Prenatal Development — MCQs
Which of the following cell types is neuroectodermal in origin?
The labia majora develop from which embryological structure?
In development of male fetus following statements are true except
Which of the following drugs is given during pregnancy, resulting in fetal abnormalities such as cleft lip and central nervous system defects?
When the fetus is at station +2 and the fetal skull reaches the pelvic floor, which of the following statements is MOST clinically relevant?
Which of the following STDs causes fetal abnormality?
In which part of the fallopian tube is there a high chance of rupture in a tubal pregnancy?
The first primary ossification centre to appear of the carpal bones is
During embryological development, failure of the urorectal septum to completely separate the cloaca results in which of the following congenital anomalies?
Which is correct about the diagram shown?
Prenatal Development Indian Medical PG Practice Questions and MCQs
Question 1: Which of the following cell types is neuroectodermal in origin?
- A. Smooth muscle cells (Correct Answer)
- B. Skeletal muscle cells
- C. Endothelial cells
- D. Cardiac muscle cells
Explanation: ***Smooth muscle cells*** - This is the **correct answer** based on a **specific exception**: smooth muscle cells of the **iris dilator and sphincter muscles** and the **ciliary muscle** in the eye are derived from **neuroectoderm** (specifically from the **optic cup**, an outgrowth of the neural tube). - **Important note:** The vast majority of smooth muscle in the body is of **mesodermal origin** (e.g., in blood vessels, GI tract, respiratory tract). This question tests knowledge of this **notable embryological exception**. - In the context of the given options, this is the only cell type with any neuroectodermal component. *Skeletal muscle cells* - Skeletal muscle cells are entirely derived from the **paraxial mesoderm**, specifically from **somites** (myotome portion). - They form the voluntary muscles of the body and are **never** of neuroectodermal origin. *Endothelial cells* - Endothelial cells lining blood vessels and lymphatic vessels are derived from the **mesoderm** (specifically from **angioblasts**). - They are part of the cardiovascular system and are **entirely mesodermal** in origin. *Cardiac muscle cells* - Cardiac muscle cells are derived from the **splanchnic mesoderm** (lateral plate mesoderm). - The heart musculature is **entirely mesodermal** with no neuroectodermal contribution. **Clinical Pearl:** Classic neuroectodermal derivatives include neurons, glial cells (astrocytes, oligodendrocytes), ependymal cells, and neural crest derivatives (Schwann cells, melanocytes, chromaffin cells). The smooth muscle of the iris represents an important exception to the general rule that smooth muscle is mesodermal.
Question 2: The labia majora develop from which embryological structure?
- A. Urogenital folds
- B. Labioscrotal swellings (Correct Answer)
- C. Müllerian ducts
- D. Genital tubercle
Explanation: ***Labioscrotal swellings*** - The **labia majora** develop from the **labioscrotal swellings**, which are paired bilateral structures that appear around week 9-10 of development [1]. - These swellings arise lateral to the urogenital folds and do not fuse in females, forming the labia majora. - In males, these same structures fuse in the midline to form the scrotum. - This is a key example of **sexual differentiation** in embryological development [1]. *Urogenital folds* - The urogenital folds form the **labia minora** in females, not the labia majora. - In males, these folds fuse to form the ventral aspect of the penis and enclose the penile urethra. *Genital tubercle* - The genital tubercle forms the **clitoris** in females and the **glans penis** in males. - It does not contribute to the formation of the labia majora. *Müllerian ducts* - The Müllerian (paramesonephric) ducts form the **upper vagina, uterus, and fallopian tubes** in females. - They are internal structures and do not contribute to external genitalia like the labia majora.
Question 3: In development of male fetus following statements are true except
- A. During intrauterine life, testes do not produce hormones essential for male development. (Correct Answer)
- B. Around 8 weeks internal and external genitalia differentiates into male pattern
- C. Gene on short arm of Y chromosome directs testes development
- D. Antimullerian hormone inhibits development of mullerian system in male fetus
Explanation: *During intrauterine life, testes do not produce hormones essential for male development.* - This statement is **INCORRECT** and is the answer to this EXCEPT question. - The **fetal testes** actively produce essential hormones during intrauterine life including **testosterone** (from Leydig cells) and **Anti-Müllerian Hormone/AMH** (from Sertoli cells). - Testosterone is converted to **dihydrotestosterone (DHT)** which drives development of male external genitalia. - These hormones are absolutely essential for **masculinization of internal and external genitalia** and regression of female structures. ***Around 8 weeks internal and external genitalia differentiates into male pattern.*** - This statement is correct. Sexual differentiation begins around **7-8 weeks of gestation**. - Under the influence of **testosterone and DHT** produced by fetal testes, the indifferent genitalia differentiate into male pattern. - The Wolffian ducts develop into male internal structures (epididymis, vas deferens, seminal vesicles). ***Gene on short arm of Y chromosome directs testes development.*** - This statement is correct. The **SRY gene (Sex-determining Region Y)** located on the **short arm (p arm) of the Y chromosome** is the master regulator of testis determination. - SRY expression triggers differentiation of the indifferent gonads into testes around 6-7 weeks. - Without SRY, the default pathway leads to ovarian development. ***Antimullerian hormone inhibits development of mullerian system in male fetus.*** - This statement is correct. **Anti-Müllerian Hormone (AMH)**, also called Müllerian-Inhibiting Substance (MIS), is secreted by **Sertoli cells** of the fetal testes. - AMH causes **regression of the Müllerian ducts** (paramesonephric ducts) around 8-10 weeks. - Without AMH, these ducts would develop into fallopian tubes, uterus, and upper vagina.
Question 4: Which of the following drugs is given during pregnancy, resulting in fetal abnormalities such as cleft lip and central nervous system defects?
- A. Warfarin
- B. Phenytoin
- C. Valproic acid
- D. Retinoic acid (Vitamin A derivative) (Correct Answer)
Explanation: ***Retinoic acid (Vitamin A derivative)*** - **Retinoic acid** (including isotretinoin) is a **potent teratogen** with a characteristic pattern of malformations including **craniofacial defects (cleft lip/palate)**, **cardiac abnormalities** (transposition of great arteries, VSD), and **severe CNS defects** (hydrocephalus, microcephaly, neural tube defects) - The mechanism involves **disruption of gene expression** during embryogenesis, particularly affecting **neural crest cell migration** critical for facial and cardiac development - The combination of **cleft lip + CNS defects** is characteristic of retinoic acid embryopathy, making it the most fitting answer *Phenytoin* - **Phenytoin** causes **fetal hydantoin syndrome** with craniofacial anomalies (cleft lip/palate in ~5-10% of cases), **hypoplastic nails and distal phalanges**, wide-set eyes, and mild developmental delays - While cleft lip can occur, the overall pattern emphasizes **digital/nail hypoplasia** and milder CNS effects compared to retinoic acid *Valproic acid* - **Valproic acid** is primarily associated with **neural tube defects** (spina bifida in 1-2% of exposures), the hallmark of valproate embryopathy - Can cause minor facial anomalies and cardiac defects, but the **characteristic feature is spina bifida**, not cleft lip *Warfarin* - **Warfarin** causes **fetal warfarin syndrome** with distinctive features: **nasal hypoplasia**, **stippled epiphyses** (chondrodysplasia punctata), and potential CNS defects from hemorrhage - Does **not** typically cause cleft lip; the skeletal abnormalities are the defining feature
Question 5: When the fetus is at station +2 and the fetal skull reaches the pelvic floor, which of the following statements is MOST clinically relevant?
- A. Forceps may be applied if necessary. (Correct Answer)
- B. Crowning occurs at this stage.
- C. There is a risk of deep transverse arrest.
- D. Episiotomy must be performed at this station.
Explanation: ***Forceps may be applied if necessary.*** - At **station +2**, the fetal head has progressed significantly into the pelvis (2 cm below the ischial spines), indicating a **low-lying head** where instrumental delivery with **forceps** or a **vacuum extractor** can be safely performed if indicated (e.g., maternal exhaustion, fetal distress). - This station qualifies as **low forceps** or **outlet forceps** delivery, which are considered safe procedures when properly indicated. - The fetal head at this level has reached or is approaching the **pelvic floor**, meeting the prerequisites for assisted vaginal delivery. *Crowning occurs at this stage.* - **Crowning** specifically refers to the stage when the largest diameter of the fetal head is visible at the **vaginal introitus** and does not recede between contractions. - This occurs at approximately **station +4 to +5**, not at station +2. - While station +2 indicates significant descent, the fetus must descend further before crowning occurs. *There is a risk of deep transverse arrest.* - **Deep transverse arrest** occurs when the fetal head fails to internally rotate from the transverse position to an occipito-anterior or occipito-posterior position. - This complication typically occurs at **station 0 to +1** (mid-pelvis level), not at station +2. - By the time the fetal head reaches station +2 and the pelvic floor, internal rotation should have already occurred. *Episiotomy must be performed at this station.* - **Episiotomy** is **not mandatory** at any particular fetal station. - It is a selective procedure performed when indicated, typically just before crowning (around station +3 to +4), to prevent severe perineal trauma or expedite delivery. - The decision is based on clinical factors like fetal size, maternal tissue quality, and risk of severe laceration—not solely on fetal station.
Question 6: Which of the following STDs causes fetal abnormality?
- A. Syphilis (Correct Answer)
- B. Herpes
- C. Gonorrhea
- D. Hepatitis B
Explanation: ***Syphilis*** - **Congenital syphilis**, resulting from maternal infection, can lead to severe fetal abnormalities such as **bone deformities**, **saddle nose**, **Hutchinson's teeth**, and **neurological problems**. - It can also cause stillbirth, prematurity, or hydrops fetalis, emphasizing the importance of early detection and treatment during pregnancy. *Herpes* - While **neonatal herpes** can be life-threatening and cause neurological damage, it is typically acquired during passage through the birth canal and does not cause **fetal abnormalities** during gestation. - Herpes simplex virus primarily causes localized lesions and systemic infection in the neonate, not developmental defects. *Gonorrhea* - Gonorrhea primarily causes **ophthalmia neonatorum** (conjunctivitis) in newborns through exposure during birth, which can lead to blindness if untreated. - It does not typically cause **fetal abnormalities** or congenital defects through transplacental transmission. *Hepatitis B* - Hepatitis B can be transmitted to the fetus during birth, leading to **chronic hepatitis B infection** in the infant. - Although it causes a chronic disease, it does not typically result in **fetal abnormalities** or congenital malformations.
Question 7: In which part of the fallopian tube is there a high chance of rupture in a tubal pregnancy?
- A. Interstitial
- B. Fimbrial
- C. Isthmus (Correct Answer)
- D. Ampulla
Explanation: ***Isthmus*** - The **isthmus** is the narrowest and most muscular part of the fallopian tube. Due to its limited ability to stretch, an ectopic pregnancy here is highly prone to rupture **earlier** than in other segments (typically 6-8 weeks). - The **isthmic portion's** small lumen and thick muscular wall make rupture a rapid and common complication, often before significant fetal growth, giving it the **highest chance of rupture** when an ectopic pregnancy implants there. *Ampulla* - The **ampulla** is the most common site for ectopic pregnancies (approximately 70%) due to its wider lumen and being the usual site of fertilization. - However, rupture in the ampulla tends to occur **later** than in the isthmus (8-12 weeks) as it can accommodate the growing embryo for a longer period due to its greater distensibility. - While more ectopic pregnancies occur here in absolute numbers, each individual ampullary pregnancy has a **lower chance of rupture** compared to isthmic pregnancies. *Interstitial* - The **interstitial** (or cornual) part is the segment within the uterine wall, making it a rare site for ectopic pregnancies (2-4%). - Ruptures in the interstitial portion occur **latest** (12-16 weeks) but are often the most dangerous, leading to severe hemorrhage due to the surrounding vascularity of the uterus and proximity to uterine and ovarian arteries. *Fimbrial* - The **fimbrial** end is the portion closest to the ovary and is exceedingly rare for ectopic implantation. - Implantation near the fimbriae usually leads to an **"abdominal pregnancy"** if the embryo is extruded, or could result in early "tubal abortion" rather than a true rupture.
Question 8: The first primary ossification centre to appear of the carpal bones is
- A. Capitate (Correct Answer)
- B. Pisiform
- C. Triquetral
- D. Scaphoid
Explanation: The first primary ossification centre to appear of the carpal bones is ***Capitate*** - The **capitate** is the first carpal bone to show an ossification center, typically appearing around **1-3 months of age**. [1] - This early ossification is an important marker in assessing **bone age** in children. *Scaphoid* - The **scaphoid** ossifies later than the capitate, usually between **4 and 6 years of age**. - Its ossification center is often **bi-lobed** and can be confused with a fracture on X-ray if not recognized. *Triquetral* - The **triquetral** ossification center generally appears between **2 and 4 years of age**. - This makes it a mid-range ossifier among the carpal bones, not the first. *Pisiform* - The **pisiform** is typically the last carpal bone to ossify, with its center appearing between **8 and 12 years of age**. - Its delayed ossification makes it a useful indicator for assessing **skeletal maturity** in older children and adolescents.
Question 9: During embryological development, failure of the urorectal septum to completely separate the cloaca results in which of the following congenital anomalies?
- A. Imperforate anus
- B. Cloacal exstrophy
- C. Rectovaginal fistula
- D. Persistent cloaca (Correct Answer)
Explanation: During embryological development, failure of the urorectal septum to completely separate the cloaca results in which of the following congenital anomalies? ***Persistent cloaca*** - This condition occurs when the **urorectal septum** fails to fully descend and partition the cloaca into the urogenital sinus anteriorly and the anorectal canal posteriorly [1]. - As a result, the rectum, vagina, and urinary tract all drain into a **single common channel**, leading to various functional and anatomical complications [1]. *Imperforate anus* - This anomaly involves the **absence or abnormal closure of the anal opening**, but it does not typically involve a shared channel with the urinary or reproductive tracts. - It arises from abnormal development of the **hindgut's caudal portion** or failure of the anal membrane to rupture. *Cloacal exstrophy* - This is a more complex and severe malformation characterized by the **exposure of the bladder, bowel, and sometimes genitalia** to the outside of the body. - While it involves cloacal derivatives, it's primarily a defect in the **closure of the ventral body wall** and does not directly result from incomplete septation in the same manner as a persistent cloaca. *Rectovaginal fistula* - This is an **abnormal connection between the rectum and the vagina**. While it involves a communication between two distinct structures, it is a localized defect. - It typically arises from **incomplete separation of the rectum and vagina**, which can be a consequence of less severe septation defects, but it is not the complete persistence of a single common channel like persistent cloaca.
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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