Ascending And Descending Tracts Of Spinal Cord

Spinal Cord Question And Answers

Question 1. Write a short note on laminar organization in spinal cord.
Answer:

Laminar organization in spinal cord

• In thick section, neurons of the spinal cord appear to have a laminar arrangement
• Starting from tip of dorsal horn towards the vertical horn ten layers are recognized
• These are as follows:

1. Lamina 1: Corresponds to posteromarginal nucleus
2. Lamina 2: Corresponds to substantia gelatinosa
3. Lamina 3 and 4: Corresponds to nucleus proprius
4. Lamina 5 and 6: Corresponds to the base of dorsal column
5. Lamina 7: Occupies the territory between dorsal and ventral horns and contains cells that function as interneurons. Nucleus dorsalis, intermediolateral, intermediomedial are clear cell columns recognized within this lamina
6. Lamina 8: Corresponds to ventral horn in thoracic segments
7. Lamina 9: Includes lateral group of nuclei of the ventral horn, supply skeletal muscles of limb
8. Lamina 10: Surrounds the central canal and contains decussating axons, neuroglia, and some neurons with interneuron properly.

Question 2. Write a short note on tracts of the spinal cord.
Answer:

Tracts of the spinal cord

• A collection of nerve fibers that connects two masses of gray matter within the central nervous system (CNS) is called a tract
• These are ascending and descending tracts, and named after gray matter connected by them.

Spinal Cord Descending Tracts: These include

• The pyramidal tract/corticospinal tracts
• Descends from cerebral cortex to spinal cord and consists of:
  • Lateral corticospinal tract
  • Anterior corticospinal tract.
• The extrapyramidal tracts include:
  • Rubrospinal tract
  • Medial reticulospinal tract
  • Lateral reticulospinal tract
  • Olivospinal tract
  • Vestibulospinal tract
  • Tectospinal tract.
• Pyramidal tracts
  • These are formed by axons of pyramidal cells lying in the motor area of cerebral cortex
  • From the base the first pass through the internal capsule, midbrain, pons, and medulla
  • At the lower border of medulla, 80% of fiers cross to opposite side, and is called as pyramidal decussation and enter the lateral column and descends on lateral corticospinal tract
  • The fibers which do not cross enter the anterior column and descend as anterior corticospinal tract.

Spinal Cord Ascending Tracts: These include the following

• Lateral spinothalamic tract
• Anterior spinothalamic tract
• Fasciculus gracilis
• Fasciculus cuneatus
• Anterior spinocerebellar tract
• Posterior spinocerebellar tract
• Spino-olivary tract
• Spinotectal tract.

Spinal Cord Multiple Choice Question And Answers

Question 1. All of the following are descending tracts except:

1. Anterior corticospinal tract
2. Rubrospinal tract
3. Spino-olivary tract
4. Olivospinal tract

Answer: 3. Spino-olivary tract

Question 2. All of the following statements about the laminar organization of spinal cord is correct except:

1. Lamina 1 corresponds to posteromarginal sulcus
2. Lamina 7 includes the intermediomedial, inter mediolateral and dorsal nuclei
3. Lamina 5 corresponds to the neck of the dorsal gray column
4. Lamina 8 occupies most of the dorsal horn in thoracic segments.

Answer: 4. Lamina 8 occupies most of the dorsal horn in thoracic segments.