Spinal Nerves (II)

Question 1

How many pairs of spinal nerves total and in each region?

Answer 1

31 total
8 cervical
12 thoracic
5 lumbar
5 sacral
1 coccygeal

Question 2

How are spinal nerves named?

Answer 2

• first pair (C1) exit above first vertibrae
• C1-C7 named for the vertebrae they are located above
• C8 is below 7th C vertebrae
• from then on, nerves named based on vertebrae they are located below (e.g. T1 is below 1st thoracic vertebrae)

Question 3

where do spinal nerves exit?

Answer 3

4 through sacral foramina
Others through intervertebral foramina

Question 4

name spinal cord plexuses and their respective nerves

Answer 4

Cervical plexus (C1-C4)
Brachial plexus (C5-T1)
Lumbar plexus (L1-L4)
Sacral Plexus (L4-S4)
(Lumbosacral plexus (L1-S4))
Coccygeal plexus (S5-Co)

Question 5

structure of peripheral nerves (deep to superficial)

Answer 5

• axon
• schwann cell
• ENDONERIUM (separates axons from each other) re grouped together in bundles called FASCICLES
• PERINERIUM surrounds fascicles
• adipose tissue, arteries and veins in this space
• EPINEURIUM surrounds entire space. Continuous with dura mater

Question 6

How many rootlets merge to form a root?

Answer 6

6-8

Question 7

name branches of spinal nerves and their functions

Answer 7

when spinal nerves branch
POSTERIOR RAMI
- innervated deep muscles on back responsible for vertebral column movement
ANTERIOR RAMI
- destination depends on location on spinal column
- Thoracic region (T2-T12) form INTERCOSTAL NERVES
- remaining form 5 plexuses (cervical C1-C4, brachial C5-T1, lumbar L1-L4, sacral L4-S4, coccygeal S5-Co)

Question 8

Cervical Plexus structure function

Answer 8

• Ventral rami C1-C4
• innervates superficial neck structures, neck skin, posterior portion of head, superior shoulders and chest

Nerves to note
PHRENIC NERVE
- bottom nerve in plexus
- C3-C5
- innervates diaphragm (breathing)

Question 9

Brachial plexus structure function

Answer 9

• Ventral rami C5-T1
• 3 trunks, 6 divisions, 3 chords, 5 branches

Nerves to note (superior to inferior)
AXILLARY
- deltoid and teres minor (arm movement)
RADIAL
- posterior muscles of arm and forearm
MUSCULOCUTANEOUS
- flexors of forearm
MEDIAN
- anterior forearm, some hand muscles for thumb movement
ULNAR
- forearm and most of hand muscles

Question 10

Lumbar and Sacral Plexus structure function

Answer 10

LUMBAR
- Ventral rami L1-L4
Nerves to note
FEMORAL+OBTURATOR
- supply lateral abdominal walls, external genitals and parts of lower limbs

SACRAL
- Ventral rami L4-S4
Nerves to note (SCIATIC NERVE group)
COMMON FIBULAR (PERONEAL) + TIBIAL
- supplies muscles and skin of lower limbs

Question 11

Coccygeal plexus structure and function

Answer 11

• Ventral rami S5-Co
• muscles of pelvic floor
• sensory info from skin over coccyx

Question 12

plural of ramus

Answer 12

rami