Development of the Vertebral Column — MCQs
Which of the following statements provides the MOST COMPLETE description of sclerotome function during vertebral development?
All are TRUE about intervertebral disc, EXCEPT:
Which of the following conditions is least likely to cause posterior scalloping of the vertebrae?
Which of the following is least likely to be associated with progressive congenital scoliosis?
What constitutes a spinal motion segment?
Which of the following parts of the vertebral canal shows the first secondary curve to develop?
During embryological development, failure of the urorectal septum to completely separate the cloaca results in which of the following congenital anomalies?
The lower two thirds of the following hematoxylin and eosin stained specimen is similar in appearance to which of the following structures?
Nucleus pulposus develops from: (AIIMS May 2018)
In a diving accident that severed the spinal cord below the sixth cervical vertebra, which of the following muscles would be affected?
Development of the Vertebral Column Indian Medical PG Practice Questions and MCQs
Question 1: Which of the following statements provides the MOST COMPLETE description of sclerotome function during vertebral development?
- A. The notochord forms the nucleus pulposus.
- B. The sclerotome contributes to the formation of vertebral bodies.
- C. The sclerotome surrounds the notochord and the neural tube during development. (Correct Answer)
- D. The sclerotome surrounds the notochord.
Explanation: ***The sclerotome surrounds the notochord and the neural tube during development.*** - The **sclerotome** is the part of the somite that differentiates into mesenchymal cells and migrates to surround both the developing **notochord** (which gives rise to the nucleus pulposus) and the **neural tube** (which forms the spinal cord). - This encirclement is crucial for the formation of the **vertebral column**, providing protection and a structural framework. *The notochord forms the nucleus pulposus.* - While true that the **notochord** contributes to the **nucleus pulposus**, this statement describes the fate of the notochord itself, not the function of the sclerotome. - The question asks for the function of the sclerotome, and this option only details one specific derivative. *The sclerotome contributes to the formation of vertebral bodies.* - This statement is partially true, as the **sclerotome** does indeed form the **vertebral bodies**, arches, and intervertebral discs. - However, it is not the *most complete* description of its function during development, as it omits the crucial aspect of surrounding the neural tube. *The sclerotome surrounds the notochord.* - This statement is correct but **incomplete** as it only mentions the notochord. - The **sclerotome** also surrounds the **neural tube**, which is a vital part of its developmental role in forming the vertebral canal.
Question 2: All are TRUE about intervertebral disc, EXCEPT:
- A. Rich vascular supply (Correct Answer)
- B. Prolapse is most common in lumbosacral region
- C. Nucleus pulposus is a remnant of notochord
- D. Annulus fibrosus is made up of fibrocartilage
Explanation: ***Rich vascular supply*** - The intervertebral disc is largely **avascular** in adults, receiving nutrients primarily through diffusion from the vertebral bodies. - This lack of direct blood supply is why it has a limited capacity for self-repair and healing after injury. *Prolapse is most common in lumbosacral region* - The **lumbosacral region** (L4-L5 and L5-S1) bears the most weight and experiences the greatest biomechanical stress, making it the most common site for disc prolapse or herniation [1]. - This area is prone to injury due to the demands placed upon it during movement and lifting. *Nucleus pulposus is a remnant of notochord* - The **nucleus pulposus**, the gelatinous center of the intervertebral disc, is indeed a direct remnant of the embryonic **notochord**. - This embryological origin explains its high water content and elastic properties, which allow it to function as a shock absorber. *Annulus fibrosus is made up of fibrocartilage* - The **annulus fibrosus** is the tough outer layer of the intervertebral disc composed of concentric layers of **fibrocartilage**. - These collagen fibers are arranged in a crisscross pattern to provide strength and contain the nucleus pulposus.
Question 3: Which of the following conditions is least likely to cause posterior scalloping of the vertebrae?
- A. Astrocytoma
- B. Neurofibromatosis
- C. Ependymoma
- D. Aortic aneurysm (Correct Answer)
Explanation: ***Aortic aneurysm*** - An **aortic aneurysm** is located **anterior to the vertebral column** and primarily affects the anterior aspect of the vertebral bodies, causing **anterior scalloping** due to chronic pulsatile erosion, not posterior scalloping. - Posterior scalloping requires intraspinal pathology that expands the spinal canal from within; an aortic aneurysm is extraspinal and anterior, making it the **least likely** cause of posterior scalloping. *Neurofibromatosis* - **Neurofibromatosis** commonly causes posterior vertebral scalloping due to **dural ectasia** (widening of the dural sac) and pressure erosion from expanding neurofibromas within the spinal canal. - This condition is also associated with paraspinal masses, posterior vertebral body erosion, and scoliosis. *Astrocytoma* - An **intramedullary astrocytoma** within the spinal cord can lead to expansion of the cord that causes chronic pressure on the posterior vertebral bodies from within the spinal canal. - This slow-growing intraspinal tumor gradually remodels the bone, causing posterior scalloping. *Ependymoma* - Similar to astrocytoma, an **intramedullary ependymoma** (the most common primary intramedullary tumor in adults) can enlarge the spinal cord, leading to pressure erosion on the posterior vertebral bodies. - This is a characteristic feature of slowly growing intraspinal masses, which cause remodeling of the bony spinal canal.
Question 4: Which of the following is least likely to be associated with progressive congenital scoliosis?
- A. Hemivertebra
- B. Unilateral unsegmented vertebra with bar
- C. Wedge vertebra (Correct Answer)
- D. Block vertebra
Explanation: ***Wedge vertebra*** - A **wedge vertebra** is a less severe form of vertebral anomaly compared to a hemivertebra, characterized by incomplete formation of the vertebral body on one side. - While it can cause scoliosis, it is significantly **less likely to progress** rapidly or severely compared to anomalies that involve complete lack of formation or fusion. *Hemivertebra* - A **hemivertebra** is a fully unsegmented vertebral body fused to one side of the adjacent segments, leading to a profound congenital deformity and a powerful growth plate on the opposite side. - This imbalance causes a **high likelihood of progression** in congenital scoliosis due to differential growth. *Unilateral unsegmented vertebra with bar* - This anomaly involves a **failure of segmentation** on one side of a vertebral body, creating a "bar" that inhibits growth on that side, while the other side grows normally. - The unrestricted growth on one side coupled with restricted growth on the other creates a significant imbalance, leading to a **high potential for progressive scoliosis**. *Block vertebra* - A **block vertebra** results from a complete failure of segmentation between two or more vertebral bodies along both sides. - While it causes a reduction in vertebral height and potentially some stiffness, it generally leads to **little or no progressive scoliosis** because the growth inhibition is symmetric and balanced on both sides of the spine.
Question 5: What constitutes a spinal motion segment?
- A. A disc and the vertebrae above and below, including their interlocking facet joints. (Correct Answer)
- B. A disc and the facet joints at that level.
- C. A vertebral body and the disc above.
- D. A section of the spine involved in a physiological curve with the similar function (i.e. thoracic kyphosis).
Explanation: ***A disc and the vertebrae above and below, including their interlocking facet joints.*** - A **spinal motion segment** or **functional spinal unit** is defined as two adjacent vertebrae and the intervertebral disc between them. - This unit includes all the associated **ligaments**, **capsules**, and especially the **facet joints**, which together allow for complex movements. *A disc and the facet joints at that level.* - This definition is incomplete as it misses the crucial component of the **vertebral bodies** themselves. - The vertebral bodies provide the main structural support and articulation points for the disc and facet joints. *A vertebral body and the disc above.* - This partial definition describes only a fraction of the components required for a functional segment. - It omits the **inferior vertebral body** and the critical **facet joints** that enable motion. *A section of the spine involved in a physiological curve with the similar function (i.e. thoracic kyphosis).* - This option describes a broader **region** of the spine rather than a single, functional motion unit. - A physiological curve involves multiple motion segments working in concert, not a single segment.
Question 6: Which of the following parts of the vertebral canal shows the first secondary curve to develop?
- A. Lumbar Vertebral Canal
- B. Thoracic Vertebral Canal
- C. Cervical Vertebral Canal (Correct Answer)
- D. Sacral Vertebral Canal
Explanation: ***Cervical Vertebral Canal*** - The **cervical curve** is the **first secondary curve** to develop as an infant learns to hold their head up (around 3-4 months). - This **lordotic curve** is concave posteriorly and helps to balance the head on the vertebral column. - It develops before the lumbar curve, making it the earliest secondary curvature. *Lumbar Vertebral Canal* - The **lumbar curve** is also a **secondary curve** but develops later when an infant begins to stand and walk (around 12-18 months). - It is a **lordotic curve**, concave posteriorly, and helps maintain an upright posture. - This is the second secondary curve to develop. *Thoracic Vertebral Canal* - The **thoracic curve** is a **primary curve**, meaning it is present at birth. - This **kyphotic curve** is convex posteriorly and accommodates the thoracic organs. *Sacral Vertebral Canal* - The **sacral curve** is another **primary curve**, also present at birth. - It is a **kyphotic curve**, convex posteriorly, and contributes to the pelvic basin's shape.
Question 7: During embryological development, failure of the urorectal septum to completely separate the cloaca results in which of the following congenital anomalies?
- A. Imperforate anus
- B. Cloacal exstrophy
- C. Rectovaginal fistula
- D. Persistent cloaca (Correct Answer)
Explanation: During embryological development, failure of the urorectal septum to completely separate the cloaca results in which of the following congenital anomalies? ***Persistent cloaca*** - This condition occurs when the **urorectal septum** fails to fully descend and partition the cloaca into the urogenital sinus anteriorly and the anorectal canal posteriorly [1]. - As a result, the rectum, vagina, and urinary tract all drain into a **single common channel**, leading to various functional and anatomical complications [1]. *Imperforate anus* - This anomaly involves the **absence or abnormal closure of the anal opening**, but it does not typically involve a shared channel with the urinary or reproductive tracts. - It arises from abnormal development of the **hindgut's caudal portion** or failure of the anal membrane to rupture. *Cloacal exstrophy* - This is a more complex and severe malformation characterized by the **exposure of the bladder, bowel, and sometimes genitalia** to the outside of the body. - While it involves cloacal derivatives, it's primarily a defect in the **closure of the ventral body wall** and does not directly result from incomplete septation in the same manner as a persistent cloaca. *Rectovaginal fistula* - This is an **abnormal connection between the rectum and the vagina**. While it involves a communication between two distinct structures, it is a localized defect. - It typically arises from **incomplete separation of the rectum and vagina**, which can be a consequence of less severe septation defects, but it is not the complete persistence of a single common channel like persistent cloaca.
Question 8: The lower two thirds of the following hematoxylin and eosin stained specimen is similar in appearance to which of the following structures?
- A. Articular disk
- B. Pinna
- C. Epiphyseal growth plate
- D. Intervertebral disk (Correct Answer)
Explanation: ***Intervertebral disk*** - The lower two-thirds of the specimen shows **hyaline-like cartilage** that histologically resembles the **transition zone** of the intervertebral disk, where the inner annulus fibrosus transitions from the nucleus pulposus. - While the nucleus pulposus itself is gelatinous and notochordal in origin, the **inner annulus fibrosus** contains fibrocartilage with regions that can appear similar to hyaline cartilage, particularly in the transitional zones. - The specimen's appearance, with **chondrocytes in lacunae** within a relatively homogeneous matrix, matches the cartilaginous components found in intervertebral disk structure. *Articular disk* - Articular disks are composed predominantly of **fibrocartilage**, characterized by **dense parallel collagen fiber bundles** clearly visible in the matrix and chondrocytes arranged in linear rows between collagen bundles. - The homogeneous matrix appearance in the specimen lacks the prominent fibrous architecture typical of articular disks. *Pinna* - The pinna (external ear) is supported by **elastic cartilage**, which contains abundant **elastic fibers** in its extracellular matrix providing flexibility and resilience. - With H&E staining, elastic cartilage would show a more textured matrix, and special stains would demonstrate extensive elastic fiber networks not present in this specimen. *Epiphyseal growth plate* - While the epiphyseal growth plate consists of **hyaline cartilage**, it exhibits highly characteristic **zonal organization**: resting zone, proliferative zone (with columnar arrangement), hypertrophic zone, and zone of calcification. - The specimen lacks the distinct columnar arrangement and zonal stratification that defines an active epiphyseal growth plate.
Question 9: Nucleus pulposus develops from: (AIIMS May 2018)
- A. A
- B. B
- C. C (Correct Answer)
- D. D
Explanation: ***Correct Option C*** - Label C points to the **notochord**, which is the embryonic structure that the **nucleus pulposus** of the intervertebral discs develops from. - The notochord provides transient axial support during early embryonic development and induces the formation of the neural tube. - During development, most of the notochord degenerates, but remnants persist as the gelatinous core of intervertebral discs. *Incorrect Option A* - Label A indicates the **neural tube**, which develops into the **brain and spinal cord**. - It arises from the neural plate, which is induced by the underlying notochord. - The neural tube does not contribute to the intervertebral disc structure. *Incorrect Option B* - Label B represents the **secondary yolk sac**, a structure involved in early nutrient transfer and the formation of primordial germ cells. - It does not directly contribute to the formation of musculoskeletal structures like the nucleus pulposus. *Incorrect Option D* - Label D points to the **ectoderm**, the outermost germ layer, which gives rise to the epidermis, nervous system (including the neural tube), and sensory organs. - While it forms the neural tube, it does not directly form the nucleus pulposus or other mesodermal derivatives.
Question 10: In a diving accident that severed the spinal cord below the sixth cervical vertebra, which of the following muscles would be affected?
- A. Deltoid
- B. Infraspinatus
- C. Levator Scapulae
- D. Latissimus Dorsi (Correct Answer)
Explanation: ***Latissimus Dorsi*** - The **latissimus dorsi muscle** is primarily innervated by the **thoracodorsal nerve**, which arises from the **C6, C7, and C8** nerve roots (with C7 and C8 being the predominant contributors) [1]. - A spinal cord injury below the sixth cervical vertebra would affect the C7 and C8 segments, thereby disrupting the nerve supply to the latissimus dorsi, leading to weakness or paralysis. - This muscle is responsible for adduction, extension, and internal rotation of the shoulder. *Deltoid* - The **deltoid muscle** is innervated by the **axillary nerve**, which arises predominantly from the **C5 and C6** nerve roots. - Since the injury is below the C6 vertebra, the upper cervical segments (C5 and C6) would remain intact above the level of injury. - Therefore, deltoid function would be preserved. *Infraspinatus* - The **infraspinatus muscle** is innervated by the **suprascapular nerve**, which arises from the **C5 and C6** nerve roots. - Similar to the deltoid, its innervation originates above the level of the spinal cord injury and would be spared. *Levator Scapulae* - The **levator scapulae muscle** receives innervation from the **C3, C4, and C5** spinal nerves, as well as contributions from the dorsal scapular nerve (predominantly C5). - All of these nerve roots originate well above the level of injury, so this muscle would not be affected.
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