Embryology and Development Practice Questions

Q: Which of the following is NOT a recognized cause of pelvic kidneys?

p53 mutation. ***p53 mutation*** - A **p53 mutation** is not a direct or recognized cause of **pelvic kidneys**. This gene is primarily involved in **tumor suppression** and cellular responses to DNA damage. - While genetic factors can contribute to congenital anomalies, a **p53 mutation** is not specifically linked to renal ectopia. *Inability to ascend during fetal life* - This is a direct cause of **pelvic kidneys**, as the kidneys normally ascend from the pelvis to the lumbar region during fetal development. - Failure of this **normal ascent** results in the kidneys remaining in the pelvic cavity. *Fusion of the lower poles of the kidneys* - This condition is known as a **horseshoe kidney**, where the lower poles fuse, often preventing complete ascent and resulting in an **aberrant location**, sometimes within the pelvis. - The fused inferior pole can get **trapped** under the inferior mesenteric artery, preventing further ascent. *Obstruction by branches of the aorta* - The **renal arteries** originate from the aorta. If these branches or other major vessels obstruct the **upward migration** of the kidney, it can lead to failure of ascent and a **pelvic kidney**. - This physical obstruction prevents the kidney from reaching its normal **retroperitoneal position**.

Q: Optic vesicle is derived from:

Neuroectoderm. ***Neuroectoderm*** - The **optic vesicle** is an outgrowth of the **diencephalon**, which is a part of the neural tube. - The neural tube itself develops from the **neuroectoderm**, making the optic vesicle inherently neuroectodermal in origin [2]. *Endoderm* - The **endoderm** is the innermost germ layer and forms structures like the lining of the **gastrointestinal tract**, lungs, and other visceral organs. - It does not contribute to the formation of the eye or its optic structures. *Mesoderm* - The **mesoderm** forms tissues such as **muscle**, **bone**, **connective tissue**, and the circulatory system. - While it contributes to some parts of the eye, such as the choroid and sclera, the optic vesicle specifically originates from neuroectoderm. *Surface Ectoderm* - The **surface ectoderm** gives rise to structures like the **epidermis of the skin**, hair, nails, and the **lens of the eye**. [1] - While essential for eye development, it is distinct from the neuroectoderm that forms the optic vesicle.

Q: From which pharyngeal pouch do the palatine tonsillar crypts develop?

Second pharyngeal pouch. ***Second pharyngeal pouch*** - The **palatine tonsils** develop within the **tonsillar fossa**, which originates from the second pharyngeal pouch. - The epithelial lining of this pouch proliferates to form the **crypts** of the palatine tonsils. *First pharyngeal pouch* - The first pharyngeal pouch develops into the **middle ear cavity** and the **eustachian tube**. - It plays no direct role in the formation of lymphoid tissue or tonsillar structures. *Third pharyngeal pouch* - The third pharyngeal pouch gives rise to the **inferior parathyroid glands** and the **thymus** [1]. - These structures are endocrine and lymphoid organs but are distinct from the palatine tonsils. *Fourth pharyngeal pouch* - The fourth pharyngeal pouch develops into the **superior parathyroid glands** and the **ultimobranchial body**, which contributes **C cells** to the thyroid. - It is not involved in the development of the palatine tonsils or their crypts.

Q: Which of the following is NOT derived from the neural crest?

Retinal pigmented epithelium. ***Retinal pigmented epithelium*** - The **retinal pigmented epithelium** (RPE) differentiates from the **optic vesicle**, which is an outgrowth of the **forebrain neuroectoderm**, not from the neural crest. - Its cells are derived from the **outer layer of the optic cup** and play a crucial role in maintaining photoreceptor function. *Adrenal medulla* - The **adrenal medulla** is derived from a population of neural crest cells that migrate to the developing adrenal gland. - These cells differentiate into **chromaffin cells**, which secrete catecholamines like epinephrine and norepinephrine. *Pigment cell in skin* - **Melanocytes**, the pigment-producing cells in the skin, originate from neural crest cells that migrate into the epidermis. - These neural crest-derived cells are responsible for skin coloration and protection against UV radiation. *Schwann cells* - **Schwann cells**, which form the myelin sheath around peripheral nerves, are derived from the neural crest [1]. - They play a critical role in nerve impulse conduction and regeneration in the peripheral nervous system [1].

Q: All of the following are derived from the neural tube EXCEPT:

Dorsal root ganglia. ***Dorsal root ganglia*** - **Dorsal root ganglia** are derived from **neural crest cells**, not the neural tube. - Neural crest cells migrate from the neural tube, forming various structures including peripheral nervous system components. *Retina* - The **retina** develops as an outgrowth or diverticulum of the **diencephalon**, which is part of the neural tube [1]. - Therefore, the retina is considered a direct derivative of the neural tube [1]. *Brain* - The entire **brain** (forebrain, midbrain, and hindbrain) develops from the cranial end of the **neural tube**. - This neural tube differentiation is crucial for the formation of all central nervous system structures. *Pineal gland* - The **pineal gland** develops as an evagination from the dorsal part of the **diencephalon**, which is a region of the neural tube. - It maintains a connection with the brain and is a central nervous system structure.

Q: Female urethra develops from -

Urogenital sinus. ***Urogenital sinus*** - The **urogenital sinus** is an endodermal structure that gives rise to the bladder, urethra, and lower vagina in females [1]. - In females, the entire urethra develops from the **pelvic part of the urogenital sinus**. *Mesonephric duct* - The **mesonephric duct** (Wolffian duct) primarily contributes to the male genital tract, forming structures like the epididymis, vas deferens, and ejaculatory ducts. - In females, the mesonephric ducts largely regress but can contribute to vestigial structures like the **Gartner's duct**. *Ureteric bud* - The **ureteric bud** is an outgrowth of the mesonephric duct that develops into the ureter, renal pelvis, calyces, and collecting ducts of the kidney. - It plays no role in the direct formation of the urethra. *Metanephric blastema* - The **metanephric blastema** is a mesenchymal tissue that interacts with the ureteric bud to form the nephrons, including the renal corpuscle and renal tubules. - It is essential for kidney development but does not contribute to the formation of the urethra.

Q: Tongue muscles are derived from

Occipital myotome. Occipital myotome - The tongue muscles are innervated by the **hypoglossal nerve (CN XII)**, which is associated with the occipital somites. - During development, **occipital somites** migrate to the floor of the pharynx to form the intrinsic and extrinsic muscles of the tongue. *Lateral plate mesoderm* - The **lateral plate mesoderm** gives rise to structures like the lining of the body cavities, the serous membranes, and the smooth muscle and connective tissue of the gut wall, but not skeletal muscles of the tongue. - It also forms the **cardiac muscle** and most of the limb connective tissues. *Intermediate mesoderm* - The **intermediate mesoderm** differentiates into the urogenital system, including the kidneys, gonads, and their ducts. - It plays no direct role in the formation of skeletal muscles like those found in the tongue. *Cervical myotome* - **Cervical myotomes** contribute to the formation of muscles in the neck and diaphragm, such as the trapezius, sternocleidomastoid, and diaphragm muscles. - They do not contribute to the development of the tongue muscles, which are derived from more caudal somites.

Q: Facial nerve is the nerve of which of the following branchial arch?

Second arch. ***Second arch*** - The **facial nerve (cranial nerve VII)** innervates muscles derived from the second pharyngeal (branchial) arch, such as the muscles of **facial expression**, the stapedius, stylohyoid, and posterior belly of the digastric. - This arch is also associated with the development of the **stapes**, styloid process, lesser horn of the hyoid, and upper part of the body of the hyoid bone. *First arch* - The first arch is associated with the **trigeminal nerve (cranial nerve V)**, which innervates the muscles of **mastication** and provides sensation to the face. - Structures derived from the first arch include the malleus, incus, and the mandible. *Third arch* - The third arch's nerve is the **glossopharyngeal nerve (cranial nerve IX)**, which supplies the **stylopharyngeus muscle** and provides taste and general sensation to the posterior tongue. - This arch gives rise to the greater horn of the hyoid and the lower part of the body of the hyoid. *Fourth arch* - The fourth arch is innervated by the **superior laryngeal branch of the vagus nerve (cranial nerve X)**, which supplies most of the muscles of the larynx and pharynx. - Structures formed from the fourth arch include the thyroid cartilage, cricoid cartilage, and other laryngeal cartilages.

Q: Which of the following statements about the thymus is INCORRECT?

It is derived from the fourth pharyngeal pouch. The **thymus** is primarily derived from the **third pharyngeal pouch**, not the fourth. The fourth pharyngeal pouch contributes to the **superior parathyroid glands** and the ultimobrachial body (which gives rise to parafollicular C cells of the thyroid). *The cortical portion is mainly composed of lymphocytes* - The **thymic cortex** is densely packed with immature **T lymphocytes** (thymocytes) undergoing differentiation and selection [1], [2]. - These T cells are supported by **cortical epithelial cells** and macrophages [1]. *The medulla contains Hassall's Corpuscles* - **Hassall's corpuscles** (thymic corpuscles) are concentric layers of epithelial cells found in the **thymic medulla**. - Their exact function is debated, but they are thought to be involved in the maturation and selection of **regulatory T cells**. *It undergoes atrophy from puberty onwards* - The thymus reaches its maximum size around **puberty** and then gradually undergoes **involution** and **atrophy** throughout adulthood. - This process involves replacement of lymphoid tissue with **adipose tissue**, although it retains some residual function.

Q: How many days does it take for a zygote with zona pellucida to reach the uterine cavity after fertilization?

4 days. ***4 days*** - Following fertilization in the **ampulla** of the fallopian tube, the zygote undergoes cleavage divisions as it travels towards the uterus. - The **zona pellucida** remains intact during this journey, and the embryo (typically at the **morula** or early blastocyst stage) enters the uterine cavity around **Day 3-4** post-fertilization. - **Day 4** is the most commonly cited timeframe for entry into the uterine cavity with zona pellucida intact. *2 days* - At 2 days post-fertilization, the embryo is usually in the **2- to 4-cell stage** and is still located within the fallopian tube. - It has not yet completed its journey through the fallopian tube to reach the uterine cavity. *5 days* - By Day 5, the embryo has typically developed into a **blastocyst** and has already been in the uterine cavity for approximately 1-2 days. - This represents a later stage of development after the embryo has already reached the uterine cavity, not the initial arrival time. *6 days* - On Day 6, the blastocyst is typically **hatching out of the zona pellucida** and beginning implantation into the endometrium. - The zona pellucida is no longer intact at this stage, and the embryo has already been in the uterine cavity for approximately 2 days.

Question 1

Which of the following is NOT a recognized cause of pelvic kidneys?

Accepted Answer

p53 mutation

Answer

Inability to ascend during fetal life

Answer

Fusion of the lower poles of the kidneys

Answer

Obstruction by branches of the aorta

Question 2

Optic vesicle is derived from:

Accepted Answer

Neuroectoderm

Answer

Endoderm

Answer

Mesoderm

Answer

Surface Ectoderm

Question 3

From which pharyngeal pouch do the palatine tonsillar crypts develop?

Accepted Answer

Second pharyngeal pouch

Answer

First pharyngeal pouch

Answer

Third pharyngeal pouch

Answer

Fourth pharyngeal pouch

Question 4

Which of the following is NOT derived from the neural crest?

Accepted Answer

Retinal pigmented epithelium

Answer

Schwann cells

Answer

Pigment cell in skin

Answer

Adrenal medulla

Question 5

All of the following are derived from the neural tube EXCEPT:

Accepted Answer

Dorsal root ganglia

Answer

Retina

Answer

Pineal gland

Answer

Brain

Question 6

Female urethra develops from -

Accepted Answer

Urogenital sinus

Answer

Mesonephric duct

Answer

Ureteric bud

Answer

Metanephric blastema

Question 7

Tongue muscles are derived from

Accepted Answer

Occipital myotome

Answer

Lateral plate mesoderm

Answer

Intermediate mesoderm

Answer

Cervical myotome

Question 8

Facial nerve is the nerve of which of the following branchial arch?

Accepted Answer

Second arch

Answer

First arch

Answer

Third arch

Answer

Fourth arch

Question 9

Which of the following statements about the thymus is INCORRECT?

Accepted Answer

It is derived from the fourth pharyngeal pouch

Answer

The cortical portion is mainly composed of lymphocytes

Answer

The medulla contains Hassall's Corpuscles

Answer

It undergoes atrophy from puberty onwards

Question 10

How many days does it take for a zygote with zona pellucida to reach the uterine cavity after fertilization?

Accepted Answer

4 days

Answer

2 days

Answer

5 days

Answer

6 days

Embryology and Development — MCQs

Embryology and Development — MCQs

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