Dermatomes Flashcards
What are the two different roots which connect to each segment of the spinal cord?
The dorsal (posterior) and ventral (anterior) roots.
What does the dorsal (posterior) root contain?
This contains the afferent/ sensory nerve fibres
What does the ventral (anterior) root contain?
This contains the efferent fibres with their motor function and also the autonomic fibres.
Where does the spinal cord exist?
From the inferior margin of the medulla oblongata to the conus medullaris which is at L2 level.
What are meningeal branches?
These are branches given off by all nerve roots which are recurrent and supply the Vetebrae, blood vessels, ligaments and meninges.
What is a rami communicantes?
These are components of the autonomic nervous system which enters the sympathetic trunk ganglion.
What is the difference between the dorsal and ventral rami?
The dorsal rami are shorter and supply an area of the back in a segmental fashion whilst the lateral rami are much longer and enter plexuses to supply the limbs.
How do we describe nerve injuries?
The level we define is the lowest level which has normal sensory and motor function.
Where are the nerves of the lumbar and sacral plexuses relative to the posts muscles?
They are posterior and emerge Medially and laterally to posts major.
What are the nerve roots of the obturator nerve?
L2,3,4
What are the nerve roots of the femoral nerve?
L2,3,4
What are the nerve roots of the lateral cutaneous nerve of thigh?
L2,3
Name two nerves which have the nerve root L1
Idiot inguinal and iliohypogastric
What are the nerve roots of the lumbrosacral trunk?
L4,5
Which nerves appear Medially to posts major?
Obturator nerve and the lumbrosacral trunk
Where is the sacral plexus found?
In the pelvic cavity, anterior to piriformis
What two nerves form part of the sciatic nerve and what are their nerve roots?
Common peroneal nerve (L4,5,S1,2) Tibial nerve (L4,5,S1,2,3)
What are the nerve roots for the inferior gluteal nerve?
L5,S1,2
What are the nerve roots for the superior gluteal nerve?
L4,5,S1
What nerve roots does the posterior cutaneous nerve of thigh have?
S1,2,3
What is a myotome?
This is a group of muscles which are supplied by a single nerve root.
What is a dermatome?
This is an area of skin supplied by a single spinal nerve
What is an axial line?
This is a junction of two Dermatomes with discontinuous nerve roots.
Where on pre/post axial compartments do axial lines lie?
These mark the middle of the compartment. The borders are marked by veins.
What is a peripheral nerve territory?
This is an area of skin which is innervated by a particular named nerve. These have fibres from multiple spinal nerves due to them being branches occuring from plexuses.
What is interesting about shingles?
When shingles occurs, it only occupies a single dermatome as it travels down a single dorsal spinal root.
What is a motor unit?
This is a single motor neurone and the skeletal muscle fibres which it innervates.
