Identify the tissue sample.

• A. Brain cortex
• B. Dorsal root ganglion
• C. Spinal cord
• D. Peripheral nerve

Answer: (C)

Recognizing tissue type from histology by its characteristic architecture. A cross-section of the spinal cord is defined by a gray matter region shaped like an H or butterfly, containing the dorsal (sensory) and ventral (motor) horns, surrounded by white matter of myelinated tracts. The central canal, lined by ependymal cells, may be visible in the center. This combination—distinct gray matter horns plus an enclosing white matter —is the hallmark that identifies the spinal cord.

Brain cortex would show a layered arrangement of neurons and glial cells across cortical layers, not an H-shaped gray region. A dorsal root ganglion consists of a cluster of neuron cell bodies in the peripheral nervous system, without the spinal-cord’s horned gray matter pattern. A peripheral nerve would reveal bundles of axons with connective tissue sheaths (endoneurium, perineurium, epineurium), lacking the central gray matter and horn organization.