Notion of A Mixed Spinal Nerve & The Brachial Plexus Flashcards
What is the neural tube?
The embryonic precursor of the brain and spinal cord.
What are dermatomyotomes?
Embryonic precursors of the dermatomes and myotomes.
What is a spinal segmental nerve?
Any of the pair of nerves that exit the spinal cord to supply the dermis and muscle of a dermatomyotome.
Where does the spinal cord start and end?
- It starts where the medulla of the brain ends.
- It ends at the conus medullaris.
What is the conus medullaris?
Where the membrane of the spinal cord tapers into a ligament known as the filum terminale.
What is the name of the region of a vertebra though which the spinal cord passes?
The vertebral foramen.
What is the name of the region of a vertebra though which spinal nerves leave the spinal canal?
The intervertebral foramen.
In the cervical spinal cord, do spinal nerves emerge superior or inferior to the vertebral level at which they have their roots?
Superior.
In the non-cervical spinal cord, do spinal nerves emerge superior or inferior to the vertebral level at which they have their roots?
Inferior.
Where are the two enlargements of the spinal cord?
At the cervical and lumbar levels.
What tissue exists between the vertebra and the dura mater of the spinal cord?
In which space is this tissue situated?
- Adipose tissue.
- In the epidural space.
Where is cerebrospinal fluid located?
In the subarachnoid space (between the arachnoid mater and the pia mater).
Describe the branching of a spinal segmental nerve.
- As it exits the intervertebral foramen, it branches into ventral and dorsal rami.
- The dorsal ramus divides further into medial and lateral branches.
How do ventral rami differ in appearance from dorsal rami?
Ventral rami are larger than dorsal rami.
Which of the rami participate in the formation of nerve plexuses?
The ventral ramus only.
What anatomical structures travel with segmental nerves?
Their equivalent segmental arteries and veins.
How do the dorsal roots of a spinal segmental nerve differ functionally from its ventral roots?
- The dorsal roots are afferent.
- The ventral roots are efferent.
What is an interoceptor?
A sensory receptor which receives stimuli from within the body (as opposed to exteroceptors).
What type of sign is a depressed reflex?
A depressed reflex is a lower motoneurone sign.
What type of sign is an exaggerated reflex?
An exaggerated reflex is an upper motoneurone sign.
How is autonomic supply of a segmental nerve tested?
By testing whether the area of its dermatome is able to sweat or not.
Where does the lumbar plexus form?
Behind the psoas major.
Where do nerves of the lumbar plexus emerge?
Either medial or lateral to the borders of the psoas major.
List 4 nerves of the lumbar plexus that emerge lateral to psoas major.
1 - Femoral nerve.
2 - Iliohypogastric nerve.
3 - Ilioinguinal nerve.
4 - Lateral cutaneous nerve of the thigh.
List 2 nerves of the lumbar plexus that emerge medial to psoas major.
1 - Obturator nerve.
2 - Lumbosacral trunk.
Which nerve forms the sacral plexus?
The lumbosacral trunk.
What are the spinal roots of the lumbosacral trunk?
Half of L4 and all of L5.
List 4 regions supplied by the sacral plexus.
1 - The pelvic region.
2 - The gluteal region.
3 - The perineal region.
4 - The lower limb.
Via which nerve does the sacral plexus supply the lower limb?
The sciatic nerve.
