Embryology and Development — MCQs

Embryology and Development Indian Medical PG Practice Questions and MCQs

Question 991: A young patient with absent thymus presents with tetany and hypoparathyroidism. Which of the following is a marked area in the picture defective in this condition?

A. B
B. C (Correct Answer)
C. D
D. A

Explanation: ***C*** - The image shows the **pharyngeal arches and pouches** during embryonic development. **C** points to the **third pharyngeal pouch**, which gives rise to the **thymus** and inferior parathyroid glands. - A defect in the development of the third pharyngeal pouch would lead to an **absent or hypoplastic thymus** and **hypoparathyroidism**, causing symptoms like tetany due to hypocalcemia. This condition is known as **DiGeorge syndrome**. *A* - **A** points to the first pharyngeal pouch, which develops into the **auditory tube** and **tympanic cavity**. - Defects in the first pharyngeal pouch would primarily affect structures in the ear, not the thymus or parathyroid glands. *B* - **B** points to the fourth pharyngeal pouch, which gives rise to the **superior parathyroid glands** and the **ultimobranchial body** (parafollicular C cells of the thyroid). - While hypoparathyroidism could be involved, the primary defect in DiGeorge syndrome affects the third pouch, leading to both thymic and parathyroid issues more comprehensively. *D* - **D** points to the first pharyngeal arch, which contributes to the formation of the **mandible**, **maxilla**, and several muscles of mastication. - Defects in the first pharyngeal arch are associated with conditions like **Treacher Collins syndrome** or **Pierre Robin sequence**, which present with facial dysmorphism rather than thymic or parathyroid agenesis.

Question 992: Nucleus pulposus develops from: (AIIMS May 2018)

A. A
B. B
C. C (Correct Answer)
D. D

Explanation: ***Correct Option C*** - Label C points to the **notochord**, which is the embryonic structure that the **nucleus pulposus** of the intervertebral discs develops from. - The notochord provides transient axial support during early embryonic development and induces the formation of the neural tube. - During development, most of the notochord degenerates, but remnants persist as the gelatinous core of intervertebral discs. *Incorrect Option A* - Label A indicates the **neural tube**, which develops into the **brain and spinal cord**. - It arises from the neural plate, which is induced by the underlying notochord. - The neural tube does not contribute to the intervertebral disc structure. *Incorrect Option B* - Label B represents the **secondary yolk sac**, a structure involved in early nutrient transfer and the formation of primordial germ cells. - It does not directly contribute to the formation of musculoskeletal structures like the nucleus pulposus. *Incorrect Option D* - Label D points to the **ectoderm**, the outermost germ layer, which gives rise to the epidermis, nervous system (including the neural tube), and sensory organs. - While it forms the neural tube, it does not directly form the nucleus pulposus or other mesodermal derivatives.

Question 993: Which of the following bones is the first one to ossify?

A. A
B. B
C. C (Correct Answer)
D. D

Explanation: ***C*** - The **capitate bone** is the first carpal bone to ossify, typically appearing around **1-3 months** of postnatal life. - As the largest carpal bone, its early ossification serves as an important radiological marker for assessing **skeletal maturity** in pediatric patients. *A* - The **scaphoid bone** ossifies much later, around **5-6 years** of age, making it one of the last carpal bones to develop. - Due to its **retrograde blood supply**, the scaphoid is particularly susceptible to **avascular necrosis** following fractures. *B* - The **trapezoid bone** typically begins ossification between **4-6 years** of age, significantly later than the capitate. - Located between the **trapezium and capitate**, it forms part of the distal carpal row and contributes to **index finger stability**. *D* - The **lunate bone** usually starts ossifying around **2-4 years** of age, making it the second carpal bone to ossify after the capitate. - The lunate is clinically significant as it's commonly affected by **Kienböck's disease** (avascular necrosis) and **perilunate dislocations**.

Question 994: Identify the clinical examination test being performed in the given image.

A. Thomas test (Correct Answer)
B. Patrick test
C. Hoover test
D. McMurray test

Explanation: ***Thomas test*** - This image illustrates the **Thomas test**, which assesses for **hip flexion contracture** or tightness of the **iliopsoas muscle**. - The patient lies supine, and one knee is fully flexed to the chest; if the contralateral hip flexes off the table, it indicates a positive test. *Patrick test* - The **Patrick test**, also known as the **FABER (Flexion, Abduction, External Rotation) test**, is performed to evaluate for hip or sacroiliac joint pathology. - It involves flexing, abducting, and externally rotating the hip, then applying downward pressure on the flexed knee and contralateral anterior superior iliac spine (ASIS). *Hoover test* - The **Hoover test** is used to detect **malingering** or non-organic weakness in a patient's lower extremity. - The examiner places hands under both heels while the patient is supine and asks them to raise one leg; if no downward pressure is felt on the contralateral heel, the test is positive for malingering. *McMurray test* - The **McMurray test** is a diagnostic test for **meniscal tears** in the knee. - It involves flexing and extending the knee with applied varus/valgus stress and rotation to elicit a click or pain indicating a tear.

Question 995: The following USG scan should prompt you to screen for which of the following disorders?

A. Neural tube defect
B. Aneuploidy (Correct Answer)
C. Achondroplasia
D. Artifact on routine scans

Explanation: ***Aneuploidy*** - The ultrasound image shows increased nuchal translucency (indicated by the red arrow), which is a key marker for **chromosomal abnormalities** like Down syndrome (Trisomy 21). - Increased nuchal translucency combined with other features like **absent nasal bone** (not clearly visible in this image but often associated) warrants further screening for aneuploidy. *Neural tube defect* - Neural tube defects are characterized by abnormalities of the brain and spine, such as **anencephaly** or **spina bifida**, which are not directly indicated by increased nuchal translucency. - While some chromosomal abnormalities can be associated with neural tube defects, nuchal translucency specifically points more strongly to aneuploidy. *Achondroplasia* - Achondroplasia is a form of **dwarfism** recognized by disproportionately short limbs and macrocephaly, which are typically identified later in pregnancy during detailed anatomical surveys. - Increased nuchal translucency is not a primary screening marker for achondroplasia. *Artifact on routine scans* - While artifacts can occur, increased nuchal translucency is a well-established and **clinically significant finding** that requires specific measurements and interpretation in screening for fetal abnormalities. - This measurement is a standard part of the **first-trimester screening** for chromosomal disorders.

Question 996: The image shows:

A. Omphalocele
B. Gastroschisis
C. Necrotising enterocolitis
D. Malformation of vitello-intestinal duct (Correct Answer)

Explanation: ***Malformation of vitello-intestinal duct*** - The image depicts a **persistent vitelline (omphalomesenteric) duct** remnant, which can present as a patent duct, fistula, cyst, or fibrous band. The appearance here is consistent with an **umbilical polyp or remnant,** presenting as a red, moist lesion often mistaken for granuloma. - This malformation occurs when the **vitello-intestinal duct**, connecting the developing gut to the yolk sac, fails to involute completely. *Omphalocele* - An **omphalocele** involves herniation of abdominal contents (covered by a membrane) through the **umbilical ring**, while this image shows a solid, polyp-like structure. - The umbilical cord is typically attached to the apex of the sac in omphalocele, which is not what is seen here. *Gastroschisis* - **Gastroschisis** is characterized by uncovered abdominal organs protruding through an abdominal wall defect, usually to the **right of the umbilical cord**. - There is no protective membrane in gastroschisis, and the image shows a covered, distinct growth at the umbilicus, not an open abdominal defect with exposed viscera. *Necrotising enterocolitis* - **Necrotizing enterocolitis (NEC)** is an inflammatory condition of the neonatal intestine, leading to **ischemic necrosis**. - This image shows an external umbilical anomaly; internal intestinal pathology like NEC would present with abdominal distension, feeding intolerance, and bloody stools, not this umbilical lesion.

Question 997: A 2-week-old neonate presents with feeding problems and otitis media. Based on the clinical image, what is the most likely diagnosis?

A. Down syndrome
B. Pierre Robin sequence (Correct Answer)
C. Beckwith-Wiedemann syndrome
D. Hypothyroidism

Explanation: ***Pierre Robin sequence*** - The image clearly exhibits **micrognathia** (small jaw), **glossoptosis** (posterior displacement of the tongue), and a **cleft palate**, which are the classic triad of Pierre Robin sequence. - These features lead to **feeding difficulties** and **airway obstruction** contributing to otitis media due to Eustachian tube dysfunction. *Down syndrome* - Characterized by distinct facial features such as a **flat facial profile**, **epicanthal folds**, and a **single palmar crease**, which are not readily apparent in the provided image. - While feeding problems can occur, the specific combination of micrognathia and cleft palate seen here is not typical of Down syndrome. *Beckwith-Wiedemann syndrome* - Identified by features like **macroglossia** (large tongue), **omphalocele**, **hemihyperplasia**, and an increased risk of tumors, none of which are evident in the image or suggested by the clinical presentation. - Although macroglossia can cause feeding issues, it presents differently than glossoptosis and the primary mandibular hypoplasia seen here. *Hypothyroidism* - In neonates, congenital hypothyroidism presents with symptoms such as **poor feeding**, **lethargy**, **constipation**, and a **hoarse cry**, often accompanied by a large tongue (macroglossia) and umbilical hernia. - While poor feeding is present, the pronounced facial and oral structural anomalies (micrognathia, glossoptosis, cleft palate), are not features of hypothyroidism.

Question 998: A 2-day-old neonate under phototherapy unit. For exchange transfusion serum bilirubin-albumin ratio should be: (Recent NEET Pattern 2016-17)

A. $>3.5$ (Correct Answer)
B. $<3.5$
C. $>35$
D. $<35$

Explanation: ***$>3.5$*** - A **serum bilirubin-albumin ratio greater than 3.5** is a common guideline indicating the need for exchange transfusion in neonates, especially those at high risk or with rapidly rising bilirubin levels. - This ratio helps assess the risk of **bilirubin-induced neurotoxicity (kernicterus)**, as unbound (free) bilirubin can cross the blood-brain barrier [1]. *$<3.5$* - A bilirubin-albumin ratio **less than 3.5** typically suggests a lower risk of neurotoxicity and may indicate that phototherapy is sufficient to manage hyperbilirubinemia [2]. - In such cases, the **binding capacity of albumin** for bilirubin is considered adequate to prevent significant free bilirubin accumulation [1]. *$>35$* - A serum bilirubin-albumin ratio of **greater than 35** would represent an extremely high and clinically improbable value. - Clinically, the bilirubin-albumin ratio is typically used with values in the single digits, making a value of 35 or higher incongruent with standard medical guidelines. *$<35$* - While technically true that $<35$ would include the correct threshold, it is not sufficiently specific to denote the critical value for exchange transfusion. - This range is too broad and does not pinpoint the specific bilirubin-albumin ratio that prompts intervention.

Question 999: A 2-day-old neonate has passed stool of the color shown in the image. Which of the following best describes the clinical possibility?

A. It is normal meconium passed within first 24 hours
B. Meconium plug syndrome, perform sweat chloride test
C. Metabolic liver disease, perform urine for reducing substances
D. Biliary atresia, perform hepatobiliary scintigraphy (Correct Answer)

Explanation: ***Biliary atresia, perform hepatobiliary scintigraphy*** - The image shows **acholic (pale or clay-colored) stools**, often appearing whitish or very light yellow, which is a classic symptom of **biliary atresia** due to the absence of bilirubin in the stool. - **Hepatobiliary scintigraphy** (HIDA scan) is a crucial diagnostic test for biliary atresia, as it assesses bile flow from the liver to the intestine. *It is normal meconium passed within first 24 hours* - **Normal meconium** is typically **dark green to black**, thick, and tar-like, and is usually passed within the first 24-48 hours. The stool in the image is pale, not dark and tarry. - By 2-3 days of age, stool color normally transitions to greenish-brown **transitional stools**, then yellow **milk stools**; pale stools at this age are concerning. *Meconium plug syndrome, perform sweat chloride test* - **Meconium plug syndrome** involves a functional intestinal obstruction due to an inspissated meconium plug, leading to abdominal distention and **failure to pass meconium**, not pale stools. A sweat chloride test is for **cystic fibrosis**, which can cause meconium ileus, but not typically pale stools in early neonates as the primary symptom. - While cystic fibrosis can sometimes present with cholestasis, pale stools are not the initial or primary symptomatic sign of meconium plug syndrome or cystic fibrosis itself in a 2-day-old that has successfully passed some meconium. *Metabolic liver disease, perform urine for reducing substances* - While some **metabolic liver diseases** can cause cholestasis and pale stools, the prompt for urine for **reducing substances** is primarily for conditions like **galactosemia**, which typically presents with **jaundice, hepatomegaly, and feeding difficulties**, but pale stools are not the most specific initial sign in that context. - The stool appearance in the image points more directly to an issue with bile secretion into the gut, making biliary atresia a more likely initial consideration.

Question 1000: Mother of a 6-hour-old neonate has pointed to passage of stool of the following color. Which of the following best describes the clinical possibility?

A. It is normal meconium passed within first 24 hours (Correct Answer)
B. Meconium plug syndrome, perform sweat chloride test
C. Metabolic liver disease, perform urine for reducing substances
D. Biliary atresia, perform hepatobiliary scintigraphy

Explanation: ***It is normal meconium passed within first 24 hours*** - The image depicts a **yellowish-brown, thick, and sticky substance**, similar to what is expected with **transitional stool** or early meconium mixed with milk components. - The neonate is 6 hours old, and the passage of normal meconium usually occurs within the **first 24-48 hours** of life, typically dark green to black but can transition to a lighter color. *Meconium plug syndrome, perform sweat chloride test* - **Meconium plug syndrome** typically presents with delayed passage of meconium and abdominal distension, not with stool of this color or consistency at 6 hours. - A **sweat chloride test** is primarily used to diagnose cystic fibrosis, which can be associated with meconium ileus (a more severe obstruction than meconium plug) but is not the first diagnostic step for a seemingly normal stool passage at this age. *Metabolic liver disease, perform urine for reducing substances* - **Metabolic liver diseases** would typically present with jaundice, hepatomegaly, or other signs of liver dysfunction, not solely with stool of this appearance at 6 hours. The stool color would also be more likely **acholic (pale/white)** if there was significant biliary obstruction. - **Urine for reducing substances** is used to screen for certain metabolic disorders like galactosemia, which would present with symptoms like vomiting, lethargy, and jaundice, not just normal stool. *Biliary atresia, perform hepatobiliary scintigraphy* - **Biliary atresia** causes obstruction of the bile ducts, leading to **acholic (pale or white) stools**, not the yellowish-brown stools seen in the image. - Symptoms of biliary atresia usually manifest later, around **2-8 weeks of age**, with persistent jaundice and pale stools. A **hepatobiliary scintigraphy** would be performed if biliary atresia is suspected later based on clinical presentation.

Practice by Chapter

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Early Embryonic Development

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Placentation

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Development of Nervous System

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Development of Cardiovascular System

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Development of Gastrointestinal System

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Development of Musculoskeletal System

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Development of Head and Neck

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Congenital Anomalies

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Teratology

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