11 Spinal Nerves Neuroanatomy 11 cxt — Transcript

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1. 0:03Now we will talk about the spinal
2. 0:05nerves. What are spinal nerves? They
3. 0:08are the nerves emerging from the spinal
4. 0:11cord. We agreed before that the spinal
5. 0:14cord is divided into 31 segments. And
6. 0:17from each segment, a pair of spinal
7. 0:19nerves emerges. This means that I have
8. 0:2231 pairs of spinal nerves. So, these
9. 0:27spinal nerves how are they formed? They
10. 0:33say, here is the spinal cord. This is
11. 0:37the posterior horn or dorsal horn. And
12. 0:39this is the ventral horn. This is motor
13. 0:43. The dorsal horn was sensory. And the
14. 0:46ventral horn was motor. This is gray
15. 0:48matter. The ventral horn is attached to
16. 0:52a root called the ventral root, right
17. 0:56here. This is the ventral root. And the
18. 1:01dorsal horn is attached to another root
19. 1:03called the dorsal root. Here is the
20. 1:06ventral root and here is the dorsal
21. 1:08root. These are attached to the ventral
22. 1:11and dorsal parts of the spinal cord.
23. 1:14The dorsal root has a group of cells
24. 1:17mounted on it. Which are called the
25. 1:21dorsal root ganglia. This distinguishes
26. 1:23it from the ventral root. It doesn't
27. 1:26have ganglia. So the dorsal root is the
28. 1:28one with the ganglion called the dorsal
29. 1:30root ganglion. So, the first stage in
30. 1:33forming the spinal nerve is the
31. 1:38emergence of the dorsal root from the
32. 1:40spinal cord. This is sensory, and the
33. 1:43ventral root. This is motor. And both
34. 1:47unite together to form a trunk called a
35. 1:51mixed trunk. Which is called the spinal
36. 1:54nerve. Now, the ventral root emerges
37. 1:57from the ventral part of the spinal
38. 1:59cord. The dorsal root is attached to
39. 2:00the dorsal part of the spinal cord.
40. 2:03Where is the mixed trunk or spinal
41. 2:05nerve located? They say in the foramen
42. 2:07called the intervertebral foramen. Keep
43. 2:10in mind, this is the body of the
44. 2:11vertebra. And this is the arch of the
45. 2:13vertebra. And this is the vertebral
46. 2:15canal. And here is the intervertebral
47. 2:17foramen. So, the intervertebral foramen
48. 2:20contains the spinal nerve here. So this
49. 2:23is the spinal nerve, which is called a
50. 2:25mixed trunk. Why? Because it is mixed
51. 2:29now. It contains sensory fibers coming
52. 2:32from the dorsal root. And motor fibers
53. 2:34coming from the ventral root. The two
54. 2:37together form a mixed trunk. Pay
55. 2:39attention, where is this spinal nerve
56. 2:42or mixed trunk formed? In the
57. 2:44intervertebral foramen. Then, God
58. 2:47created this spinal nerve to supply the
59. 2:52back of the body and the front of the
60. 2:56body. It splits into two. Ventral rami
61. 3:01that go to the front of the body. And
62. 3:04dorsal rami going to the back of the
63. 3:06body. The ventral rami go to the
64. 3:08muscles and skin on the front of the
65. 3:11body. And the dorsal rami go to the
66. 3:14muscles and skin on the back. That is
67. 3:16why the ventral rami are mixed and the
68. 3:20dorsal rami are mixed. So when someone
69. 3:24asks me about the formation of the
70. 3:27spinal nerve, I tell them, a ventral
71. 3:29root, which is motor. A dorsal root,
72. 3:33which is sensory. And I tell them to
73. 3:35distinguish the ventral root from the
74. 3:36dorsal root by the presence of the
75. 3:38ganglia. The ganglia are found on the
76. 3:40dorsal root. After that, the dorsal
77. 3:42root and ventral root unite in the
78. 3:45intervertebral foramen to form the
79. 3:47mixed trunk. The mixed trunk splits
80. 3:49into a ventral ramus, which is mixed.
81. 3:51And a dorsal ramus, which is mixed. The
82. 3:53dorsal ramus goes to the back of the
83. 3:54body. The front of the body. And then
84. 3:58we find that there is a ganglion. Which
85. 4:01are the sympathetic ganglia. They send
86. 4:05to the spinal nerves and receive from
87. 4:08the spinal nerves. They receive from
88. 4:12the spinal nerve here via the white
89. 4:14rami communicantes. And they give to
90. 4:17the spinal nerve via the gray rami
91. 4:19communicantes. Of course, white rami
92. 4:21communicantes means the fibers in them
93. 4:24have myelin—they are myelinated. And
94. 4:26gray rami communicantes—the fibers in
95. 4:28them do not have a myelin sheath.
96. 4:31Let’s summarize again the few words
97. 4:33we just said regarding the spinal. The
98. 4:35spinal cord, the spinal nerves, there
99. 4:37are 31, emerging from each segment of
100. 4:39the spinal cord. They emerge as a pair.
101. 4:41Meaning one spinal nerve on this side,
102. 4:43one spinal nerve on the other side.
103. 4:44Stages of spinal nerve formation: there
104. 4:46is a ventral root, which is motor, and
105. 4:49a dorsal root, which is sensory. The
106. 4:50two together form the spinal nerve or
107. 4:52the mixed trunk. It is formed in the
108. 4:53intervertebral foramen. After that, the
109. 4:56nerve divides into ventral rami, which
110. 4:59are motor, and dorsal rami, which are
111. 5:03mixed. They go to provide nerve supply
112. 5:06to the skin of the entire body. Here,
113. 5:13this view shows two perspectives. Here
114. 5:18is the ventral root, and this is the
115. 5:20dorsal root. I identified the dorsal
116. 5:22root because there is a ganglion called
117. 5:24the dorsal root ganglion here. And they
118. 5:26give rise to the spinal nerve. Here I
119. 5:28am showing you the vertebral canal with
120. 5:31the spinal cord inside it. And the
121. 5:34spinal cord gives me these 31 segments.
122. 5:37It gives me 31 pairs of spinal nerves
123. 5:40on each side here. These nerves, the 31
124. 5:45pairs of spinal nerves emerging from
125. 5:49the spinal cord, are: eight cervical
126. 5:52here, 12 thoracic here, five lumbar
127. 5:55here, five sacral here below, and one
128. 5:59coccygeal. These are the numbers of 12
129. 6:07and coccygeal.