Internal morphology of the spinal cord
On completion of this study unit, you will be able to:
- Identify the divisions of the white and gray matter of the spinal cord.
- Describe the ascending and descending tracts of the white matter.
- Name and locate the nuclei of the anterior, posterior and intermediate horns of the gray matter.
- Identify the laminae of the gray matter.
The spinal cord is composed of a gray matter core which is surrounded by an outer mantle of white matter. Like in the brain, gray matter in the spinal cord is made up of neuronal cell bodies, glial cells and neuropil (unmyelinated axons, dendrites and glial cell processes), while white matter is composed of predominantly myelinated axons which form the ascending and descending tracts of the spinal cord.
The gray matter of the spinal cord can be divided functionally into three main regions: the anterior, posterior and lateral (intermediate) horns (only present in the thoracic region). The anterior horn is largely responsible for motor function, the posterior horn for sensory function and the intermediate horn for autonomic functions.
The gray matter of the spinal cord can also be divided into ten layers or Rexed laminae on the basis of its cytoarchitecture rather than location and function of the cells. The rexed laminae are numbered sequentially (I-X) from dorsal to ventral.
White matter marks the outer portion of the spinal cord, and is divided into three paired columns: the posterior, lateral, and anterior funiculi. The funiculi of the spinal cord are composed of longitudinally arranged nerve fibers which are bundled together into tracts (fasciculi). There are three main types of tracts, divided by their direction and function: ascending, which transmit sensory information, descending, which transmit motor information and intersegmental/propriospinal, which transmit information between spinal cord segments.
Find out more about the structures of the white and gray matter of the spinal cord with the videos below.
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Take a closer look at the structures of the gray and white matter in the galleries below.
|Divisons||Anterior, posterior and intermediate (lateral) horns|
|Posterior horn||Marginal nucleus (Rexed lamina I)
Gelatinous substance (Rexed lamina II)
Nucleus proprius (Rexed laminae III, IV, V)
Posterior thoracic nucleus (Rexed lamina VII)
Function: Sensory innervation
|Lateral horn||Intermediolateral nuclei (Rexed lamina VII)
Function: Sympathetic innervation
|Anterior horn||Medial group (Rexed lamina IX)
Central group (Rexed lamina IX)
Lateral group (Rexed lamina IX)
Function: Motor innervation
|Pericentral canal||Gray commissure (Rexed lamina X)
Function: Connects anterior and posterior horns of gray matter
|Divisons||Anterior, posterior and lateral funiculi|
|Tracts||Ascending, descending and intersegmental tracts (fasciculi)|
Anterolateral system: Spinothalamic, spinoreticular, and spinoolivary tract
Posterior column-medial lemniscus pathway: Cuneate and gracile fasciculus
Somatosensory pathways to the cerebellum: Anterior and posterior spinocerebellar tract
Functions: Transmit conscious and unconscious sensory information specific to pain, temperature, touch, pressure, vibration and proprioception
Pyramidal tracts: Anterior and lateral corticospinal tract
Extrapyramidal tracts: Tectospinal, medial reticulospinal, vestibulospinal, lateral reticulospinal and rubrospinal tract
Functions: Transmit voluntary and involuntary motor information
|Intersegmental tracts||Posterolateral tract (ascending and descending), medial longitudinal fasciculus (ascending and descending), septomarginal fasciculus (descending), interfascicular fasciculus (descending)
Functions: Interconnect neurons at different spinal segments, transmit autonomic functions