Embryology and Development — MCQs
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Inferior parathyroid develops from which pharyngeal pouch?
Coronary sinus develops from?
Kobelt tubercle is a remnant of which part of the Wolffian duct in females?
Which of the following is a derivative of the mesonephric tubules in males?
Majority of bronchogenic lung cysts occur in which?
What is the typical number of bones present at birth?
Uterus is derived from which structure?
Cleft palate is associated with disturbances in the development of the palatine shelves during which gestational weeks?
Branchial arches give rise to various structures in the head and neck region. From which arch does the maxillary artery develop?
What is the classification of a urachus fistula?
Embryology and Development Indian Medical PG Practice Questions and MCQs
Question 1151: Inferior parathyroid develops from which pharyngeal pouch?
- A. 1st
- B. 2nd
- C. 3rd (Correct Answer)
- D. 4th
Explanation: The inferior parathyroid glands develop from the dorsal wing of the third pharyngeal pouch. Due to their origin, they often migrate further caudally than the superior parathyroid glands, sometimes even locating within the thymus which also develops from the third pouch. *1st* - The first pharyngeal pouch contributes to the formation of the eustachian tube, tympanic cavity, and mastoid air cells. - It has no role in the development of the parathyroid glands. *2nd* - The second pharyngeal pouch mainly gives rise to the palatine tonsils and their crypts. - It is not involved in the development of parathyroid tissue. *4th* - The fourth pharyngeal pouch gives rise to the superior parathyroid glands and the parafollicular cells (C cells) of the thyroid, which produce calcitonin. - While it forms parathyroid tissue, it is for the superior glands, not the inferior ones.
Question 1152: Coronary sinus develops from?
- A. Truncus arteriosus
- B. Conus
- C. Sinus venosus (Correct Answer)
- D. AV canal
Explanation: Sinus venosus - The sinus venosus is a primordial cardiac chamber that receives venous blood from the body and placenta in the early embryonic heart. - The left horn of the sinus venosus loses its connection with the systemic venous circulation and becomes the coronary sinus, which drains most of the cardiac veins into the right atrium [1, 4]. Truncus arteriosus - The truncus arteriosus is the embryonic precursor to the ascending aorta and pulmonary trunk. - It does not contribute to the development of the coronary sinus. Conus - The conus (or conus cordis) is the outflow portion of the primitive ventricle and differentiates into the outflow tracts of the right (infundibulum) and left (aortic vestibule) ventricles. - It is not involved in the formation of the coronary sinus. AV canal - The atrioventricular (AV) canal connects the primitive atrium and ventricle and is crucial for the formation of the AV valves and septation of the heart chambers. - It does not directly develop into the coronary sinus.
Question 1153: Kobelt tubercle is a remnant of which part of the Wolffian duct in females?
- A. Metanephros
- B. Entire Wolffian duct
- C. Mesonephros (Correct Answer)
- D. Pronephros
Explanation: ***Mesonephros*** - **Kobelt's tubercle** is a remnant of the **epoophoron**, which is derived from the **mesonephric (Wolffian) tubules** of the mesonephros [1] - In females, most of the mesonephric system degenerates, but remnants persist including the epoophoron (which contains Kobelt's tubercle) and **Gartner's duct** (from the main Wolffian duct) [1] - The **mesonephros** is the transient embryonic kidney whose tubular system gives rise to these vestigial structures [1] *Metanephros* - The **metanephros** develops independently to form the permanent kidney (nephrons, collecting system) - It is not part of the Wolffian duct system and is unrelated to Kobelt's tubercle formation - The ureteric bud (from metanephric diverticulum) induces metanephric development *Entire Wolffian duct* - Kobelt's tubercle specifically arises from the **mesonephric tubules** (lateral to the main duct), not from the entire Wolffian duct itself [1] - The main **Wolffian duct** remnant in females is **Gartner's duct**, which runs along the lateral vaginal wall - These are distinct embryological structures from the same mesonephric system *Pronephros* - The **pronephros** is the earliest, most primitive kidney that appears briefly in early embryonic life and completely degenerates - It does not contribute to the Wolffian duct system or any permanent structures in humans - Kobelt's tubercle has no relationship to pronephric structures
Question 1154: Which of the following is a derivative of the mesonephric tubules in males?
- A. Paradidymis (Correct Answer)
- B. Paroophoron
- C. Epoophoron
- D. Gartner duct
Explanation: ***Paradidymis*** - The paradidymis is an **embryological remnant** derived from the mesonephric tubules in males. - It is typically a small, vestigial structure found near the **epididymis**. *Epoophoron* - The epoophoron is a remnant of the **mesonephric tubules in females**, located in the broad ligament. - It is not found in males and is homologous to the paradidymis. *Paroophoron* - The paroophoron is also a vestigial remnant of the **mesonephric tubules in females**, located more medially than the epoophoron. - Like the epoophoron, it is a female-specific structure. *Gartner duct* - The Gartner duct is an embryological remnant derived from the **mesonephric duct in females**, running along the lateral wall of the vagina. - It is not derived from mesonephric tubules and is not present in males.
Question 1155: Majority of bronchogenic lung cysts occur in which?
- A. Mediastinum (Correct Answer)
- B. Near the carina
- C. Peribronchial tissue
- D. Base of the lung
Explanation: ***Mediastinum*** - **Bronchogenic cysts** most commonly occur in the **mediastinum** (approximately 60-70% of cases), particularly in the **subcarinal** or **paratracheal** regions [1]. - These cysts develop from abnormal budding of the primitive foregut during embryonic development [1]. - The mediastinum is the most comprehensive answer, as cysts can occur in various mediastinal locations. *Near the carina* - The **subcarinal region** (near the carina) is indeed one of the most common specific sites for mediastinal bronchogenic cysts [1]. - However, this represents only one specific location within the mediastinum, whereas cysts also commonly occur in paratracheal, hilar, and other mediastinal regions. - "Mediastinum" is the more complete answer as it encompasses all these locations. *Peribronchial tissue* - While bronchogenic cysts are derived from bronchial tree anomalies, the term **peribronchial tissue** is too vague and not the standard anatomical classification used. - The majority are found in well-defined mediastinal compartments, not simply described as "peribronchial." *Base of the lung* - **Intrapulmonary bronchogenic cysts** account for only 30-40% of cases, making them less common than mediastinal cysts. - Intrapulmonary cysts may be mistaken for other lung pathologies like **pulmonary sequestration** or congenital cystic adenomatoid malformation.
Question 1156: What is the typical number of bones present at birth?
- A. 270 (Correct Answer)
- B. 206
- C. 250
- D. 350
Explanation: 270 - At birth, humans have approximately **270 bones**, many of which are composed of cartilage. - Over time, these **cartilaginous structures ossify** [1] and some bones fuse together. 206 - The adult human skeleton typically consists of **206 bones** [2] after most of the fusion processes are complete. - This number is achieved as many of the smaller bones and cartilage structures present at birth **fuse** to form larger, single bones. 250 - This number is **lower** than the typical number of bones at birth and **higher** than the adult number, making it an inaccurate estimate for either stage. - It does not represent a specific developmental stage of the human skeleton. 350 - While newborns do have a higher number of individual bony elements and cartilaginous precursors, **350 is generally considered too high** for the typical number of distinct bones at birth. - The average is closer to 270, with some individual variation.
Question 1157: Uterus is derived from which structure?
- A. Wolffian duct
- B. Urogenital sinus
- C. Müllerian duct (Correct Answer)
- D. Mesonephric tubule
Explanation: ***Müllerian duct*** - In females, the **Müllerian ducts** (paramesonephric ducts) develop into the **uterus**, fallopian tubes, and the upper part of the vagina [1]. - This development occurs in the absence of **anti-Müllerian hormone (AMH)**. *Wolffian duct* - The **Wolffian ducts** (mesonephric ducts) are precursors to male internal reproductive organs such as the epididymis, vas deferens, and seminal vesicles. - In females, these ducts typically regress due to the absence of **testosterone**. *Urogenital sinus* - The **urogenital sinus** gives rise to the bladder, urethra, and in females, the lower part of the vagina and vestibule [1]. - It does not contribute to the formation of the uterus itself. *Mesonephric tubule* - **Mesonephric tubules** are part of the mesonephros, an embryonic kidney that mostly degenerates. - A few tubules persist as part of the male reproductive tract (e.g., efferent ductules) but do not form the uterus [2].
Question 1158: Cleft palate is associated with disturbances in the development of the palatine shelves during which gestational weeks?
- A. 6 to 8 weeks of intrauterine life
- B. 8 to 10 weeks of intrauterine life (Correct Answer)
- C. 10 to 12 weeks of intrauterine life
- D. 4 to 6 weeks of intrauterine life
Explanation: ***8 to 10 weeks of intrauterine life*** - The **palatine shelves** elevate (around 7-8 weeks) and fuse during **8-10 weeks** to form the secondary palate. - This is the **critical period** for secondary palate formation, and disturbances during this time lead to **cleft palate**. - Failure of the palatine shelves to fuse properly results in cleft of the secondary palate. *6 to 8 weeks of intrauterine life* - During this period, the palatine shelves are **developing and beginning to elevate** in preparation for fusion. - However, the actual **fusion** (whose failure causes cleft palate) occurs primarily in the 8-10 week period. *4 to 6 weeks of intrauterine life* - This period is associated with the development of the **primary palate** (from the median palatine process). - Disturbances during this stage are more commonly linked to **cleft lip** and anterior cleft palate. *10 to 12 weeks of intrauterine life* - By this stage, the palatine shelves have typically **completed fusion**. - This period involves final maturation and ossification rather than the initial fusion process. - Major structural anomalies like **cleft palate** would have already occurred during the 8-10 week fusion period.
Question 1159: Branchial arches give rise to various structures in the head and neck region. From which arch does the maxillary artery develop?
- A. 3rd arch
- B. 4th arch
- C. 1st arch (Correct Answer)
- D. 5th arch
Explanation: ***Correct Option: 1st arch*** - The **maxillary artery** develops from the **first pharyngeal arch artery** (mandibular arch). - The first arch artery is the arterial component of the mandibular arch and gives rise to the **maxillary artery**, which supplies the maxillofacial region. - This is consistent with the first arch's role in forming structures of the **maxilla and mandible**. *Incorrect Option: 3rd arch* - The third arch artery contributes to the **common carotid artery** and the **internal carotid artery**. - It is not involved in the formation of the maxillary artery. *Incorrect Option: 4th arch* - The fourth arch artery forms part of the **aortic arch** on the left and the **subclavian artery** on the right. - Its contributions are primarily to the systemic great vessels, not the maxillofacial vasculature. *Incorrect Option: 5th arch* - The fifth pharyngeal arch is often **rudimentary** or **absent** in humans, and when present, it regresses entirely. - It does not contribute to any significant adult arterial structures.
Question 1160: What is the classification of a urachus fistula?
- A. Patent allantois (Correct Answer)
- B. Ectopic hernia
- C. Patent vitello-intestinal tract
- D. Meckel's diverticulum
Explanation: ***Patent allantois*** - A **urachus fistula** represents a persistent, open connection between the **bladder** and the **umbilicus**, which is a direct remnant of a **patent allantois**. - The allantois normally obliterates to form the **median umbilical ligament**; failure to do so results in a fistula through which urine can drain from the umbilicus. *Ectopic hernia* - An **ectopic hernia** refers to the protrusion of an organ or tissue through an abnormal opening or site, and is not a classification specifically for a urachus fistula. - This term describes the location of the hernia rather than the underlying embryonic defect. *Patent vitello-intestinal tract* - A **patent vitello-intestinal tract** (or **omphalomesenteric duct**) is a persistent connection between the **ileum** and the **umbilicus**, which can lead to fecal discharge from the umbilicus [1]. - This is a distinct embryonic anomaly from a patent allantois, involving a different fetal structure [1]. *Meckel's diverticulum* - **Meckel's diverticulum** is a common congenital anomaly resulting from the incomplete obliteration of the **vitelline duct**, but it is typically a blind-ended pouch of the small intestine [1]. - It does not involve a connection to the umbilicus via a fistula that drains urine, distinguishing it from a urachus fistula.
Practice by Chapter
Gametogenesis and Fertilization
Practice Questions
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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