Embryology and Development Practice Questions

Q: A child with fused carpal bones comes to your clinic. What is the gene associated with Hand-Foot-Genital Syndrome?

HOXA13. ***HOXA13 (Correct Answer)*** - Mutations in the **HOXA13** gene, a member of the HOX family of transcription factors, are responsible for **Hand-Foot-Genital Syndrome (HFGS)** - HFGS is an autosomal dominant disorder characterized by skeletal defects, including **fused carpal and tarsal bones** (as presented in this case), short digits, and genitourinary anomalies - The carpal fusion is a classic diagnostic feature of HOXA13 mutations *Incorrect: BCL6* - **BCL6** (B-cell lymphoma 6) is a transcriptional repressor primarily known for its role in regulating B-cell maturation and germinal center formation - Mutations or translocations involving BCL6 are implicated in **diffuse large B-cell lymphoma** and follicular lymphoma, not congenital skeletal abnormalities *Incorrect: FGFR* - **FGFR** (Fibroblast Growth Factor Receptor) genes are associated with skeletal dysplasias involving abnormal endochondral ossification - Mutations in FGFR genes cause conditions like **Achondroplasia** (FGFR3) or **craniosynostoses** (FGFR2), rather than the specific carpal-tarsal fusion pattern seen in HOXA13 defects *Incorrect: COL11* - **COL11A1** and **COL11A2** genes encode collagen type XI and are associated with **Stickler syndrome** and various collagenopathies - These conditions affect connective tissue broadly, causing features like myopia, hearing loss, and joint hypermobility, rather than the isolated carpal fusions characteristic of Hand-Foot-Genital Syndrome

Q: Which of the following structures develop from the 6th pharyngeal arch artery on the left side?

Ductus arteriosus. ***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.

Q: The condition seen in the image results from failure of fusion of:

Medial nasal prominence and maxillary prominence. ***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.

Q: If the division in the zygote occurs between 9-12 days after fertilization, which of the following twins is expected?

Monochorionic monoamniotic. ***Monochorionic monoamniotic*** - Division of the inner cell mass (ICM) occurring between **9 and 12 days** after fertilization results in a twin pregnancy where both fetuses share a single **chorion** and a single **amnion**.- This stage marks division after the amnion has formed (around day 8) but before complete differentiation, leading to high risks like **cord entanglement**. *Dichorionic diamniotic* - This pattern results from division occurring very early, typically within the first **3 days** (2-cell stage to morula stage).- Since separation happens before the differentiation of the trophoblast and inner cell mass, both the **chorion** and the **amnion** are separate. *Conjoint twins* - Conjoint twins (Siamese twins) occur when the separation is delayed beyond the **13th day** after fertilization.- The division is incomplete, as it occurs *after* the formation of the **embryonic disc**. *Monochorionic diamniotic* - This type of twinning arises from division occurring between **4 and 8 days** after fertilization, typically during the blastocyst stage.- It leads to the sharing of the **chorion** but the development of separate **amnions**.

Q: 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?

2nd cleft. ***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.

Q: During a clinical examination, a senior resident asks an intern to examine the umbilical cord. How many arteries and veins are normally present in a healthy umbilical cord?

1 vein and 2 arteries. ***1 vein and 2 arteries*** - The normal configuration of a healthy umbilical cord is three vessels: **two umbilical arteries** and **one umbilical vein**. - The **umbilical vein** transports oxygenated blood from the placenta to the fetus, whereas the **two umbilical arteries** carry deoxygenated blood and metabolic waste from the fetus back to the placenta. *1 artery and 2 veins* - This configuration is incorrect; normally, the right umbilical vein **atrophies** early in gestation, leaving only a single left umbilical vein. - A cord with two veins suggests a **developmental anomaly** and is not the standard finding. *1 artery and 1 vein* - This pattern is an anomaly known as a **Single Umbilical Artery (SUA)**, which is found in 0.5% to 1% of pregnancies. - SUA is clinically significant as it is associated with an increased risk of **congenital anomalies**, especially renal, cardiac, and chromosomal defects. *2 arteries and 2 veins* - This is an abnormal configuration; while two arteries are standard, the presence of two veins instead of one is due to the failure of the **right umbilical vein** to involute, which is typically a normal event. - The persistence of two veins is highly **atypical** and often requires specialized fetal surveillance.

Q: The image shows a congenital cardiac defect. Abnormal development of which branch of aortic arch leads to this defect?

Left 6th aortic arch. ***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.

Q: Which is wrong about the image given below?

Dorsal mesentery degenerates. ***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.

Q: The condition shown below is due to ?

Patent vitello-intestinal duct. ***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.

Question 1

A child with fused carpal bones comes to your clinic. What is the gene associated with Hand-Foot-Genital Syndrome?

Accepted Answer

HOXA13

Answer

BCL6

Answer

FGFR

Answer

COL11

Question 2

Which of the following structures develop from the 6th pharyngeal arch artery on the left side?

Accepted Answer

Ductus arteriosus

Answer

Arch of Aorta

Answer

Subclavian artery

Answer

Carotid arteries

Question 3

The condition seen in the image results from failure of fusion of:

Accepted Answer

Medial nasal prominence and maxillary prominence

Answer

Lateral nasal prominence and mandibular prominence

Answer

Lateral nasal prominence and maxillary prominence

Answer

Medial nasal prominence and mandibular prominence

Question 4

If the division in the zygote occurs between 9-12 days after fertilization, which of the following twins is expected?

Accepted Answer

Monochorionic monoamniotic

Answer

Dichorionic diamniotic

Answer

Monochorionic diamniotic

Answer

Conjoint twins

Question 5

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?

Accepted Answer

2nd cleft

Answer

1st cleft

Answer

3rd cleft

Answer

4th cleft

Question 6

During a clinical examination, a senior resident asks an intern to examine the umbilical cord. How many arteries and veins are normally present in a healthy umbilical cord?

Accepted Answer

1 vein and 2 arteries

Answer

1 artery and 1 vein

Answer

2 arteries and 2 veins

Answer

1 artery and 2 veins

Question 7

The image shows a congenital cardiac defect. Abnormal development of which branch of aortic arch leads to this defect?

Accepted Answer

Left 6th aortic arch

Answer

Right 6th aortic arch

Answer

Left 4th aortic arch

Answer

Right 4th aortic arch

Question 8

Which is correct sequence about the blood supply of the primitive gut?

Accepted Answer

Foregut= Celiac trunk, Midgut= Superior mesenteric artery, Hindgut= inferior mesenteric artery

Answer

Foregut= Superior mesenteric artery, Midgut= Celiac trunk, Hindgut= inferior mesenteric artery

Answer

Foregut= Celiac trunk, Midgut= Superior mesenteric artery, Hindgut= ileocolic artery

Answer

Foregut= Celiac trunk, Midgut= Inferior mesenteric artery, Hindgut= inferior mesenteric artery

Question 9

Which is wrong about the image given below?

Accepted Answer

Dorsal mesentery degenerates

Answer

Foregut meets the stomodeum at bucco-pharyngeal membrane which ruptures at 4 weeks

Answer

Hindgut meets the proctodeum which ruptures at 8th week

Answer

Lining epithelium of gut is endodermal

Question 10

The condition shown below is due to ?

Accepted Answer

Patent vitello-intestinal duct

Answer

Patent urachus

Answer

Patent allantois

Answer

Midgut loop hernia

Embryology and Development — MCQs

Embryology and Development — MCQs

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