Brief handout on spinal cord : helpful for oral examination

Spinal Cord & Nerves

This is the viscera of spinal cord and spinal meninges

1.         Anatomical points:

              I.         anteriror median fissure lies anteriorly

           II.      cauda equina lies inferiorly

2.         length : 45cm                    wide 2.5 cm

3.          Extension of spinal cord:

   Adult: start at the level of foramen magnum to lower border of 1^st lumbar vertebra

   Children: at the level of the foramen magnum to the 3^rd lumber vertebra

4.         Terminal part of sub-arachnoid space of the spinal cord : lower border of 2^nd sacral vertebra

5.         termination of filum terminalis: at the 1^st coccyx

External feature of spinal cord :

i)                    anteriorly : anterior median fissure

ii)                  posteriorly : posterior median septum

iii)                inferiorly : filum terminalis and cauda equine

iv)                two enlargement in cervical and lumbar region

v)                  external surface is covered by spinal meninges : outer meningeal dura mater, middle arachnoid mater and  inner pia mater

vi)                ventral roots, dorsal roots and dorsal root ganglia and spinal nerve

6.         How many enlargement present within the spinal cord and why?

i)                    Cervical enlargement: extend from the foramen magnum to 1^st thoracic vertebra. Supply upper limb

ii)                  Lumbar enlargement: extend from thoracic 10^th to 12^th vertebra. Supply lower limb.

7.         What is spinal segment?

 Ans: Part of the spinal cord to which one pairs of spinal nerve is attached.

8.         How many spinal segments present in the spinal cord? – 31 spinal segments

9.         What is conus medullaris? – cone shaped terminal part of spinal cord

10.     What is filum terminalis ? – it is the prolongation of pia mater which extend from the cunus medullaris to 1^st coccyx

11.     What is cauda equine: the lumbar and sacral roots below the termination of spinal cord continue as a leash of nerve roots known as cauda equine.

What is legamentum denticulate: it is the thickening of pia mater situated on either side of spinal cord between nerve roots.

Internal feature of spinal cord:

Inner grey matter contains a central canal. Parts of grey matter, ant horn and pos horn and lateral horn only in thoracic and lumbar region

Grey matter contain motor and internuncial neuron

Parts of outer white matter: 1. anterior (ventral) column

                        2. posterior (dorsal) column

                        3. lateral (intermediate) column

white matter contain ascending and descending tracts:

fasciculi/tracts –they are collection  axon bundles within the CNS. They are two types:                               

      a. ascending tracts – carry sensory impulse to the brain. Spinothalamic tract  

            b. descending tracts – carry motor impulse from brain to the effector organ (skeletal muscle). corticospinal tract

Important tract within the spinal cord :

ASCENDING TRACTS (SENSORY)
anterior (ventral) spinothalamic	touch and pressure to thalamus
lateral spinothalamic tract	pain & temperature to thalamus
fasciculus gracilis	touch, 2-pt. discrimination,
fasciculus cuneatus	conscious proprioception,      vibration
posterior spinocerebellar                                  anterior spinocerebellar	subconscious proprioception

DESCENDING TRACTS (MOTOR)
lateral corticospinal                                          anterior corticospinal tract	Carry motor output from cortex to motor neuron of ant. Grey horn which stimulate the skeletal muscles

Blood supply: one ant and two posterior spinal arteries. Other branches: ascending cervical a, pos intercostals a, and the lumbar a

Vein: ant and pos spinal vein.

Development : caudal part of neural tube (neuroectodarm)