9/15 Dermatomes, Myotomes, and Spinal Nerve Plexuses - Dennis Flashcards
What receives stimulus from joints, skin, and skeletal muscle? 3
Somatosensory fibers (afferent, sensory)
what sends stimulus to skeletal muscle? 3
Somatomotor fibers (efferent, motor)
What receives stimulus from viscera and vessels? 3
Viscerosensory fibers (afferent, sensory)
What sends stimulus to glands, smooth muscle, and cardiac muscle? 3
visceromotor fibers (efferent, motor)
What embryonic tissue are the kidney and gonads derived from? 4
Intermediate mesoderm
What embryonic tissue is the splanchnic (circulatory system) derived from? 4
lateral plate mesoderm
What embryonic tissue is the somatic (body cavity, pelvis, and limb bones derived from? 4
lateral plate mesoderm
What embryonic tissue is the notochord derived from? 4
chordamesoderm
What embryonic tissue is cartilage, tendons, skeletal muscle (myotomes), and dermis, skeletal muscle (dermatomes) derived from? 4
paraxial mesoderm (somites)
Which is the most dorsal structure: neural tube or notochord? Where is the floor plate found? 6
The floor of the neural tube is called the floor plate and is dorsal to the notochord
What does the myotome form after migrating? 8
epimere - migrates posteriorly (dorsal)
hypomere - migrates anteriorly (ventral)
What are the muscle derivatives of the epimere and hypomere? 8
Epimere - epaxial muscle
Hypomere - hypaxial muscle
What cells condense around the notochord to form the vertebrae? 9
Sclerotome cells
What contributes to the nucleus pulposus of an intervertebral disk? 9
Notochord
How many occipital myotomes are there? 11
4
How many cervical myotomes are there? 11
8
How many thoracic myotomes are there? 11
12
How many Lumbar myotomes are there?
5
How many sacral myotomes are there? 11
5
What are the dorsal (epaxial) columns of epimeres? 11
C6 - T4
What three dermatomes innervate the hands? 14
C6, 7, 8
What dermatomes innervate the foot?
L4
L5
S1
What dermatomes innervate the face?
V1, V2, V3
C2, C3, C4
What is a dermatome? 18
A unilateral area of skin innervated by the sensory fibers of a single spinal nerve
What is a myotome? 18
A unilateral muscle mass receiving innervation from fibers from a single spinal nerve
What information do posterior and anterior rootlets carry? 16
Posterior root - sensory information
Anterior root - motor information
What is unique about a spinal nerve? 16
Spinal nerve has both posterior and anterior rootlets within it (both sensory and motor modalities)
Once a spinal nerve emerges from the spinal cord what does it split into? 16
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
What does the posterior horn of the grey matter of the spinal cord divide into? 17
Somatic sensory
Visceral sensory
What does the anterior horn of spinal cord grey matter divide into? 17
Autonomic motor
Somatic motor
What is the posterior ramus specifically innervating? What do we classify the innervated product as? What is its embryological origin? 19
Dorsal musculature and skin
Epaxial muscle derived from epimere
What is the anterior ramus specifically innervating? What do we classify the innervated product as? What is its embryological origin? 19
Lateral & ventral body wall musculature & skin
Hypaxial muscle derived from hypomere
Differentiate the anterior ramus vs posterior ramus. 19
Anterior ramus - larger/longer
Posterior ramus - thinner/shorter
What kind of patterns does a segmental pattern create? 21
Straight, linear pattern of dermatome coverage
Ex. Trunk region
What kind of patterns does a plexus pattern create? 21
Anterior rami extension
Randomized, but still overlapping dermatome pattern
Why is there overlapping of innervation of both segmental and plexus type innervation? 21
It requires that two spinal nerves be injured before loss of function, sensation to that area
What segmental innervation is required for Inversion and eversion? 23
Inversion —> L4, L5
Eversion —> L5, S1
What type of thoracic autonomic plexuses are there? What type of innervation do they provide? 26
Esophageal plexus
Cardiac plexus
Both control visceral sensory/motor functions
What is the cervical plexus formed by? 30
Anterior rami of C1 - C4
What does the cervical plexus innervate? 30
Anterior neck muscles
Skin of neck, head, shoulders
What are the branches of the lumbrosacral plexus to the lower extremity? 34
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)
What kind of damage would you see with a cervical and a thoracic spinal cord lesion? 35
Cervical - quadriplegic
Thoracic - paraplegic
