SPINAL CORD

I.   INTRODUCTION
-- spinal cord rests within vertebral canal
-- from foramen magnum to L1 vertebra

II.  SPINAL CORD MORPHOLOGY
--  oval in cross-section

-- enlarged in two areas

1.  Cervical Enlargement
* contains neurons that innervate upper limb

2.  Lumbar Enlargement
* contains neurons that innervate lower limb

 

-- conus medullaris:

 

 

-- cauda equina:

 

 

 

 

-- filum terminale:

 

 

 

 

-- 31 pairs of spinal nerves

* 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal

--  So what exactly IS a nerve?
*  typically a structure you can see with the naked eye (MACROscopic)
(in contrast, an axon is a MICROscopic structure)

*  formed from MANY axons bundled together in connective tissue wrappings

III. MENINGES OF SPINAL CORD
-- epidural space

A.  Dura Mater

B.  Arachnoid

* subarachnoid space

C.  Pia Mater

IV.  CROSS SECTION OF SPINAL CORD
-- central canal
* lined with ependymal cells
* produces CSF

-- spinal cord divided into gray matter and white matter

A.  Gray Matter: nerve cell bodies, unmyelinated axons, supporting cells, and interneurons

1.  Anterior (Ventral) Horns: cell bodies of somatic motor neurons
** innervate skeletal muscle

2.  Lateral Horns: cell bodies of autonomic motor neurons
** prominent only in the T1-L2 regions of the spinal cord
** innervate cardiac muscle, smooth muscle and glands

3.  Posterior (Dorsal) Horns: interneurons and axons of sensory neurons

4. Gray Commissure
** unmyelinated axons crossing from one side to another
**  contains central canal

 

B.  White Matter: myelinated axons

 

 

1.  Anterior funiculi:

2.  Lateral funiculi:

3.  Posterior funiculi:

 

V.   SPINAL CORD TRACTS
--  Def: bundles of axons that run in the white matter of the spinal cord

-- two kinds:
1.  Ascending tracts: sensory axons

2.  Descending tracts: motor axons

-- each funiculus contains both ascending and descending tracts

-- tracts are given names, according to their starting and ending points:

* ex: corticospinal tract

* you do NOT need to learn the names and functions of the individual spinal cord tracts!

VI.    SPINAL NERVES
–  each spinal nerve is formed from:

1.  anterior (ventral) root: axons from motor neurons                                  

       

2.  posterior (dorsal) root:  sensory axons

 

 

* posterior (dorsal) root ganglion

Which statement is TRUE about the spinal cord?

a. it extends down to the level of the 4th sacral vertebra

b. there are 29 pairs of spinal nerves

c. it was formed from neural crest cells

d. it has 3 coverings (pia mater, arachnoid, dura mater) surrounding it

e. it consists of gray matter ONLY

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