Exam 2 Flashcards
How many neurons does the spinal cord have?
long and thin and can contain up to 100 million neurons
how long is the spinal cord?
40-45 cm or 16-18 inches (most 18 inches)
what is the diameter of the spinal cord?
1.3cm maximum diameter (in cervical enlargement)
At what area does the cord occupy 75% of the vertebral canal
C5-C6
How much does the spinal cord weigh
27-35 grams in weight only 2% of the total CNS weight
what is the superior boundary of the spinal cord
both convenient and precise
foramen magnum for convenience: the superior most ventral rootlet of the first cervical spinal nerve when being precise. C1 nerve rootlet/superior most anterior C1 rootlet
what is the inferior boundary of the spinal cord (adult)
the disc between vertebral levels L1-L2 (90%) (leaves almost one third of vertebral canal and sacral canal below) Conus Medularis disc level between L1-L2
How many spinal nerve pairs exist
31 pairs
Each spinal nerve will have what kind of rootlets within the vertebral canal
dorsal and ventral roots
states that dorsal roots contain sensory (afferent) fibers and ventral roots are motor (efferent) fibers. exceptions when a few afferent fibers come through the ventral roots
Bell-Magendi Law
Roots (rootlets) spinal nerves and their rami are PNS or CNS structures
PNS
The only CNS structure in the vertebral canal is the spinal cord itself
C1 exits between what
occiput and atlas (occasionally missing dorsal rootlets)
C4 exits at IVF between what
C3 and C4 vertebrae (always one above and the one below)
C8 exits at the IVF between what
C7 and T1 vertebrae
What are the cervical nerves
C1-C8 vertebrae
What are the thoracic nerves
T1-T12 vertebrae
T1 exits at IVF between what
T1 and T2 vertebrae (same level then one below)
T6 exits at IVF between what
T6 and T7 vertebrae
T12 exits at IVF between what
T12 and L1 vertebrae
The rami consist of what kinds of nerves
mixed: motor and sensory
The rootlets consist of what kinds of nerves
Motor or Sensory
What are the Lumbar Nerves
L1-L5
L1 exits at IVF between what
L1 and L2 Vertebrae (like thoracic)
L5 exits IVF between what
L5 and S1 vertebrae
how many bones fuse together to form the sacrum
5 bones
what are the sacral nerves
S1-S5
S1-S4 nerves exit where
The dorsal and ventral sacral foramina
S5 exits where
The sacral hiatus
What is the coccygeal nerve abbreviated as
Co1
Where does the Co1 exit at
the sacral hiatus (this nerve may be missing)
