Embryology and Development — MCQs

Embryology and Development Indian Medical PG Practice Questions and MCQs

Question 1031: Which of the following is a derivative of otic capsule?

A. Perilymphatic space
B. Bony labyrinth (Correct Answer)
C. Ossicles
D. Membranous labyrinth (inner ear structure)

Explanation: ***Bony labyrinth*** - The **otic capsule** is a cartilaginous structure that undergoes endochondral ossification to form the **bony labyrinth** of the inner ear. - This process is crucial for housing and protecting the delicate structures of the **membranous labyrinth** [2]. *Perilymphatic space* - The **perilymphatic space** is the fluid-filled area located between the bony labyrinth and the membranous labyrinth [3]. - It is not a derivative of the otic capsule itself, but rather a space defined by its presence. *Ossicles* - The **ossicles** (malleus, incus, stapes) are derived primarily from the **first and second pharyngeal arches**, not directly from the otic capsule [1]. - These bones are part of the middle ear, involved in sound amplification, while the otic capsule forms structures of the inner ear [3]. *Membranous labyrinth (inner ear structure)* - The **membranous labyrinth** is an epithelial derivative of the **otic placode**, which invaginates to form the otic vesicle [2]. - It contains the sensory organs for hearing and balance and is housed within, but not derived from, the otic capsule.

Question 1032: Space of Cloquet is phylogenetically related to

A. Iris
B. Central Retinal artery
C. Central retinal vein
D. Hyaloid artery (Correct Answer)

Explanation: ***Hyaloid artery*** - The **Space of Cloquet** (also known as the hyaloid canal or retrolental space of Cloquet) is the embryonic remnant of the **hyaloid artery**. - During fetal development, the hyaloid artery nourishes the developing lens and vitreous, and usually regresses completely before birth, leaving behind the empty canal. *Iris* - The iris is the colored part of the eye responsible for controlling pupil size and light entry, and its development is distinct from the hyaloid artery system. - While it plays a crucial role in the mature eye, it does not share a direct phylogenetic or developmental connection with Cloquet's space. *Central Retinal artery* - The central retinal artery supplies blood to the inner layers of the retina and is a branch of the ophthalmic artery. - It develops separately and has a different function than the hyaloid artery system, which is primarily involved in early ocular development. *Central retinal vein* - The central retinal vein drains blood from the retina and is also a distinct vascular structure separate from the hyaloid artery. - Its development and function are related to retinal blood outflow, not the regression of fetal vitreous structures.

Question 1033: Branchial cyst arises from which branchial cleft:

A. Second (Correct Answer)
B. Third
C. First
D. Fourth

Explanation: ***Second*** - **Branchial cysts** most commonly arise from the **incomplete obliteration of the second branchial cleft** (90-95% of all branchial cysts). - They typically present as a **smooth, mobile, non-tender mass** in the lateral neck, anterior to the sternocleidomastoid muscle [1]. - Most common presentation: a painless swelling in the **upper third of the neck** along the anterior border of SCM [1]. *Third* - Cysts arising from the **third branchial cleft** are very rare and typically present lower in the neck, often extending towards the **pyriform sinus**. - These are less common than second branchial cleft cysts and may be associated with **thyroid or parathyroid abnormalities**. *First* - Anomalies of the **first branchial cleft** are rare and typically manifest as cysts or sinuses close to the **external auditory canal** or angle of the mandible. - They are often associated with the **parotid gland** and facial nerve. *Fourth* - **Fourth branchial cleft anomalies** are also very rare and usually present as a sinus or fistula in the lower neck, often entering the **pyriform sinus** and associated with recurrent infections. - They have a distinct tract that can connect to the pharynx.

Question 1034: The following ocular structure is not derived from surface ectoderm –

A. Epithelium of lacrimal glands
B. Crystalline lens
C. Sclera (Correct Answer)
D. Corneal epithelium

Explanation: **Sclera** - The **sclera** develops from the **neural crest cells**, which differentiate into mesenchymal tissue around the optic cup, forming the fibrous coats of the eye [1]. - It is part of the **fibrous tunic** of the eye, along with the cornea, and provides structural support. *Epithelium of lacrimal glands* - The **epithelium of lacrimal glands** originates from the **surface ectoderm** through invaginations and subsequent differentiation. - These glands are responsible for producing the **watery component of tears**. *Crystalline lens* - The **crystalline lens** also develops from the **surface ectoderm**, specifically from the lens placode, which invaginates to form the lens vesicle. - It is crucial for **focusing light** onto the retina. *Corneal epithelium* - The **corneal epithelium** is derived from the **surface ectoderm** and forms the outermost layer of the cornea [1]. - It provides a **protective barrier** and helps maintain the smooth refractive surface of the cornea [1].

Question 1035: Acrosome cap of the sperm derived from ?

A. Golgi body (Correct Answer)
B. Nucleus
C. Mitochondria
D. Centriole

Explanation: Golgi body - During spermiogenesis, the Golgi apparatus in the spermatid migrates to the anterior pole of the cell and condenses to form the acrosomal vesicle [1]. - This vesicle then spreads over the anterior half of the nucleus to become the acrosome cap, which contains hydrolytic enzymes crucial for fertilization [1]. Nucleus - The nucleus contains the genetic material (DNA) of the sperm, but it does not directly form the acrosome cap [1]. - The nucleus is located posterior to the acrosome, and its primary function is to transmit paternal chromosomes. Mitochondria - Mitochondria are concentrated in the midpiece of the sperm, providing ATP for flagellar movement [1]. - They are essential for sperm motility but play no role in the formation of the acrosome cap. Centriole - The proximal and distal centrioles are located at the base of the nucleus and are involved in forming the axoneme (the core of the flagellum). - Centrioles are critical for sperm tail development and function, but not for acrosome formation.

Question 1036: All of the following develops from surface ectoderm except

A. Lens
B. Lacrimal gland
C. Epithelial lining of iris (Correct Answer)
D. Epithelial lining of conjunctiva

Explanation: Epithelial lining of iris (Correct Answer) - The epithelial lining of the iris develops from the neuroectoderm (specifically, the anterior extension of the optic cup), not the surface ectoderm. - This neuroectodermal origin differentiates it from other ocular structures that do arise from surface ectoderm. - Both layers of the iris epithelium (anterior and posterior pigmented layers) are derived from the two layers of the optic cup. [1] Lens (Incorrect) - The lens is a classic derivative of the surface ectoderm, forming as the lens placode invaginates after induction by the optic vesicle. - Its development is crucial for vision and is a key example of surface ectoderm differentiation in the head region. Lacrimal gland (Incorrect) - The lacrimal gland, responsible for tear production, develops from the surface ectoderm of the conjunctival sac. - It forms through a series of epithelial buds that invaginate into the surrounding mesenchyme. Epithelial lining of conjunctiva (Incorrect) - The epithelial lining of the conjunctiva, which covers the sclera and lines the eyelids, is derived from the surface ectoderm. [2] - This layer provides protection and lubrication to the eye.

Question 1037: Nasolabial cyst occurs at-

A. Union of nasal and maxillary process (Correct Answer)
B. Union of palatal process with maxillary
C. Union of nasal with palatal process
D. Union of two nasal processes

Explanation: ***Union of nasal and maxillary process*** - A nasolabial cyst (also known as a nasoalveolar cyst or Klestadt's cyst) is a **non-odontogenic cyst** believed to arise from remnants of the **nasolacrimal duct** at the junction of embryonic facial processes. - This specific location corresponds to the fusion of the **lateral nasal process** and the **maxillary process**, leading to a cyst in the soft tissue of the upper lip lateral to the ala of the nose. *Union of palatal process with maxillary* - Cysts arising from the fusion of the palatal process with the maxillary process typically result in **globulomaxillary cysts**, which are located between the maxillary lateral incisor and canine. - This embryological origin differs significantly from the location of a nasolabial cyst. *Nasal with palatal process* - This union is not a recognized embryonic facial fusion point that correlates with the formation of a specific cyst type like the nasolabial cyst. - Cysts related to the palate generally involve palatal processes or median palatal structures. *Union of two nasal processes* - The fusion of the medial nasal processes forms the **primary palate** and the premaxilla; cysts in this central region are often **median palatal cysts** or **nasopalatine duct cysts**. - This location is distinct from the lateral soft tissue location of a nasolabial cyst.

Question 1038: The hydatid of Morgagni is a cystic remnant of

A. Cervix
B. Fallopian tube (Correct Answer)
C. Ovary
D. Uterus

Explanation: ***Fallopian tube*** - The **hydatid of Morgagni** (also called **appendix vesiculosa**) is a small cystic structure found on the **fimbriated end of the fallopian tube** in females [1]. - It represents an embryonic remnant of the **paramesonephric (Müllerian) duct** [1]. - These cysts are typically **asymptomatic** unless they undergo **torsion**, which can cause acute pelvic pain. - The term "hydatid of Morgagni" can also refer to the **appendix testis** in males, which is also a Müllerian duct remnant. *Cervix* - The cervix is the lower part of the uterus and develops from the **paramesonephric duct**, but the hydatid of Morgagni specifically refers to the fimbrial cyst, not cervical structures. - **Nabothian cysts** can occur in the cervix but are **retention cysts** from blocked cervical glands, not embryonic remnants. *Ovary* - Ovaries develop from the **gonadal ridge** and can have various cysts (**follicular, corpus luteum**), but these are functional or neoplastic, not embryonic duct remnants [2]. - The hydatid of Morgagni is specifically an **adnexal structure** associated with the fallopian tube, not the ovary itself. *Uterus* - The uterine body develops from fusion of the **paramesonephric ducts**, but the hydatid of Morgagni is specifically located at the **fimbriated end of the fallopian tube** [3]. - Uterine pathologies include **leiomyomas** and **endometrial polyps**, which are unrelated to the hydatid of Morgagni.

Question 1039: SRY gene is located on -

A. Long arm of X chromosome
B. Short arm of X chromosome
C. Long arm of Y chromosome
D. Short arm of Y chromosome (Correct Answer)

Explanation: ***Short arm of Y chromosome*** - The **SRY gene** (Sex-determining Region Y gene) is located on the **short arm of the Y chromosome** at position Yp11.3. - This gene is crucial for initiating **male sexual development** by triggering the differentiation of the gonads into testes. *Long arm of X chromosome* - The **X chromosome** is generally much larger than the Y chromosome and carries many genes crucial for both sexes. - Genes on the **long arm of the X chromosome** are involved in various functions but not primary sex determination in males. *Short arm of X chromosome* - The **short arm of the X chromosome** contains genes fundamental for development, like SHOX, but not the SRY gene. - The SRY gene's presence on the Y chromosome is what defines biological male sex. *Long arm of Y chromosome* - The **long arm of the Y chromosome** (Yq) contains genes involved in **spermatogenesis** and other male-specific functions. - However, the SRY gene, which is responsible for the initial male sex determination, is not located on the long arm.

Question 1040: Branchial cyst develops from-

A. Branchial arch
B. 2nd branchial cleft (Correct Answer)
C. 4th branchial cleft
D. 3rd branchial cleft

Explanation: 2nd branchial cleft - Branchial cysts, also known as **cervical sinus cysts**, are congenital epithelial cysts that arise from incomplete obliteration of the **pharyngeal (branchial) apparatus** during embryonic development. - The most common type, composing over 90% of cases, originates from the **second branchial cleft**. *Branchial arch* - Branchial arches are mesenchymal structures that give rise to various **head and neck structures** including muscles, bones, nerves, and vessels. - While related to overall head and neck development, cysts specifically develop from unclosed clefts or pouches, not the arches themselves. *4th branchial cleft* - Cysts from the **fourth branchial cleft** are very rare, accounting for less than 1% of all branchial anomalies. - These typically present with a more inferior neck mass and can be associated with **pyriform sinus fistulas**. *3rd branchial cleft* - Cysts from the **third branchial cleft** are uncommon and often present as a mass in the upper part of the neck, deep to the sternocleidomastoid muscle. - They are less frequent than second cleft cysts but more common than fourth cleft anomalies.

Practice by Chapter

Gametogenesis and Fertilization

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Early Embryonic Development

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Placentation

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Development of Nervous System

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Development of Cardiovascular System

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Development of Gastrointestinal System

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Development of Urogenital System

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Development of Musculoskeletal System

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Development of Head and Neck

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Congenital Anomalies

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Teratology

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Molecular Mechanisms in Development

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