Chapter 12: Internal Anatomy of the Spinal Cord

columns (funiculi)

The three regional (dorsal/posterior, lateral, ventral/anterior) collections of white matter on each side of the spinal cord which are further subdivided into various specifically named ascending and descending white tracts (fasciculi); they transmit nerve impulses between upper and lower regions of the cord and to and from the brain; they are best observed in cross sections of the spinal cord and brain stem.

descending (motor) tracts

The white fiber tracts/fasciculi in the brain stem and spinal cord which carry primarily somatic and visceral motor (efferent) information inferiorly to lower centers with synaptic connections lower in the cord.

ascending (sensory) tracts

The white fiber tracts/fasciculi in the brain stem and spinal cord which carry primarily somatic and visceral sensory (afferent) information superiorly to higher centers with synaptic connections higher in the cord or within the brain.

tracts (fasciculi)

Specific groups of neuron processes (axons and/or dendrites) which carry similar functional types of impulses to and from similar destinations within the central nervous system (CNS); individual ascending and descending white fiber tracts which are grouped into three regional (dorsal/posterior, lateral, ventral/anterior) columns (funiculi) on each side of the spinal cord; in general, their names combine and indicate both their origin and destination; they transmit nerve impulses between upper and lower regions of the cord and to and from the brain; they are best observed in cross sections of the spinal cord and brain stem.

gray commissure

The central crossbar of gray matter, observable in every segment of the spinal cord, which encloses the central canal and connects with the masses of gray matter on each side.

anterior gray horn = ventral gray horn

The mass of gray matter, observable in every segment of the spinal cord, which houses the soma/cell bodies of the somatic motor (efferent) neurons (and various interneurons) and from which motor (efferent) axons emerge, exiting the cord, to form the anterior/ventral root of each spinal nerve.

posterior gray horn = dorsal gray horn

The mass of gray matter, observable in every segment of the spinal cord, which houses the soma/cell bodies of the various interneurons which receive sensory (afferent) impulses, which enter the cord via the posterior/dorsal root of each spinal nerve, from the somatic and visceral sensory (afferent) neurons which reside in the posterior/dorsal/sensory root ganglion.

lateral gray horn

The masses of gray matter, observable in only the thoracic, lumbar and sacral segments of the spinal cord, which houses the the soma/cell bodies of the autonomic/visceral motor (efferent) neurons (and various interneurons) and from which visceral motor (efferent) axons emerge, exiting the cord, to form the anterior/ventral root of each spinal nerve; this is a major control center for the Autonomic Nervous System (ANS).

central canal

The narrow tube originating posteriorly from the fourth ventricle which runs throughout the center of the medulla oblongata and the spinal cord; it is lined by ependymal cells and contains cerebrospinal fluid which is flowing posteriorly.

anterior white commissure = ventral white commissure

The relatively narrow crossbar of white matter, observable in every segment of the spinal cord, which lies anterior/ventral to the gray commissure and posterior/dorsal to the anterior median fissure, and which contains various nerve fibers crossing from one side of the cord to the other.

posterior white commissure = dorsal white commissure

The relatively narrow crossbar of white matter, observable in every segment of the spinal cord, which lies posterior/dorsal to the gray commissure and anterior/ventral to the posterior median sulcus, and which contains various nerve fibers crossing from one side of the cord to the other.