Developmental Anatomy — MCQs

Developmental Anatomy Indian Medical PG Practice Questions and MCQs

Question 81: Most common type of VSD in Tetralogy of Fallot is

A. Muscular type
B. Inlet type
C. Outlet type
D. Perimembranous type (Correct Answer)

Explanation: ***Perimembranous type*** - The **perimembranous ventricular septal defect (VSD)** is the most common type encountered in Tetralogy of Fallot. - This defect is located adjacent to the **membranous septum**, often extending into the inlet, outlet, or muscular septum [1]. *Muscular type* - **Muscular VSDs** are located within the muscular portion of the ventricular septum [1]. - While present in some cases of Tetralogy of Fallot, they are significantly less common than perimembranous defects. *Inlet type* - **Inlet VSDs** are located posterior to the septal leaflet of the tricuspid valve, within the inlet septum [1]. - Although possible, they are not the most frequent type of VSD observed in Tetralogy of Fallot. *Outlet type* - **Outlet VSDs** are found beneath the semilunar valves, in the conal or outlet septum [1]. - While relevant to the outflow obstruction in Tetralogy of Fallot, the **perimembranous defect** is the predominant VSD morphology.

Question 82: What is the primary cause of omphalocele?

A. Failure of lateral body wall closure
B. Reversed rotation of intestinal loops
C. Duplication of intestinal loops
D. Failure of the gut to return to the abdominal cavity after physiological herniation (Correct Answer)

Explanation: ***Failure of the gut to return to the abdominal cavity after physiological herniation.*** - **Omphalocele** results from the **failure of the midgut to properly retract** into the abdominal cavity by the 10th week of gestation, leading to abdominal contents herniating through the umbilical ring. - The herniated organs are covered by a **peritoneal sac** formed by amnion and peritoneum. *Reversed rotation of intestinal loops* - This congenital anomaly involves the **malpositioning of the intestines** with the colon lying anterior to the superior mesenteric artery. - While a severe rotational anomaly can cause intestinal obstruction or volvulus, it is **not the primary cause of omphalocele**. *Failure of lateral body wall closure* - The **failure of the lateral body wall folds to fuse** in the midline during embryonic development is the primary cause of **gastroschisis** [1]. - In gastroschisis, the intestines are exposed to the amniotic fluid and **are not covered by a sac** [1]. *Duplication of intestinal loops* - **Intestinal duplications** are rare congenital malformations that can occur anywhere along the gastrointestinal tract. - They are typically **cystic or tubular structures** alongside the normal bowel, lined by alimentary mucosa, and are not directly related to omphalocele.

Question 83: Closure of coronal sutures starts at the age of:

A. 50-60 years
B. 30-35 years (Correct Answer)
C. 20 years
D. 25 years

Explanation: ***30-35 years*** - **Coronal suture closure** typically begins around the age of **30 years**, starting endocranially and progressing to the ectocranial surface. - The fusion usually initiates at the **pterion** (lateral aspect) and progresses medially, though patterns can vary. - This represents the normal timeline for **initiation** of coronal suture obliteration in the adult skull. *20 years* - At this age, the **sagittal suture** typically begins its closure process, not the coronal suture. - The coronal suture remains patent and open at 20 years in normal development. [1] - Premature closure at this age would indicate **craniosynostosis**, a pathological condition. *25 years* - The **lambdoid suture** begins closure around 26 years, making this closer but still earlier than coronal suture fusion. - The coronal suture typically remains largely unfused at this age. - This is still within the normal period where most cranial sutures remain patent. *50-60 years* - By this age, most major cranial sutures including the coronal are in **advanced stages** of obliteration or completely fused. - This represents the age of **complete obliteration**, not the initiation of closure. - The question specifically asks about when closure **starts**, not when it completes.

Question 84: What embryological failure leads to the formation of a double aortic arch?

A. Failure of neural crest cell migration
B. Abnormal development of the ductus arteriosus
C. Failure of the 6th aortic arch to develop
D. Failure of regression of the right dorsal aorta (Correct Answer)

Explanation: **Failure of regression of the right dorsal aorta** - A double aortic arch results from the **persistence of both right and left aortic arches** that encircle the trachea and esophagus, forming a vascular ring [1]. - In normal development, the **distal right dorsal aorta** (the segment between the right subclavian artery origin and the descending aorta) regresses, leaving only the left arch as the definitive aortic arch. - When this regression fails, both the right and left arches persist, creating a **complete vascular ring** around the trachea and esophagus, which can cause compression symptoms [1]. - This is one of the most common causes of a **symptomatic vascular ring** in infants [1]. *Failure of the 6th aortic arch to develop* - The 6th aortic arches contribute to the **pulmonary arteries** and the **ductus arteriosus**. Their failure to develop would lead to pulmonary circulation anomalies, not a double aortic arch. - This failure is associated with conditions like **pulmonary atresia** or **absent pulmonary artery**. *Abnormal development of the ductus arteriosus* - The ductus arteriosus is derived from the **distal part of the left 6th aortic arch**. Abnormal development typically leads to conditions like **patent ductus arteriosus (PDA)**. - This would not cause two complete aortic arches to persist around the trachea and esophagus. - While a right-sided ductus can be part of some vascular ring anomalies, it is not the primary cause of double aortic arch. *Failure of neural crest cell migration* - Neural crest cells are crucial for the **septation of the truncus arteriosus** and the formation of the aorticopulmonary septum. - Failure of neural crest cell migration is associated with conotruncal heart defects such as **Tetralogy of Fallot**, **Persistent truncus arteriosus**, or **Transposition of the Great Arteries**, not a double aortic arch. - Double aortic arch is primarily a failure of normal regression, not a neural crest cell defect.

Question 85: What is the MOST clinically significant anatomical difference between pediatric and adult airways?

A. Funnel-shaped vs cylindrical airway shape
B. Proportionally larger tongue
C. Larynx in higher position
D. Narrowest part is cricoid cartilage (Correct Answer)

Explanation: ***Narrowest part is cricoid cartilage*** - In **pediatric airways**, the **cricoid cartilage** is the narrowest point, making it the **most critical consideration** for endotracheal tube sizing and intubation. - This contrasts with adults where the **glottic opening** (vocal cords) is typically the narrowest. - This difference is **clinically crucial** as it determines tube selection, risk of subglottic stenosis, and why uncuffed tubes were traditionally preferred in children. *Proportionally larger tongue* - Pediatric patients indeed have a **proportionally larger tongue** relative to their oral cavity, which can contribute to airway obstruction [1]. - While this is a true anatomical difference, it is **less critical** for intubation decisions than the cricoid narrowing. *Funnel-shaped vs cylindrical airway shape* - Pediatric airways are **funnel-shaped** with narrowing at the cricoid, whereas adult airways are more **cylindrical**. - This morphological difference is a **consequence** of the cricoid being the narrowest point, not a separate primary consideration. *Larynx in higher position* - The **larynx** in infants and young children is positioned more **superiorly** (C3-C4 vs C4-C6 in adults). - While this affects intubation technique and angle, it is **less directly relevant** to airway sizing than the cricoid narrowing.

Question 86: How many fontanelles are present in a newborn child?

A. 1
B. 2
C. 3
D. 6 (Correct Answer)

Explanation: ***Correct Answer: 6*** - A newborn typically has **six fontanelles**: the **anterior** (bregma), **posterior** (lambda), two **sphenoidal** (anterolateral), and two **mastoid** (posterolateral) [1]. - These are fibrous membranes where the cranial bones meet, allowing for **brain growth** and flexibility of the skull during birth [1]. *Incorrect: 1* - This is incorrect as newborns have more than one fontanelle. - While the **anterior fontanelle** is the most prominent and commonly assessed, it is not the only one present [2]. *Incorrect: 2* - This is incorrect. While the anterior and posterior fontanelles are the most commonly discussed, there are additional, smaller fontanelles. - Focusing only on the **anterior** and **posterior fontanelles** overlooks the paired sphenoidal and mastoid fontanelles. *Incorrect: 3* - This is incorrect, as a newborn has a total of six fontanelles. - Three fontanelles account for less than the total number of fontanelles present at birth.

Question 87: Anterior fontanelle corresponds to all structures except which of the following?

A. Coronal suture
B. Sagittal suture
C. Frontal bones
D. Lambdoid suture (Correct Answer)

Explanation: ***Lambdoid suture*** - The **anterior fontanelle** is located at the intersection of the **coronal**, **sagittal**, and **metopic sutures** [1]. - It is bounded by the **frontal bones anteriorly** and the **parietal bones posteriorly** [1]. - The **lambdoid suture** is located at the posterior aspect of the skull, separating the parietal bones from the occipital bone, and corresponds to the **posterior fontanelle**, NOT the anterior fontanelle [1]. - This is the structure that does NOT correspond to the anterior fontanelle. *Frontal bones* - The **frontal bones** (or two halves of the frontal bone before fusion) form the anterior boundary of the anterior fontanelle [1]. - The anterior fontanelle is located where the frontal bones meet the parietal bones [1]. *Coronal suture* - The **coronal suture** forms part of the lateral boundaries of the anterior fontanelle, separating the frontal bone from the parietal bones [1]. - It runs transversely across the top of the skull on both sides. *Sagittal suture* - The **sagittal suture** runs through the middle of the anterior fontanelle, lying between the two parietal bones [1]. - It extends longitudinally along the midline from the anterior fontanelle posteriorly to the posterior fontanelle [1].

Question 88: The first primary ossification centre to appear of the carpal bones is

A. Capitate (Correct Answer)
B. Pisiform
C. Triquetral
D. Scaphoid

Explanation: The first primary ossification centre to appear of the carpal bones is ***Capitate*** - The **capitate** is the first carpal bone to show an ossification center, typically appearing around **1-3 months of age**. [1] - This early ossification is an important marker in assessing **bone age** in children. *Scaphoid* - The **scaphoid** ossifies later than the capitate, usually between **4 and 6 years of age**. - Its ossification center is often **bi-lobed** and can be confused with a fracture on X-ray if not recognized. *Triquetral* - The **triquetral** ossification center generally appears between **2 and 4 years of age**. - This makes it a mid-range ossifier among the carpal bones, not the first. *Pisiform* - The **pisiform** is typically the last carpal bone to ossify, with its center appearing between **8 and 12 years of age**. - Its delayed ossification makes it a useful indicator for assessing **skeletal maturity** in older children and adolescents.

Question 89: Which of the following is supplied by the abdominal aorta?

A. Bronchopulmonary segment
B. Accessory lung lobes
C. Sequestrated lung tissue (Correct Answer)
D. Base of lung

Explanation: Sequestrated lung tissue - Sequestrated lung tissue is lung tissue that lacks normal connection to the tracheobronchial tree and receives its blood supply from a systemic artery, most commonly a branch of the abdominal aorta or thoracic aorta. - This anomalous arterial supply from the abdominal aorta is a key defining feature of pulmonary sequestration, distinguishing it from normal lung tissue. Accessory lung lobes - Accessory lung lobes are anatomical variations where an additional lobe of lung tissue is present, but it typically has a normal bronchial connection and receives blood supply from the pulmonary arteries, not the systemic circulation. - These lobes develop from the normal foregut and share the same vascular supply as the rest of the lung. Bronchopulmonary segment - A bronchopulmonary segment is a functionally independent unit of the lung, defined by its own segmental bronchus and segmental artery, both derived from the main pulmonary artery and primary bronchi. - Its blood supply is invariably from the pulmonary circulation, not systemic arteries like the abdominal aorta. Base of lung - The base of the lung refers to the lower surface of the lung resting on the diaphragm, and its blood supply is primarily from the pulmonary arteries, which originate from the right ventricle of the heart. - Normal lung parenchyma, including the base, receives its functional blood supply from the pulmonary circulation [1].

Question 90: By what age is the metopic suture typically completely fused?

A. 2 years (Correct Answer)
B. 8 years
C. 4 years
D. 6 years

Explanation: ***2 years*** - The **metopic suture** typically begins to fuse shortly after birth and is usually completely **obliterated by 2 years of age**. - Complete fusion by this age results in a **single frontal bone**, a normal anatomical variation. *8 years* - This age is **too_late** for normal metopic suture fusion; persistence beyond 2-3 years is considered **metopism**. - Other cranial sutures, such as the sagittal or coronal, fuse much later, but not the metopic. *4 years* - While some variability exists, fusion of the metopic suture by 4 years would be considered **delayed** or a mild form of metopism. - The majority of individuals have complete fusion significantly earlier than this age. *6 years* - Fusion at 6 years would be an even **later** presentation of metopism, indicating a persistent metopic suture into childhood. - This is far beyond the typical age range for natural obliteration of this specific suture.

Practice by Chapter

Prenatal Development

Practice Questions

Postnatal Growth and Development

Practice Questions

Age-Related Anatomical Changes

Practice Questions

Developmental Abnormalities

Practice Questions

Principles of Teratology

Practice Questions

Developmental Basis of Congenital Anomalies

Practice Questions

Molecular Aspects of Development

Practice Questions

Genetic Factors in Developmental Anatomy

Practice Questions

Environmental Influences on Development

Practice Questions

Clinical Aspects of Developmental Anatomy

Practice Questions

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free