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Lumbosacral trunk
Lumbosacral trunk
	Plan of lumbar plexus.
	Dissection of side wall of pelvis showing sacral and pudendal plexuses.
Details
From	L4-L5
Identifiers
Latin	truncus lumbosacralis
TA98	A14.2.07.026
TA2	6504
FMA	65535
	Anatomical terms of neuroanatomy [edit on Wikidata]

The lumbosacral trunk is nervous tissue that connects the lumbar plexus with the sacral plexus. It is formed by the union of parts of the fourth and fifth lumbar nerves and descends to join the sacral plexus.

Anatomy

The lumbosacral trunk is formed by the union of the entire anterior ramus of lumbar nerve L5 and a part of L4^{[clarification needed]}.^[1]^[2]^[3] L4 first issues its branches to the lumbar plexus, then emerges from the medial border of the psoas muscle^[3] to unite with the anterior ramus of L5 just superior to the pelvic brim to form the thick, cord-like trunk which^[4] crosses the pelvic brim (medial to the obturator nerve)^[3] to descend upon the anterior surface of the ala of sacrum before joining the sacral plexus.^[4]

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.^[3]

Clinical significance

The lumbosacral trunk may be compressed by the fetal head during the second stage of labour.^[5] This causes some muscle weakness in the legs.^[5] A full recovery is usually expected.^[5]

Additional images

Lumbosacral trunk
Ramus communicans.Sacral symphatetic with S1.

References

^ 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
^ 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 ^b ^c ^d Sinnatamby, Chummy S. (2011). Last's Anatomy (12th ed.). p. 310. ISBN 978-0-7295-3752-0.
^ ^a ^b Moore, Keith L.; Dalley, Arthur F.; Agur, Anne M. R. (2017). Essential Clinical Anatomy. Lippincott Williams & Wilkins. p. 584. ISBN 978-1496347213.
^ ^a ^b ^c 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

External links

Anatomy photo:43:15-0103 at the SUNY Downstate Medical Center - "The Female Pelvis: The Posterolateral Pelvic Wall"
posteriorabdomen at The Anatomy Lesson by Wesley Norman (Georgetown University)
figures/chapter_30/30-6.HTM: Basic Human Anatomy at Dartmouth Medical School

[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

[:0-2] 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

[:022-3] Sinnatamby, Chummy S. (2011). Last's Anatomy (12th ed.). p. 310. ISBN 978-0-7295-3752-0.

[Moore-20112-4] Moore, Keith L.; Dalley, Arthur F.; Agur, Anne M. R. (2017). Essential Clinical Anatomy. Lippincott Williams & Wilkins. p. 584. ISBN 978-1496347213.

[:1-5] 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

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Spinal nerves
Cervical	C1 C2 C3 C4 C5 C6 C7 C8 anterior Cervical plexus Brachial plexus posterior Posterior branches of cervical nerves Suboccipital – C1 Greater occipital – C2 Third occipital – C3
Thoracic	T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 T11 T12 anterior Intercostal Intercostobrachial – T2 Thoraco-abdominal nerves – T7–T11 Subcostal – T12 posterior Posterior branches of thoracic nerves
Lumbar	L1 L2 L3 L4 L5 anterior Lumbar plexus Lumbosacral trunk posterior Posterior branches of the lumbar nerves Superior cluneal L1–L3
Sacral	S1 S2 S3 S4 S5 anterior Sacral plexus posterior Posterior branches of sacral nerves Medial cluneal nerves
Coccygeal	anterior Coccygeal plexus posterior Posterior branch of coccygeal nerve