Embryology and Development — MCQs

Embryology and Development Indian Medical PG Practice Questions and MCQs

Question 981: The condition shown below is due to ?

A. Patent vitello-intestinal duct
B. Patent urachus (Correct Answer)
C. Patent allantois
D. Mid gut loop hernia

Explanation: ***Patent urachus*** - A **patent urachus** is a congenital anomaly where the **urachus (embryonic connection between the bladder dome and umbilicus) fails to obliterate**, resulting in a persistent communication between the bladder and umbilicus. - Clinical presentation includes **urine leakage from the umbilicus**, especially with crying or straining, or a **cystic swelling at the umbilicus** that may discharge clear fluid (urine). - The urachus is the remnant of the **allantois** and normally obliterates to form the **median umbilical ligament**. *Patent vitello-intestinal duct* - Also called **patent vitelline duct** or **patent omphalomesenteric duct**, this represents failure of obliteration of the connection between the **ileum and umbilicus**. - Presents with **fecal discharge from umbilicus**, passage of intestinal contents, or prolapsed ileal mucosa (raspberry tumor). - May present as **Meckel's diverticulum** if only the intestinal end persists. *Patent allantois* - The **allantois** is an embryonic structure that contributes to the formation of the **urachus and urinary bladder**. - "Patent allantois" is not standard clinical terminology; the correct term for persistent allantois-bladder-umbilical connection is **patent urachus**. - The allantois itself is part of the developmental pathway leading to the urachus. *Mid gut loop hernia* - An **omphalocele** is a type of abdominal wall defect where **midgut herniates through the umbilical ring**, covered by a membrane (peritoneum and amnion). - Presents as a **large, membrane-covered sac containing abdominal organs** (intestines, liver) at the umbilicus, apparent at birth. - This is a **structural defect**, not a failure of duct obliteration, and does not involve patent urachus.

Question 982: All of the following structures develop from the structure marked as $X$ in a male fetus except:

A. Seminal vesicle
B. Epididymis
C. Ductus deferens
D. Prostate (Correct Answer)

Explanation: ***Prostate*** - The **prostate gland** develops from outgrowths of the **urogenital sinus**, specifically the pelvic portion, and not from the mesonephric (Wolffian) duct. - Its development is influenced by **dihydrotestosterone (DHT)**. *Seminal vesicle* - The **seminal vesicles** develop as an outgrowth from the **mesonephric (Wolffian) duct**, specifically the caudal end, near its junction with the urogenital sinus. - This structure (marked as X) represents the mesonephric duct. *Epididymis* - The **epididymis** develops from the cranial and middle portions of the **mesonephric (Wolffian) duct (X)**. - In males, this duct persists and forms the efferent ductules, epididymis, vas deferens, and seminal vesicles. *Ductus deferens* - The **ductus deferens** (vas deferens) develops from the persistent portion of the **mesonephric (Wolffian) duct (X)**, distal to the epididymis. - It functions in transporting sperm from the epididymis to the ejaculatory duct.

Question 983: The testis reaches the point marked $X$ at which month of gestation? (Recent NEET Pattern 2016-17)

A. 5th month
B. 6th month
C. 7th month (Correct Answer)
D. 8th month

Explanation: ***7th month*** - The diagram shows the **testis** descending through the **inguinal canal** into the scrotum. - Testicular descent typically occurs during the **seventh month** of gestation, guided by the **gubernaculum**. *5th month* - By the fifth month, the testes have typically descended to the **deep inguinal ring** but have not yet entered the inguinal canal. - This stage precedes the point marked X, indicating an earlier phase of descent. *6th month* - During the sixth month, the testes are usually found within the **inguinal canal**, but not yet nearing its exit into the scrotum. - The point X represents the testis having passed through the inguinal canal, which occurs later. *8th month* - By the eighth month, the testes are typically **fully descended into the scrotum**. - The image depicts the testis at the exit of the inguinal canal, signifying the completion of descent rather than full scrotal positioning.

Question 984: The part of the collecting duct system marked in blue develops from:

A. Metanephric blastema
B. Ureteric bud (Correct Answer)
C. Allantois
D. Pronephros

Explanation: ***Ureteric bud*** - The blue-marked structure in the image is the **collecting tubule**, which is part of the **collecting duct system** of the kidney. - The entire collecting duct system, including the collecting tubules, collecting ducts, minor and major calyces, renal pelvis, and ureter, develops from the **ureteric bud**. *Metanephric blastema* - The **metanephric blastema** (also known as metanephric mesenchyme) develops into the **nephron** itself, which includes the renal corpuscle (glomerulus and Bowman's capsule), proximal convoluted tubule, loop of Henle, and distal convoluted tubule. - It does not give rise to the collecting system. *Allantois* - The **allantois** is an extraembryonic membrane that contributes to the formation of the **urachus** and ultimately the median umbilical ligament and the urinary bladder. - It is not directly involved in the formation of the renal tubules or collecting system. *Pronephros* - The **pronephros** is the earliest and most rudimentary excretory organ in vertebrate embryonic development, which **regresses completely** in humans. - It does not contribute to the definitive kidney structures in humans.

Question 985: Which of the following develops from the part shown as X in the development of heart?

A. Truncus arteriosus (Correct Answer)
B. Ductus arteriosus
C. Crista terminalis
D. Cavo-tricuspid isthmus

Explanation: ***Truncus arteriosus*** - The image shows the primitive heart tube, and **X represents the truncus arteriosus**, which is the **most cranial (superior) part** of the developing heart tube - The truncus arteriosus is a single large arterial trunk that undergoes septation to form the **ascending aorta** and the **pulmonary trunk (pulmonary artery)** - During development, **spiral aorticopulmonary septum** divides the truncus arteriosus into the two great vessels - This occurs during weeks 5-8 of embryonic development *Ductus arteriosus* - The ductus arteriosus is a **fetal blood vessel** that connects the pulmonary artery to the descending aorta, allowing blood to bypass the non-functional fetal lungs - It is **not a segment of the primitive heart tube** but develops separately as part of the 6th pharyngeal arch artery system - It forms after the truncus arteriosus has already divided into the aorta and pulmonary trunk *Crista terminalis* - The crista terminalis is a **ridge in the adult right atrium** that separates the smooth-walled sinus venarum posteriorly from the rough-walled pectinate muscles anteriorly - It is a **morphological feature of the mature heart** that develops from the junction between the sinus venosus and primitive atrium - It does not correspond to the cranial portion of the primitive heart tube (which is the truncus arteriosus) *Cavo-tricuspid isthmus* - The cavo-tricuspid isthmus is a region of the **adult right atrium** located between the inferior vena cava orifice and the tricuspid valve annulus - It is an important **anatomical landmark in cardiac electrophysiology** (target for cavotricuspid isthmus-dependent atrial flutter ablation) - It is a feature of the developed heart and does not represent any segment of the early primitive heart tube

Question 986: 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.

Question 987: Which of the following is correct for the image shown below?

A. A= Neural tube, B= Somites, C= Splanchnopleuric intraembryonic mesoderm, D= Notochord (Correct Answer)
B. A= Neural tube, B= Somatopleuric intraembryonic mesoderm, C= Somites, D= Notochord
C. A= Neural tube, B= Splanchnopleuric intraembryonic mesoderm, C= Somites, D= Notochord
D. A= Neural tube, B= Somites, C= Somatopleuric intraembryonic mesoderm, D= Notochord

Explanation: ***A= Neural tube, B= Somites, C= Splanchnopleuric intraembryonic mesoderm, D= Notochord*** - **A** clearly points to the central, hollow structure which is the **neural tube**, formed from the invagination of the neural plate. - **B** indicates the segmental blocks of paraxial mesoderm, which are the **somites**. - **C** is pointing to the layer of lateral plate mesoderm associated with the endoderm, forming the future visceral pleura; this is the **splanchnopleuric intraembryonic mesoderm**. - **D** is the central rod-like structure beneath the neural tube, which is the **notochord**. *A= Neural tube, B= Somites, C= somatopleuric intraembryonic mesoderm, D= Notochord* - While A, B, and D are correctly identified, **C** is incorrectly labeled as somatopleuric intraembryonic mesoderm. - **Somatopleuric intraembryonic mesoderm** refers to the lateral plate mesoderm associated with the ectoderm, forming the future parietal pleura. *A= neural tube, B= Somatopleuric intraembryonic mesoderm, C= Somites, D= Notochord* - This option incorrectly identifies both **B** and **C**. **B** represents somites, not somatopleuric intraembryonic mesoderm. - **C** is the splanchnopleuric intraembryonic mesoderm, not somites. *A= neural tube, B= Splanchnopleuric intraembryonic mesoderm, C= Somites, D= Notochord* - This option incorrectly identifies both **B** and **C**. **B** represents somites, not splanchnopleuric intraembryonic mesoderm. - **C** is the splanchnopleuric intraembryonic mesoderm, not somites.

Question 988: As shown in the figure, abnormal subclavian artery develops as a result of: (AIIMS May 2016)

A. Persistence of B
B. Persistence of A
C. Obliteration of A with persistence of B
D. Obliteration of B with persistence of A (Correct Answer)

Explanation: ***Obliteration of B with persistence of A*** - The image depicts the 7th intersegmental artery (labeled **A**) and the right dorsal aorta (labeled **B**). An **abnormal subclavian artery** (retroesophageal subclavian artery or arteria lusoria) results from the **obliteration of B** (the right dorsal aorta) distal to the 7th intersegmental artery (A). - When the right dorsal aorta (B) obliterates prematurely, the right subclavian artery (derived from A plus portions of the 4th aortic arch and right dorsal aorta) gets its distal blood supply from the left dorsal aorta, causing it to cross behind the esophagus to reach the right arm. *Persistence of B* - The normal development of the right subclavian artery involves the **regression** of a segment of the right dorsal aorta (part of **B**). If **B** (the right dorsal aorta) persists, it could lead to other malformations, but not typically an abnormal subclavian artery coursing behind the esophagus. - The persistence of the right dorsal aorta, usually proximal to the 7th intersegmental artery, would be part of a **double aortic arch** or other arch anomalies, rather than directly causing arteria lusoria. *Persistence of A* - **A** represents the **7th intersegmental artery**, which normally persists to form a crucial part of the subclavian artery. Persistence of **A** alone is a normal developmental event and does not lead to an abnormal subclavian artery. - An abnormal subclavian artery requires an alteration in the usual regression patterns of other embryological vessels, not merely the persistence of a normally persistent vessel. *Obliteration of A with persistence of B* - **Obliteration of A** (the 7th intersegmental artery) would prevent the formation of a normal subclavian artery altogether. This would lead to a severely underdeveloped or absent right subclavian artery, rather than one with an abnormal course. - If **A** obliterates, and **B** (right dorsal aorta) persists, the right arm would lack its primary arterial supply, which is a much more severe anomaly than a retroesophageal subclavian artery.

Question 989: The diagram given below depicts the various parts from which the diaphragm develops. Defect in which part most commonly leads to congenital diaphragmatic hernia? (AIIMS May 2016)

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

Explanation: ***A*** - A indicates the **pleuroperitoneal membranes**, which are posterior and lateral structures that form a significant portion of the diaphragm. - Failure of these membranes to fuse with other diaphragmatic components, particularly on the left side, leads to a **Bochdalek hernia**, the most common type of congenital diaphragmatic hernia. *B* - B represents the **septum transversum**, which forms the central tendon of the diaphragm and contributes to the anterior portion. - Defects in the septum transversum can lead to **Morgagni hernias**, which are less common than Bochdalek hernias and are typically anterior and retrosternal. *C* - C indicates the **mesentery of the esophagus**, which forms the crura of the diaphragm. - Defects in this region are rare causes of diaphragmatic hernia and usually involve the posterior medial aspect. *D* - D points to the **muscular ingrowth from the body wall**, which forms the peripheral musculature of the diaphragm. - While essential for complete diaphragm formation, isolated defects in this part are less commonly implicated as the primary cause of major congenital diaphragmatic hernias compared to the pleuroperitoneal membranes.

Question 990: Portal vein develops from which of these structures? (AIIMS May 2016)

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

Explanation: ***B*** - In this diagram illustrating embryonic vein development, the structure labeled **B** represents the **right vitelline vein**, which contributes significantly to the formation of the portal vein system. - The **portal vein** is formed from the anastomosing network of the vitelline veins around the duodenum, with the right vitelline vein becoming its main stem. *A* - The structure labeled **A** represents the **anterior cardinal veins**, which contribute to structures like the superior vena cava, not the portal vein. - These veins drain the cranial part of the embryo. *C* - The structure labeled **C** represents the **left vitelline vein** which, in later development, largely **regresses** or contributes to smaller veins, unlike the right vitelline vein shown at B. - While part of the vitelline system, its contribution to the definitive portal vein is minor compared to the right vitelline vein. *D* - The structure labeled **D** represents the **umbilical veins**, which carry oxygenated blood and nutrients from the placenta to the fetus. - Postnatally, the umbilical veins obliterate to form the **ligamentum teres hepatis** and the **ligamentum venosum**, and do not form the portal vein.

Practice by Chapter

Gametogenesis and Fertilization

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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 Urogenital 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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Molecular Mechanisms in Development

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