A 3.8-kg boy born to a mother with poorly controlled diabetes is deeply cyanosed within hours of birth, and oxygen barely improves his saturation. Chest X-ray shows a narrow upper mediastinum giving an 'egg on a string' heart. Which developmental error explains this?

Failure of the aorticopulmonary septum to spiral

Anterosuperior displacement of the infundibular septum

Failure of the truncus to divide at all

Downward displacement of the tricuspid valve

A 4-month-old girl with 22q11.2 deletion syndrome, low CD3 counts and an interrupted aortic arch is scheduled for cardiac surgery, and the anaesthetist orders packed red cells. Which requirement for the cellular blood products is most important in this child?

Washing of the red cells in saline

Embryology: heart, gut and pharyngeal arches

16 NEET-PG practice questions on Embryology: heart, gut and pharyngeal arches, part of Anatomy. The first 16 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Medium
A 3.8-kg boy born to a mother with poorly controlled diabetes is deeply cyanosed within hours of birth, and oxygen barely improves his saturation. Chest X-ray shows a narrow upper mediastinum giving an 'egg on a string' heart. Which developmental error explains this?
1. AAnterosuperior displacement of the infundibular septum
2. BFailure of the truncus to divide at all
3. CFailure of the aorticopulmonary septum to spiral
4. DDownward displacement of the tricuspid valve
Show answerHide answer
Answer: C · Failure of the aorticopulmonary septum to spiral
Transposition of the great arteries results from the aorticopulmonary (conotruncal) septum growing straight instead of spiralling, so the aorta arises from the right ventricle and the pulmonary trunk from the left. The two circulations run in parallel, and survival depends on mixing through the foramen ovale, ductus arteriosus or a septal defect. It is the commonest cyanotic lesion presenting in the first days of life and is associated with maternal diabetes. Prostaglandin E1 keeps the duct open and balloon atrial septostomy improves mixing before the arterial switch operation.
- A: Infundibular septal displacement causes tetralogy of Fallot, which usually presents later.
- B: Complete failure of division gives persistent truncus arteriosus with a single outflow vessel.
- D: Downward displacement of the tricuspid valve is Ebstein anomaly, linked with maternal lithium.
Question 2 · Easy
A newborn in a Chennai hospital has downward-slanting palpebral fissures, notching of the lower eyelids, small cheekbones, a small lower jaw and malformed external ears. Hearing is reduced. Abnormal development of which pharyngeal arch mainly explains these findings?
1. ASecond arch
2. BFourth arch
3. CThird arch
4. DFirst arch
Show answerHide answer
Answer: D · First arch
This is Treacher Collins syndrome (mandibulofacial dysostosis), caused by defective migration or survival of neural crest cells in the first pharyngeal arch. The first arch forms the maxilla, zygoma, mandible, malleus and incus, so malar and mandibular hypoplasia with middle ear and external ear anomalies follow. Most cases involve the TCOF1 gene with autosomal dominant inheritance. The small jaw can obstruct the airway in the newborn.
- A: The second arch forms the stapes, styloid process and muscles of facial expression, not the jaw.
- B: The fourth arch forms laryngeal cartilages and pharyngeal constrictors, not facial bones.
- C: The third arch forms the greater horn and lower body of the hyoid and stylopharyngeus.
Question 3 · Hard
A 4-month-old girl with 22q11.2 deletion syndrome, low CD3 counts and an interrupted aortic arch is scheduled for cardiac surgery, and the anaesthetist orders packed red cells. Which requirement for the cellular blood products is most important in this child?
1. AIgA-deficient donor units
2. BGamma irradiation of the units
3. CWashing of the red cells in saline
4. DUnits less than 24 hours old
Show answerHide answer
Answer: B · Gamma irradiation of the units
Poor development of the third pharyngeal pouch, from which the thymus arises, leaves this child with thymic hypoplasia and a deficiency of T cells. Viable donor lymphocytes in transfused cellular products cannot be rejected and may engraft and attack her tissues, causing transfusion-associated graft-versus-host disease, which is usually fatal. Gamma or X-ray irradiation stops donor lymphocytes from dividing and prevents it, so it is required in severe T-cell deficiency. Leucodepletion lowers but does not reliably remove this risk.
- A: IgA-deficient units are needed only for patients with anti-IgA antibodies.
- C: Washing removes plasma proteins for allergic or IgA-deficient recipients but does not inactivate lymphocytes.
- D: Fresh units carry more viable lymphocytes and so do not protect against graft-versus-host disease.
Question 4 · Medium
An anomaly scan at 20 weeks shows bowel and part of the liver outside the fetal abdomen in a membrane-covered sac at the umbilicus, with the cord inserting into the sac. The couple is counselled about the defect. Consider these statements: 1. It results from failure of the midgut to return to the abdomen after physiological herniation. 2. The sac is formed of amnion and peritoneum. 3. It lies to the right of an intact umbilical cord. 4. Chromosomal anomalies are more frequent than in gastroschisis. Which statements are correct?
1. A1, 2 and 4 only
2. B2 and 4 only
3. C1, 2 and 3 only
4. D1 and 2 only
Show answerHide answer
Answer: A · 1, 2 and 4 only
Statements 1, 2 and 4 are correct. Omphalocele (exomphalos) results when herniated midgut, sometimes with liver, fails to return to the abdominal cavity; it is covered by amnion and peritoneum and the cord inserts into the sac. It is often associated with trisomies 13 and 18, Beckwith-Wiedemann syndrome and cardiac defects, so fetal karyotyping and echocardiography are offered. Statement 3 describes gastroschisis, a defect lateral (usually right) to an intact cord with uncovered bowel.
- B: Leaves out statement 1, the basic mechanism of omphalocele.
- C: Includes statement 3, which describes gastroschisis, not omphalocele.
- D: Leaves out the higher rate of chromosomal anomalies, which is why karyotyping is offered.
Question 5 · Medium
A 24-year-old man had a difficult tonsillectomy under general anaesthesia in a Kochi hospital. A week later he complains that the back of his tongue feels numb and food tastes odd there, while the front of the tongue is normal; his gag reflex is weak on the operated side. The mucosa of the affected part of the tongue develops mainly from which pharyngeal arch?
1. AFourth arch
2. BThird arch
3. CFirst arch
4. DSecond arch
Show answerHide answer
Answer: B · Third arch
The glossopharyngeal nerve runs close to the bed of the palatine tonsil and can be stretched or injured at tonsillectomy, causing loss of general sensation and taste over the posterior third of the tongue and a weak gag reflex. This nerve supplies the posterior third because that mucosa comes mainly from the third arch (the hypobranchial eminence overgrows the second arch). The anterior two-thirds come from the first arch, with general sensation from the lingual nerve (V3) and taste from the chorda tympani, a second arch nerve. The nerve supply of the adult tongue therefore maps its arch origin.
- A: The fourth arch forms only a small area near the epiglottis, supplied by the superior laryngeal nerve.
- C: The first arch forms the anterior two-thirds, which is normal in this patient.
- D: Second arch tissue is overgrown by the third arch and gives no lasting mucosa to the posterior third.
Question 6 · Medium
A preterm baby born at 30 weeks has bounding pulses, a wide pulse pressure and a continuous murmur below the left clavicle. His mother had a fever with a rash in the first trimester. The vessel that has failed to close in this baby develops from which embryonic artery?
1. ARight sixth pharyngeal arch artery
2. BThird pharyngeal arch artery
3. CLeft fourth pharyngeal arch artery
4. DLeft sixth pharyngeal arch artery
Answer and explanation in LearnFree account
Question 7 · Hard
A 5-year-old boy with conductive hearing loss is found to have a small, malformed middle ear ossicle chain on CT. While explaining the anatomy, the ENT resident lists the derivatives of the pharyngeal arch cartilages: 1. The stapes comes from the second arch cartilage. 2. The malleus and incus come from the first arch cartilage. 3. The thyroid cartilage comes from the second arch. 4. The greater horn of the hyoid comes from the third arch. Which statements are correct?
1. A1 and 4 only
2. B1, 2 and 4 only
3. C1 and 2 only
4. D1, 2 and 3 only
Answer and explanation in LearnFree account
Question 8 · Medium
A 6-day-old baby in a NICU starts having bilious vomiting and becomes irritable. An upper GI contrast study shows the duodenojejunal flexure lying to the right of the spine, with the proximal jejunum in the right abdomen. Which developmental error explains this finding?
1. AFailure of recanalisation of the second part of the duodenum
2. BFailure of neural crest cells to reach the distal colon
3. CPersistence of the vitellointestinal duct
4. DIncomplete rotation of the midgut around the superior mesenteric artery
Answer and explanation in LearnFree account
Question 9 · Easy
An 8-year-old girl has a painless, round swelling in the midline of the neck just below the hyoid bone. It moves upwards when she protrudes her tongue. This swelling arises from a remnant of which structure?
1. ASecond pharyngeal cleft
2. BCervical sinus of His
3. CThird pharyngeal pouch
4. DThyroglossal duct
Answer and explanation in LearnFree account
Question 10 · Medium
A term baby has not passed meconium by 52 hours and has a distended abdomen. On rectal examination there is an explosive gush of stool and gas. A suction rectal biopsy shows no ganglion cells in the submucosa and hypertrophied nerve trunks. What is the developmental basis of this condition?
1. AFailure of neural crest cells to migrate to the distal bowel
2. BIncomplete rotation of the hindgut loop
3. CFailure of recanalisation of the rectum
4. DAbnormal division of the cloaca by the urorectal septum
Answer and explanation in LearnFree account
Question 11 · Hard
A 54-year-old woman with a multinodular goitre has long-standing difficulty swallowing solids. Barium swallow shows an oblique posterior indentation of the oesophagus at the level of T3-T4, and CT shows the right subclavian artery arising as the last branch of the arch and passing behind the oesophagus. She is listed for total thyroidectomy. What should the surgeon expect on the right side?
1. AA right-sided arch of the aorta
2. BAbsence of the right inferior thyroid artery
3. CA recurrent nerve hooking around the ductus
4. DA non-recurrent inferior laryngeal nerve
Answer and explanation in LearnFree account
Question 12 · Medium
A 17-year-old boy has had a tiny opening low on the anterior border of the right sternocleidomastoid since birth, which discharges mucus. A fistulogram shows a tract running up between the internal and external carotid arteries. Where is the internal opening of this tract most likely to be?
1. APiriform fossa
2. BTonsillar fossa
3. CExternal acoustic meatus
4. DForamen caecum of the tongue
Answer and explanation in LearnFree account
Question 13 · Medium
An 11-year-old girl is referred from a school health camp in Kerala because a murmur was heard. She is active and acyanotic. A soft ejection murmur is heard in the pulmonary area, and the second sound stays widely split in both inspiration and expiration. ECG shows incomplete right bundle branch block with right axis deviation. Which developmental error most likely caused her defect?
1. AFailure of the two atrial septa to fuse after birth
2. BIncomplete closure of the interventricular foramen
3. CFailure of fusion of the endocardial cushions
4. DExcessive resorption of the septum primum
Answer and explanation in LearnFree account
Question 14 · Medium
A 19-year-old student is operated on for suspected appendicitis, but the appendix looks normal. The surgeon decides to search for a Meckel diverticulum before closing. Where should he look?
1. AMesenteric border of the terminal ileum, at the ileocaecal valve
2. BMesenteric border of the jejunum, near the duodenojejunal flexure
3. CAntimesenteric border of the ileum, within about 60 cm of the ileocaecal valve
4. DAntimesenteric border of the caecum, near the appendix base
Answer and explanation in LearnFree account
Question 15 · Medium
A 3-year-old boy from a village in Odisha has central cyanosis that worsens when he cries, and his mother says he squats after walking a short distance. There is a harsh ejection systolic murmur at the left upper sternal border, and the chest X-ray shows a boot-shaped heart with oligaemic lung fields. Which embryological error underlies his condition?
1. AAnterosuperior displacement of the infundibular septum
2. BFailure of the aorticopulmonary septum to spiral
3. CFailure of fusion of the endocardial cushions
4. DExcessive resorption of the septum primum
Answer and explanation in LearnFree account
Question 16 · Easy
A 2-year-old boy is brought to a Lucknow hospital with painless passage of a large amount of maroon blood per rectum. He is pale but otherwise well, and a technetium-99m pertechnetate scan shows a focus of uptake in the right lower abdomen. This lesion is a remnant of which embryonic structure?
1. AUrachus
2. BAllantois
3. CDuctus venosus
4. DVitellointestinal duct
Answer and explanation in LearnFree account

Embryology: heart, gut and pharyngeal arches

A 3.8-kg boy born to a mother with poorly controlled diabetes is deeply cyanosed within hours of birth, and oxygen barely improves his saturation. Chest X-ray shows a narrow upper mediastinum giving an 'egg on a string' heart. Which developmental error explains this?

A newborn in a Chennai hospital has downward-slanting palpebral fissures, notching of the lower eyelids, small cheekbones, a small lower jaw and malformed external ears. Hearing is reduced. Abnormal development of which pharyngeal arch mainly explains these findings?

A 4-month-old girl with 22q11.2 deletion syndrome, low CD3 counts and an interrupted aortic arch is scheduled for cardiac surgery, and the anaesthetist orders packed red cells. Which requirement for the cellular blood products is most important in this child?

A preterm baby born at 30 weeks has bounding pulses, a wide pulse pressure and a continuous murmur below the left clavicle. His mother had a fever with a rash in the first trimester. The vessel that has failed to close in this baby develops from which embryonic artery?

A 6-day-old baby in a NICU starts having bilious vomiting and becomes irritable. An upper GI contrast study shows the duodenojejunal flexure lying to the right of the spine, with the proximal jejunum in the right abdomen. Which developmental error explains this finding?

An 8-year-old girl has a painless, round swelling in the midline of the neck just below the hyoid bone. It moves upwards when she protrudes her tongue. This swelling arises from a remnant of which structure?

A term baby has not passed meconium by 52 hours and has a distended abdomen. On rectal examination there is an explosive gush of stool and gas. A suction rectal biopsy shows no ganglion cells in the submucosa and hypertrophied nerve trunks. What is the developmental basis of this condition?

A 17-year-old boy has had a tiny opening low on the anterior border of the right sternocleidomastoid since birth, which discharges mucus. A fistulogram shows a tract running up between the internal and external carotid arteries. Where is the internal opening of this tract most likely to be?

A 19-year-old student is operated on for suspected appendicitis, but the appendix looks normal. The surgeon decides to search for a Meckel diverticulum before closing. Where should he look?

A 2-year-old boy is brought to a Lucknow hospital with painless passage of a large amount of maroon blood per rectum. He is pale but otherwise well, and a technetium-99m pertechnetate scan shows a focus of uptake in the right lower abdomen. This lesion is a remnant of which embryonic structure?