Part 2 - Dermatomes And Myotomes Flashcards
What is a Dermatome?
Area of skin supplied by a single spinal nerve
What is a Myotome?
A group of muscles supplied by a single spinal nerve
What is an axial line?
The junction of two Dermatomes supplied from discontinuous spinal levels (the dermatomes may be adjacent but their spinal nerves are not)
What do axial lines mark the centre of in limbs?
Ventral or dorsal compartments of the limb
What is meant by their is functional overlap between adjacent dermatomes?
If the C5 spinal nerve is damaged, C6 will also supply part of C5 Dermatome and C4 will supply some of the C4 Dermatome
Really only the centre of the C5 dermatome will be affected
Will there be any functional overlap between Dermatome that are adjacent but are separated by an axial line?
NO
What is the pre-axial border of the limb buds of the embryo?
The border of the limb nearest to the head
What is the post-axial border of the limb bud of the embryo?
The border of the limb bud closer to the tail end of the embryo
How are the upper and lower limbs of the embryo initially orientated?
Begin pointing anteriorly with the thumb and great toe pointing UP
How do the upper limbs rotate in the embryo?
They rotate externally so the thumbs point laterally
How do the lower limbs rotate in the embryo?
Rotated medially so the great toes are on the medial aspect of the feet
What do the pre and post axial borders of the limb mark?
The boundaries of the posterior and anterior compartments
What superficial veins mark the pre axial border of the upper limb?
Cephalic vein
What superficial vein marks the post axial border of the upper limb?
Basilic vein
What superficial vein marks the pre axial border of the lower limb? (Approximately)
Great/long saphenous vein
What superficial vein marks the post axial border of the lower limb? (Approximately)
Small/short saphenous vein
What are peripheral nerves usually made up of?
Normally a combination of several spinal nerves
What are some examples of peripheral nerves?
Femoral nerve
Obturator nerve
Can one spinal nerve enter/contribute to multiple peripheral nerves?
Yes
Fibres from one spinal nerve can enter multiple peripheral nerves
What makes up a spina nerve and where does it emerge?
Dorsal spinal root + Ventral spinal root
Intervertebral Foramen
How does a spinal nerve divide/branch once it leaves the intervertebral Foramen?
Anterior (ventral) rami
Posterior (dorsal) rami
For limbs, is it the dorsal (Posterior) or ventral (Anterior) rami which contribute to the plexuses to form the peripheral nerves?
Anterior/ventral rami
What is the region called where all the anterior rami form their branches contributing to the formation of the peripheral nerves?
Plexus
What peripheral nerves do the fibres of the anterior ramus of L2 contribute to?
Genitofemoral nerve
Lateral femoral cutaneous nerve
Obturator nerve
Femoral nerve
What spinal nerve anterior rami are part of the lumbar plexus?
T12
L1-L5
Where does the Obturator nerve supply?
Medial thigh (Upper)
If the upper medial thigh is stimulated, how does the body detect this?
Sensory axons run via Obturator, through the lumbar plexus to the L2 spinal nerve, L2 dorsal root then to the L2 segment of the spinal cord
Where does the femoral nerve supply?
Anterior thigh
Medial leg
If the anterior thigh is stimulated, how does the body detect this?
Sensory axon runs through femoral nerve to lumbar plexus, to the L2 spinal nerve, to L2 dorsal root to the L2 segment of the spinal cord
Where is the L2 Dermatome?
Proximal part of thigh and lateral part of thigh
(Above the knee)
What spinal nerves contribute to the femoral nerve?
L2, L3 and L4
What is a peripheral nerve territory?
Area of skin supplied by the peripheral nerves (different to Dermatome)
Within each peripheral nerve there may be axons from ______ spinal nerves
MULTIPLE
A single spinal nerve _____ contribute to formation of more than one peripheral nerve
CAN
What virus causes chicken pox?
Varicella zoster virus
What is the name of the disease/illness that is caused by the reactivation of the dormant chicken pox causing (Varicella Zoster virus) virus?
Shingles
Why does shingles only typically affect the skin of a single Dermatome?
Virus remains dormant in a dorsal root ganglion after chicken pox
When reactivated travels down/through a peripheral nerve that the dorsal root ganglions spinal nerve contributes to to the skin
