Spinal Cord Overview: Anatomy & Histology
Summary
cross-section of the spinal cord: anatomic view
General Notes
Note the following:
- The posterior and anterior orientation of our anatomical cross-section has the opposite orientation of radiographic view.
- The central canal is mostly obliterated by the second decade of life.
- See: Spinal Cord Photos
Key spinal cord anatomical structures
The gray matter horns
From posterior to anterior:
- The posterior horn, which comprises sensory nuclei.
- Intermediate zone, which comprises autonomic and spinocerebellar nuclei.
- Anterior horn, which comprises motor nuclei.
White matter funiculi (aka columns)
- The white matter of the spinal cord is segmented into the following funiculi (aka columns):
From posterior to anterior:
- Posterior funiculus, which carries large proprioceptive sensory afferents for movement and position sensation.
- Lateral funiculus, which carries large motor efferents (ie, the corticospinal tracts).
- Anterior funiculus, which carries small, thermoceptive and nociceptive sensory afferents for pain and temperature sensation, respectively.
- Fasciculus proprius, which comprises the collective bundle of interspinal rostro-caudal white matter projections; thus, it is also referred to as the spinospinal tract.
Spinal Cord Histology
Luxol fast blue stain turns the proteolipid of myelin blue, making it prominent.
- We delineate the: posterior horn, intermediate zone, and anterior horn; posterior funiculus, lateral funiculus, and anterior funiculus; fasciculus proprius.
10 Rexed laminae
- They constitute the functional categorization of neurons within the gray matter horns.
Here, we list some key lamnia nomenclature within their gray matter horns.
Posterior horn
From posterior to anterior:
- Laminae I–VI, correspondingly, these are the sensory laminae.
- Lamina I: the marginal nucleus (aka posteromarginal nucleus)
- Lamina II: substantia gelatinosa, so-named because its lack of myelinated fibers gives it a gelatinous appearance on myelin staining.
- As a simplification, laminae I and II (and also lamina V) receive small, poorly myelinated or unmyelinated fibers, which carry pain and temperature sensation.
- Laminae III and IV comprise nucleus proprius
- They receive large cutaneous sensory fibers. However, that the majority of large fibers do not synapse within the Rexed laminae at all but instead directly ascend the posterior columns.
- Laminae V and VI
- They receive descending motor fibers and assist in sensorimotor integration.
Intermediate zone
- Lamina VII
- Comprises the dorsal nucleus of Clarke (a key spinocerebellar nuclear column) and the intermediolateral cell column (a key autonomic nuclear column).
Anterior horn
- Laminae VIII and IX, which are the motor laminae.
- Lamina X surrounds the central canal.
Section of anterior spinal cord
Notes on Staining
- In this slide, myelin is blue, because the Luxol fast blue stain turns the proteolipid of myelin blue.
- Here, Cresyl violet staining stains the gray matter neurons and cell processes because the Nissl substance in the neurons has a high RNA content, which makes it basophilic, and turns in violet with this stain.
Histology
- The anterior nerve roots stain blue from their myelin.
- The prominent anterior median fissure is the deep longitudinal fissure along the anterior surface of the spinal cord.
- The leptomeninges are the pia/arachnoid mater covering of the spinal cord.
- The prominent anterior spinal artery lies in midline.
Histology of a motor neuron
See: Spinal Motor Neuron
- Lies within the anterior horn of the spinal cord.
- We note its cell body, nucleus, nucleolus (which is prominent), and a dendrite (a dendritic process), and its cone-shaped axon hillock, which connects the cell body to the base of the axon.
Clinical Correlations:
Related Tutorials
Histological Images
Histological images modified with permission from:
- http://medsci.indiana.edu/a215/virtualscope/docs/chap6_3.htm
- http://medsci.indiana.edu/c602web/602/c602web/toc.htm