Spinal Cord External Features , Coverings And Blood Supply

Question 1

What are the components of the central nervous system?

Answer 1

Brain (cerebrum & cerebellum), Brain stem (midbrain, pons & medulla oblongata), Spinal cord.

Question 2

How many pairs of cranial nerves are there?

Answer 2

12 pairs

Question 3

What are the divisions of the autonomic nervous system?

Answer 3

Parasympathetic (cranio-sacral) part and Sympathetic (thoracolumbar) part

Question 4

How many spinal segments are there?

Answer 4

31 segments

Question 5

What are the coverings (spinal meninges) of the spinal cord?

Answer 5

Pia mater, Arachnoid mater, Dura mater

Question 6

What are the 3 membranes surrounding the spinal cord?

Answer 6

Pia, arachnoid, and dura maters

Spinal cord is surrounded by 3 membranes (meninges) ; pia, arachnoid & dura maters (from inside outwards).

Question 7

What is the Lumbar cistern?

Answer 7

Lower part of spinal sub-arachnoid space (devoid of spinal cord) extending from L2-S2. It contains CSF, cauda equine & filum terminale. Important site for lumbar puncture.

N.B. 1-Lumbar cistern: Lower part of spinal sub-arachnoid space (devoid of spinal cord) extending from L2-S2. It contains CSF, cauda equine & filum terminale. Important site for lumbar puncture.

Question 8

What is Lumbar puncture?

Answer 8

A needle is introduced in subarachnoid space to obtain CSF sample or to inject drug. Done below L2 to avoid spinal cord injury, cauda nerves are not liable to be injured by needle being floating in CSF.

2-Lumbar puncture: A needle is introduced in subarachnoid space to obtain CSF sample or to inject drug. Done below L2 to avoid spinal cord injury, cauda nerves are not liable to be injured by needle being floating in CSF.

Question 9

What are the 4 bands formed by the pia mater?

Answer 9

• Linea splendens: Median glistening pia mater band, extending along ant. median fissure.
• Subarachnoid septum: Backward pia mater extension at post. median sulcus, to attach to dura mater.
• Filum terminale: Slivery glistening pia mater fibrous band, extending downwards from tip of conus medullaris among cauda equine. At level of S2 vertebra it pierces arachnoid & dura, acquires a dural investment to attach to coccyx back.
• Denticulate ligaments: 2 pia mater lat. bands, piercing arachoid to attach to dura mater. Its lat. edge is serrated & has 21 processes. It extends from foramen magnum to L1 vertebra, lying midway between ventral & dorsal spinal nerve roots.

Question 10

What is the site of the Epidural space?

Answer 10

Between dura mater & vertebral canal periosteum, contains: Loose areolar tissue & fat. Internal vertebral v. plexus. Spinal nerve roots.

• Epidural (extra- dural) space: Between dura mater & vertebral canal periosteum, contains: *Loose areolar tissue & fat. *Internal vertebral v. plexus. *Spinal nerve roots.

Question 11

What is the arterial blood supply to the spinal cord?

Answer 11

Ant. spinal a. Post. spinal aa. Radicular spinal aa.

Arterial supply; Ant. spinal a. Post. spinal aa. Radicular spinal aa.

Question 12

What is the venous drainage of the spinal cord?

Answer 12

6 longitudinal ven

Venous drainage: 6 longitudinal ven

Question 13

What is the main blood supply source to the lower 1/3 of the spinal cord?

Answer 13

Central branches of the spinal arteries

They are the main blood supply source to the spinal cord lower 1/3.

Question 14

What do the spinal arteries anastomose together around?

Answer 14

Conus medullaris

They anastomose together around the conus medullaris.

Question 15

What is the name of the artery that supplies the lumbar enlargement and is very large?

Answer 15

Arteria radicularis magna

The one supplying lumbar enlargement is very large (arteria radicularis magna).

Question 16

How many longitudinal venous channels are involved in the venous drainage of the spinal cord?

Answer 16

6

There are 6 longitudinal venous channels involved in the venous drainage.

Question 17

Where are the longitudinal venous channels drained into?

Answer 17

Internal vertebral venous plexus in epidural space

The longitudinal venous channels are drained by radicular vv. into the internal vertebral venous plexus in the epidural space.

Question 18

Site & length of spinal cord

Answer 18

Occupies upper 2/3 of vertebral canal, 45cm long in males & 42 cm long in females.

These changes are due to differential growth between spinal cord (slower) & vertebral column (faster).

Question 19

Beginning of spinal cord

Answer 19

At lower border of foramen magnum at level of 1st cervical n., as continuation of medulla oblongata.

None

Question 20

End of spinal cord

Answer 20

Lower end tapers forming conus medullaris which ends at different levels based on age: a.By 3rd month intrauterine life, it occupies whole vertebral canal. b.At birth, it ends at L3 vertebra level c.In adults, it ends at level of disc between L1/L2 vertebrae.

Question 21

Shape of spinal cord

Answer 21

Cylindrical, showing 2 enlargements; a.Cervical enlargement: from C5-T1 spinal segments b.Lumbar enlargement: from L1-S3.

Question 22

Sulci (grooves) of spinal cord

Answer 22

It shows 6 external longitudinal sulci (grooves); Deepest For exit of ventral (motor) roots For entry of dorsal (sensory) of spinal nerves. roots of spinal nerves. Ant. median fissure Post. median sulcus Two antero-lateral sulci Two postero-lateral sulci