Central Nervous System The Spinal Cord 脊 髓 Ling Shucai

The Spinal Cord External features Internal structure Functions

1. External features: Location: foramen magnum → lower border of first lumbar vertebra External longitudinal fissure (or)sulci: 6 Enlargements: 2 cervical enlargement: C4-T1 lumbar enlargement: L2-S3 Conus medullaris: 1 Filum terminale: 1 Segments of spinal cord: 31

External longitudinal fissure and sulci posterior lateral sulcus posterior median sulcus anterior lateral anterior median Filum terminale Cauda equina sulcus fissure

Spinal segment It's a part of spinal cord, which is connected with the rootlets of a pair of spinal nerve. 31 segments cervical segments 8 thoracic segments 12 lumbar segments 5 sacral segments 5 coccygeal segments 1

Corresponding relationship between spinal segments and vertebrae spinal segments vertebrae bodies C1-C4 C1-C4 C5 ~ C8, T l~ T4 C4 ~ T3 T5 ~ T8 T3 ~ T6 T9-T12 T6-T9 L1-L5 T10-T12 S l~S5,Co1 LI 

2. Internal structure Gray matter and central canal White matters

Gray matter parts: posterior horn central canal main nuclei: Lateral horn (only extends from Tl to L3 segments.) gray commissure (anterior and posterior ) lateral horn posterior horn gray commissure Intermediate zone anterior horn central canal Gray matter

medial group intermediate zone: posterior horn: anterior horn: the nucleus posteromarginalis anterior horn: medial group lateral group intermediate zone: intermediolateral nucleus intermediomedial nucleus posterior horn: the nucleus posteromarginalis the substantial gelatinosa the nucleus proprius: the dorsal nucleus (thoracic nucleus) the substantia gelatinosa the nucleus proprius the dorsal nucleus (thoracic nucleus) Intermediomedial nucleus: intermediolateral nucleus lateral group medial group

The nuclei and the laminas the nucleus posteromarginalis the substantia gelatinosa the nucleus proprius the dorsal nucleus (thoracic nucleus) intermediolateral nucleus Intermediomedial nucleus: medial group lateral group

White matter: parts: posterior median sulcus posterior funiculus posterior lateral sulcus funiculus proprius lateral funiculus anterior lateral sulcus anterior white commissure anterior median fissure anterior funiculus

Main tracts (or fasciculi): Ascending tracts: fasciculus gracilis(薄束）: come from sacral, lumbar and lower six thoracic nerves, terminate upon nucleus gracilis fascicules cuneatus（楔束）: come from cervical and upper six thoracic nerves, terminate upon nucleus cuneatus. *conducts the fine tactile and kinesthetic sense of the ipsilateral trunk and limbs. fascicules cuneatus fascicules gracilis

Spinothalamic tracts（脊髓丘脑束）anterior spinothalamic tracts thalamus Spinothalamic tracts（脊髓丘脑束）anterior spinothalamic tracts posterior spinothalamic tracts --- arises from opposite nucleus proprius --- terminate on thalamus --- conduct pain, thermal and rough tactile sense of opposite trunk and limbs anterior spinothalamic tracts lateral spinothalamic tracts nucleus proprius

lateral corticospinal tract: Descending tracts lateral corticospinal tract: --- arises from opposite cerebral cortex --- descends through lateral funiculus of spinal cord --- terminate on ipsilateral anterior horn (lateral group) --- controls the contraction of skeletal muscles of ipsilateral limbs anterior corticospinal tract: --- controls the movement of bilateral muscles of trunk lateral corticospinal tract anterior corticospinal tract

Decussatio Pyramidum

Other descending tracts: they are related to regulate muscle tonus Fascicules gracilis fascicules cuneatus lateral corticospinal tract Rubrospinal tract anterior spinothalamic tracts Reticulospinal tract anterior spinothalamic tracts vestibulospinal tract tectospinal tract anterior corticospinal tract

3. Functions: To convey afferent impulses, which come from somatic and visceral receptors to the brain, and conduct efferent impulses from brain to effectors. Related to reflexes