Back and Spinal Cord

Question 1

How many vertebrae are there of each type?

Answer 1

7 cervical
12 thoracic
5 lumbar
5 sacral

=29

Question 2

difference between posterior herniation of the lumbar spine and posterolateral herniation?

Answer 2

posterior = local pain in the spine
posterolateral = Causes pain in the dermatome of the corresponding spinal root

Question 3

How many spinal nerves are there?

Answer 3

31 pairs

8 cervical
12 thoracic
5 lumbar
5 sacral
1 coccygeal
One spinal nerve is formed from the union of an ventral and dorsal root from the spinal cord

Then, each spinal nerve splits into an anterior (ventral) and posterior (dorsal) ramus.

Question 4

what does the posterior (dorsal ramus) of spinal nerve innervate?

Answer 4

Posterior ramus is for the back muscles and some cutaneous innervation.

Question 5

what does the anterior (ventral ramus) of the spinal nerves innervate?

Answer 5

Anterior rami merge to form the major plexi
Brachial for Upper Limb C5-T1
Lumbosacral for Lower Limb L2-S2

Question 6

What do the anterior rami do?

Answer 6

C1 – C4 are for the neck
C5-T1 for the upper limb
T2-L1 for the trunk
L2-S3 for lower limb
S2 – Coccyx root for the perineum

Question 7

what is the lumbar plexus formed of?

Answer 7

ventral rami of L1-4

Question 8

What is the sacral plexus formed by?

Answer 8

Ventral rami of S1-S4
Lumbosacral trunk (L4,5)
This is a branch of the lumbar plexus

Question 9

What dervies the femoral nerve?

Answer 9

Femoral Nerve (L2,3,4)
Derived from the posterior divisions

Question 10

What derives the obturator nerve?

Answer 10

Obturator Nerve (L2,3,4)
Derived from the anterior divisions

Question 11

Nerves to the abdomen and perineum only?

Answer 11

Iliohypogastric (L1)

Question 12

Nerves to the abdomen and perineum, also with cutaneous branches to the lower limb?

Answer 12

lioinguinal nerves (L1)
Genitofemoral nerve (L1, L2)

Question 13

Cutaneous nerves to the lower limb?

Answer 13

Lateral femoral cutaneous (L2, L3)

Question 14

What nerve roots are the sacral plexus?

Answer 14

L4-S3

Question 15

which two nerves is the sciatic nerve a combination of?

Answer 15

Peroneal (fibular) nerve
Tibial nerve

Question 16

What are the superficial gluteal compartment nerves from the sacral plexus?

Answer 16

The superior gluteal nerve (L4-S1)
Gluteus medius, minimus and tensor fascia lata
The inferior gluteal nerve (L5-S2)
Gluteus maximus

Question 17

What are the deep gluteal compartment nerves from the sacral plexus?

Answer 17

-The nerve to piriformis (S1,S2)
-The nerve to obturator internus (L5-S2)
-Obturator internus and gamellus superior
-The nerve to the quadratus femoris (L4-S1)
-Quadratus femoris and gamellus inferior

Question 18

What is the difference between dermatomal innervation and peripheral innervation?

Answer 18

Dermatomal Innervation – The strip of skin supplied by a pair of spinal nerves is referred to as a dermatome (e.g. L2 to anterior thigh)
Peripheral Innervation – The area of skin supplied by a single peripheral nerve (e.g. femoral nerves cutaneous branches to anterior thigh)

Question 19

Why are dermatomal and peripheral innervations different?

Answer 19

Spinal nerves mix to form the peripheral nerves
Same explanation for brachial plexus

Question 20

Pathways of signal transmission in the CNS?

Answer 20

1.Spinothalamic tract- Pain and temperature
2.Vestibulospinal tract- Motor neuronal signals relating to posture
3.Cuneate fasciculus- Fine touch, pressure and proprioception
4.Posterior spinocerebellar tract- Proprioceptive signals to cerebellum
5.Anterior corticospinal tract- Conveys motor signals from precentral gyrus to motor cells within the cord

Question 21

Structures encountered when needle is inserted for lumbar puncture?

Answer 21

1. supraspinous ligament
2. interspinous ligament
3. ligamentum flavum (may cause a pop)
4. dura mater (second pop)
5. subarachnoid space(clear CSF at this point)