Developmental Anatomy — MCQs

Developmental Anatomy Indian Medical PG Practice Questions and MCQs

Question 61: Styloid process is derived from?

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

Explanation: **Second pharyngeal arch** - The **styloid process** of the temporal bone is derived from the **cartilage of the second pharyngeal arch**, also known as Reichert's cartilage. - This arch also contributes to the **lesser horn** and upper part of the body of the **hyoid bone**, the stapes, and several muscles of facial expression. *First pharyngeal arch* - The first pharyngeal arch, or **Meckel's cartilage**, gives rise to the **malleus** and **incus** of the middle ear. - It also forms the **mandible** and maxilla. *Third pharyngeal arch* - The third pharyngeal arch contributes to the **greater horn** and lower part of the body of the **hyoid bone**. - It does not form the styloid process. *Fourth pharyngeal arch* - The fourth pharyngeal arch contributes to the **laryngeal cartilages**, specifically parts of the **thyroid** and **cricoid cartilages**. - It is not involved in the formation of the styloid process.

Question 62: At what stage of fetal development do the testes descend through the inguinal canal?

A. 4 months
B. 5 months
C. 9 months
D. 7 months (Correct Answer)

Explanation: 7 months - Testicular descent typically begins around the **seventh month of gestation**, guided by the gubernaculum, through the **inguinal canal** into the scrotum. - This process is crucial for proper testicular function, as the cooler scrotal environment is necessary for **spermatogenesis** [1]. *4 months* - At this stage, the testes have not yet begun their full descent and are usually located in the **abdominal cavity**, near the kidneys. - While hormonal influences are beginning, the **gubernaculum** has not yet fully matured to guide the descent. *5 months* - The testes are still generally confined to the **abdominal cavity** at this point, though some early preparatory changes for descent may be occurring. - Significant **descent through the inguinal canal** has not yet commenced. *9 months* - By the ninth month, or term gestation, the testes should have **completed their descent** and are typically found within the **scrotum** [1]. - If descent has not occurred by this time, it is considered **cryptorchidism** [1].

Question 63: Stroma of cornea develops from ?

A. Neural ectoderm
B. Surface ectoderm
C. Mesoderm
D. Neural crest (Correct Answer)

Explanation: ***Neural crest*** - The **stroma of the cornea**, along with the corneal endothelium and Descemet's membrane, is derived from **neural crest cells**. - Neural crest cells migrate into the developing ocular region and differentiate into these connective tissue components of the cornea. *Neural ectoderm* - The neural ectoderm primarily gives rise to structures like the **retina**, **optic nerve**, and the posterior pigmented layer of the ciliary body and iris. - It does not contribute to the formation of the corneal stroma. *Surface ectoderm* - The surface ectoderm forms the **corneal epithelium** and the lens of the eye. - It does not give rise to the mesenchymal components of the cornea, such as the stroma. *Mesoderm* - While some mesodermal elements are involved in ocular development (e.g., extrinsic eye muscles, vascular components), the **corneal stroma** is specifically derived from neural crest cells, not general mesoderm. - The mesoderm contributes to structures like the sclera and choroid, but not directly to the corneal stroma.

Question 64: When does the basiocciput fuse with the basisphenoid?

A. 8-10 years
B. 2-4 years
C. 12-15 years
D. 5-7 years (Correct Answer)

Explanation: Note: This is a NEET-PG 2018 previous year question. The provided options and marked answer reflect the exam's original content. However, standard anatomical references indicate that the spheno-occipital synchondrosis (junction between basiocciput and basisphenoid) typically fuses between 18-25 years of age, not in early childhood. 5-7 years (Marked as correct in original exam) - This was the expected answer in the NEET-PG 2018 exam. - However, standard anatomical texts (Gray's Anatomy, Standring) indicate that spheno-occipital fusion occurs much later, typically between 18-25 years. - There may be confusion with other cranial base developments that occur in early childhood. 2-4 years - This is earlier than even the exam's intended answer. - The spheno-occipital synchondrosis remains cartilaginous at this age. 8-10 years - Still within the childhood period. - The spheno-occipital synchondrosis typically remains unfused at this age. 12-15 years - Early to mid-adolescence. - The spheno-occipital synchondrosis is usually still present, though beginning to show signs of fusion in some individuals by late adolescence. Clinical Note: The fusion of the spheno-occipital synchondrosis is an important forensic marker for age estimation, with complete fusion generally occurring by the mid-20s.

Question 65: Most common site for Cystic Hygroma is -

A. Lower third of neck (Correct Answer)
B. Overlying the parotid gland
C. Along the Zygomatic Prominence
D. Post auricular

Explanation: ***Lower third of neck*** - **Cystic hygromas** (also known as **lymphatic malformations**) most commonly occur in the **posterior triangle of the neck**, which is located in the lower lateral aspect of the neck [1]. - Approximately **75-80%** of cystic hygromas are found in the neck region, with the **posterior triangle** being the predominant site. - The **posterior jugular lymph sac** fails to connect properly with the venous system during embryonic development, leading to these cystic malformations in this characteristic location [1]. - The posterior triangle encompasses the lower lateral neck, making "lower third of neck" an acceptable description of this most common site. *Overlying the parotid gland* - While lymphatic malformations can occur in the parotid region, this represents only about **10-15%** of cases. - This is a less common site compared to the posterior triangle of the neck. - Lesions in this area might raise concern for other parotid pathologies like **pleomorphic adenoma** or **hemangioma**. *Along the Zygomatic Prominence* - This is an unusual location for a cystic hygroma, as the lymphatic drainage and embryonic development in this area are not typically associated with these malformations. - Lesions here might suggest different developmental or neoplastic etiologies such as **dermoid cysts** or **vascular malformations**. *Post auricular* - The post-auricular region is not a common site for cystic hygromas. - Swelling in this area could be due to other conditions like **mastoiditis**, **lymphadenopathy**, or **sebaceous cysts**.

Question 66: Base of sphenoid fuses with occiput at the age of -

A. 20 years (Correct Answer)
B. 30 years
C. 40 years
D. 50 years

Explanation: ***20 years*** - The **spheno-occipital synchondrosis** typically fuses by the age of **20 to 25 years**, marking the cessation of growth in the cranial base. - This fusion is an important indicator of skeletal maturity and is often used in **forensic anthropology** for age estimation. *30 years* - Fusion of the **spheno-occipital synchondrosis** beyond the early twenties is considered late and is not the typical age for this event. - By 30 years, most cranial sutures and synchondroses are already fused. *40 years* - At 40 years of age, the **spheno-occipital synchondrosis** would have been completely fused for many years, making this an incorrect age for the fusion process itself. - This age is well past the usual developmental timeframe for cranial base closure. *50 years* - Fusion at 50 years would be an **anomalous finding** as this synchondrosis is known to fuse much earlier in life. - By this age, the skull is fully mature, and fusion events of this nature have long since completed.

Question 67: Prolactin secreting gland develops from -

A. Infundibulum
B. Rathke's pouch (Correct Answer)
C. Tuber cinereum
D. 3rd ventricle

Explanation: ***Rathke's pouch*** - The **anterior pituitary gland**, which secretes prolactin [2], develops embryologically from **Rathke's pouch**. - Rathke's pouch is an **ectodermal evagination** from the roof of the primitive oral cavity (stomodeum). *Infundibulum* - The **infundibulum** is also known as the pituitary stalk, connecting the hypothalamus to the posterior pituitary [1]. - It is derived from **neuroectoderm** and forms part of the posterior pituitary, not the prolactin-secreting anterior pituitary [1]. *Tuber cinereum* - The **tuber cinereum** is a part of the **hypothalamus**. - It is involved in regulating several bodily functions but does not directly give rise to the prolactin-secreting gland. *3rd ventricle* - The **3rd ventricle** is one of the four ventricles of the brain, filled with **cerebrospinal fluid**. - It is a part of the central nervous system and is not involved in the embryological development of the pituitary gland.

Question 68: What is the remnant of the umbilical artery?

A. Ligamentum arteriosum
B. Ligament teres
C. Ligamentum venosum
D. Medial umbilical ligament (Correct Answer)

Explanation: ***Medial umbilical ligament*** - The **umbilical arteries** (paired structures) carry deoxygenated blood from the fetus to the placenta during development [2]. - After birth, these arteries obliterate and persist as the **medial umbilical ligaments** (two in number, one on each side), extending from the internal iliac arteries to the umbilicus along the anterior abdominal wall. - The proximal portions of the umbilical arteries remain patent as the **superior vesical arteries**, which supply the bladder. *Ligamentum arteriosum* - This is the remnant of the **ductus arteriosus**, which shunted blood from the pulmonary artery to the aorta, bypassing the fetal lungs [2]. - It connects the arch of the aorta to the pulmonary artery. *Ligament teres* - Also known as the **round ligament of the liver**, this is the remnant of the **fetal umbilical vein** (a single midline structure) [1]. - The umbilical vein carried oxygenated blood from the placenta to the fetus [1], [2]. *Ligamentum venosum* - This is the fibrous remnant of the **ductus venosus**, a shunt in fetal circulation that bypassed the liver by connecting the umbilical vein to the inferior vena cava [1]. - It is located deep within the liver, forming a fissure.

Question 69: Fossa ovalis is a remnant of -

A. Septum primum (Correct Answer)
B. Septum secundum
C. Septum spurium
D. AV cushion

Explanation: ***Septum primum*** - The **fossa ovalis** is a depression in the right atrium that represents the sealed-off foramen ovale [2]. - It is formed from the **septum primum**, which becomes the floor of the fossa ovalis. *Septum secundum* - The **septum secundum** forms the limbus or rim of the fossa ovalis, not the fossa itself. - This structure develops later than the septum primum and partially covers the foramen ovale during fetal development [2]. *Septum spurium* - The **septum spurium** is an embryonic ridge in the right atrium that typically regresses during development and does not contribute to the fossa ovalis. - It is a transient structure formed by the confluence of the right and left venous valves. *AV cushion* - The **atrioventricular (AV) cushions** contribute to the formation of the AV valves and the atrial and ventricular septa, but not directly to the fossa ovalis [1]. - They are crucial for separating the atria from the ventricles and forming the mitral and tricuspid valves.

Question 70: Mastoid process is which type of epiphysis?

A. Pressure epiphysis
B. Traction epiphysis (Correct Answer)
C. Atavistic epiphysis
D. Aberrant epiphysis

Explanation: Traction epiphysis - A traction epiphysis is an apophysis that does not contribute to the longitudinal growth of the bone but is located at the site of muscle attachment, serving to provide leverage for the muscle. - The mastoid process serves as an attachment point for various muscles, including the sternocleidomastoid, splenius capitis, and longissimus capitis, making it a classic example of a traction epiphysis. Pressure epiphysis - A pressure epiphysis is primarily responsible for the longitudinal growth of bone and is found at the ends of long bones, such as the femoral head or humeral head [1]. - The mastoid process does not contribute to longitudinal bone growth. Atavistic epiphysis - Atavistic epiphyses are those that are phylogenetically separate bones but become fused with the main bone during development, like the coracoid process of the scapula. - The mastoid process is an integral part of the temporal bone and is not considered a separate, phylogenetically distinct bone. Aberrant epiphysis - Aberrant epiphyses are variations that appear irregularly, are not always present, and do not have a consistent physiological role. - The mastoid process is a constant anatomical feature of the temporal bone in humans.

Practice by Chapter

Prenatal Development

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Postnatal Growth and Development

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Age-Related Anatomical Changes

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Developmental Abnormalities

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Principles of Teratology

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Developmental Basis of Congenital Anomalies

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Molecular Aspects of Development

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Genetic Factors in Developmental Anatomy

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Environmental Influences on Development

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Clinical Aspects of Developmental Anatomy

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