Developmental Anatomy

Developmental Anatomy Indian Medical PG Question 1: The incidence of congenital fetal anomalies is highest when a pregnancy is complicated by

• A. Hydramnios detectable on clinical examination
• B. Maternal diabetes (Correct Answer)
• C. Congenital heart disease of the mother
• D. Intrauterine growth retardation of the foetus

Developmental Anatomy Explanation: ***Maternal diabetes*** - **Poorly controlled maternal diabetes** significantly increases the risk of various congenital anomalies due to the teratogenic effects of hyperglycemia. - This includes defects like **sacral agenesis**, cardiovascular malformations, neural tube defects, and renal anomalies. *Hydramnios detectable on clinical examination* - **Hydramnios (polyhydramnios)**, an excess of amniotic fluid, is often associated with fetal anomalies, particularly those affecting swallowing (e.g., esophageal atresia) or urination. - However, it is a *marker* or *consequence* of a potential anomaly, rather than the primary cause of the highest incidence of anomalies. *Congenital heart disease of the mother* - While maternal congenital heart disease can influence pregnancy outcomes and may have a genetic component, it does not, by itself, lead to the highest overall incidence of *fetal congenital anomalies* compared to uncontrolled diabetes. - The risk of congenital heart disease in the fetus of a mother with congenital heart disease is increased, but this is a specific risk, not a broad increase in all anomalies. *Intrauterine growth retardation of the foetus* - **Intrauterine growth restriction (IUGR)** is a condition where the fetus is smaller than expected for its gestational age and is a common complication in pregnancies with underlying issues. - IUGR can be *caused* by placental insufficiency, genetic disorders, or infections, some of which may also cause congenital anomalies, but IUGR itself is not the condition that directly leads to the highest incidence of congenital anomalies.

Developmental Anatomy Indian Medical PG Question 2: Phenotypic expression of a gene depending on the parent of origin is referred to as:

• A. Genomic imprinting (parent-of-origin gene expression) (Correct Answer)
• B. Mosaic genetic variation
• C. Nonpenetrance of genotype
• D. Genetic anticipation

Developmental Anatomy Explanation: ***Genomic imprinting (parent-of-origin gene expression)*** - **Genomic imprinting** is an epigenetic phenomenon where gene expression is dependent on whether the gene was inherited from the mother or the father. - This results in monoallelic expression of specific genes, with only one copy (maternal or paternal) being active. *Mosaic genetic variation* - **Mosaicism** refers to the presence of two or more populations of genetically different cells in one individual, all derived from a single zygote. - This typically arises from a somatic mutation during development, not from differential expression based on parental origin. *Nonpenetrance of genotype* - **Nonpenetrance** occurs when individuals carrying a disease-causing genotype do not express the associated phenotype. - This concept relates to the presence or absence of a phenotype, not the differential expression based on parental origin. *Genetic anticipation* - **Genetic anticipation** is the phenomenon where the symptoms of a genetic disorder become more severe and/or appear at an earlier age in successive generations. - This is commonly observed in disorders caused by expansions of trinucleotide repeats, such as Huntington's disease, and is distinct from parent-of-origin gene expression.

Developmental Anatomy Indian Medical PG Question 3: Neural tube defects have which one of the following inheritance patterns ?

• A. Multi-factorial (Correct Answer)
• B. X-linked recessive
• C. Autosomal dominant
• D. Autosomal recessive

Developmental Anatomy Explanation: ***Multi-factorial*** - Neural tube defects (NTDs) are considered **multi-factorial**, meaning they result from a complex interaction between multiple genetic predispositions and environmental factors. - While there are genetic components, no single gene mutation typically explains the recurrence risk, and external factors like **folic acid deficiency** play a significant role. *X-linked recessive* - This inheritance pattern typically affects males more severely and exclusively, with females often being carriers, which is not the primary pattern observed in NTDs. - Conditions like **Duchenne muscular dystrophy** exhibit X-linked recessive inheritance. *Autosomal dominant* - A single copy of an altered gene on a non-sex chromosome is sufficient to cause the condition, resulting in a 50% chance of transmission to offspring, which does not match the observed inheritance pattern for NTDs. - Examples include **Huntington's disease** and **Marfan syndrome**. *Autosomal recessive* - Both copies of a gene on a non-sex chromosome must be altered for the condition to manifest, meaning parents are often carriers but unaffected, which isn't the primary inheritance pattern for NTDs. - Conditions like **cystic fibrosis** and **sickle cell anemia** follow autosomal recessive inheritance.

Developmental Anatomy Indian Medical PG Question 4: Anencephaly can be diagnosed by ultrasound (USG) at

• A. 20-24 weeks of gestation
• B. 24-28 weeks of gestation
• C. 10-12 weeks of gestation
• D. 14-18 weeks of gestation (Correct Answer)

Developmental Anatomy Explanation: ***14-18 weeks of gestation*** - **Anencephaly**, characterized by the absence of a major portion of the brain and skull, can be reliably diagnosed by **ultrasound (USG)** during this gestational period. - At this stage, the fetal head structures are sufficiently developed to clearly visualize the **absence of the cranium and cerebral hemispheres**. *10-12 weeks of gestation* - While some gross anomalies might be suspected, the developing fetal skull and brain are often **too small** for a definitive diagnosis of anencephaly. - The **ossification of the calvaria** (skull bones) is still incomplete, making it difficult to confidently identify its absence. *20-24 weeks of gestation* - Anencephaly would be clearly detectable by this stage, but it is **later than the optimal window** for early diagnosis and intervention, if desired. - Many screening programs aim for diagnosis before this period to allow for more options for parental decision-making. *24-28 weeks of gestation* - At this advanced stage, the diagnosis of anencephaly would be evident, but it represents a **significantly delayed diagnosis** given the availability of earlier screening methods. - The primary purpose of **antenatal screening** is to detect such severe congenital anomalies in the mid-trimester.

Developmental Anatomy Indian Medical PG Question 5: Match List-I with List-II and select the correct answer using the code given below the Lists:

• A. A→4 B→1 C→3 D→2
• B. A→2 B→1 C→3 D→4
• C. A→2 B→3 C→1 D→4 (Correct Answer)
• D. A→4 B→3 C→1 D→2

Developmental Anatomy Explanation: ***A→2 B→3 C→1 D→4*** - **Hand prolapse (A)** occurs when a fetal hand prolapses alongside the presenting part, leading to obstructed labor. If the fetus is dead and vaginal delivery is impossible due to severe obstruction, **Decapitation (2)** may be performed as a destructive procedure to facilitate delivery. - **Placental delivery (B)** is managed by the **Brandt-Andrews maneuver (3)**, which involves controlled cord traction with counter-pressure on the uterus to prevent uterine inversion and facilitate safe placental separation. - **Extended arms of breech at delivery (C)** occurs when the fetal arms are extended above the head during breech presentation. The **Lovset maneuver (1)** is specifically designed to deliver extended arms by rotating the fetus to bring the posterior arm down and anteriorly. - **Deep transverse arrest (D)** occurs when the fetal head arrests in the transverse diameter of the pelvis. **Forceps delivery or vacuum extraction (4)** can be used with manual or instrumental rotation to deliver the fetal head. *A→4 B→1 C→3 D→2* - This incorrectly matches hand prolapse with vacuum extraction, which cannot address the obstruction caused by a prolapsed hand. It also reverses the Brandt-Andrews maneuver and Lovset technique. *A→2 B→1 C→3 D→4* - This incorrectly matches placental delivery with Lovset technique (which is for breech) and extended arms with Brandt-Andrews maneuver (which is for placental delivery). *A→4 B→3 C→1 D→2* - This incorrectly matches hand prolapse with vacuum extraction and deep transverse arrest with decapitation. Decapitation is not indicated for deep transverse arrest, which can be managed with forceps or vacuum.

Developmental Anatomy Indian Medical PG Question 6: What maternal condition is commonly associated with congenital heart defects in the fetus?

• A. ACE inhibitor
• B. GDM
• C. Pregestational DM (Correct Answer)
• D. Valproate

Developmental Anatomy Explanation: ***Pregestational DM*** - **Pre-existing diabetes** in the mother is a significant risk factor for various **congenital anomalies**, including **congenital heart defects**, due to suboptimal glycemic control during early embryogenesis. - Poorly controlled **maternal hyperglycemia** leads to increased oxidative stress and altered cellular metabolism in the developing fetus, impacting cardiovascular development. *ACE inhibitor* - **ACE inhibitors** are teratogenic, primarily causing **renal dysfunction** (e.g., renal tubular dysplasia, oligohydramnios, anuria) and **fetal growth restriction**, especially when used in the second and third trimesters. - While they can have adverse fetal effects, their association with **congenital heart defects** is less pronounced compared to other teratogenic exposures. *GDM* - **Gestational diabetes mellitus (GDM)** typically develops in the second or third trimester when major organogenesis is complete, making its association with **structural congenital anomalies**, including heart defects, significantly lower than pregestational diabetes. - GDM is more commonly associated with fetal **macrosomia**, **hypoglycemia**, and respiratory distress syndrome at birth. *Valproate* - **Valproate** is a known teratogen associated with a specific pattern of anomalies, most notably **neural tube defects** (e.g., spina bifida), and facial dysmorphisms. - While it can be associated with an increased risk of some congenital heart defects, its primary and most significant fetal risk is **neural tube defects**.

Developmental Anatomy Indian Medical PG Question 7: 18 weeks pregnant female presents with no high risk of NTD and low risk of trisomy 21 on quad test. What is the most appropriate next step in management?

• A. Repeat non-invasive screening test.
• B. Perform invasive diagnostic testing.
• C. Perform amniotic fluid analysis.
• D. Perform a detailed fetal ultrasound. (Correct Answer)

Developmental Anatomy Explanation: ***Perform a detailed fetal ultrasound.*** - A **detailed fetal ultrasound** (often referred to as an **anatomy scan**) at around 18-22 weeks is a standard component of prenatal care for all pregnant women, regardless of screening test results. - This ultrasound evaluates fetal anatomy for structural anomalies, assesses fetal growth, and confirms gestational age, providing crucial information even with low-risk screening. *Repeat non-invasive screening test.* - Repeating a non-invasive screening test (like another quad screen or NIPT) is generally **not indicated** when initial results show a low risk and there are no other clinical concerns. - Such tests are primarily for screening purposes, and a second low-risk result would offer little additional actionable information, as their positive predictive value is low. *Perform invasive diagnostic testing.* - **Invasive diagnostic testing**, such as **amniocentesis** or **chorionic villus sampling (CVS)**, carries a risk of miscarriage and is reserved for situations with a high risk of chromosomal abnormalities or genetic conditions. - Given the low-risk quad screen results for trisomy 21 and no high risk for NTDs, invasive testing is **not warranted** at this stage. *Perform amniotic fluid analysis.* - **Amniotic fluid analysis** is part of an amniocentesis, an **invasive diagnostic procedure** designed to detect chromosomal abnormalities or genetic disorders. - This procedure is typically reserved for cases where screening tests indicate a high risk or there is a clinical suspicion of a genetic condition; it's **not a routine step** after a low-risk quad screen.

Developmental Anatomy Indian Medical PG Question 8: At what week of gestation do limb buds appear?

• A. Week 3
• B. Week 4 (Correct Answer)
• C. Week 6
• D. Week 9

Developmental Anatomy Explanation: ***Week 4*** - The **upper limb buds** appear at the beginning of the fourth week, followed shortly by the **lower limb buds**. - This marks the crucial initial stage of **limb development** as mesenchymal outgrowths from the ventrolateral body wall. *Week 3* - This is the period of **gastrulation** and early **neurulation**, where the three germ layers are established and the neural tube begins to form. - While significant developmental events occur, the formation of visible **limb buds** has not yet begun. *Week 6* - By week 6, the limb buds have not only appeared but have undergone considerable development, with **hand and foot plates** becoming distinct. - The upper and lower limbs are beginning to show more defined structures, including the appearance of **digital rays**. *Week 9* - By week 9, the limbs are well-developed, with all major segments and **digits clearly visible**. - This stage is characterized by ongoing **ossification** and refined anatomical structures.

Developmental Anatomy Indian Medical PG Question 9: What is the duration of embryogenesis in human development?

• A. From fertilization to the twelfth week
• B. From the second week to the eighth week
• C. From fertilization to the tenth week
• D. From fertilization to the eighth week (Correct Answer)

Developmental Anatomy Explanation: ***From fertilization to the eighth week*** - **Embryogenesis** is the period during which the major **organ systems develop** [1]. - This critical phase begins at **fertilization** and extends through approximately the **eighth week of gestation** [1]. - The eighth week marks the end of the embryonic period, after which the **fetal period** begins [2]. *From the second week to the eighth week* - This period correctly identifies the **end of embryogenesis** but incorrectly states the **beginning**. - The first week post-fertilization involves **cleavage, morula, and blastocyst formation**, which are essential initial steps of embryonic development. - Excluding the first week misses critical early embryonic events. *From fertilization to the tenth week* - This duration is **too long** for embryogenesis, as the **ninth week marks the beginning of the fetal period** [1], [2]. - The fetal period is characterized by **growth and maturation** of already formed organ systems rather than organogenesis [2]. *From fertilization to the twelfth week* - This period is also **too long** for embryogenesis, encompassing a significant portion of the **fetal period**. - By the twelfth week, most major structures are already established and are undergoing further **development and growth**, not organogenesis.

Developmental Anatomy Indian Medical PG Question 10: Which of the following is a derivative of ventral mesogastrium ?

• A. Lesser omentum (Correct Answer)
• B. Splenorenal ligament
• C. Greater omentum
• D. Gastrosplenic ligament

Developmental Anatomy Explanation: ***Lesser omentum*** - The **lesser omentum** is formed from the **ventral mesogastrium**, which connects the developing stomach to the anterior abdominal wall [1]. - It specifically derives from the part of the ventral mesogastrium that encloses the developing liver and extends to the lesser curvature of the stomach and the duodenum [1]. *Greater omentum* - The **greater omentum** develops from the **dorsal mesogastrium**, which means it is a derivative of the dorsal rather than the ventral mesentery [1]. - It arises from a rapid growth and fusion of the **dorsal mesogastrium**, hanging from the greater curvature of the stomach. *Splenorenal ligament* - The **splenorenal ligament** develops from the **dorsal mesogastrium**, specifically from the portion that connects the spleen to the posterior abdominal wall (near the kidney). - Its formation is a consequence of the rotation of the stomach and the development of the spleen within the dorsal mesentery. *Gastrosplenic ligament* - The **gastrosplenic ligament** is also derived from the **dorsal mesogastrium**, connecting the greater curvature of the stomach to the hilum of the spleen. - As the stomach rotates, the dorsal mesogastrium expands, eventually forming both the gastrosplenic and splenorenal ligaments.

Developmental Anatomy Flashcard 1 of 9

Question: Vaginal artery is homologous to the _____ artery in males

Answer: inferior vesical

Developmental Anatomy Flashcard 2 of 9

Question: Elbow joint centres fuse by the age of _____ years

Answer: 16

Developmental Anatomy Flashcard 3 of 9

Question: Which 2 processes fail to fuse in oblique facial cleft?_____

Answer: lateral nasal processes and maxillary process

Developmental Anatomy Flashcard 4 of 9

Question: Failure of the _____ to close in distal part results in a cleft of the iris known as coloboma iridis

Answer: choroid fissure

Developmental Anatomy Flashcard 5 of 9

Question: The sac of omphalocele is composed of an outer layer of _____ and an inner layer of peritoneum

Answer: amnion

Developmental Anatomy Flashcard 6 of 9

Question: In children, the spinal cord terminates at the _____ border of the L3 vertebra.

Answer: upper

Developmental Anatomy Flashcard 7 of 9

Question: Two types of bronchogenic cysts can be either _____ (10-15%) or mediastinal (65-90%)

Answer: pulmonary

Developmental Anatomy Flashcard 8 of 9

Question: Sutures ossify on the _____ surface before they ossify on the ectocranial surface (endo/ectocranial)

Answer: endocranial

Developmental Anatomy Flashcard 9 of 9

Question: The earliest tooth to erupt in secondary (permanent) dentition is a _____ molar.

Answer: first