Download The Spinal Cord

Biology 211
Anatomy & Physiology I
Dr. Thompson
The Spinal Cord
Human Central Nervous System
Starts as a hollow tube
in the embryo;
Remains hollow &
fluid-filled throughout
life; These spaces form
the ventricles of the
brain and the central
canal of the spinal
cord.
Cranial end of this hollow tube enlarges & folds to form the
brain and its various parts
Caudal end of this hollow tube does not enlarge or fold;
Develops into spinal cord
Spinal cord surrounded by 3 layers of connective tissue:
Pia Mater
Arachnoid Mater
Dura Mater
Pia Mater
Subarachnoid Space
Arachnoid Mater
Subdural Space
Dura Mater
Epidural Space
(Vertebrae)
The spinal cord is protected in three ways:
1) Vertebrae (bone)
2) Meninges
Pia Mater
Arachnoid Mater
Dura Mater
3) Floats in cerebrospinal
fluid in subarachnoid
space
Cerebrospinal fluid produced
within ventricles by choroid
plexus.
Exits from fourth ventricle
through three openings
(apertures or foramina) into the
subarachnoid space.
Median Aperture
Two Lateral Apertures
Surrounds brain & spinal cord.
Reabsorbed into blood
through arachnoid villi on
surface of brain
Posterior Median Sulcus
Central
Canal
Anterior Median Fissure
Recall: In brain and spinal cord
Gray Matter: Nervous
tissue of the CNS
consisting of neuron cell
bodies, their supporting
glia, and unmyelinated
axons & dendrites.
White Matter: Nervous
tissue of the CNS
consisting of myelinated
axons & dendrites and
their supporting glia
White Matter
Gray Matter
Gray Matter of Spinal Cord
Dorsal (Posterior) Horn: Cell bodies of neurons which
receive afferent information from spinal nerves and send
it toward the brain
Lateral Horn: Cell bodies of
neurons which receive
efferent information from the
brain and send it to smooth
myocytes, cardiac myocytes,
and glands (autonomic motor
innervation)
Ventral (Anterior) Horn: Cell bodies of neurons which
receive efferent information from the brain and send it to
skeletal myocytes (somatic motor innervation)
White Matter of Spinal Cord
Myelinated axons carrying information between brain and
gray matter of spinal cord (both directions).
Dorsal (Posterior) Column:
Lateral Column:
Ventral (Anterior) Column:
Within each column, axons with same functions organized
into bundles called tracts
Tracts of the spinal cord are described in your text.
You should be able to describe, in moderate detail, at least
one ascending tract and one descending tract:
Where it begins
Where it ends
If it deccusates
Where it is located in the spinal cord
What type of information it carries
What would happen if it were damaged
Spinal cord gives rise to spinal nerves.
A pair of spinal nerves (one on
each side) exits between each
pair of vertebrae from the atlas
(cervical 1) to the first vertebra
of the coccyx
Each nerve connects with spinal cord through two roots:
Dorsal (posterior) root
Carries afferent
information into
dorsal horn of gray
matter
Ventral (anterior) root
Carries efferent
information away
from ventral horn
of gray matter
Spinal nerves are named according to
which vertebrae they pass between:
8 cervical nerves
12 thoracic nerves
5 lumbar nerves
5 sacral nerves
1 coccygial nerve
Levels of the spinal cord
named according to which
spinal nerve carries
information in/out of it.
Spinal nerves are named according to
which vertebrae they pass between:
8 cervical nerves
12 thoracic nerves
5 lumbar nerves
5 sacral nerves
1 coccygial nerve
Levels of the spinal cord
named according to which
spinal nerve carries
information in/out of it.
Thus: Spinal cord level "cervical 5"
is defined as the region where
spinal nerve "cervical 5" connects
Months before you were born, your spinal cord reached all the
way through your sacrum, but as you continued to develop it
grew less quickly than the vertebrae which surround it.
At birth, your conus medullaris was at lumbar vertebrae 3 or 4.
It now lies between lumbar vertebrae 1 and 2.
That means that dorsal
Roots and ventral roots of
the spinal nerves must
extend inferiorly to reach
the proper intervertebral
foramina, forming the
cauda equine which is in
the subarachnoid space
Next: Let's follow the spinal nerves distally as they
form the peripheral nervous system.