Embryology and Development — MCQs
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Which blood vessel carries deoxygenated blood back to the placenta?
Fingerprint first develops in how many weeks of intrauterine life?
A child lacks thymus and inferior parathyroid glands. Defective development of which of the following structures is likely to be the cause?
What is the incorrect statement?
Identify the type of marked chromosome in the given karyotype.
The marked structure develops from which of the following structures?
During embryological development, failure of the lateral palatine processes to fuse with the primary palate results in which of the following conditions?
During development, a fetus is found to have incomplete fusion of the neural tube. Which of the following structures would most likely be affected by this developmental defect?
During embryological development, failure of the urorectal septum to completely separate the cloaca results in which of the following congenital anomalies?
Secondary ossification centre appears before birth at
Embryology and Development Indian Medical PG Practice Questions and MCQs
Question 1011: Which blood vessel carries deoxygenated blood back to the placenta?
- A. Inferior vena cava
- B. Umbilical vein
- C. Umbilical artery (Correct Answer)
- D. Ductus venosus
Explanation: ***Umbilical artery*** - The **umbilical arteries** carry **deoxygenated blood** and waste products from the fetus to the placenta [2], [3]. - There are typically **two umbilical arteries** that branch off the internal iliac arteries in the fetus [2]. *Inferior vena cava* - The **inferior vena cava** carries deoxygenated blood from the lower body back to the **fetal heart**, not the placenta. - In a fetus, the inferior vena cava also carries **oxygenated blood** from the umbilical vein through the ductus venosus [1]. *Umbilical vein* - The **umbilical vein** carries **oxygenated blood** and nutrients from the placenta to the fetus [1]. - It bypasses the liver via the **ductus venosus** to deliver blood directly to the inferior vena cava [1]. *Ductus venosus* - The **ductus venosus** is a shunt that allows **oxygenated blood** from the umbilical vein to bypass the fetal liver [1]. - It connects the umbilical vein directly to the **inferior vena cava**, not to the placenta with deoxygenated blood [1].
Question 1012: Fingerprint first develops in how many weeks of intrauterine life?
- A. 20-24
- B. 12-16 (Correct Answer)
- C. 28-32
- D. 32-36
Explanation: ***12-16*** - **Fingerprint patterns**, specifically the **friction ridges** on the fingers, begin to form between 12 and 16 weeks of gestation. - This period marks the development of the **dermal papillae** and epidermal ridges that create the unique patterns. *20-24* - By 20-24 weeks, the fingerprint patterns are already **well-established** and clearly visible. - This stage is beyond the initial developmental period when the patterns first emerge. *28-32* - At 28-32 weeks, the fingerprint patterns are **fully formed** and permanent. - This timeframe is too late for the initial development of these unique dermal features. *32-36* - By 32-36 weeks, the fetus is nearing full term, and the **fingerprint morphology** is complete and stable. - The initial formation process has long since concluded before this stage.
Question 1013: A child lacks thymus and inferior parathyroid glands. Defective development of which of the following structures is likely to be the cause?
- A. 2
- B. 4
- C. 1
- D. 3 (Correct Answer)
Explanation: ***Option 3 (Structure 3 - Third pharyngeal pouch)*** - Structure **3** represents the **third pharyngeal pouch**, which is the embryological origin of both the **thymus** and **inferior parathyroid glands**. - Defective development of the third pharyngeal pouch leads to **DiGeorge syndrome** (22q11.2 deletion syndrome), characterized by thymic hypoplasia/aplasia and hypoparathyroidism. - This explains the clinical presentation of absent thymus and inferior parathyroid glands. *Option 2 (Structure 2 - Second pharyngeal pouch)* - Structure **2** represents the **second pharyngeal pouch**. - This gives rise to the **palatine tonsils** and the **tonsillar fossa**. - Not related to thymus or parathyroid gland development. *Option 1 (Structure 1 - First pharyngeal pouch)* - Structure **1** represents the **first pharyngeal pouch**. - This develops into the **eustachian tube** (auditory tube) and **middle ear cavity** (tympanic cavity). - Not related to thymus or inferior parathyroid gland development. *Option 4 (Structure 4 - Fourth pharyngeal pouch)* - Structure **4** represents the **fourth pharyngeal pouch**. - This gives rise to the **superior parathyroid glands** (dorsal wing) and **ultimobranchial body** (ventral wing), which contributes parafollicular C cells to the thyroid gland. - Note: The inferior parathyroids (from 3rd pouch) migrate further caudally than superior parathyroids (from 4th pouch).
Question 1014: What is the incorrect statement?
- A. MIS inhibits the formation of Mullerian duct
- B. WD form male internal genitalia
- C. Zygote is Bipotential at 8 weeks (Correct Answer)
- D. DHT is necessary for the development of external genitals
Explanation: ***Zygote is Bipotential at 8 weeks*** - A **zygote** is formed at conception and is the single-cell diploid organism, not bipotential at 8 weeks. - The **bipotential gonad** can develop into either testes or ovaries, and this stage of sexual differentiation occurs earlier in gestation, typically around the 6th to 7th week, before differentiating into male or female gonads, not at 8 weeks as an entire zygote. *MIS inhibits the formation of Mullerian duct* - **Müllerian Inhibiting Substance (MIS)**, also known as **Anti-Müllerian Hormone (AMH)**, is produced by the Sertoli cells of the developing testes [1]. - Its primary function is to cause the **regression of the Müllerian ducts**, which would otherwise develop into female internal reproductive structures (fallopian tubes, uterus, and upper vagina) [1]. *WD form male internal genitalia* - The **Wolffian ducts (WD)**, also known as mesonephric ducts, are precursors to male internal genitalia in the presence of testosterone [1]. - stimulated by **testosterone** produced by the Leydig cells of the fetal testes, they develop into the **epididymis, vas deferens, and seminal vesicles** [1]. *DHT is necessary for the development of external genitals* - **Dihydrotestosterone (DHT)**, a more potent form of testosterone, is crucial for the development of male external genitalia [1]. - The enzyme **5α-reductase** converts testosterone to DHT in target tissues, leading to the formation of the **penis, scrotum, and prostate** [1].
Question 1015: Identify the type of marked chromosome in the given karyotype.
- A. Metacentric
- B. Telocentric
- C. Submetacentric
- D. Acrocentric (Correct Answer)
Explanation: ***Acrocentric*** - Acrocentric chromosomes have a **centromere positioned very close to the end**, resulting in one very short arm (p arm) and one long arm (q arm). - Chromosome 13, as indicated by the arrow in the karyotype, clearly exhibits this morphology with a distinctly short p arm. *Metacentric* - **Metacentric chromosomes** have the centromere located approximately in the **middle of the chromosome**, resulting in two arms of roughly equal length. - Examples of metacentric chromosomes in a human karyotype include chromosomes 1, 3, 16, 19, and 20. *Telocentric* - **Telocentric chromosomes** have the **centromere at the very end of the chromosome**, meaning there is essentially only one arm. - This type of chromosome structure is not found in normal human karyotypes. *Submetacentric* - **Submetacentric chromosomes** have the centromere off-center, leading to one arm being **moderately shorter** than the other. - Chromosomes 2, 4-12, 17, 18, and X are generally classified as submetacentric in human karyotypes.
Question 1016: The marked structure develops from which of the following structures?
- A. Anterior cardinal vein
- B. Subcardinal vein
- C. Supracardinal vein (Correct Answer)
- D. Common cardinal vein
Explanation: ***Supracardinal vein*** - The arrow points to the **azygos vein**, which drains the thoracic wall. - The azygos vein is primarily derived from the right **supracardinal vein**. *Anterior cardinal vein* - The anterior cardinal veins contribute to the formation of the **superior vena cava** and internal jugular veins. - They are located more superiorly and drain the head and upper limbs. *Subcardinal vein* - The subcardinal veins are involved in the formation of the **renal veins**, gonadal veins, and a segment of the inferior vena cava. - These veins are found in the abdominal region, inferolateral to the developing kidneys. *Common cardinal vein* - The common cardinal veins fuse to form the **superior vena cava** and enter the sinus venosus. - They are important in the early embryonic stage for collecting blood from the anterior and posterior cardinal veins.
Question 1017: During embryological development, failure of the lateral palatine processes to fuse with the primary palate results in which of the following conditions?
- A. Pierre Robin sequence
- B. Submucous cleft
- C. Isolated cleft palate (Correct Answer)
- D. Bifid uvula
Explanation: ***Isolated cleft palate*** - This condition occurs when the **lateral palatine processes** (secondary palate) **fail to fuse** with each other and/or with the **primary palate**. [1] - It results in an **opening between the oral and nasal cavities**, affecting feeding and speech. [1] *Pierre Robin sequence* - Characterized by **micrognathia**, **glossoptosis**, and often a **U-shaped cleft palate**. - While a cleft palate can be present, the defining features are the small mandible and posterior displacement of the tongue. *Submucous cleft* - Involves failure of **muscle or bone fusion under intact mucous membranes**. - It can be difficult to diagnose visually, often identified by a **bifid uvula**, notch in the hard palate, or abnormal muscle function of the soft palate. *Bifid uvula* - This is a mild form of **cleft palate**, where only the **uvula is split**. - It indicates incomplete fusion of the palatine shelves but does not represent a full failure of the lateral palatine processes to fuse with the primary palate.
Question 1018: During development, a fetus is found to have incomplete fusion of the neural tube. Which of the following structures would most likely be affected by this developmental defect?
- A. Notochord
- B. Somites
- C. Vertebral bodies
- D. Spinal cord and meninges (Correct Answer)
Explanation: ***Spinal cord and meninges*** - Incomplete fusion of the neural tube directly results in defects of the **neural tube closure**, which include the formation of the **spinal cord** and its protective coverings, the **meninges**. [1, 2] - Conditions like **spina bifida** (meningocele, myelomeningocele) are direct consequences of these fusion failures, exposing or abnormally developing the spinal cord and meninges. [1, 2] *Notochord* - The **notochord** is a transient embryonic structure that induces the formation of the neural tube by signaling to the overlying ectoderm; it is not directly formed by the neural tube itself. - While it plays a critical role in neural tube development, its own structural integrity is typically not primarily affected by neural tube fusion defects. *Somites* - **Somites** are blocks of paraxial mesoderm that differentiate into sclerotome (vertebrae and ribs), myotome (skeletal muscle), and dermatome (dermis of the skin). - While somite development is closely coordinated with neural tube formation, incomplete neural tube fusion primarily affects the neural structures themselves, not the somites directly. *Vertebral bodies* - **Vertebral bodies** develop from the sclerotome portion of the somites, which migrate to surround the neural tube and notochord. - While vertebral defects can be associated with severe neural tube defects (e.g., in spina bifida, the vertebral arches may fail to close), the primary defect of incomplete neural tube fusion directly impacts the neural tissue (spinal cord and meninges), with skeletal defects being secondary or associated. [1, 2]
Question 1019: 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 1020: Secondary ossification centre appears before birth at
- A. Upper end of femur
- B. Lower end of tibia
- C. Lower end of fibula
- D. Lower end of femur (Correct Answer)
Explanation: Lower end of femur - The distal femur is one of the very few secondary ossification centers that appears before birth, specifically during the 9th month of gestation. - Its presence is an important indicator of fetal maturity and can be seen on prenatal imaging. Upper end of femur - The proximal femoral epiphysis typically develops its secondary ossification center after birth, usually between 3-6 months of age. - This timing is considerably later than the distal femur. Lower end of tibia - The secondary ossification center for the distal tibia appears after birth, generally around 1-2 years of age. - This is a common timeline for many secondary ossification centers. Lower end of fibula - The secondary ossification center for the distal fibula also appears after birth, typically between 6 months and 1 year of age. - This timing is later than the distal femur but earlier than the distal tibia.
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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