INICET Anatomy Previous Year Questions (2017–2026)

The correct answer is 1-c, 2-d, 3-b.

The thyroid arises from endoderm - a median endodermal thickening (thyroid diverticulum) in the floor of the pharynx (1-c). The adrenal medulla develops from neural crest cells (chromaffin cells from adjacent sympathetic ganglia), whereas the adrenal cortex is mesodermal (2-d). The kidney develops from the intermediate mesoderm (pronephros to mesonephros to metanephros) (3-b). Hence 1-c, 2-d, 3-b.

Why the other options are wrong:

• 1-a, 2-c, 3-d: thyroid is endoderm (not ectoderm) and the kidney is intermediate mesoderm (not neural crest).
• 1-b, 2-c, 3-d: thyroid is endoderm (not mesoderm); adrenal medulla is neural crest (not endoderm).
• 1-c, 2-a, 3-b: adrenal medulla is from neural crest, not surface ectoderm - so 2-a is wrong.

High-Yield Facts:

• Thyroid = endoderm (pharyngeal floor diverticulum).
• Adrenal medulla = neural crest; adrenal cortex = mesoderm.
• Kidney and gonads = intermediate mesoderm.
• Neural crest also forms melanocytes, Schwann cells, dorsal root ganglia, and enteric neurons.

Figure: Fates of the germ layers - endoderm (gut/glands), mesoderm (kidney, muscle, circulatory), and ectoderm (skin, nervous system, including neural-crest derivatives).

The correct answer is 1 and 2.

An inhaled foreign body preferentially enters the right main bronchus because it is more vertical (in direct line with the trachea) (statement 1) and wider in diameter (statement 2). The right main bronchus is also SHORTER, not longer - so statement 3 is FALSE. Statement 4 (the right lung having 3 lobes) is a true anatomical fact but is NOT the reason a foreign body lodges on the right; lobe number does not determine the side of aspiration. Hence only statements 1 and 2 are the correct anatomical basis.

Why the other options are wrong:

• 1, 2 and 3: includes statement 3, which is false - the right bronchus is shorter, not longer.
• 1, 2 and 4: the 3-lobed right lung is true but is not the anatomical basis for the side of aspiration.
• 1, 2, 3 and 4: wrong because statement 3 is false and statement 4 is not the basis.

High-Yield Facts:

• Right main bronchus is wider, shorter, and more vertical.
• Aspirated foreign bodies therefore lodge on the right.
• The right bronchus is SHORTER (not longer) - a common trap.
• The carina sits slightly left of midline, reinforcing right-sided entry.

Figure: The trachea (windpipe) divides into the main bronchi; the right main bronchus is wider, shorter, and more vertical, so aspirated objects tend to enter it.

The correct answer is 2, 3, 4 and 5.

The sensory decussation is in the caudal (closed) medulla, where internal arcuate fibers from the dorsal column nuclei cross to form the medial lemniscus. At this level the structures present include the nucleus gracilis (the source of those crossing fibers, #2), the spinal nucleus of the trigeminal nerve (which runs the whole length of the medulla, #3), and the centrally placed hypoglossal nucleus (#5) with the adjacent dorsal motor nucleus of vagus (#4). The lateral vestibular nucleus (#1) lies more ROSTRALLY (around the pontomedullary junction), so it is not affected here - making 2, 3, 4, 5 correct.

Why the other options are wrong:

• 1, 2, 4, 5: includes the lateral vestibular nucleus, which is rostral (pontomedullary) and not at the sensory decussation.
• 2, 3, 5: omits the dorsal motor nucleus of vagus, which is present centrally at this level.
• 3, 4, 5: omits the nucleus gracilis, which IS present (it gives rise to the decussating internal arcuate fibers).

High-Yield Facts:

• Sensory decussation = caudal/closed medulla (medial lemniscus forms here).
• Dorsal column nuclei (gracilis, cuneatus) give internal arcuate fibers.
• The spinal trigeminal nucleus spans the entire medulla.
• Vestibular nuclei are rostral (pontomedullary), not at this level.

Figure: Closed medulla at the sensory decussation - internal arcuate fibers from the dorsal column nuclei cross the midline (9) to form the medial lemniscus.