9/15 Dermatomes, Myotomes, and Spinal Nerve Plexuses - Dennis

Question 1

What receives stimulus from joints, skin, and skeletal muscle? 3

Answer 1

Somatosensory fibers (afferent, sensory)

Question 2

what sends stimulus to skeletal muscle? 3

Answer 2

Somatomotor fibers (efferent, motor)

Question 3

What receives stimulus from viscera and vessels? 3

Answer 3

Viscerosensory fibers (afferent, sensory)

Question 4

What sends stimulus to glands, smooth muscle, and cardiac muscle? 3

Answer 4

visceromotor fibers (efferent, motor)

Question 5

What embryonic tissue are the kidney and gonads derived from? 4

Answer 5

Intermediate mesoderm

Question 6

What embryonic tissue is the splanchnic (circulatory system) derived from? 4

Answer 6

lateral plate mesoderm

Question 7

What embryonic tissue is the somatic (body cavity, pelvis, and limb bones derived from? 4

Answer 7

lateral plate mesoderm

Question 8

What embryonic tissue is the notochord derived from? 4

Answer 8

chordamesoderm

Question 9

What embryonic tissue is cartilage, tendons, skeletal muscle (myotomes), and dermis, skeletal muscle (dermatomes) derived from? 4

Answer 9

paraxial mesoderm (somites)

Question 10

Which is the most dorsal structure: neural tube or notochord? Where is the floor plate found? 6

Answer 10

The floor of the neural tube is called the floor plate and is dorsal to the notochord

Question 11

What does the myotome form after migrating? 8

Answer 11

epimere - migrates posteriorly (dorsal)

hypomere - migrates anteriorly (ventral)

Question 12

What are the muscle derivatives of the epimere and hypomere? 8

Answer 12

Epimere - epaxial muscle

Hypomere - hypaxial muscle

Question 13

What cells condense around the notochord to form the vertebrae? 9

Answer 13

Sclerotome cells

Question 14

What contributes to the nucleus pulposus of an intervertebral disk? 9

Answer 14

Notochord

Question 15

How many occipital myotomes are there? 11

Answer 15

4

Question 16

How many cervical myotomes are there? 11

Answer 16

8

Question 17

How many thoracic myotomes are there? 11

Answer 17

12

Question 18

How many Lumbar myotomes are there?

Answer 18

5

Question 19

How many sacral myotomes are there? 11

Answer 19

5

Question 20

What are the dorsal (epaxial) columns of epimeres? 11

Answer 20

C6 - T4

Question 21

What three dermatomes innervate the hands? 14

Answer 21

C6, 7, 8

Question 22

What dermatomes innervate the foot?

Answer 22

L4
L5
S1

Question 23

What dermatomes innervate the face?

Answer 23

V1, V2, V3

C2, C3, C4

Question 24

What is a dermatome? 18

Answer 24

A unilateral area of skin innervated by the sensory fibers of a single spinal nerve

Question 25

What is a myotome? 18

Answer 25

A unilateral muscle mass receiving innervation from fibers from a single spinal nerve

Question 26

What information do posterior and anterior rootlets carry? 16

Answer 26

Posterior root - sensory information

Anterior root - motor information

Question 27

What is unique about a spinal nerve? 16

Answer 27

Spinal nerve has both posterior and anterior rootlets within it (both sensory and motor modalities)

Question 28

Once a spinal nerve emerges from the spinal cord what does it split into? 16

Answer 28

Splits into a posterior and anterior ramus both of which carry both a sensory and motor modality

Posterior ramus - muscles of back
Anterior ramus - skin

Question 29

What does the posterior horn of the grey matter of the spinal cord divide into? 17

Answer 29

Somatic sensory

Visceral sensory

Question 30

What does the anterior horn of spinal cord grey matter divide into? 17

Answer 30

Autonomic motor

Somatic motor

Question 31

What is the posterior ramus specifically innervating? What do we classify the innervated product as? What is its embryological origin? 19

Answer 31

Dorsal musculature and skin

Epaxial muscle derived from epimere

Question 32

What is the anterior ramus specifically innervating? What do we classify the innervated product as? What is its embryological origin? 19

Answer 32

Lateral & ventral body wall musculature & skin

Hypaxial muscle derived from hypomere

Question 33

Differentiate the anterior ramus vs posterior ramus. 19

Answer 33

Anterior ramus - larger/longer

Posterior ramus - thinner/shorter

Question 34

What kind of patterns does a segmental pattern create? 21

Answer 34

Straight, linear pattern of dermatome coverage

Ex. Trunk region

Question 35

What kind of patterns does a plexus pattern create? 21

Answer 35

Anterior rami extension

Randomized, but still overlapping dermatome pattern

Question 36

Why is there overlapping of innervation of both segmental and plexus type innervation? 21

Answer 36

It requires that two spinal nerves be injured before loss of function, sensation to that area

Question 37

What segmental innervation is required for Inversion and eversion? 23

Answer 37

Inversion —> L4, L5

Eversion —> L5, S1

Question 38

What type of thoracic autonomic plexuses are there? What type of innervation do they provide? 26

Answer 38

Esophageal plexus
Cardiac plexus

Both control visceral sensory/motor functions

Question 39

What is the cervical plexus formed by? 30

Answer 39

Anterior rami of C1 - C4

Question 40

What does the cervical plexus innervate? 30

Answer 40

Anterior neck muscles

Skin of neck, head, shoulders

Question 41

What are the branches of the lumbrosacral plexus to the lower extremity? 34

Answer 41

Femoral (L2-L4)

Obturator (L2-L4)

Sciatic (L4-S3) —> tibial L4-S3 + Common fibular L4-S2

Lateral Femoral Cutaneous (L2-L3)

Posterior Femoral Cutaneous (S1-S3)

Question 42

What kind of damage would you see with a cervical and a thoracic spinal cord lesion? 35

Answer 42

Cervical - quadriplegic

Thoracic - paraplegic