Dermatomes and Myotomes Flashcards
Define motor unit
Muscle fibres innervated by a single motor nerve fibre
Define dermatomyotome
Embryonic precursors of the dermis and muscle units. Differentiate into dermatome and myotome
Which part of the spinal cord has segmental nerves which emerge superiorly to the corresponding vertebral level?
The cervical cord
Give the regions of the spinal cord and the number each region goes up to
Cervical - C1-C7
Thoracic - T1-T12
Lumbar - L1-L5
Sacral - S1-S4
What are the efferent and afferent roots given out by each spinal segment nerves?
Dorsal roots are afferent
Ventral roots are efferent
(DA, VE)
What functions do ventral roots have?
Motor (skeletal muscle)
Autonomic (smooth muscle and glands)
Explain how a mixed segmental nerve divides once it has emerged from the intervertebral foramen
(Dorsal and ventral converge to form a mixed segmental nerve)
Splits into posterior and anterior rami
Posterior ramus divides into medial and lateral branches
Which roots make up the lumbar plexus?
L1-L4
Which roots make up the sacral plexus?
L4-S4
Where is the lumbar plexus?
Behind the psoas major muscle
Which nerves emerge from the lumbar plexus lateral to psoas major?
Femoral
Iliohypogastric
Ilioinguinal
Lateral cutaneous of thigh
Which nerves emerge medial to psoas major from the lumbar plexus?
Obturator
Lumbksacral trunk
Where is the sacral plexus?
In the pelvic cavity
What does the sacral plexus supply?
Pelvic, gluteal and perineal regions
Lower limb via the sciatic nerve
What is a sensory nerve territory?
Cutaneous distribution of peripheral nerve.
Area of skin that the peripheral nerve innervates.
Can have nerve fibres from several spinal roots.
Which myotome is flexion of the forearm predominantly done by?
C6
Which myotome is extension of the forearm at the elbow predominantly done by?
C7
Which myotome is flexion of the fingers mostly controlled by?
C8
Which myotome is abduction and adduction of the fingers controlled by?
T1
Which myotomes is flexion of the hip controlled by?
L1 and L2
Which myotomes is extension of the knee controlled by?
L3 and L4
Which myotomes is flexion of the knee controlled by?
L5-S2
Which myotomes is plantarflexion of the foot controlled by?
S1 and S2
A tap on the biceps tendon in the cubital fossa tests which spinal cord level?
C6
Tapping the tendon of the triceps on the posterior tendon tests which spinal root?
C7
A tap on the patellar ligament test which spinal roots?
L3 and L4
A tap on the calcaneal tendon posterior to the ankle tests which spinal roots?
S1 and S2
