Lumbosacral trunk

<h2 id="anatomy">Anatomy</h2>
The lumbosacral trunk is formed by the union of the entire <a href="/facts/Ventral_ramus_of_spinal_nerve/cFDEvFyy">anterior ramus</a> of <a href="/facts/Lumbar_nerves/ex4CuayR">lumbar nerve L5</a> and a part of L4.<a class="footnote-ref" id="fnref:1" href="#fn:1">1</a><a class="footnote-ref" id="fnref:2" href="#fn:2">2</a><a class="footnote-ref" id="fnref:3" href="#fn:3">3</a> L4 first issues its branches to the lumbar plexus, then emerges from the medial border of the psoas muscle<a class="footnote-ref" id="fnref:4" href="#fn:4">4</a> to unite with the anterior ramus of L5 just superior to the <a href="/facts/Pelvic_brim/lP7au9EC">pelvic brim</a> to form the thick, cord-like trunk which<a class="footnote-ref" id="fnref:5" href="#fn:5">5</a> crosses the pelvic brim (medial to the <a href="/facts/Obturator_nerve/cAKh7hEb">obturator nerve</a>)<a class="footnote-ref" id="fnref:6" href="#fn:6">6</a> to descend upon the anterior surface of the <a href="/facts/Ala_of_sacrum/CTFnjSm0">ala of sacrum</a> before joining the <a href="/facts/Sacral_plexus/6HVyBl1m">sacral plexus</a>.<a class="footnote-ref" id="fnref:7" href="#fn:7">7</a>
Like the sacral nerves, the lumbosacral trunks splits into an anterior division and a posterior division before recombining to form nerves for the flexor and extensor compartments of the lower limb.<a class="footnote-ref" id="fnref:8" href="#fn:8">8</a>

<h2 id="clinical-significance">Clinical significance</h2>
The lumbosacral trunk may be compressed by the <a href="/facts/Fetal_head/TUmK8c3h">fetal head</a> during the <a href="/facts/Childbirth/KaWFJ4kG">second stage of labour</a>.<a class="footnote-ref" id="fnref:9" href="#fn:9">9</a> This causes some muscle weakness in the <a href="/facts/Leg/3W0vcemY">legs</a>.<a class="footnote-ref" id="fnref:10" href="#fn:10">10</a> A full recovery is usually expected.<a class="footnote-ref" id="fnref:11" href="#fn:11">11</a>

<h2 id="additional-images">Additional images</h2>

<h2 id="external-links">External links</h2>
<ul><li><a href="http://ect.downstate.edu/courseware/haonline/labs/l43/150103.htm">Anatomy photo:43:15-0103</a> at the SUNY Downstate Medical Center - "The Female Pelvis: The Posterolateral Pelvic Wall"</li>
<li><a href="http://www.wesnorman.com/posteriorabdomen.htm">posteriorabdomen</a> at The Anatomy Lesson by Wesley Norman (Georgetown University)</li>
<li><a href="http://www.dartmouth.edu/~humananatomy/figures/chapter_30/30-6.HTM">figures/chapter_30/30-6.HTM</a>: Basic Human Anatomy at Dartmouth Medical School</li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1">Mirjalili, S. Ali (2015-01-01), Tubbs, R. Shane; Rizk, Elias; Shoja, Mohammadali M.; Loukas, Marios (eds.), "Chapter 46 - Anatomy of the Sacral Plexus L4-S4", Nerves and Nerve Injuries, San Diego: Academic Press, pp. 619–626, ISBN 978-0-12-410390-0, retrieved 2021-01-13 <a href="978-0-12-410390-0" target="_blank">978-0-12-410390-0</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></li>
<li id="fn:2">Katirji, Bashar (2007-01-01), Katirji, Bashar (ed.), "Case 5", Electromyography in Clinical Practice (Second Edition), Philadelphia: Mosby, pp. 117–124, ISBN 978-0-323-02899-8, retrieved 2021-01-13 <a href="978-0-323-02899-8" target="_blank">978-0-323-02899-8</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></li>
<li id="fn:3">Sinnatamby, Chummy S. (2011). Last's Anatomy (12th ed.). p. 310. ISBN 978-0-7295-3752-0. <a href="978-0-7295-3752-0" target="_blank">978-0-7295-3752-0</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></li>
<li id="fn:4">Sinnatamby, Chummy S. (2011). Last's Anatomy (12th ed.). p. 310. ISBN 978-0-7295-3752-0. <a href="978-0-7295-3752-0" target="_blank">978-0-7295-3752-0</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></li>
<li id="fn:5">Moore, Keith L.; Dalley, Arthur F.; Agur, Anne M. R. (2017). Essential Clinical Anatomy. Lippincott Williams & Wilkins. p. 584. ISBN 978-1496347213. <a href="978-1496347213" target="_blank">978-1496347213</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></li>
<li id="fn:6">Sinnatamby, Chummy S. (2011). Last's Anatomy (12th ed.). p. 310. ISBN 978-0-7295-3752-0. <a href="978-0-7295-3752-0" target="_blank">978-0-7295-3752-0</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></li>
<li id="fn:7">Moore, Keith L.; Dalley, Arthur F.; Agur, Anne M. R. (2017). Essential Clinical Anatomy. Lippincott Williams & Wilkins. p. 584. ISBN 978-1496347213. <a href="978-1496347213" target="_blank">978-1496347213</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></li>
<li id="fn:8">Sinnatamby, Chummy S. (2011). Last's Anatomy (12th ed.). p. 310. ISBN 978-0-7295-3752-0. <a href="978-0-7295-3752-0" target="_blank">978-0-7295-3752-0</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></li>
<li id="fn:9">Goyal, N.; Chad, D. A. (2014-01-01), "Lumbar Plexopathy", in Aminoff, Michael J.; Daroff, Robert B. (eds.), Encyclopedia of the Neurological Sciences (Second Edition), Oxford: Academic Press, pp. 923–926, ISBN 978-0-12-385158-1, retrieved 2021-01-13 <a href="978-0-12-385158-1" target="_blank">978-0-12-385158-1</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></li>
<li id="fn:10">Goyal, N.; Chad, D. A. (2014-01-01), "Lumbar Plexopathy", in Aminoff, Michael J.; Daroff, Robert B. (eds.), Encyclopedia of the Neurological Sciences (Second Edition), Oxford: Academic Press, pp. 923–926, ISBN 978-0-12-385158-1, retrieved 2021-01-13 <a href="978-0-12-385158-1" target="_blank">978-0-12-385158-1</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></li>
<li id="fn:11">Goyal, N.; Chad, D. A. (2014-01-01), "Lumbar Plexopathy", in Aminoff, Michael J.; Daroff, Robert B. (eds.), Encyclopedia of the Neurological Sciences (Second Edition), Oxford: Academic Press, pp. 923–926, ISBN 978-0-12-385158-1, retrieved 2021-01-13 <a href="978-0-12-385158-1" target="_blank">978-0-12-385158-1</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></li>
</ol>

Lumbosacral trunk open-in-new

Lumbosacral trunk