Dermatomes

Question 1

What are the two different roots which connect to each segment of the spinal cord?

Answer 1

The dorsal (posterior) and ventral (anterior) roots.

Question 2

What does the dorsal (posterior) root contain?

Answer 2

This contains the afferent/ sensory nerve fibres

Question 3

What does the ventral (anterior) root contain?

Answer 3

This contains the efferent fibres with their motor function and also the autonomic fibres.

Question 4

Where does the spinal cord exist?

Answer 4

From the inferior margin of the medulla oblongata to the conus medullaris which is at L2 level.

Question 5

What are meningeal branches?

Answer 5

These are branches given off by all nerve roots which are recurrent and supply the Vetebrae, blood vessels, ligaments and meninges.

Question 6

What is a rami communicantes?

Answer 6

These are components of the autonomic nervous system which enters the sympathetic trunk ganglion.

Question 7

What is the difference between the dorsal and ventral rami?

Answer 7

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.

Question 8

How do we describe nerve injuries?

Answer 8

The level we define is the lowest level which has normal sensory and motor function.

Question 9

Where are the nerves of the lumbar and sacral plexuses relative to the posts muscles?

Answer 9

They are posterior and emerge Medially and laterally to posts major.

Question 10

What are the nerve roots of the obturator nerve?

Answer 10

L2,3,4

Question 11

What are the nerve roots of the femoral nerve?

Answer 11

L2,3,4

Question 12

What are the nerve roots of the lateral cutaneous nerve of thigh?

Answer 12

L2,3

Question 13

Name two nerves which have the nerve root L1

Answer 13

Idiot inguinal and iliohypogastric

Question 14

What are the nerve roots of the lumbrosacral trunk?

Answer 14

L4,5

Question 15

Which nerves appear Medially to posts major?

Answer 15

Obturator nerve and the lumbrosacral trunk

Question 16

Where is the sacral plexus found?

Answer 16

In the pelvic cavity, anterior to piriformis

Question 17

What two nerves form part of the sciatic nerve and what are their nerve roots?

Answer 17

Common peroneal nerve (L4,5,S1,2)
Tibial nerve (L4,5,S1,2,3)

Question 18

What are the nerve roots for the inferior gluteal nerve?

Answer 18

L5,S1,2

Question 19

What are the nerve roots for the superior gluteal nerve?

Answer 19

L4,5,S1

Question 20

What nerve roots does the posterior cutaneous nerve of thigh have?

Answer 20

S1,2,3

Question 21

What is a myotome?

Answer 21

This is a group of muscles which are supplied by a single nerve root.

Question 22

What is a dermatome?

Answer 22

This is an area of skin supplied by a single spinal nerve

Question 23

What is an axial line?

Answer 23

This is a junction of two Dermatomes with discontinuous nerve roots.

Question 24

Where on pre/post axial compartments do axial lines lie?

Answer 24

These mark the middle of the compartment. The borders are marked by veins.

Question 25

What is a peripheral nerve territory?

Answer 25

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.

Question 26

What is interesting about shingles?

Answer 26

When shingles occurs, it only occupies a single dermatome as it travels down a single dorsal spinal root.

Question 27

What is a motor unit?

Answer 27

This is a single motor neurone and the skeletal muscle fibres which it innervates.