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Spinal Cord Notes
ANATOMY OF SPINAL CORD
 Extends from medulla oblongata
 Ends at second lumbar (L2)
vertebra in adults
 31 pairs of spinal nerves
 Conus medularis – end of cord
 Two enlargements:


Cervical enlargement - C4 –
T1 – nerves to & from upper
limbs
Lumbar enlargement – T9-T12
– nerves to & from lower limbs
 Cauda equina = “horse’s tail”
 After
conus medullaris, spinal
cord divides into nerves that
leave at lower levels
CROSS SECTION ANATOMY
 Two grooves divide spinal cord:
Anterior median fissure
(deeper)
 Posterior median sulcus
 Gray matter (unmyelinated) forms
an “H” in center
 Gray commissure where fibers
cross from side to side

 Central canal – center of gray
commisure; continuous with fourth
ventricle
 Gray matter is divided into horns:
 Anterior (ventral) gray horns cell bodies of motor neurons to
skeletal muscle
 Posterior
( dorsal ) gray horns
 Lateral gray horns – cell bodies
of motor neurons to cardiac, and
smooth muscle & glands
 Part of autonomic nervous
system
 White matter (myelinated nerve
fibers) is divided into columns
 Anterior (ventral), posterior
(dorsal), lateral white columns
 Each column is divided into nerve
tracts
 Each tract carries one type of
information (sensory or motor)
 Ascending (sensory) tracts impulses toward brain
 Descending (motor) tracts –
impulses from brain
 Spinal cord has two functions:


White matter tracts serve as
information highways to and
from brain
Gray matter receives and
integrates information,
especially for spinal reflexes
 Name of tract indicate position in
cord, where it begins and ends,
and direction of impulses
DEVELOPMENT OF NS
 Begins in third week of
development
 Ectoderm forms a neural tube
 Neural tube defect due to low levels
of a folic acid
 Spina bifida – failure of laminae of
spine to unite, caused by low levels
of folic acid
 Portions of neural tube form fluid-
filled vesicles
 Hypothalamus is one of last areas
of brain to develop
 No new neurons form after birth,
only grow and maturation
 Brain reaches maximum weight as
a young adult