Embryology and Development Practice Questions

Q: Which of the following marked structures would give rise to the heart?

D. ***D*** - Structure **D** indicates the region where the **cardiac prominence** or **heart bulge** is forming in this early embryo. - The heart is one of the earliest organs to develop and begin functioning during embryogenesis, appearing as a prominent bulge in the ventral region. *A* - Structure **A** points to the **cephalic region** or **head fold** of the embryo, which will develop into the brain and associated structures. - This region is primarily involved in the formation of the **nervous system** and sensory organs. *B* - Structure **B** indicates the **somites**, which are segmented blocks of mesoderm that form along the neural tube. - Somites give rise to the **vertebrae, ribs, skeletal muscles** of the trunk, and dermis of the skin, not the heart. *C* - Structure **C** points to the **developing brain** or neural tube in the head region of the embryo. - This structure is critical for the formation of the **central nervous system**.

Q: A young patient with absent thymus presents with tetany and hypoparathyroidism. Which of the following is a marked area in the picture defective in this condition?

C. ***C*** - The image shows the **pharyngeal arches and pouches** during embryonic development. **C** points to the **third pharyngeal pouch**, which gives rise to the **thymus** and inferior parathyroid glands. - A defect in the development of the third pharyngeal pouch would lead to an **absent or hypoplastic thymus** and **hypoparathyroidism**, causing symptoms like tetany due to hypocalcemia. This condition is known as **DiGeorge syndrome**. *A* - **A** points to the first pharyngeal pouch, which develops into the **auditory tube** and **tympanic cavity**. - Defects in the first pharyngeal pouch would primarily affect structures in the ear, not the thymus or parathyroid glands. *B* - **B** points to the fourth pharyngeal pouch, which gives rise to the **superior parathyroid glands** and the **ultimobranchial body** (parafollicular C cells of the thyroid). - While hypoparathyroidism could be involved, the primary defect in DiGeorge syndrome affects the third pouch, leading to both thymic and parathyroid issues more comprehensively. *D* - **D** points to the first pharyngeal arch, which contributes to the formation of the **mandible**, **maxilla**, and several muscles of mastication. - Defects in the first pharyngeal arch are associated with conditions like **Treacher Collins syndrome** or **Pierre Robin sequence**, which present with facial dysmorphism rather than thymic or parathyroid agenesis.

Q: Nucleus pulposus develops from: (AIIMS May 2018)

C. ***Correct Option C*** - Label C points to the **notochord**, which is the embryonic structure that the **nucleus pulposus** of the intervertebral discs develops from. - The notochord provides transient axial support during early embryonic development and induces the formation of the neural tube. - During development, most of the notochord degenerates, but remnants persist as the gelatinous core of intervertebral discs. *Incorrect Option A* - Label A indicates the **neural tube**, which develops into the **brain and spinal cord**. - It arises from the neural plate, which is induced by the underlying notochord. - The neural tube does not contribute to the intervertebral disc structure. *Incorrect Option B* - Label B represents the **secondary yolk sac**, a structure involved in early nutrient transfer and the formation of primordial germ cells. - It does not directly contribute to the formation of musculoskeletal structures like the nucleus pulposus. *Incorrect Option D* - Label D points to the **ectoderm**, the outermost germ layer, which gives rise to the epidermis, nervous system (including the neural tube), and sensory organs. - While it forms the neural tube, it does not directly form the nucleus pulposus or other mesodermal derivatives.

Q: For the formation of the shown monozygotic twins, division should take place by

>14 days. ***>14 days*** - The image shows **conjoined twins**, which results from an incomplete separation of a single zygote. - This very late and incomplete division occurs when the zygote splits after **more than 14 days** post-fertilization, after the formation of the embryonic disc. *<3 days* - Division within the first three days results in **dichorionic-diamniotic twins**, meaning each twin has its own chorion and amnion. - This scenario would show **two separate placentas** and two distinct amniotic sacs. *4-8 days* - Division between 4 and 8 days typically leads to **monochorionic-diamniotic twins**, where twins share a placenta but have separate amniotic sacs. - The image depicts a shared sac and an incomplete division of the embryo itself. *8-14 days* - Division between 8 and 14 days results in **monochorionic-monoamniotic twins**, where twins share both a placenta and an amniotic sac. - While sharing a sac, this period usually leads to two distinct, non-conjoined fetuses within that single sac.

Q: Which neural tube defect is shown here:

Anencephaly. ***Anencephaly*** - This image depicts a fetus with anencephaly, characterized by the **absence of a major portion of the brain, skull, and scalp**. - The distinctive features are the **exposed brain tissue** (represented by the light blue and white mass on the head) and the **lack of a developed skullcap** above the eyes. - **Neural tube defect** resulting from failure of the **rostral (anterior) neuropore to close** during weeks 3-4 of embryonic development. - Incompatible with life; most infants are stillborn or die shortly after birth. *Schizencephaly* - **NOT a neural tube defect** - this is a rare **neuronal migration disorder** characterized by abnormal clefts in the cerebral hemispheres. - Results from abnormal neuronal migration during brain development, not from neural tube closure failure. - Does not present with external cranial defects or absence of skull and brain tissue as seen in anencephaly. *Lissencephaly* - **NOT a neural tube defect** - this is a **neuronal migration disorder** characterized by absent or decreased gyri and sulci, giving a smooth brain appearance. - Results from defective neuronal migration during cortical development. - This is an internal structural defect without the obvious external cranial and brain tissue absence characteristic of anencephaly. *Cranioschisis* - Cranioschisis refers to a defect where the **cranium fails to close properly**. - While related to neural tube defects, the image specifically shows **complete absence of the forebrain and skull above the orbits** (anencephaly) rather than simply a skull closure defect with intact but exposed brain tissue.

Q: Name the neural tube defect shown here:

Cranioschisis. ***Cranioschisis*** - *Cranioschisis* refers to a **fissure or defect in the skull**, often associated with exposure of brain tissue. The image shows significant disruption of the cranial vault and exposed tissue, consistent with this condition. - This is a broad term that encompasses various degrees of skull non-closure, typically occurring in the **earlier stages of neural tube development**. *Anencephaly* - *Anencephaly* specifically involves the **absence of a major portion of the brain, skull, and scalp**, resulting from failed closure of the anterior neural tube. While there is a cranial defect, the image appears to show some disorganized brain tissue, not a complete absence. - The characteristic presentation of anencephaly is a **frog-like appearance** due to the exposed brain and absent vault, which is not fully depicted as such here. *Meningocele* - A *meningocele* is a neural tube defect where the **meninges protrude through a defect in the skull or spine**, forming a sac filled only with cerebrospinal fluid. There are no neural elements in the sac. - The image shows exposed neural tissue rather than a fluid-filled sac, making meningocele an unlikely diagnosis. *Iniencephaly* - *Iniencephaly* is a rare and severe neural tube defect characterized by **extreme retroflexion of the head**, a short neck, and often extensive spina bifida. - The image does not clearly demonstrate the characteristic retroflexion of the head or the severe neck anomalies associated with iniencephaly.

Q: The image shows:

Malformation of vitello-intestinal duct. ***Malformation of vitello-intestinal duct*** - The image depicts a **persistent vitelline (omphalomesenteric) duct** remnant, which can present as a patent duct, fistula, cyst, or fibrous band. The appearance here is consistent with an **umbilical polyp or remnant,** presenting as a red, moist lesion often mistaken for granuloma. - This malformation occurs when the **vitello-intestinal duct**, connecting the developing gut to the yolk sac, fails to involute completely. *Omphalocele* - An **omphalocele** involves herniation of abdominal contents (covered by a membrane) through the **umbilical ring**, while this image shows a solid, polyp-like structure. - The umbilical cord is typically attached to the apex of the sac in omphalocele, which is not what is seen here. *Gastroschisis* - **Gastroschisis** is characterized by uncovered abdominal organs protruding through an abdominal wall defect, usually to the **right of the umbilical cord**. - There is no protective membrane in gastroschisis, and the image shows a covered, distinct growth at the umbilicus, not an open abdominal defect with exposed viscera. *Necrotising enterocolitis* - **Necrotizing enterocolitis (NEC)** is an inflammatory condition of the neonatal intestine, leading to **ischemic necrosis**. - This image shows an external umbilical anomaly; internal intestinal pathology like NEC would present with abdominal distension, feeding intolerance, and bloody stools, not this umbilical lesion.

Q: A newborn presents with a mass in the sacrococcygeal region as shown in the image. Identify the condition:

Sacrococcygeal teratoma. ***Sacrococcygeal teratoma*** - The image clearly shows a **large, tumor-like mass** protruding from the sacral region of the newborn, which is characteristic of a sacrococcygeal teratoma. - These tumors arise from **pluripotent stem cells** in Hensen's node and present as external or internal masses at the base of the spine. *Spina bifida aperta* - **Spina bifida aperta** (e.g., myelomeningocele) involves the protrusion of meninges and/or neural tissue through a spinal defect, usually covered by a thin membrane or skin. - While it occurs in the same region, the mass in the image appears to be a **solid or cystic growth, consistent with a tumor**, rather than exposed neural elements or a meningeal sac. *Cranioschisis* - **Cranioschisis** is a severe form of neural tube defect where the skull bones fail to form, leaving the brain exposed. - This condition affects the **cranium and brain**, not the sacral region of the spine, and therefore does not match the image. *Anencephaly* - **Anencephaly** is a fatal neural tube defect characterized by the absence of a major portion of the brain, skull, and scalp. - Like cranioschisis, it is a **cranial defect** and would not present as a mass in the sacral region.

Q: A 28 -year-old male was found to have a condition shown in the image below. At which level is the fused part seen usually?

L4-L5 vertebral level. ***L4-L5 vertebral level (due to inferior mesenteric artery)*** - The image depicts a **horseshoe kidney**, a congenital condition where the lower poles of the kidneys are fused. - The fused portion, or **isthmus**, is typically located at the **L4-L5 vertebral level** because its ascent is blocked by the **inferior mesenteric artery**. *L1 - L2 vertebral level* - This level is usually where the **renal arteries** originate and corresponds to the normal position of the majority of the kidney mass, not typically the fused inferior pole. - The kidneys normally ascend during development to this level, but in a horseshoe kidney, the fusion prevents this full ascent. *T12 - L1 vertebral level* - This vertebral level is too high for the fused portion of a horseshoe kidney. - The kidneys initially develop in the pelvis and ascend; T12-L1 would be the upper extent of normal kidney position. *S1 - S2 vertebral level* - This level is too low for the fused portion of a horseshoe kidney, which typically is found in the lumbar region. - S1-S2 is more associated with pelvic structures, indicating the kidneys would have barely ascended at all.

Q: Identify the inheritance pattern shown below.

X linked recessive. ***X linked recessive*** - The pattern shows that mainly **males are affected**, and the trait skips generations (e.g., individual I-1 is unaffected, but his children are affected). - Affected fathers (like II-3) do not pass the trait to their sons, but their daughters are carriers and can pass it on to their sons (like IV-1). *Y linked recessive* - In Y-linked inheritance, only **males would be affected**, and all sons of an affected father would inherit the trait. - This pedigree shows unaffected fathers having affected sons, and not all sons of affected males are affected directly. *X linked dominant* - In X-linked dominant inheritance, affected fathers pass the trait to **all their daughters**, and at least one parent would be affected in each generation. - This pedigree shows skipping of generations and affected individuals being born to unaffected parents (e.g., II-3 and III-5). *Y linked dominant* - Y-linked inheritance, whether dominant or recessive, would only affect **males** and would be directly passed from father to all sons. - The pedigree shows unaffected parents having affected offspring (e.g., I-1 and I-2 produced II-3), which rules out Y-linked inheritance.

Question 1

Which of the following marked structures would give rise to the heart?

Accepted Answer

D

Answer

A

Answer

B

Answer

C

Question 2

A young patient with absent thymus presents with tetany and hypoparathyroidism. Which of the following is a marked area in the picture defective in this condition?

Accepted Answer

C

Answer

B

Answer

D

Answer

A

Question 3

Nucleus pulposus develops from: (AIIMS May 2018)

Accepted Answer

C

Answer

A

Answer

B

Answer

D

Question 4

For the formation of the shown monozygotic twins, division should take place by

Accepted Answer

>14 days

Answer

<3 days

Answer

4-8 days

Answer

8-14 days

Question 5

Which neural tube defect is shown here:

Accepted Answer

Anencephaly

Answer

Schizencephaly

Answer

Lissencephaly

Answer

Cranioschisis

Question 6

Name the neural tube defect shown here:

Accepted Answer

Cranioschisis

Answer

Anencephaly

Answer

Meningocele

Answer

Iniencephaly

Question 7

The image shows:

Accepted Answer

Malformation of vitello-intestinal duct

Answer

Omphalocele

Answer

Gastroschisis

Answer

Necrotising enterocolitis

Question 8

A newborn presents with a mass in the sacrococcygeal region as shown in the image. Identify the condition:

Accepted Answer

Sacrococcygeal teratoma

Answer

Spina bifida aperta

Answer

Cranioschisis

Answer

Anencephaly

Question 9

A 28 -year-old male was found to have a condition shown in the image below. At which level is the fused part seen usually?

Accepted Answer

L4-L5 vertebral level

Answer

L1-L2 vertebral level

Answer

T12-L1 vertebral level

Answer

S1-S2 vertebral level

Question 10

Identify the inheritance pattern shown below.

Accepted Answer

X linked recessive

Answer

Y linked recessive

Answer

X linked dominant

Answer

Y linked dominant

Embryology and Development — MCQs

Embryology and Development — MCQs

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