Embryology and Development Practice Questions

Q: During intrauterine life, the development of which of the following glands occurs first?

Thyroid gland.. ***Thyroid gland*** - The **thyroid gland** is the first endocrine gland to develop in the human embryo, initiating around day 24 of gestation from a median endodermal invagination in the floor of the pharynx [1]. - Its early development and functional maturation are crucial for subsequent neural and somatic development; microscopic follicles first appear as lateral lobes develop, and hormone secretion begins in the third month [2]. *Parotid gland* - The **parotid gland** begins its development much later, specifically around the 6th week of gestation, as an ectodermal bud from the oral cavity. - Its growth and branching morphogenesis continue throughout the fetal period and even post-natally. *Submandibular gland* - The **submandibular gland** starts to develop around the 6th week of gestation, originating as an endodermal bud from the floor of the oral cavity. - Its formation occurs later than the thyroid, alongside or shortly after parotid gland development. *Sublingual gland* - The **sublingual gland** is the last major salivary gland to develop, beginning between the 8th and 12th weeks of gestation. - It arises from multiple small endodermal buds in the sublingual fold of the oral cavity.

Q: What does the presence of an ossification center in the talus indicate about the fetus?

The fetus is viable.. ***The fetus is viable.*** - The presence of an **ossification center in the talus** is a key indicator of **fetal viability and maturity**, often observable radiographically in medicolegal contexts. - This ossification typically appears around the **7th-8th month of gestation (28-32 weeks)**, suggesting the fetus has reached a stage of developmental maturity. - In forensic medicine, the presence of ossification centers is used to assess **fetal age and viability**. *The foetus is full term* - While a full-term fetus would have an ossified talus, the presence of **talus ossification itself does not confirm full term**, as it appears earlier in development. - Full term is usually considered after 37 weeks. For assessing term pregnancy, the **distal femoral epiphysis** (appearing around 36 weeks) is a more reliable marker. *The foetus was live born* - The presence of an ossification center is a marker of **developmental maturity**, not of whether the birth was live or still. - A fetus can have advanced ossification and still be stillborn, as **live birth** depends on many factors beyond skeletal maturation. *The foetus was still born* - As with live birth, **skeletal ossification** is a developmental milestone and does not determine whether a fetus was stillborn. - Stillbirth is defined by the death of a fetus before or during delivery, irrespective of its bone maturity.

Q: Facial muscles are derived from which pharyngeal arch?

2nd branchial arch. ***2nd branchial arch*** - The **facial muscles** (muscles of facial expression) are derived from the mesenchyme of the **second pharyngeal (branchial) arch**. - This arch is innervated by the **facial nerve (cranial nerve VII)**, which explains why the facial nerve controls these muscles. *1st branchial arch* - The first pharyngeal arch primarily forms the **muscles of mastication** (e.g., temporalis, masseter) and is innervated by the **trigeminal nerve (cranial nerve V)**. - It also contributes to the formation of the **mandible** and maxilla. *3rd branchial arch* - The third pharyngeal arch gives rise to the **stylopharyngeus muscle** and is innervated by the **glossopharyngeal nerve (cranial nerve IX)**. - It contributes to the formation of the **hyoid bone**. *4th branchial arch* - The fourth pharyngeal arch forms most of the **muscles of the pharynx and larynx** (except the stylopharyngeus), and is innervated by the **superior laryngeal branch of the vagus nerve (cranial nerve X)**. - This arch also contributes to the formation of the **thyroid cartilage**.

Q: Just before birth, which epiphysis appears?

Lower end of femur. ***Lower end of femur*** - The **distal femoral epiphysis** is one of the first epiphyses to ossify, appearing around **36 weeks of gestation** (9th month), making it consistently present just before birth [1]. - Its presence on antenatal imaging or X-ray at birth is a reliable indicator of **fetal maturity** and is used medico-legally to assess gestational age [1]. - This is a **classic anatomical landmark** frequently tested in medical examinations. *Upper end of humerus* - The epiphysis at the **proximal end of the humerus** typically appears between **birth and 6 months of age**. - This ossification center is primarily responsible for the growth in length of the upper arm. - It is **not present at birth** in most cases. *Lower end of fibula* - The **distal fibular epiphysis** usually appears much later, typically around **1-2 years of age**. - It contributes to the formation of the lateral malleolus of the ankle joint. - This is one of the **later-appearing** epiphyses. *Upper end of tibia* - The **proximal tibial epiphysis** ossifies around the **time of birth or shortly after**, usually appearing after the distal femur. - It forms the superior part of the tibia and contributes to the knee joint. - While close in timing, it is **not as reliably present** just before birth as the distal femoral epiphysis.

Q: The prostate gland is derived from?

Urogenital sinus. ***Urogenital sinus*** - The **prostate gland** develops from endodermal buds that arise from the **urethral epithelium** of the urogenital sinus during the third month of gestation. - These buds grow into the surrounding mesenchyme, which differentiates into the stromal and smooth muscle components of the prostate. *Urogenital folds* - The **urogenital folds** (or urethral folds) in males fuse to form the **spongy urethra** and the ventral aspect of the penis. - In females, these folds remain separate and form the labia minora. *Labioscrotal swelling* - The **labioscrotal swellings** in males fuse in the midline to form the **scrotum**. - In females, these swellings remain unfused and give rise to the labia majora. *Gubernaculum* - The **gubernaculum** is a mesenchymal cord that plays a crucial role in the **descent of the testes** into the scrotum. - It guides the migrating testis and anchors it to the scrotal floor.

Q: What does the umbilical vein become in adults?

Ligamentum teres. ***Ligamentum teres*** - The **umbilical vein** carries oxygenated blood from the placenta to the fetus [1] and after birth, it **obliterates** to form the **ligamentum teres hepatis** [2]. - This ligament is primarily found within the **falciform ligament** and runs from the umbilicus to the portal vein [1]. *Ligamentum venosum* - The **ductus venosus**, which shunts a portion of the umbilical vein's blood supply directly to the inferior vena cava, forms the **ligamentum venosum** after birth [2]. - This structure lies in a fissure on the **visceral surface of the liver**, posterior to the caudate lobe. *Medial umbilical ligament* - The **umbilical arteries**, which carry deoxygenated blood from the fetus to the placenta, become the **medial umbilical ligaments** in adults [2]. - These ligaments are located on the **anterior abdominal wall** and extend from the internal iliac arteries to the umbilicus. *Ligamentum arteriosum* - The **ductus arteriosus**, a fetal blood vessel connecting the pulmonary artery to the aorta, closes after birth to become the **ligamentum arteriosum** [2]. - This ligament connects the **aortic arch** to the **pulmonary artery** and is a remnant of fetal circulation.

Q: Cells from the neural crest are involved in all except?

Wilm's tumour. ***Wilm's tumour*** - **Wilms' tumor** (nephroblastoma) is a childhood kidney cancer that arises from immature kidney cells (metanephric blastema derived from **intermediate mesoderm**), NOT neural crest cells. - This is the correct answer as it is NOT derived from neural crest cells. *Hirschsprung's disease* - Hirschsprung's disease is caused by the failure of **neural crest cells** to migrate completely during development, leading to an absence of ganglion cells (enteric nervous system) in the distal colon [1]. - This results in a functional obstruction due to lack of peristalsis in the affected segment. *Neuroblastoma* - **Neuroblastoma** is a common extracranial solid tumor in children, arising from **neural crest cells** that form the sympathetic nervous system. - It often originates in the adrenal medulla or paraspinal sympathetic ganglia. *Primitive neuroectodermal tumour* - **Note:** The classification and origin of PNETs is complex and controversial. - While traditionally included in neural crest questions, **central PNETs** (like medulloblastoma) arise from the **cerebellar neuroepithelium**, NOT neural crest [2]. - **Peripheral PNETs** (Ewing sarcoma family) may have neural crest or mesodermal origin, which remains debated. - In the context of this question, this option is considered to have neural crest involvement for traditional examination purposes.

Q: At the end of the 5th week of gestation, how many somites can be seen?

44. ***44*** - By the end of the **5th week of gestation**, human embryos typically develop approximately **42 to 44 pairs of somites**. - Somites are **segmental blocks of mesoderm** that give rise to much of the axial skeleton, skeletal muscle, and dermis. *24* - The number **24** is too low for the end of the 5th week; this count is more representative of an earlier stage of somite formation, around the **mid-4th week**. - Somite development progresses rapidly, so a significantly higher number would be expected by week 5. *26* - The number **26** is also too low, corresponding to an earlier stage of development, typically observed during the **4th week of gestation**. - This count does not reflect the full extent of somite development by the end of the 5th week. *38* - While closer, **38** is generally an underestimation and typically represents somite numbers seen around the **middle to late 4th week**, not the very end of the 5th week when maximum somite pairs are usually formed. - The development of somites continues until the total number reaches 42-44 pairs.

Q: Which of the following is a derivative of the neural crest?

Adrenal medulla. Adrenal medulla - The adrenal medulla is derived from a specialized group of neural crest cells [2]. - These cells migrate and differentiate into chromaffin cells that produce and secrete catecholamines like epinephrine and norepinephrine [1], [3]. - This is a classic and primary example of neural crest derivatives commonly tested in examinations. Parafollicular cells of thyroid - Parafollicular C cells of the thyroid gland are also neural crest derivatives, originating from the ultimobranchial body. - They produce calcitonin for calcium regulation. - While correct, adrenal medulla is the more direct and commonly emphasized neural crest derivative in this context, making it the best answer when both appear as options. Adrenal cortex - The adrenal cortex develops from the intermediate mesoderm, NOT from neural crest [2]. - It produces steroid hormones (cortisol, aldosterone, androgens), distinguishing it embryologically and functionally from the neural crest-derived adrenal medulla [1], [3]. All of the options - This is incorrect because the adrenal cortex is derived from mesoderm, not neural crest [2]. - Only the adrenal medulla and parafollicular cells have neural crest origins.

Q: Which of the following is a primary growth site in the maxilla?

nasal septum. ***Nasal septum*** - The **nasal septum** is considered a primary growth site in the maxilla due to its **chondrocranium origin** and its role in influencing midfacial growth. - Its **growth cartilage** provides a forward and downward translatory force on the maxilla, contributing significantly to maxillary enlargement. *Maxillary tuberosity* - The **maxillary tuberosity** is a site of **surface apposition** (modeling), contributing to the posterior growth of the maxilla. - While it adds to maxillary length, it is not considered a primary growth center with intrinsic growth potential like cartilage. *Sutures* - **Sutures** are important for the **adaptive growth** of the maxilla, responding to forces from other growth sites. - They are considered **secondary growth sites** because they fill in bone as the maxilla is repositioned by primary growth centers, rather than initiating growth themselves. *All of the options* - This option is incorrect because while all mentioned structures contribute to maxillary development, only the **nasal septum** is classified as a **primary growth site** due to its intrinsic growth potential.

Question 1

During intrauterine life, the development of which of the following glands occurs first?

Accepted Answer

Thyroid gland.

Answer

Sublingual gland.

Answer

Parotid gland.

Answer

Submandibular gland.

Question 2

What does the presence of an ossification center in the talus indicate about the fetus?

Accepted Answer

The fetus is viable.

Answer

The foetus is full term

Answer

The foetus was live born

Answer

The foetus was still born

Question 3

Facial muscles are derived from which pharyngeal arch?

Accepted Answer

2nd branchial arch

Answer

3rd branchial arch

Answer

4th branchial arch

Answer

1st branchial arch

Question 4

Just before birth, which epiphysis appears?

Accepted Answer

Lower end of femur

Answer

Upper end of humerus

Answer

Lower end of fibula

Answer

Upper end of tibia

Question 5

The prostate gland is derived from?

Accepted Answer

Urogenital sinus

Answer

Urogenital folds

Answer

Labioscrotal swelling

Answer

Gubernaculum

Question 6

What does the umbilical vein become in adults?

Accepted Answer

Ligamentum teres

Answer

Ligamentum venosum

Answer

Medial umbilical ligament

Answer

Ligamentum arteriosum

Question 7

Cells from the neural crest are involved in all except?

Accepted Answer

Wilm's tumour

Answer

Hirschsprung's disease

Answer

Neuroblastoma

Answer

Primitive neuroectodermal tumour

Question 8

At the end of the 5th week of gestation, how many somites can be seen?

Accepted Answer

44

Answer

24

Answer

26

Answer

38

Question 9

Which of the following is a derivative of the neural crest?

Accepted Answer

Adrenal medulla

Answer

Para follicular cells of thyroid

Answer

Adrenal cortex

Answer

All of the options

Question 10

Which of the following is a primary growth site in the maxilla?

Accepted Answer

nasal septum

Answer

maxillary tuberosity

Answer

sutures

Answer

All of the options

Embryology and Development — MCQs

Embryology and Development — MCQs

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