Dermatomes, Myotomes And Plexuses Flashcards
What does intermediate mesoderm give rise to?
Kidneys and gonads
What does paraxial mesoderm give rise to?
Head and somites
Somites then give rise to sclerotome (cartilage), myotome (skeletal muscle) and dermatome (dermis)
What does the lateral mesoderm give rise to?
Splanchnic (circulatory system), somatic (body cavity, pelvis and limb bones) and extraembryonic structures
What does the dermatome give rise to?
Dermis
What does the myotome give rise to?
Muscle
What does the sclerotome give rise to?
Cartilage; vertebrae and ribs
Cells that migrate anteriorly give rise to what during development?
Muscles of the limbs and trunk (hypaxial muscles) and to the associated dermis
Cells that migrate posteriorly give rise to what during development?
Intrinsic muscles of the back (epaxial muscles) and the associated dermis
The posterior horn is what?
Sensory
The lateral horn of the spinal cord is what?
Visceromotor
The anterior horn of the spinal cord is what?
Motor
The anterior and posterior rootlets are differentiated, however once they combine to form a spinal nerve they become what?
Undifferentiated
When does limb development begin?
During week 4 (involves rotation and bending)
What is a dermatome?
The area of skin supplied with afferent nerve fibers by a single posterior spinal root
What is the difference between dermatome maps and nerve maps?
For every dermatome region there is a single dorsal root contributor
However named nerves have more than one rami contribution
What are myotomes?
All the muscles that are innervated by a single efferent anterior root
Most muscles are composed of what?
More than one myotome*
What is monosegmental muscle innervation?
One myotome contribution
What is multisegmental muscle innervation?
Multiple myotome contributions
Injury to a dorsal root will lead to what?
Only to sensory deficits/symptoms (e.g. paresthesia)
Injury to a ventral root will lead to what?
Only to motor deficits (e.g. weakness)
Impingement or injury that affects a single segment can be ascertained with some degree of certainty by what?
Turning to a dermatome map
Impingement or injury that effects a single nerve proper can be ascertained with some degree of certainty by what?
Turning to a nerve map
What is the caveat with dermatomes and dermatome maps?
Dermatomes are not as precise as shown on dermatome maps and consist of segments/nerves with overlapping territories
The fact that one muscle may be composed of multiple dermatomes (one myotome may contribute to multiple muscles) means what?
That impingement or injury to one segment will probably lead to weakness and not a complete loss of function
What is the basic spinal innervation pattern for the spinal cord?
Dorsal and ventral roots
What is the basic spinal innervation pattern for spinal nerves?
Dorsal and ventral rami
What are the branches of the lumbosacral plexus?
Femoral, obturator, sciatic, lateral formal cutaneous and posterior femoral cutaneous nerves
What is the spinal root for the femoral nerve?
L2-L4
What is the spinal root for the obturator nerve?
L2-L4
What is the spinal root for the sciatic nerve?
L4-S3
What is the spinal root for the tibial nerve (of sciatic nerve)?
L4-S3
What is the spinal root for the common fibular nerve (of sciatic nerve)?
L4-S2
What is the spinal root for the lateral femoral cutaneous nerve?
L2-3
What is the spinal root for the posterior femoral cutaneous nerve?
S1-S3
