Embryology and Development — MCQs
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What is the embryological basis for the uterine anomaly shown in the images?
What stage of embryonic development is shown in the following image?
What is the most common type of ventricular septal defect?
Which of the following structures develop from the 6th pharyngeal arch artery on the left side?
The condition seen in the image results from failure of fusion of:
A patient presents cyst on the neck with anterior to the sternocleidomastoid at the junction of the upper and middle third of the muscle. This cyst is due to the persistence of which of the following embryological clefts?
The image shows a congenital cardiac defect. Abnormal development of which branch of aortic arch leads to this defect?
Which is correct sequence about the blood supply of the primitive gut?
Which is wrong about the image given below?
The condition shown below is due to ?
Embryology and Development Indian Medical PG Practice Questions and MCQs
Question 971: What is the embryological basis for the uterine anomaly shown in the images?
- A. Failure of fusion of metanephric duct
- B. Non-fusion of mesonephric duct
- C. Complete agenesis of Müllerian structures
- D. Non-fusion of paramesonephric ducts (Correct Answer)
Explanation: ***Non-fusion of paramesonephric ducts*** - The image shows a **uterus didelphys**, which is a complete duplication of the uterus and cervix. This anomaly occurs due to a complete failure of the two **paramesonephric (Müllerian) ducts** to fuse medially during embryogenesis. - The **paramesonephric ducts** are the embryological precursors to the fallopian tubes, uterus, cervix, and the upper one-third of the vagina. Their proper fusion is essential for forming a single uterine cavity. *Non-fusion of mesonephric duct* - The **mesonephric (Wolffian) ducts** are precursors to male internal genitalia (e.g., epididymis, ductus deferens, seminal vesicles) and largely regress in females. - Remnants of the mesonephric duct in females may form **Gartner's cysts**, but they do not contribute to the formation of the uterus. *Failure of fusion of metanephric duct* - The **metanephric duct**, or **ureteric bud**, is involved in the development of the urinary system, specifically the ureters, renal pelves, calyces, and collecting ducts of the kidneys. - This structure is entirely unrelated to the embryological development of the female reproductive tract. *Complete agenesis of Müllerian structures* - Complete agenesis of the **Müllerian structures** results in the congenital absence of the uterus, fallopian tubes, and upper vagina, a condition known as **Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome**. - The image clearly depicts the presence of uterine horns and a cervix, which contradicts a diagnosis of agenesis (complete absence).
Question 972: What stage of embryonic development is shown in the following image?
- A. Gastrula
- B. Morula
- C. Blastocyst (Correct Answer)
- D. Ova
Explanation: ***Blastocyst*** - The image shows a structure with a distinct fluid-filled cavity (the **blastocoel**, labeled X), an inner cell mass (**embryoblast**), and an outer cell layer (**trophoblast**), which are the defining features of a blastocyst. - This stage occurs around day 5 post-fertilization and is responsible for implantation into the **endometrium** of the uterine wall, which is depicted superior to the blastocyst in the illustration. *Morula* - A morula is a solid, compacted ball of 16-32 cells (**blastomeres**) that precedes the blastocyst stage; it does not have the large internal cavity shown in the image. - The morula forms around day 3-4 after fertilization, and it is the entry of fluid into the morula that transforms it into a blastocyst. *Ova* - An ovum (plural: ova) is a single, unfertilized female gamete (egg cell). - The image shows a multicellular embryo that is the result of fertilization and several rounds of cell division, not a single cell. *Gastrula* - Gastrulation is the process that follows the blastocyst stage, where the embryo organizes into three primary germ layers: **ectoderm**, **mesoderm**, and **endoderm**. - The structure shown is a pre-implantation embryo and has not yet undergone gastrulation, which is characterized by the formation of the **primitive streak**.
Question 973: What is the most common type of ventricular septal defect?
- A. Incomplete fusion of the septum
- B. Non-development of the perimembranous part of the septum
- C. Muscular defect
- D. Membranous defect (Correct Answer)
Explanation: ***Membranous defect***- This type of defect, also known as **perimembranous VSD**, is the most common form, accounting for approximately 70-80% of all ventricular septal defects [1].- It is located just below the aortic valve, involving the **proximal third** of the septum and is defined by its relationship to the fibrous trigones [1].*Muscular defect*- **Muscular VSDs** (or trabecular VSDs) are less common than membranous defects and can be found anywhere within the thick muscular portion of the septum.- These defects often have a higher rate of **spontaneous closure**, especially the small, multiple defects referred to as 'Swiss cheese' VSDs.*Non-development of the perimembranous part of the septum*- While the failure of complete septation of the **membranous portion** is the underlying embryological cause, the specific anatomical diagnosis defining the common VSD type is the *membranous defect*. - This phrasing is descriptive of the etiology but **membranous defect** identifies the most common resulting structure.*Incomplete fusion of the septum*- This is a generic description of the mechanism leading to VSD development (failure of the septal components to fuse correctly), but it does not specify the **most common anatomical location**.- The most critical and common fusion failure involves the development of the **membranous septum**, which results in the named *membranous defect*.
Question 974: Which of the following structures develop from the 6th pharyngeal arch artery on the left side?
- A. Arch of Aorta
- B. Subclavian artery
- C. Carotid arteries
- D. Ductus arteriosus (Correct Answer)
Explanation: ***Ductus arteriosus*** - The **ductus arteriosus** develops from the persistence of the distal portion of the **left 6th pharyngeal arch artery**. [2] - This structure is critical in fetal circulation, allowing blood to bypass the non-functional fetal lungs by shunting flow from the left pulmonary artery to the descending aorta. [1], [3] *Arch of Aorta* - The **arch of the aorta** mainly develops from the **aortic sac** and the distal part of the **left 4th pharyngeal arch artery**. - The 6th arch contributes only to the pulmonary system and the ductus shunt, not the primary aortic arch. *Carotid arteries* - Both the **common carotid arteries** and the **internal carotid arteries** are major derivatives of the **3rd pharyngeal arch arteries**. - The 3rd arch artery structure is completely separate from the 6th arch involvement in lung circulation development. *Subclavian artery* - The **left subclavian artery** arises largely from the **7th cervical intersegmental artery**, which is not part of the aortic arch system itself. - The **right subclavian artery** develops from the right 4th pharyngeal arch artery, the 7th intersegmental artery, and the right dorsal aorta.
Question 975: The condition seen in the image results from failure of fusion of:
- A. Lateral nasal prominence and mandibular prominence
- B. Lateral nasal prominence and maxillary prominence
- C. Medial nasal prominence and maxillary prominence (Correct Answer)
- D. Medial nasal prominence and mandibular prominence
Explanation: ***Medial nasal prominence and maxillary prominence*** - The upper lip is formed embryologically by the fusion of the two **medial nasal prominences** (which form the central philtrum) and the two **maxillary prominences** (which form the lateral parts of the upper lip). - Failure of these prominences to fuse results in a **cleft lip** (cheiloschisis), as depicted in the image, which can be unilateral or bilateral. *Lateral nasal prominence and maxillary prominence* - The fusion of the **lateral nasal prominence** and the **maxillary prominence** forms the side of the face and the nasolacrimal duct. - Failure of these structures to fuse results in an **oblique facial cleft**, a rare condition extending from the upper lip to the eye. *Lateral nasal prominence and mandibular prominence* - These two prominences do not fuse during facial development. The **lateral nasal prominence** forms the alae (wings) of the nose. - The **mandibular prominence** forms the lower jaw and the lower lip, which is anatomically separate from the nasal structures. *Medial nasal prominence and mandibular prominence* - The **medial nasal prominence** contributes to the upper lip and nose, while the **mandibular prominence** forms the lower lip and jaw. - These structures are located superior and inferior to the developing mouth, respectively, and do not fuse with each other.
Question 976: A patient presents cyst on the neck with anterior to the sternocleidomastoid at the junction of the upper and middle third of the muscle. This cyst is due to the persistence of which of the following embryological clefts?
- A. 1st cleft
- B. 2nd cleft (Correct Answer)
- C. 3rd cleft
- D. 4th cleft
Explanation: ***2nd cleft***- A cyst appearing anterior to the **sternocleidomastoid muscle (SCM)**, especially at the junction of the upper and middle third, is the classical presentation of a second branchial cleft cyst (BCC) [1].- Persistence of the **cervical sinus**, which is formed by the rapid growth of the second arch covering the 2nd, 3rd, and 4th clefts, results in the most common type of BCC (over 90%).*1st cleft*- First branchial cleft cysts are rare and typically manifest near the **external auditory canal**, the angle of the mandible, or within the parotid gland [1].- These defects are often associated with the structures of the first arch, such as the **facial nerve** or parotid gland parenchyma.*3rd cleft*- Cysts derived from the third cleft are uncommon and usually present lower in the neck, often close to or piercing the **thyrohyoid membrane**.- A third cleft fistula would course **posterior to the carotid arteries** and anterior to the vagus nerve before ending in the pyriform sinus.*4th cleft*- Remnants of the fourth cleft are extremely rare and typically involve a fistula that tracks inferiorly to the great vessels (e.g., the **aortic arch** on the left side).- Fourth arch defects are often associated with recurrent **thyroiditis** or infection originating from the pyriform sinus.
Question 977: The image shows a congenital cardiac defect. Abnormal development of which branch of aortic arch leads to this defect?
- A. Right 6th aortic arch
- B. Left 6th aortic arch (Correct Answer)
- C. Left 4th aortic arch
- D. Right 4th aortic arch
Explanation: ***Left 6th aortic arch*** - The **Ductus Arteriosus**, which shunts blood from the pulmonary artery to the aorta in fetal life, is embryologically derived from the distal portion of the **Left 6th Aortic Arch**. - **Patent Ductus Arteriosus (PDA)** is the failure of this fetal connection to close after birth. *Right 4th aortic arch* - The **Right 4th Aortic Arch** contributes to the formation of the proximal segment of the **Right Subclavian Artery**. - Defects in the right 4th arch are typically associated with vascular ring anomalies, such as an aberrant right subclavian artery. *Right 6th aortic arch* - The **Right 6th Aortic Arch** forms the proximal segment of the **Right Pulmonary Artery**. - The distal part of the right 6th arch normally involutes and disappears completely, unlike the persistence seen on the left side (PDA). *Left 4th aortic arch* - The **Left 4th Aortic Arch** forms the segment of the **Arch of the Aorta** located between the left common carotid and the left subclavian arteries. - This arch is primarily involved in forming the main aortic arch structure.
Question 978: Which is correct sequence about the blood supply of the primitive gut?
- A. Foregut= Celiac trunk, Midgut= Superior mesenteric artery, Hindgut= inferior mesenteric artery (Correct Answer)
- B. Foregut= Superior mesenteric artery, Midgut= Celiac trunk, Hindgut= inferior mesenteric artery
- C. Foregut= Celiac trunk, Midgut= Superior mesenteric artery, Hindgut= ileocolic artery
- D. Foregut= Celiac trunk, Midgut= Inferior mesenteric artery, Hindgut= inferior mesenteric artery
Explanation: ***Foregut= Celiac trunk, Midgut= Superior mesenteric artery, Hindgut= inferior mesenteric artery*** - The primitive gut is divided embryologically into three main sections: **foregut, midgut, and hindgut**, each supplied by a distinct major artery originating from the dorsal aorta [1]. - The **celiac trunk** supplies the derivatives of the foregut, the **superior mesenteric artery (SMA)** supplies the midgut derivatives, and the **inferior mesenteric artery (IMA)** supplies the hindgut derivatives [1]. *Foregut= Superior mesenteric artery, Midgut= Celiac trunk, Hindgut= inferior mesenteric artery* - This option incorrectly assigns the **superior mesenteric artery** to the foregut and the celiac trunk to the midgut. - The celiac trunk supplies the foregut, and the superior mesenteric artery supplies the midgut. *Foregut= Celiac trunk, Midgut= Superior mesenteric artery, Hindgut= ileocolic artery* - While the foregut and midgut associations are correct, the **ileocolic artery** is a branch of the superior mesenteric artery [1] and supplies only a portion of the midgut and hindgut transition, not the entire hindgut. - The main artery for the entire hindgut is the **inferior mesenteric artery** [1]. *Foregut= Celiac trunk, Midgut= Inferior mesenteric artery, Hindgut= inferior mesenteric artery* - This option correctly identifies the **celiac trunk** for the foregut but incorrectly assigns the **inferior mesenteric artery** to the midgut. - The **superior mesenteric artery** is the primary blood supply for the midgut.
Question 979: Which is wrong about the image given below?
- A. Foregut meets the stomodeum at bucco-pharyngeal membrane which ruptures at 4 weeks
- B. Hindgut meets the proctodeum which ruptures at 8th week
- C. Lining epithelium of gut is endodermal
- D. Dorsal mesentery degenerates (Correct Answer)
Explanation: ***Dorsal mesentery degenerates*** - The **dorsal mesentery** persists and develops into various mesenteries supporting the abdominal organs (e.g., mesentery proper, transverse mesocolon, sigmoid mesocolon). It does not degenerate. - The **ventral mesentery degenerates** in areas due to the rotation of the gut and fusion processes, but the dorsal mesentery generally remains. *Foregut meets the stomodeum at bucco-pharyngeal membrane which ruptures at 4 weeks* - The **buccopharyngeal membrane separates the foregut from the stomodeum** (primitive mouth). - This membrane normally **ruptures around the 4th week** of development to establish communication between the oral cavity and the foregut. *Hindgut meets the proctodeum which ruptures at 8th week* - The **hindgut meets the proctodeum** (primitive anal pit) at the **cloacal membrane**. - This **cloacal membrane ruptures around the 7th or 8th week** of development, forming the anal opening. *Lining epithelium of gut is endodermal* - The **endoderm is the primary germ layer** that forms the lining epithelium of the entire gastrointestinal tract. - This includes the epithelium of the esophagus, stomach, intestines, and associated glands.
Question 980: The condition shown below is due to ?
- A. Patent vitello-intestinal duct (Correct Answer)
- B. Patent urachus
- C. Patent allantois
- D. Midgut loop hernia
Explanation: ***Patent vitello-intestinal duct*** - The image shows a **patent vitello-intestinal duct** (also called patent omphalomesenteric duct or patent vitelline duct), which is a persistent connection between the **ileum** and the **umbilicus**. - This represents failure of the vitelline duct to obliterate during the 5th-9th week of embryonic development. - Clinically presents as **umbilical fistula** with discharge of intestinal contents, **umbilical polyp**, or **umbilical sinus**. - The persistent duct connects the intestine to the umbilicus, which is visible in the image. *Patent urachus* - A patent urachus is a persistent connection between the **bladder** and the **umbilicus**, resulting from failure of obliteration of the allantois. - Presents with **urine leakage** from the umbilicus, not intestinal contents. - This is a urological anomaly, not associated with intestinal connection to the umbilicus. *Patent allantois* - The allantois is an embryonic structure that normally becomes the **urachus** connecting bladder to umbilicus. - Patent allantois is essentially the same as **patent urachus**. - Would present with urinary discharge, not the intestinal connection shown in the image. *Midgut loop hernia* - Midgut loop herniation is a **normal physiological process** occurring at 6-10 weeks of gestation where midgut herniates into the umbilical cord and then returns. - Failure of this to reduce leads to **omphalocele** (herniation of abdominal contents covered by peritoneum and amnion). - This is different from a patent vitello-intestinal duct, which is a **tubular connection** between ileum and umbilicus, not a herniation of abdominal organs.
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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