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Score — click each question to reveal the answer
Q1
The adult vertebral column has how many vertebrae?
L1 — Trunk Notes
L1 — Trunk Notes
A. 26
B. 24
C. 33
D. 30
✅ Answer: A — 26 vertebrae
The adult vertebral column has 26 bones: 7 cervical + 12 thoracic + 5 lumbar + 1 sacrum (5 sacral vertebrae fused) + 1 coccyx (3–5 coccygeal vertebrae fused). In the embryo there are 33 separate vertebrae — fusion occurs during development.
⚠ Trap: 33 is the embryonic count, not the adult. 24 refers only to the movable pre-sacral vertebrae (C + T + L). Know all three numbers: 33 (embryo), 26 (adult), 24 (movable).
Q2
Which vertebrae are uniquely identified by having transverse foramina?
L1 — Trunk Notes
L1 — Trunk Notes
A. Thoracic
B. Cervical
C. Lumbar
D. Sacral
✅ Answer: B — Cervical vertebrae
Transverse foramina are the defining feature of cervical vertebrae. They are present in C1–C6 and transmit the vertebral artery, vertebral vein, and sympathetic nerve plexus. C7 has a transverse foramen but it is small and transmits only the vertebral vein. No other region has transverse foramina.
⚠ Trap: All vertebrae have transverse processes — but only cervical vertebrae have transverse foramina within those processes. This is the single most reliable feature for identifying a cervical vertebra.
Q3
The intervertebral disc consists of which two components?
L1 — Trunk Notes
L1 — Trunk Notes
A. Hyaline cartilage plates only
B. Dense irregular connective tissue
C. Anulus fibrosus and nucleus pulposus
D. Fibrocartilage ring and ligamentum flavum
✅ Answer: C — Anulus fibrosus and nucleus pulposus
The intervertebral disc has two main components: (1) Anulus fibrosus — the tough outer ring of 10–20 concentric fibrocartilage lamellae; adjacent lamellae run at ~30° to each other, resisting torsional forces. (2) Nucleus pulposus — the gel-like central core containing 70–90% water, type II collagen, and proteoglycans. The disc also has vertebral endplates (hyaline cartilage) but these are not the "two components."
⚠ Trap: Vertebral endplates exist but are not the structural components of the disc itself. Ligamentum flavum connects laminae — it is not part of the disc.
Q4
The nucleus pulposus is derived embryologically from:
L1 — Trunk Notes
L1 — Trunk Notes
A. Paraxial mesoderm
B. Lateral plate mesoderm
C. Neural crest cells
D. The notochord
✅ Answer: D — The notochord
The nucleus pulposus is a direct remnant of the embryonic notochord, the axial structure that induces neural tube formation and gives rise to the floor of the neural tube. It retains its high water-binding proteoglycan content throughout life, though it dehydrates progressively with age — a key factor in disc herniation.
⚠ Trap: The vertebral bodies and most of the disc (including the anulus fibrosus) develop from paraxial mesoderm (sclerotomes of somites) — but the nucleus pulposus is specifically notochordal. This distinction appears frequently in embryology questions.
Q5
A posterolateral disc herniation at L4–L5 compresses which nerve root?
L1 — Trunk Notes
L1 — Trunk Notes
A. L5 nerve root
B. L3 nerve root
C. S1 nerve root
D. L4 nerve root
✅ Answer: A — L5 nerve root
In a posterolateral herniation, the disc compresses the traversing (descending) root — the root travelling down to exit at the level below. At L4–L5, the traversing root is L5. Features: pain radiating down the posterolateral thigh and leg, weakness of ankle dorsiflexion and great toe extension, numbness over the lateral leg and dorsum of foot (L5 dermatome).
⚠ Trap: L4 exits between L3–L4 as the "exiting root" — it is compressed by a far lateral (extraforaminal) herniation, not posterolateral. L5–S1 herniation compresses S1 (calf weakness, reduced ankle jerk).
Q6
Ligamentum flavum connects which structures?
L1 — Trunk Notes
L1 — Trunk Notes
A. Anterior surfaces of vertebral bodies
B. Laminae of adjacent vertebrae
C. Tips of spinous processes
D. Transverse processes of adjacent vertebrae
✅ Answer: B — Laminae of adjacent vertebrae
Ligamentum flavum ("yellow ligament") connects the laminae of adjacent vertebrae. It has the highest elastin content of any ligament in the body, giving it a yellow colour. It helps maintain upright posture, limits flexion, and recoils the spine. During spinal extension, it prevents infolding into the spinal canal. A needle passes through it during lumbar puncture.
⚠ Trap: ALL = anterior surfaces of vertebral bodies (prevents hyperextension). Supraspinous ligament = spinous process tips. Intertransverse ligaments = transverse processes. Know all five main spinal ligaments and their attachments.
Q7
The sternal angle (angle of Louis) is at which vertebral level?
L1 — Trunk Notes
L1 — Trunk Notes
A. T2–T3
B. T3–T4
C. T4–T5
D. T5–T6
✅ Answer: C — T4–T5
The sternal angle is the palpable ridge at the manubriosternal junction. It is at the level of T4–T5 and marks: the 2nd costal cartilage (starting point for counting ribs), the bifurcation of the trachea (carina), the arch of the aorta superiorly and inferiorly, the superior vena cava formation, and the boundary between superior and inferior mediastinum.
⚠ Trap: T2 is at the top of the manubrium (suprasternal notch). The sternal angle is specifically at T4–T5 — not T2 or T3. This is a high-yield clinical anatomy landmark.
Q8
Which ribs are classified as "true ribs" with direct sternal attachment?
L1 — Trunk Notes
L1 — Trunk Notes
A. Ribs 1–5
B. Ribs 8–10
C. Ribs 11–12
D. Ribs 1–7
✅ Answer: D — Ribs 1–7 (true ribs)
The 12 pairs of ribs are classified as: True ribs (1–7) — attach directly to the sternum via their own costal cartilages. False ribs (8–10) — attach via the costal cartilage of rib 7 (not directly to sternum). Floating ribs (11–12) — have free anterior ends with no sternal or cartilaginous attachment.
⚠ Trap: "True" means direct sternal attachment — 7 ribs, not 5. The first 7 costal cartilages each reach the sternum independently. Ribs 8–10 share rib 7's cartilage.
Q9
The posterior longitudinal ligament (PLL):
L1 — Trunk Notes
L1 — Trunk Notes
A. Prevents hyperflexion and resists posterior disc herniation
B. Prevents hyperextension of the spine
C. Is widest in the lumbar region
D. Runs along the anterior surfaces of vertebral bodies
✅ Answer: A — Prevents hyperflexion and resists posterior disc herniation
The PLL runs along the posterior surfaces of the vertebral bodies within the vertebral canal. It prevents hyperflexion and limits posterior disc herniation. However, it is narrower and weaker in the lumbar region (compared to the ALL) — this is why posterolateral herniations are more common in the lumbar spine, where the PLL offers least resistance.
⚠ Trap: The anterior longitudinal ligament (ALL) prevents hyperextension and runs along the anterior vertebral bodies. The PLL is narrower — especially in the lumbar region — NOT wider.
Q10
Lumbar vertebrae are distinguished from thoracic vertebrae by:
L1 — Trunk Notes
L1 — Trunk Notes
A. Heart-shaped bodies with costal facets
B. Massive kidney-shaped bodies with no costal facets
C. Small bodies with transverse foramina
D. Long downward-pointing spinous processes
✅ Answer: B — Massive kidney-shaped bodies with no costal facets
Lumbar vertebrae have massive kidney-shaped bodies for weight-bearing (L5 has the largest body), short thick "hatchet" spinous processes, no transverse foramina, and no costal facets (ribs only articulate with thoracic vertebrae). L5–S1 is the most common level for disc herniation due to the greatest axial load.
⚠ Trap: Heart-shaped bodies with costal facets = thoracic vertebrae. Small bodies with transverse foramina = cervical. Long downward spinous processes = thoracic. Each region has a distinct combination of features.
Q11
The erector spinae consists of which three columns (lateral to medial)?
L1 — Trunk Notes
L1 — Trunk Notes
A. Multifidus, semispinalis, rotatores
B. Splenius, semispinalis, longissimus
C. Iliocostalis, longissimus, spinalis
D. Quadratus lumborum, psoas major, iliacus
✅ Answer: C — Iliocostalis, longissimus, spinalis
The erector spinae is the largest back muscle group, running from the sacrum to the skull. From lateral to medial: Iliocostalis (lateral column, inserts on ribs), Longissimus (intermediate column, inserts on transverse processes + ribs), Spinalis (medial column, inserts on spinous processes). Together they extend and laterally flex the vertebral column and maintain upright posture.
⚠ Trap: Multifidus, semispinalis, and rotatores are the transversospinal group, not erector spinae. Mnemonic: "I Love Spine" — Iliocostalis, Longissimus, Spinalis.
Q12
Lumbar puncture is safely performed at L3–L4 or L4–L5 because:
L1 — Trunk Notes
L1 — Trunk Notes
A. The aorta bifurcates at L4
B. The cauda equina is most dense at this level
C. The ligamentum flavum is thinnest here
D. The conus medullaris ends at L1–L2 — no spinal cord below
✅ Answer: D — Conus medullaris ends at L1–L2
The conus medullaris (tip of the spinal cord) is at L1–L2 in adults. Below this, the subarachnoid space contains only the cauda equina (nerve roots floating in CSF) — no cord. LP at L3–L4 or L4–L5 avoids direct cord injury. The needle passes through: skin → supraspinous ligament → interspinous ligament → ligamentum flavum → epidural space → dura mater → arachnoid mater → subarachnoid space (CSF obtained).
⚠ Trap: LP at L1–L2 risks piercing the conus medullaris directly. The aorta bifurcating at L4 is a separate anatomical fact, not the reason for LP safety. The cauda equina does occupy this space, but the reason the LP is safe is the absence of the spinal cord.
1Vertebral column+
The flexible supporting column of 26 vertebrae (7 cervical, 12 thoracic, 5 lumbar, 1 sacrum, 1 coccyx). It protects the spinal cord, supports body weight, and provides attachment for muscles and ligaments.
L1 — Bones of Trunk and Joints
2Cervical vertebrae+
Seven vertebrae (C1–C7) characterized by small bodies, bifid spinous processes, transverse foramina (transmit vertebral artery C1–C6), and triangular vertebral foramina. C1 (atlas) and C2 (axis) are atypical and specialized for head movement.
L1 — Bones of Trunk and Joints
3Thoracic vertebrae+
Twelve vertebrae (T1–T12) characterized by heart-shaped bodies, long downward-pointing spinous processes (overlapping like roof tiles), and costal facets for rib articulation on both the bodies and transverse processes.
L1 — Bones of Trunk and Joints
4Lumbar vertebrae+
Five vertebrae (L1–L5) with massive kidney-shaped bodies, short thick spinous processes, and no transverse foramina or costal facets. L5 has the largest body to bear the greatest weight.
L1 — Bones of Trunk and Joints
5Sacrum+
A large triangular bone formed by the fusion of 5 sacral vertebrae. It articulates with L5 superiorly, the hip bones laterally (sacroiliac joints), and the coccyx inferiorly. Transmits body weight to the pelvis.
L1 — Bones of Trunk and Joints
6Coccyx+
The tailbone, formed by the fusion of 3–5 coccygeal vertebrae. Attaches to the sacrum via the sacrococcygeal joint. Provides attachment for the levator ani and coccygeus muscles of the pelvic floor.
L1 — Bones of Trunk and Joints
7Intervertebral disc+
A fibrocartilaginous structure between adjacent vertebral bodies consisting of an outer anulus fibrosus and inner nucleus pulposus. Acts as a shock absorber and allows limited movement between vertebrae. Accounts for 25% of spinal column height in young adults.
L1 — Bones of Trunk and Joints
8Anulus fibrosus+
The tough outer ring of the intervertebral disc composed of 10–20 concentric lamellae of fibrocartilage. Fibres of adjacent lamellae run in opposite directions (~30° to horizontal), resisting torsional forces. The posterior anulus is thinner and weaker — the site of herniation.
L1 — Bones of Trunk and Joints
9Nucleus pulposus+
The gel-like central core of the intervertebral disc derived from the notochord. Contains type II collagen and proteoglycans that attract water (70–90% water in young adults), providing disc turgor and shock-absorbing properties. Dehydrates with age.
L1 — Bones of Trunk and Joints
10Ligamentum flavum+
Elastic ligaments connecting the laminae of adjacent vertebrae. They have the highest elastin content of any ligament, giving a yellow colour and elastic recoil. Help maintain upright posture, limit flexion, and prevent infolding into the spinal canal during extension.
L1 — Bones of Trunk and Joints
11Anterior longitudinal ligament+
A strong band running along the anterior surfaces of the vertebral bodies and discs from the occiput to the sacrum. Prevents hyperextension of the spine. Widest in the lumbar region and tightest at the midpoint of each vertebral body.
L1 — Bones of Trunk and Joints
12Posterior longitudinal ligament+
A narrow band running along the posterior surfaces of the vertebral bodies within the vertebral canal. Prevents hyperflexion and resists posterior herniation of the nucleus pulposus. Narrower and weaker in the lumbar region — contributing to lumbar disc herniation risk.
L1 — Bones of Trunk and Joints
13Supraspinous ligament+
A strong cord connecting the tips of the spinous processes from C7 to the sacrum. Limits spinal flexion. Continuous superiorly with the ligamentum nuchae in the cervical region. A lumbar puncture needle passes through it.
L1 — Bones of Trunk and Joints
14Ligamentum nuchae+
The broadened, fan-shaped superior continuation of the supraspinous ligament in the cervical region, extending from C7 to the external occipital protuberance. Provides attachment for the trapezius and rhomboid muscles. Homologous to the nuchal ligament of quadrupeds.
L1 — Bones of Trunk and Joints
15Erector spinae+
The largest muscle group of the back, forming three columns from lateral to medial: iliocostalis, longissimus, spinalis. It is the primary extensor of the vertebral column and maintains erect posture. Runs from the sacrum to the skull.
L1 — Bones of Trunk and Joints
16Thoracic cage+
The bony framework of the thorax consisting of 12 thoracic vertebrae posteriorly, 12 pairs of ribs laterally, and the sternum anteriorly. Protects the heart, lungs, and great vessels, and provides attachment for respiratory muscles.
L1 — Bones of Trunk and Joints
17Sternum+
The breastbone, consisting of the manubrium (upper), body (middle), and xiphoid process (inferior). The manubrium articulates with the clavicles and first costal cartilages. The sternal angle marks the manubriosternal junction at T4–T5.
L1 — Bones of Trunk and Joints
18Sternal angle (angle of Louis)+
The palpable ridge at the junction of the manubrium and body of the sternum at the level of the second costal cartilage (T4–T5). Key landmark for counting ribs, marks the tracheal bifurcation, the aortic arch, and the superior/inferior mediastinum boundary.
L1 — Bones of Trunk and Joints
19Ribs+
Twelve pairs of curved bones forming the thoracic wall. True ribs (1–7) attach directly to the sternum; false ribs (8–10) attach via the costal cartilage of rib 7; floating ribs (11–12) have free anterior ends. All articulate with thoracic vertebrae posteriorly.
L1 — Bones of Trunk and Joints
20Costal cartilage+
Hyaline cartilage connecting the anterior ends of ribs to the sternum (ribs 1–7) or to the costal cartilage above (ribs 8–10). Allows flexibility of the thoracic wall during respiration. Calcifies with age, reducing chest wall compliance.
L1 — Bones of Trunk and Joints
Essay 1
Describe the structure of a typical intervertebral disc. Explain the anatomical basis for disc herniation and the clinical features of a posterolateral disc herniation at L4–L5.
10 marks
Structure of the intervertebral disc
The intervertebral disc is a fibrocartilaginous structure between adjacent vertebral bodies, accounting for ~25% of spinal column height in young adults. It has two main components:
- Anulus fibrosus: The outer ring of 10–20 concentric lamellae of fibrocartilage. Fibres of adjacent lamellae run in opposite directions (~30° to horizontal), resisting torsional and compressive forces. The posterior anulus is thinner and weaker than the anterior.
- Nucleus pulposus: The central gel-like core derived from the notochord. Contains 70–90% water in young adults, type II collagen, and proteoglycans that attract and retain water. Distributes pressure evenly across the vertebral endplates.
The disc is also bounded superiorly and inferiorly by vertebral endplates (hyaline cartilage fused to the vertebral body), through which diffusion supplies the avascular disc.
Mechanism of disc herniation
With age, the nucleus dehydrates and the anulus degenerates. Combined flexion and rotation stresses (e.g., lifting while twisting) can tear the anulus, allowing the nucleus to herniate. The posterior longitudinal ligament is narrower in the lumbar region, offering less resistance to posterolateral herniation — the most common direction.
L4–L5 posterolateral herniation
The herniated disc compresses the L5 nerve root (the traversing root descending to exit at L5–S1):
- Pain radiating down the posterolateral thigh and leg to the dorsum of foot (L5 dermatomal sciatica)
- Weakness of ankle dorsiflexion (tibialis anterior, L4–L5) and great toe extension (extensor hallucis longus, L5)
- Numbness over the lateral leg and dorsum of foot (L5 dermatome)
- Ankle jerk usually preserved (S1); knee jerk may be mildly reduced
Marking guide (10 marks): Anulus fibrosus structure — lamellae, fibre direction (2) · Nucleus pulposus — notochord origin, water/proteoglycan content (2) · Mechanism of herniation — degeneration, anulus tear, PLL weakness posterolaterally (2) · L5 root — correct traversing root identified (1) · Clinical features — sciatica pattern, dorsiflexion weakness, sensory loss in correct distribution (3)
Essay 2
Describe the anatomy of the vertebral column, including its regions, curvatures, and typical/atypical vertebrae. Explain the clinical significance of the conus medullaris and lumbar cistern in lumbar puncture.
10 marks
Regions and count
The vertebral column has 26 bones in the adult (33 in the embryo): 7 cervical, 12 thoracic, 5 lumbar, 1 sacrum (5 fused), 1 coccyx (3–5 fused).
Curvatures
- Primary (kyphotic): Thoracic and sacral — present at birth, concave anteriorly
- Secondary (lordotic): Cervical (develops when infant holds head) and lumbar (develops when infant begins walking) — convex anteriorly
Typical and atypical cervical vertebrae
- Typical (C3–C6): Small body, bifid spinous process, transverse foramen, triangular vertebral foramen
- C1 (Atlas): No body, no spinous process, anterior and posterior arches, lateral masses — supports the skull
- C2 (Axis): Dens (odontoid process) projects superiorly — forms pivot joint with atlas for head rotation ("no" movement)
- C7 (Vertebra prominens): Longest non-bifid spinous process — most prominent palpable neck landmark
Thoracic and lumbar vertebrae
- Thoracic: Heart-shaped body, long downward-pointing spinous process, costal facets
- Lumbar: Massive kidney-shaped body, short thick spinous process, no costal facets
Conus medullaris and lumbar puncture
The conus medullaris (tip of the spinal cord) lies at L1–L2 in adults. Below this, the subarachnoid space contains the cauda equina (L2–S5 nerve roots floating in CSF) — this region is the lumbar cistern.
Lumbar puncture is performed at L3–L4 or L4–L5, below the conus medullaris, to avoid direct cord injury. The needle passes through: skin → supraspinous ligament → interspinous ligament → ligamentum flavum → epidural space → dura mater → arachnoid mater → subarachnoid space (CSF collected).
Marking guide (10 marks): Regions and count (1) · Primary vs secondary curvatures with development timing (2) · Atypical cervical vertebrae — atlas, axis, C7 (2) · Typical C + thoracic + lumbar features (2) · Conus medullaris level (L1–L2) + cauda equina/lumbar cistern concept (1.5) · LP level + all layers needle passes through (1.5)