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Plexus - med school question

Hi! I thought plexuses are formed by the anterior division of the spinal nerves

However, this video shows both the posterior and anterior division of the spinal nerves contributing to the sacral plexus.

https://www.youtube.com/watch?v=VwaJqDnsBC4

Could someone please help me here? Thank you very much!
Reply 1
Avatar for Kalabamboo
Kalabamboo
OP
14
Bump
Hi,
Sorry you have not received a reply for so long!

A plexus is simply a highly branched/interconnected group of structures (nerves, arteries, etc.) - you will know that the ventral (anterior) spinal roots contain motor fibres, and the dorsal (posterior) roots the sensory fibres.

I cannot advise you on the sacral plexus (I got away with nearly omitting it for my anatomy exams!), but I know that the brachial plexus for the upper limb has branches from the ventral roots of (if I remember right) C5 to T1. I would expect the sacral plexus to be also formed from the ventral roots - I shall try and find a good pic for you - watch this space!

M
Hi @Kalabamboo, just looked at the video you placed a link on.
I can now explain to you the reason for the confusion:-

You must distinguish between:
---- the rami (spinal roots) that contribute to the brachial and sacral plexi (proximal parts in a way), WHICH ARE ONLY THE VENTRAL (=anterior) ONES,

AND:

---- the divisions or branches of the sacral plexus (in this instance), which are the outward going distal parts of the sacral plexus, AND OF WHICH THERE ARE VENTRAL AND DORSAL ONES.

I am not sure that, although the video you cited is quite good, the person who created it herself realizes or clarifies this distinction.

I am sure you will be in a position now to have resolved your query.
M (former medical student)
Reply 4
Avatar for Kalabamboo
Kalabamboo
OP
14
Original post by macpatgh-Sheldon
Hi @Kalabamboo, just looked at the video you placed a link on.
I can now explain to you the reason for the confusion:-

You must distinguish between:
---- the rami (spinal roots) that contribute to the brachial and sacral plexi (proximal parts in a way), WHICH ARE ONLY THE VENTRAL (=anterior) ONES,

AND:

---- the divisions or branches of the sacral plexus (in this instance), which are the outward going distal parts of the sacral plexus, AND OF WHICH THERE ARE VENTRAL AND DORSAL ONES.

I am not sure that, although the video you cited is quite good, the person who created it herself realizes or clarifies this distinction.

I am sure you will be in a position now to have resolved your query.
M (former medical student)


Ah thank you so much! Apologies for such a late reply! Was meant to reply back but then forgot and then had exams :frown: Not sure why TSR is telling me to rep other members before giving rep to you :/
@Kalabamboo

No probs - hope your exams went well! Are you a 2nd year student in medicine?

The system is not letting you rep me cos you probs repped me recently (relatively!) - thanks for trying - dw, it's the thought that counts!

M
Reply 6
Avatar for Kalabamboo
Kalabamboo
OP
14
Original post by macpatgh-Sheldon
@Kalabamboo

No probs - hope your exams went well! Are you a 2nd year student in medicine?

The system is not letting you rep me cos you probs repped me recently (relatively!) - thanks for trying - dw, it's the thought that counts!

M

Thanks a lot! Going into my second year :smile:

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