Which of the following tracts carries proprioceptive and discriminative touch sensation from the lower limbs and crosses at the medulla?

Explanation

## Fasciculus Gracilis — Anatomy and Function **Key Point:** The fasciculus gracilis is the medial component of the dorsal column (posterior funiculus) that carries fine touch, vibration, and proprioception from the lower limbs and lower trunk. ### Anatomical Pathway 1. First-order neurons: peripheral receptors → dorsal root ganglia → enter spinal cord at dorsal root 2. Ascend ipsilaterally in fasciculus gracilis (medial dorsal column) 3. Synapse in nucleus gracilis at the medulla 4. Second-order neurons: decussate as internal arcuate fibers → form medial lemniscus 5. Ascend contralaterally to VPL thalamus → primary sensory cortex (postcentral gyrus) ### Key Features | Feature | Fasciculus Gracilis | | --- | --- | | **Location** | Medial dorsal column (below T6) | | **Sensory modality** | Proprioception, vibration, discriminative touch | | **Decussation level** | Medulla (at nucleus gracilis) | | **Ipsilateral vs contralateral** | Ipsilateral ascent → contralateral after crossing | | **Body region** | Lower limbs, lower trunk | | **Clinical sign** | Loss = sensory ataxia (Romberg +), loss of vibration/proprioception | **High-Yield:** Fasciculus gracilis is **medial** (remember: **G**racilis = **G**reat (lower body) and medial position). Fasciculus cuneatus is **lateral** (upper limbs/trunk). **Mnemonic:** **DCML** = Dorsal Column–Medial Lemniscus pathway. Decussates at the **Medulla**, not the spinal cord. **Clinical Pearl:** Tabes dorsalis (neurosyphilis) classically damages the dorsal columns, causing loss of proprioception and vibration sense with preserved pain/temperature (spinothalamic tract intact).