Anatomy Flashcards

At which vertebral level does the conus medullaris (tip of the spinal cord) typically terminate in a healthy adult?

Answer: L1–L2

In adults the spinal cord ends at approximately the L1–L2 level. This is why lumbar puncture and spinal anaesthesia are performed below L2 (typically L3–L4 or L4–L5) to avoid direct cord trauma. In neonates the cord ends lower (around L3) and ascends with growth.

The brachial plexus is formed by the anterior primary rami of which spinal nerve roots?

Answer: C5–T1

The brachial plexus arises from C5, C6, C7, C8, and T1. C4 may contribute a small branch (pre-fixed variant) and T2 a small contribution (post-fixed variant), but the classic five roots are C5–T1. This is essential knowledge for interscalene, supraclavicular, infraclavicular, and axillary block planning.

The cricothyroid membrane, the target for emergency surgical airway access, connects which two cartilaginous structures?

Answer: Thyroid and cricoid cartilage

The cricothyroid membrane spans between the inferior border of the thyroid cartilage and the superior border of the cricoid cartilage. It lies in the midline, is relatively avascular, and is the preferred site for needle or surgical cricothyroidotomy in a 'can't intubate, can't oxygenate' scenario.

In the antecubital fossa, what is the positional relationship of the median nerve to the brachial artery?

Answer: Medial to the artery

The median nerve lies medial to the brachial artery in the antecubital fossa. The mnemonic VAN (Vein–Artery–Nerve, medial to lateral) helps recall that the median nerve is the most medial structure. Awareness of this relationship is important during antecubital IV placement and brachial artery cannulation.

The phrenic nerve descends through the thorax. Which statement best describes its intrathoracic course?

Answer: It descends anterior to the lung root along the lateral surface of the fibrous pericardium

The phrenic nerve (C3, C4, C5) descends anterior to the lung root (hilum) and travels along the lateral surface of the fibrous pericardium to reach the diaphragm. The vagus nerve, by contrast, descends posterior to the lung root. This anatomy explains why pericardial surgery or mediastinal tumours can injure the phrenic nerve, causing diaphragmatic paralysis.

Which bony landmark defines the superior boundary of the 'safe triangle' for intercostal chest drain insertion in the midaxillary line?

Answer: The upper border of the rib below the target intercostal space

Intercostal neurovascular bundles (vein, artery, nerve — VAN order, superior to inferior) run in the groove on the inferior surface of each rib. Inserting a chest drain over the upper border of the lower rib avoids the bundle. The 'safe triangle' for a drain is bounded by pectoralis major anteriorly, latissimus dorsi posteriorly, and the 5th intercostal space inferiorly, with entry over the superior rib border.