Dermatomes, Myotomes And Plexuses

Question 1

What does intermediate mesoderm give rise to?

Answer 1

Kidneys and gonads

Question 2

What does paraxial mesoderm give rise to?

Answer 2

Head and somites

Somites then give rise to sclerotome (cartilage), myotome (skeletal muscle) and dermatome (dermis)

Question 3

What does the lateral mesoderm give rise to?

Answer 3

Splanchnic (circulatory system), somatic (body cavity, pelvis and limb bones) and extraembryonic structures

Question 4

What does the dermatome give rise to?

Answer 4

Dermis

Question 5

What does the myotome give rise to?

Answer 5

Muscle

Question 6

What does the sclerotome give rise to?

Answer 6

Cartilage; vertebrae and ribs

Question 7

Cells that migrate anteriorly give rise to what during development?

Answer 7

Muscles of the limbs and trunk (hypaxial muscles) and to the associated dermis

Question 8

Cells that migrate posteriorly give rise to what during development?

Answer 8

Intrinsic muscles of the back (epaxial muscles) and the associated dermis

Question 9

The posterior horn is what?

Answer 9

Sensory

Question 10

The lateral horn of the spinal cord is what?

Answer 10

Visceromotor

Question 11

The anterior horn of the spinal cord is what?

Answer 11

Motor

Question 12

The anterior and posterior rootlets are differentiated, however once they combine to form a spinal nerve they become what?

Answer 12

Undifferentiated

Question 13

When does limb development begin?

Answer 13

During week 4 (involves rotation and bending)

Question 14

What is a dermatome?

Answer 14

The area of skin supplied with afferent nerve fibers by a single posterior spinal root

Question 15

What is the difference between dermatome maps and nerve maps?

Answer 15

For every dermatome region there is a single dorsal root contributor
However named nerves have more than one rami contribution

Question 16

What are myotomes?

Answer 16

All the muscles that are innervated by a single efferent anterior root

Question 17

Most muscles are composed of what?

Answer 17

More than one myotome*

Question 18

What is monosegmental muscle innervation?

Answer 18

One myotome contribution

Question 19

What is multisegmental muscle innervation?

Answer 19

Multiple myotome contributions

Question 20

Injury to a dorsal root will lead to what?

Answer 20

Only to sensory deficits/symptoms (e.g. paresthesia)

Question 21

Injury to a ventral root will lead to what?

Answer 21

Only to motor deficits (e.g. weakness)

Question 22

Impingement or injury that affects a single segment can be ascertained with some degree of certainty by what?

Answer 22

Turning to a dermatome map

Question 23

Impingement or injury that effects a single nerve proper can be ascertained with some degree of certainty by what?

Answer 23

Turning to a nerve map

Question 24

What is the caveat with dermatomes and dermatome maps?

Answer 24

Dermatomes are not as precise as shown on dermatome maps and consist of segments/nerves with overlapping territories

Question 25

The fact that one muscle may be composed of multiple dermatomes (one myotome may contribute to multiple muscles) means what?

Answer 25

That impingement or injury to one segment will probably lead to weakness and not a complete loss of function

Question 26

What is the basic spinal innervation pattern for the spinal cord?

Answer 26

Dorsal and ventral roots

Question 27

What is the basic spinal innervation pattern for spinal nerves?

Answer 27

Dorsal and ventral rami

Question 28

What are the branches of the lumbosacral plexus?

Answer 28

Femoral, obturator, sciatic, lateral formal cutaneous and posterior femoral cutaneous nerves

Question 29

What is the spinal root for the femoral nerve?

Answer 29

L2-L4

Question 30

What is the spinal root for the obturator nerve?

Answer 30

L2-L4

Question 31

What is the spinal root for the sciatic nerve?

Answer 31

L4-S3

Question 32

What is the spinal root for the tibial nerve (of sciatic nerve)?

Answer 32

L4-S3

Question 33

What is the spinal root for the common fibular nerve (of sciatic nerve)?

Answer 33

L4-S2

Question 34

What is the spinal root for the lateral femoral cutaneous nerve?

Answer 34

L2-3

Question 35

What is the spinal root for the posterior femoral cutaneous nerve?

Answer 35

S1-S3