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 Flashcard 1 of 5

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

Answer: inferior vesical

Developmental Anatomy Flashcard 2 of 5

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

Answer: 16

Developmental Anatomy Flashcard 3 of 5

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

Answer: lateral nasal processes and maxillary process

Developmental Anatomy Flashcard 4 of 5

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 5

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

Answer: amnion