2) Dermatomes And Myotomes Flashcards
1
Q
What is each neural segment known as?
A
- Neural level
2
Q
What does the neural tube contain?
A
- Precursor cells of nervous system
3
Q
What does the sclerotome become?
A
- Vertebra and ribs
4
Q
What does the dermatomyotome (DMT) become?
A
- Demis (dermatome)
- Muscles (myotome)
5
Q
What does DMT develop in association with?
A
- Neural level of the spinal cord
- Takes the nerve supply with them from neural tube as spinal nerve
- E.g. C6
6
Q
What do spinal nerve roots do?
A
- Connect each spinal nerve to a segment of the cord
7
Q
What do dorsal roots contain? (posterior)
A
- Afferent sensory nerve fibres only
8
Q
What is a dorsal root ganglion?
A
- Cell bodies of the sensory neurons from the periphery
9
Q
What do ventral spinal nerve roots contain?
A
- Efferent motor and autonomic nerve fibres only
10
Q
What are spinal nerves?
A
- Parallel bundles of axons encased in connective tissue
- Motor and sensory
11
Q
How many spinal nerves are there?
A
- 31 pairs numbered according to level of vertebral column from which they emerge
12
Q
What is a vertebral segment?
A
- 1 vertebra
13
Q
What does the spinal cord run through?
A
- Vertebral foramen (foramina if multiple)
14
Q
What is the spinal canal?
A
- Multiple vertbral foramina
15
Q
How do th spinal nerves leave the spinal canal?
A
- Intervertebral formaina
16
Q
Where does the spinal cord start and end?
A
- Starts at the inferior margin of medulla oblongata
- Ends as conus medullaris at L2
17
Q
Are most spinal cord segments vertically aligned with there corresponding vertbrae?
A
- No
18
Q
What do long roots from inferior segments descend in to exit their respective formamina?
A
- Cauda equina
19
Q
Where do the first pair of spinal nerves emerge?
A
- Between the occipital bone and the atlas
20
Q
Where do C1-C7 spinal nerves exit?
A
- Above corresponding vertebrae
21
Q
Where does C8 spinal nerve eit?
A
- Between C7 and T1 vertebrae
22
Q
Where do T1-L5 spinal nerves exit?
A
- Below corresponding vertebrae
23
Q
How do S1-S4 spinal nerves exit?
A
Via 4 paris of sacral formaina
24
Q
How do S5 and Co1 spinal nerves exit?
A
Via posterior sacral hiatus
25
What is the posterior/dorsal ramus?
Deep muscles and skin of dorsal trunk
26
What is the Anterior/ventral ramus?
* Muscles and skin of the upper and lower limbs and lateral ventral trunk
27
What does the meingeal branch of spinal nerves do?
* Re-enters spinal canal through interverbral canal
* Supplies the vertebrae, ligaments, blood vessels and meninges
28
What are Rami communicantes?
* Components of the autonomic system
29
What do Dorsal/posterior rami supply?
* Supply skin of back in a segmental manner
* medial and lateral branches
* narrow strip of muscle/skin in line with intervertebral foramen
30
What does ventral/anterior rami supply?
* Complicated
* Segmental for the trunk
* Enter the plexuses to supply the limbs
* Brachial plexus
* Lumbo-sacral plexus
31
What does the dermatome map loop like?
32
What is a Myotome?
* Group of muscles supplied by a single spinal nerve
33
What is a dermatome?
* Area of skin supplied by a single spinal nerve
34
What is an axial line?
* Junction of two dermatomes supplied from discontinuous spinal levels
* centre of ventral or dorsal comparments of the limb
35
What is a pre-axial and post-axial border?
* Boundaries of dorsal and ventral compartments
* Marked by superficial veins
* Upper limb- cephalic vein (pre) and basilic vein (post)
* Lower limb- long saphenous vein (pre) Short saphenous vein (post)
36
Where do spinal nerves become peripheral nerves?
* Peripheral nerves contain several spinal nerves neurons
* Fibres from multiple spinal nerves combine to form peripheral nerves
* rearrangement from one to the other occurs in the plexuses
37
What does the C6 spinal nerve become?
* Musculocutaneuus nerve (also 5 and 7)
* Radial nerve
* Median nerve
38
What are peripheral nerve territories?
* Not the same as dermatomes!!!
* areas of skin supplied by peripheral nerves
39
What is Herpes Zosters significance with dermatomes?
* Shingles
* Almost always affects the skin of a single dermatome
* Reactivcation of chickenpox
* Virus travels through a cutaneous nerve and remains dermant in dorsal root ganglion after chickenpox
* When host is immunosuppressed can reactivate and travel through peripheral nerve to skin of a single dermatome
40
What nerves supply myotomes?
* 1 spinal nerve contains neurons of many motor units
* 1 soinal nerve supplies one myotome
41
What does C5 myotome do?
* Shoulder abduction
* external rotation
42
What does C6 myotome do?
* Elbow flexion
* wrist extension
* supination
43
What does C7 myotome do?
* Elbow extension
* wrist flexion
* pronation
44
What does C8 myotome do?
* Finger flexion
* Finger extension
45
What does T1 myotome do?
* Finger abduction
* Finger adduction
46
What does L2 myotome do?
Hip flexion
47
What does L3 myotome do?
* Knee extension
48
What does L4 myotome do?
* Ankle dorsiflexion
49
What does L5 myotome do?
* Great toe extension
50
What does S1 myotome do?
* Ankle plantar-flexion
51
What does S2 myotome do?
* Great toe flexion
52
What is Hiltons Law?
* Femoral nerve (L2,3,4)
* Supplies the quadriceps femoris group of muscles
* Extends the knee joint
* supplies skin overlying the knee
* L3 is myotome for knee extension
* Dermatome overluing the anterior knee is L3
* Femoral nerve inury causes paralysis and anethesia in the muscles and areas
