Communicating loops for the plexus in green. where rami swap fibers to form nerves (i.e. 3,4,5 keep the diaphragm alive - phrenic nerve is formed of fibers from C3, C4, & C5)
Plexuses are formed by ventral rami. The dorsal rami ennervate the spinal muscles. Cranial nerves come out of the brainstem. *everything else* that you might ever call a nerve or plexus is formed initally from ventral rami
I think that when a ventral ramus gives off a branch, the ventral ramus stops being a ventral ramus yup and becomes some type of nerve,maybe, but in plexi, it's not necessarily to the nerve part yet, could be a root or trunk or whatever other division. ..so in other words, a ventral ramus stops being a ventral ramus at the point it gives off a branch. yes Therefore, the bits coloured in purple in the image below are ventral rami and nothing else is. yes. generally once it's past the bone of the spine, it's no longer a ramus, since they tend to split/merge pretty immediately. you will only see a ramus in the flesh if you do a laminectomy and see it coming off the spinal cord.
EDIT: Also, maybe don't make a new post every time you have another question. That's what annoys people. Keep it all in one thread and they can not look at that one, but start filling the 1st page of the forum with different iterations of the same topic and folks get snarky.
Hi Kraskadva! I have a few questions but would also really appreciate if you possibly check what I've written down below ( I am so sorry it's quite lengthy & don't worry about replying if you are busy
)
In regards to green highlighted bit above:
If only the purple bits
in the image below are ventral rami, then that means that the 4 cervical ventral rami are not connected by the three communicating loops - this is evident because the purple bits don't even touch the three green communicating loops. So this doesn't make any sense.
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About the blue highlighted bit above:
I think the bit I've coloured in yellow
in the image below is a root . So there are different types of roots? The ventral root and the dorsal root connect to form the spinal nerve....
.....And a root of the cervical plexus - this comes right after the ventral ramus (so towards the periphery) and it gives off a bunch of groups of fibres which form different nerves.
Also, it says
above that all four roots of the cervical plexus receive the grey communicating branch from the superior cervical ganglion. This doesn't make sense because it is the spinal nerve which receives the grey communicating branch
as shown in the 2nd image below.
Honestly, I think I am still struggling to understand what a root of a cervical plexus is. Although I can pinpoint where a root of the cervical plexus is (I think), I don't really know how to define it. >> I am more clearer about what I don't get about it further down below.. my essay lol
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What's the difference between the black (blue arrow), the black dotted with white (green arrow), the white (brown arrow) and the grey (orange arrow) things
in the image below.
I think with the black (forming the phrenic nerve), some nerve fibres in C3 and C4 cervical plexus roots move away and group to form the phrenic nerve.
Just wanted to put it out there : You cannot have a branch of a nerve fibre but you can have a branch of a nerve. That is because a nerve fibre is just the dendrite or axon of a neuron and a dendrite or axon doesn't give branches. Oh wait, a dendrite does give branches
Checked on wikipedia: apparently, a dendrite isn't a nerve fibre!
Anyways, as for the black dotted with white, nerves fibres from C1 cervical root, C2 cervical root and C3 cervical root join together to form nerves which branch out to innervate muscles (so nerves which specifically innervate muscles).
I can't really see the difference between the black and the black dotted with white. The black forms the phrenic nerve which innervates a muscle (the diaphragm). The black dotted with white also forms nerves which innervate muscles (omohyoid, sternohyoid, sternothyroid, thyrohyoid, geniohyoid).
The only difference I see between the black and the black dotted with white is that the black dotted with white forms the ansa,...you have nerve (ansa) branches which go on to branch out more and innervate muscles.
In the periphery, whenever a nerve is not formed when you have fibres from different spinal segments coming together, you call it a trunk,..only exception is the ansa.
So when fibres from different spinal segments come together, what is formed can either be a nerve, trunk or ansa..
There isn't any difference between they black and the grey. In fact, I don't get why they are different colours.
The white just represents the hypoglossal nerve.
I have coloured the trunks in pink
in the image below. Don't know if it's correct though.
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I still don't get where a root of a cervical plexus starts and then ends, especially the C4 cervical root.
Is the C4 cervical root of the cervical plexus, this (the bit in brown)? pink is a trunk (I have no name for this trunk - do they even have names?) purple is ventral ramus of C4 nerve
Or is the C4 cervical root of the cervical plexus, this (the bit in red)?
Or is it neither?
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In regards to this part that you wrote in your reply back:
"Communicating loops for the plexus in green. where rami swap fibres to form nerves (i.e. 3,4,5 keep the diaphragm alive - phrenic nerve is formed of fibers from C3, C4 & C5)"
So a fibre can be sensory or motor.
There are many types of fibres e.g. somatosensory, viscerosensory, somatomotor, autonomic (so basically visceromotor or otherwise we would say sympathetic/ paraysmpathetic)
The phrenic nerve is formed from some fibres from C3, some fibres from C4 & some fibres from C5.
Some nerves can be made from just 2 fibres (quantity wise so literally 2 fibres,.. I am not talking about the type of fibres but the number of fibres. For example, the transverse cervical nerve is made from exactly one fibre from C2 root and one fibre from C3 root. I think this idea is really wrong but this is what it sort of shows
in the image below. edit:
Actually tbh I strongly disagree with this (this is what I was thinking last night)
(By the way, this right below is also another idea I was thinking about last night) Would appreciate though if you could see if there is some "correctness" to this.
I apologise in advance as I tend to repeat myself at times to reiterate a point)...
So I came to the conclusion that each of the bits that I've circled in green contain one
type of fibre (the number of fibres is irrelevant).
So do you call these green circled bits , a bunch of fibres of
the same type? e.g. one green circled bit in the image has purely somatosensory fibres, another green circled bit has purely viscerosensory fibres etc.... I don't mean this literally but for understanding purposes, let's just say that the first green circled bit has purely somatosensory fibres and the second green circle bit has purely viscerosensory fibres just to show this on the
diagram below
By the same type, I mean that for example,...one of the green circled bits has all fibres which are somatosensory - it's not that all the somatosensory fibres in the green circled bit are going to the same location (e.g. to innervate the neck only) which makes it of the same type but the fact that all the fibres in the green circled bit are somatosensory which makes the fibres in the green circled bit of the same type. #I feel like putting my head through a wall by the number of times I've said green circled bit lol
This is what I think now!!
Or have I got it all wrong and each of those green circled bits can contain many types of fibres (viscerosensory, somatomotor etc...), a single type of fibre (e.g. all somatosensory fibres), 2 types of fibre (e.g. somatosensory and viscerosensory fibres) - basically it doesn't matter what type of fibre is in them and the number of fibres in them?
What is certain is that any of the green circled bits does not contain just 1 single fibre.
The famous image with green circled bits is below:
Thank you so much for your time to help me - I am so so grateful. No worries if you are busy - lol I keep saying that haha
