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Control and Co-ordination — BIOLOGY STD 12 Science — Question

Maharashtra BoardEnglish MediumSTD 12 ScienceBIOLOGYControl and Co-ordination5 Marks
Question
Describe T.S. of spinal cord.
✓

Answer

  1. Externally there are three meninges covering spinal cord Duramater, arachnoid membrane and pia mater.
  2. Dorsoventrally there are two fissures, the shallow dorsal or posterior fissure and the deeper ventral or anterior fissure.
  3. From dorsal fissure a dorsal septum extends inside.
  4. Neurocoel or central canal is situated in the centre of spinal cord.
  5. The central canal is filled with cerebro¬spinal fluid and is lined by cuboidal epithelial cells called layer of ependyma.
  6. There is inner grey and outer white matter in the spinal cord. This grey matter is in the shape of ‘H’ with two dorsolateral horns and two ventro-lateral horns.
  7. Dorsal horns form dorsal roots and ventral horns form ventral roots.
  8. White matter is divided into three columns, viz., the dorsal funiculi, ventral funiculi and lateral funiculi on either side.
  9. Ascending and descending tracts of nerve fibres arise from dorsal and ventral roots of the spinal cord. Ascending tracts are sensory while descending tracts are motor in nature.

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