Which vein is considered the least firmly anchored?

The basilic vein is considered the least firmly anchored among the veins listed. This is largely due to its anatomical positioning and relationship with surrounding structures. The basilic vein runs along the medial aspect of the forearm and arm and is generally located more superficial compared to the other veins. Its proximity to the skin and its tendency to have a more variable course contribute to its less stable anchoring.

In contrast, the median cubital vein, which is commonly used for venipunctures, has a firmer anchoring due to its location and the way it crosses over the tendons. The cephalic vein, located on the lateral side of the arm, is typically well-anchored as it often runs along the biceps muscle and is more structurally supported. The subclavian vein, being deeper and larger, is also firmly anchored, especially in relation to the clavicle and surrounding thoracic structures.

The anatomical variability and less robust relationship of the basilic vein with surrounding tissues highlight why it is categorized as the least firmly anchored among the options.