi* - **A** is incorrectly identified as **amnion** for the reasons stated above; it is the allantois. - **C** is incorrectly identified as **allantois**; the structure labeled C is the yolk sac, which is much larger and more central than the allantois at this stage.
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