出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/09/04 11:02:00」(JST)
| Nerve: Lumbar plexus | |
|---|---|
| Plan of lumbar plexus. | |
| The lumbar plexus and its branches. | |
| Latin | plexus lumbalis |
| Gray's | subject #212 949 |
| From | T12, L1-L4 |
| MeSH | Lumbosacral+Plexus |
The lumbar plexus is a nervous plexus in the lumbar region of the body which forms part of the lumbosacral plexus. It is formed by the divisions of the first four lumbar nerves (L1-L4) and from contributions of the subcostal nerve (T12), which is the last thoracic nerve. Additionally, the ventral rami of the fourth lumbar nerve pass communicating branches, the lumbosacral trunk, to the sacral plexus. The nerves of the lumbar plexus pass in front of the hip joint and mainly support the anterior part of the thigh.[1]
The plexus is formed lateral to the intervertebral foramina and passes through psoas major. Its smaller motor branches are distributed directly to psoas major, while the larger branches leave the muscle at various sites to run obliquely downward through the pelvic area to leave the pelvis under the inguinal ligament, with the exception of the obturator nerve which exits the pelvis through the obturator foramen.[1]
The iliohypogastric nerve[2] runs anterior to the psoas major on its proximal lateral border to run laterally and obliquely on the anterior side of quadratus lumborum. Lateral to this muscle, it pierces the transversus abdominis to run above the iliac crest between that muscle and abdominal internal oblique. It gives off several motor branches to these muscles and a sensory branch to the skin of the lateral hip. Its terminal branch then runs parallel to the inguinal ligament to exit the aponeurosis of the abdominal external oblique above the external inguinal ring where it supplies the skin above the inguinal ligament (i.e. the hypogastric region) with the anterior cutaneous branch. [3]
The ilioinguinal nerve closely follows the iliohypogastric nerve on the quadratus lumborum, but then passes below it to run at the level of the iliac crest. It pierces the lateral abdominal wall and runs medially at the level of the inguinal ligament where it supplies motor branches to both transversus abdominis and sensory branches through the external inguinal ring to the skin over the pubic symphysis and the lateral aspect of the labia majora or scrotum. [3]
The genitofemoral nerve pierces psoas major anteriorly below the former two nerves to immediately split into two branches that run downward on the anterior side of the muscle. The lateral femoral branch is purely sensory. It pierces the vascular lacuna near the saphenous hiatus and supplies the skin below the inguinal ligament (i.e. proximal, lateral aspect of femoral triangle). The genital branch differs in males and females. In males it runs in the spermatic cord and in females in the inguinal canal together with the teres uteri ligament. It then sends sensory branches to the scrotal skin in males and the labia majora in females. In males it supplies motor innervation to the cremaster. [3]
The lateral cutaneous femoral nerve pierces psoas major on its lateral side and runs obliquely downward below the iliac fascia. Medial to the anterior superior iliac spine it leaves the pelvic area through the lateral muscular lacuna. In the thigh it briefly passes under the fascia lata before it breaches the fascia and supplies the skin of the anterior thigh. [3]
The obturator nerve leaves the lumbar plexus and descends behind psoas major on it medial side, then follows the linea terminalis into the lesser pelvis, and finally leaves the pelvic area through the obturator canal. In the thigh, it sends motor branches to obturator externus before dividing into an anterior and a posterior branch, both of which continues distally. These branches are separated by adductor brevis and supply all thigh adductors with motor innervation: pectineus, adductor longus, adductor brevis, adductor magnus, adductor minimus, and gracilis. The anterior branch contributes a terminal, sensory branch which passes along the anterior border of gracilis and supplies the skin on the medial, distal part of the thigh. [4]
The femoral nerve is the largest and longest of the plexus' nerves. It gives motor innervation to iliopsoas, pectineus, sartorius, and quadriceps femoris; and sensory innervation to the anterior thigh, posterior lower leg, and hindfoot. In the pelvic area, it runs in a groove between psoas major and iliacus giving off branches to both muscles, and exits the pelvis through the medial aspect of muscular lacuna. In the thigh it divides into numerous sensory and muscular branches and the saphenous nerve, its long sensory terminal branch which continues down to the foot. [4]
| Nerve | Segment | Innervated muscles | Cutaneous branches |
|---|---|---|---|
| Iliohypogastric | T12-L1 |
• Transversus abdominis |
• Anterior cutaneous ramus |
| Ilioinguinal | L1 |
• Anterior scrotal nerves in males |
|
| Genitofemoral | L1, L2 |
• Cremaster in males |
• Femoral ramus |
| Lateral femoral cutaneous | L2, L3 | • Lateral femoral cutaneous | |
| Obturator | L2-L4 |
• Obturator externus |
• Cutaneous ramus |
| Femoral | L2-L4 |
• Iliopsoas |
• Anterior cutaneous branches |
| Short, direct muscular branches | T12-L4 |
• Psoas major |
Similar to lumbar plexus there is brachial plexus in upper limb.
The right sympathetic chain and its connections with the thoracic, abdominal, and pelvic plexuses.
Lumbar plexus after dissection
Lumbar plexus after dissection
Schematic diagram of the lumbar plexus
| This article relies largely or entirely upon a single source. Relevant discussion may be found on the talk page. Please help improve this article by introducing citations to additional sources. (January 2009) |
| Wikimedia Commons has media related to: Lumbar plexus |
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| リンク元 | 「腰神経叢」 |
| 関連記事 | 「plexus」「plexuses」 |
| T12 | L1 | L2 | L3 | L4 | 走行(M.181) | 機能（Ｍ.181) | |
| 肋下神経 | ○ | 外側弓状靱帯の後方を通って腹部に入り、外下方に走り、腰方形筋の前面を横切る。腹横筋と内腹斜筋を通り抜けて外腹斜筋と腹壁前外側面の皮膚に分布 | 外腹斜筋と腹壁前外側面の皮膚を支配 | ||||
| 腸骨下腹神経 | ○ | ○ | 内側弓状靱帯の後方で腹部に入り、下外方に走って腰方形筋の前面を通る。腹壁の筋を上腸骨棘の近くで貫き、内腹斜筋と外腹斜筋を貫いて恥骨上部に分布 | 恥骨上部 | |||
| 腸骨鼡径神経 | ○ | ○ | 内側弓状靱帯の後方で腹部に入り、下外方に走って腰方形筋の前面を通る。腹壁の筋を上腸骨棘の近くで貫き、内腹斜筋と外腹斜筋を貫いて鼡径領域に分布 | 鼡径領域 | |||
| 陰部大腿神経 | ○ | ○ | 大腰筋の前面を貫き、下方に走り、腰筋筋膜の深層に潜る。総・外腸骨動脈の外側で分岐し大腿枝と陰部枝に分岐する | ||||
| 外側大腿皮神経 | ○ | ○ | 腸骨筋の表面を下外方に走り、鼡径靱帯の深層かつ上前腸骨棘のすぐ内側で大腿に入る | 代替の前外側面の皮膚 | |||
| 大腿神経 | ○ | ○ | ○ | ||||
| 閉鎖神経 | ○ | ○ | ○ | 大腰筋の内側縁に沿って下行。閉鎖孔の閉鎖管を抜ける。前枝と後枝に分かれる。 | 筋枝(外閉鎖筋、長内転筋、短内転筋、大内転筋、恥骨筋、薄筋)皮枝(閉鎖神経皮枝) |
Henry Gray (1825-1861). Anatomy of the Human Body. 1918.