1. Spinal Cord and Brain Stem
Prof. K. Sivapalan

2. Spinal Cord and Brain Stem
Gross Structure
The upper end continues as the medulla oblongata at the upper border of the C1 vertebra
31 pairs of spinal nerves come out of spinal cord.
Cervical and lumbar enlargements to accommodate neurons that innervate the limbs
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Spinal Cord and Brain Stem

3. Spinal Cord and Brain Stem
Nerve Roots
Anterior and posterior nerve roots.
Each root is formed by aggregation of several rootlets that arise over a certain length of the cord
Rootlets of one root arise from one spinal segment
The dorsal rootlets arise along the postero-lateral salcus
The dorsal root has the dorsal root ganglion.
The two roots meet to form the spinal nerve that emerges through the intervertebral foramen.
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Spinal Cord and Brain Stem

4. Spinal Cord and Brain Stem
Length of the Cord
The spinal cord is equal to the vertebral canal during early fetal life.
The vertebra out grow the spinal cord and the lower end is at L3 at birth
The lower end of the adult cord is at the lower border of the L1± 1 vertebra.
The spinal nerves travel in the vertebral canal until they reach the appropriate intervertebral foramina.
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Spinal Cord and Brain Stem

5. Spinal Cord and Brain Stem
Conus Medullaris
The lower end is called conus medullaris.
It continues as fibrous cord called filum terminale up to the sacrum.
The spinal nerves beyond the end of the spinal cord form the cauda equina
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Spinal Cord and Brain Stem

6. Spinal Cord and Brain Stem
Structure of the Cord
Butterfly shaped [H shaped] gray matter surrounded by white matter.
White matter is in three funiculi [columns] on either side:
Anterior funiculus between anterior median fissure and anterior root
Lateral funiculus between anterior and posterior roots
Posterior funiculus between the posterior root and the posterior median septum
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Spinal Cord and Brain Stem

7. Spinal Cord and Brain Stem
The Gray Matter
Central gray with a minute central canal
Anterior [motor] and posterior [sensory] horns on either side
A lateral gray horn [autonomic- dorsal sensory and ventral motor] in the spinal segments from T1 to L2 , S2-S4.
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Spinal Cord and Brain Stem

8. Communication Between Both Sides
Gray commissure anterior to the central canal
Anterior white commisure deep to the anterior median fissure
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Spinal Cord and Brain Stem

9. Spinal Cord and Brain Stem
The spinal cord continues as the brain stem in the base of the skull.
The arrangement of gray in the centre and white matter around in the spinal cord is disturbed in the brain stem because of the flexures and development .
The ascending, descending and transverse tracts divide the gray into collection of cells called nuclei.
In addition to recognizable nuclei, neurons are disbursed through out the brainstem performing autonomic and other functions.
These neurons are named reticular formation collectively
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Spinal Cord and Brain Stem

10. Spinal Cord and Brain Stem
Medulla
Transition of spinal cord to medulla is not abrupt at the upper border of atlas but over a certain distance.
It is narrow [closed- around central canal] below and widens above [open- under fourth ventricle].
3 cm long and 2 cm at the upper end
The surface has longitudinal fissures and sulci that divide it into regions.
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Spinal Cord and Brain Stem

11. Spinal Cord and Brain Stem
Anterior aspect
Anterior median fissure and posterior median sulcus are continuations from spinal cord.
Antero lateral sulcus lies in line with ventral roots of the spinal nerves
The rootlets of the hypoglossal nerve [12] emerge from this sulcus
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Spinal Cord and Brain Stem

12. Spinal Cord and Brain Stem
Anterior aspect ctd
The area between anterior median fissure and anterior medial sulcus is occupied by an elevation called the pyramid
Fibers in pyramid decussate obliterating the fissure.
The region between anterolateral and posterolateral sulci has a prominent, oval about 1.3 cm long swelling named olive
Inferior olivery nucleus lies under this
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Spinal Cord and Brain Stem

13. Spinal Cord and Brain Stem
Posterior Aspect
Posterolateral sulcus lies in line with dorsal roots and ninth, tenth and eleventh nerves emerge from this.
The area between the posterior median sulcus and posterior lateral sulcus two rounded elevations called gracile and cuneate tubercles are seen.
They contain nucleus gracilis and nucleus cuneatus under them.
The fourth ventricle continues below as the central canal.
Connects to cerebellum by the inferior cerebellar peduncle.
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Spinal Cord and Brain Stem

14. Spinal Cord and Brain Stem
Pons
The junction of pons and medulla is marked by a groove through which sixth, seventh and eighth nerves emerge.
Trigerminal nerve [5] emerges from the anterior surface.
Nerve fibers run transversely and form the middle cerebellar peduncle laterally.
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Spinal Cord and Brain Stem

15. Spinal Cord and Brain Stem
Pons ctd.
Connects to cerebellum by the middle cerebellar peduncle
The lateral aperture of the fourth ventricle lies on either side of the lower pons near the cerebello-pontine angle
Posterior aspect forms the floor of fourth ventricle.
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Spinal Cord and Brain Stem

16. Spinal Cord and Brain Stem
Mid Brain
Anteriorly two large bundles of fibers are seen on either side of the midline.
These are named the crura of the midbrain [cerebral peduncles]
The crura are separated by a deep fissure, diverging to enter the cerebral hemispheres.
The occulomotor nerve emerges from the medial aspect of the crus.
Fourth nerve emerges from the dorsal surface
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Spinal Cord and Brain Stem

17. Spinal Cord and Brain Stem
Mid Brain ctd.
Midbrain is continuous with cerebral hemisphers above
The posterior aspect is marked by two pairs of rounded swellings known as superior and inferior colliculi.
The aqueduct continues below as the fourth ventricle
Connects to cerebellum by the superior cerebellar peduncle.
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Spinal Cord and Brain Stem