Spinal Cord

The spinal cord

Function 1.To convey affernt impulses from receptors to the brain and to conduct efferent impulses from the brain to the effectors. 2.Be related to the reflexes.

I. The external features

6 longitudinal grooves Ant. median fissure Post. median sulcus Anterolateral sulci Posterolateral sulci

31 segments 8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccygeal

The relationship of spinal cord with vertebral body Spinal cord segments C1---C4

Vertebral bodis the same number of vertebrae (C1---C4)

C5---T4

the same number of vertebrae － 1 (C4---T3)

T5---T8

the same number of vertebrae － 2 (T3---T6)

T9---T12

the same number of vertebrae － 3 (T6---T9)

L1---L5

T10-12

S1---S5, CO1

L1

two enlargements cervical C5---T1 lumbosacral L2---S3

conus medullaris filum terminale cauda equine

II. The internal structure ant. horn gray matter

intermediate zone post. horn

white matter

ant. funiculus lat. funiculus post. funiculus

lateral horn

1. The gray matter the ant. horn

lower motor neurons intermediolateral nucleus (C8-L2 or L3)

the intermediate zone

Clarke’s nucleus (C8-L3) the sacral parasympathetic nucleus(S2—S4)

the post. horn

sensory interneurons and project neurons

substantia gelatinosa

substantia gelatinosa Clarke’s nucleus (C8-L3)

intermediolateral nucleus (C8-L2 or L3)

motor neurons

substantia gelatinosa

motor neurons

the sacral parasympathetic nucleus(S2—S4)

2. The white matter

① long ascending tracts

fasciculus gracilis and fasciculus cuneatus spinothalamic tract ant. & post. spinocerebellar tracts

② long descending tracts ③ shorter propriospinal tracts

corticospinal tracts

fasciculus cuneatus

fasciculus gracilis

posterior spinocerebellar tract

lateral corticospinal tract

anterior spinocerebellar tract

lateral spinothalamic tract

anterior spinothalamic tract

anterior corticospinal tract

summary

In the cross section of the spinal cord, based on neuronal size,shape,cytological features and density in different regions, ten laminas have been distinguished,which are arrayed more or less parallel with the dorsal and ventral limits of the gray matter and extend throughout most of the length of the spinal cord. These laminas are called the laminae of Rexed. Briefly,the structure of laminae is as follows.

the laminae of Rexed

Transverse section of C6 segment

Transverse section of L5 segment

Part of the laminae of Rexed Nucleus

Levels

Lamina

Function

All

II

Modulate transmission of pain and temperature info.

Clarke’s nucleus

C8—L2

VII

Post. spinocerebellar tract cells

Intermediolateral nucleus

C8—L3

VII

Preganglionic sympathetic neurons

Sacral parasympathetic nucleus

S2—S4

VII

Substantia gelatinosa

Preganglionic parasympathetic neurons