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Flashcards in Spinal Nerves 1 Deck (12):
1

What do we mean by the spinal nerve is mixed

We mean that the spinal nerve (root) is made of a union of the dorsal and ventral nerves. Meaning their branches are both sensory and motor

2

How many spinal nerves do we have, where do they form? How do they extend to the periphery?

8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1-3 coccygeal . In total there are 31 (33). In the intervertebral foramina. These form terminal branchs into a ventral and dorsal branch which are mixed

3

What are the collateral branches of the spinal nerves

They are the white and Gray rami communications (from T1 to L2) and the recurrent branches (which reenter the spinal cord and innervates the meninges- these are mostly sensory)

4

Where are Gray rami communications found? Where are white rami communications found?

Gray rami communications are found everywhere, they contain post ganglionic fibers from the Paravertebral chain.
The white rami communicates are found only from T1 to L2 - this is because they have preganglionic sympathetic fibers. These only exist on T1 - L2

5

Why is there a dorsal and ventral branch of the spinal nerves

Because the spinal nerves innervate the intrinsic muscles of the back and the muscles of the thorax/abdomen/upper, lower limbs. These structures derive from the epimere and hypomere respectively. These (epimere and hypomere) are divisions of the somites which are innervated by the spinal nerves.
So to reach both these areas we need a dorsal and ventral branch

6

The posterior rami innervates What? What does it divide into?

They innervates the deep/intrinsic muscles of the back.
They have a segementary distribution - the spinal nerves have a dedicated area they innervate, this is because the muscles of the back come from a single myotome each.
It divides into a medial and lateral part. Note that these also innervate the skin above the muscle.

7

Name 3 posterior rami of spinal nerves

Medial and lateral branches : innervate deep intervertebral muscles and long back muscles and overlying skin
Posterior ramus of C1: suboccipital nerve.
posterior ramus of C2 : is a large sensitive medial branch, called the greater occipital nerve of arnold

8

What nerves innervates the face? The back of the head and neck? The area behind the ear?

The face is by the trigeminus and it's 3 branches : ophthalmic, ,mandibular, maxillary branches.
The back of the neck is by the first occipital nerve and branches of the C4
The back of the ear is by the great auricular nerve

9

What is the occipital neuralgia of Arnold

It is a pain in the back of the neck and head, and is treated by anaesthesia or electric current.

10

The meninges of the posterior cranial fossa are innervated By?

The first cervical nerves (C2, C3)

11

The ventral rami form plexus except which nerves? Name the plexus' that are formed

The thoracic nerves don't form rani as they are nearly segmentally organised into intercostal spaces.
The plexus formed are :
- cervical : C4/C5
- brachial : C5/T1
- lumbar : L1/L4
- sacral : L4/S3
- pudendus : S2/S4
- coccygeal : S5/coccyx

12

Why do plexa form?

Because muscles (anterior) originate from more than one myotome. And a myotome can give rise to more than one muscle