Long fusiform muscle located in the lumbar region
The
psoas major
(
or
; from
Ancient Greek
:
ψ??
,
romanized
:
pso?
,
lit.
'muscles of the loins') is a long
fusiform muscle
located in the lateral lumbar region between the
vertebral column
and the brim of the
lesser pelvis
. It joins the
iliacus muscle
to form the
iliopsoas
. In animals, this muscle is equivalent to the
tenderloin
.
Structure
[
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]
The psoas major is divided into a superficial and a deep part. The deep part originates from the
transverse processes
of
lumbar vertebrae
L1?L5. The superficial part originates from the lateral surfaces of the last
thoracic vertebra
, lumbar vertebrae L1?L4, and the neighboring
intervertebral discs
. The
lumbar plexus
lies between the two layers.
[1]
Together, the iliacus muscle and the psoas major form the iliopsoas, which is surrounded by the
iliac fascia
. The iliopsoas runs across the
iliopubic eminence
through the
muscular lacuna
to its insertion on the
lesser trochanter
of the femur. The
iliopectineal bursa
separates the tendon of the iliopsoas muscle from the external surface of the
hip-joint capsule
at the level of the
iliopubic eminence
.
[2]
The iliac subtendinous bursa lies between the lesser trochanter and the attachment of the iliopsoas.
[1]
Nerve supply
[
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]
Innervation of the psoas major is through the anterior rami of L1 to L3 nerves.
[3]
Variation
[
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]
In fewer than 50 percent of human subjects,
[1]
the psoas major is accompanied by the
psoas minor
muscle.
One study using autopsy data found that the psoas major muscle is substantially thicker in men of African descent than in Caucasian men, and that the occurrence of the psoas minor is also ethnically variant, being present in most of the white subjects and absent in most of the black subjects.
[4]
In mice, it is mostly a
fast-twitching, type II muscle
,
[5]
while in humans it combines slow- and fast-twitching fibers.
[6]
Function
[
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]
The psoas major joins the upper body and the lower body, the axial to the appendicular skeleton, the inside to the outside, and the back to the front.
[7]
As part of the iliopsoas, psoas major contributes to
flexion
in the hip joint. On the lumbar spine, unilateral contraction bends the trunk laterally, while bilateral contraction raises the trunk from its
supine position
.
[8]
In addition, attachment to the lesser trochanter, located on the
posteromedial
aspect of the
femur
, causes lateral rotation and weak adduction of the hip.
It forms part of a group of muscles called the
hip flexors
, whose action is primarily to lift the upper leg towards the body when the body is fixed or to pull the body towards the leg when the leg is fixed.
For example, when one performs a
sit-up
that brings the torso (including the lower back) away from the ground and towards the front of the leg, the hip flexors (including the iliopsoas) will flex the spine upon the pelvis.
Owing to the frontal attachment on the vertebrae, rotation of the spine will stretch the psoas.
Clinical significance
[
edit
]
Tightness of the psoas can result in spasms or
lower-back pain
by compressing the lumbar discs.
[9]
A hypertonic and inflamed psoas can lead to irritation and entrapment of the
ilioinguinal
and the
iliohypogastric nerves
, resulting in a sensation of heat or water running down the front of the thigh.
Psoas can be palpated with active flexion of the hip. A positive psoas contracture test and pain with palpation reported by the patient indicate clinical significance. Care should be taken around the abdominal organs, especially the colon when palpating deeply.
The appearance of a protruding belly can visually indicate a hypertonic psoas, which pulls the spine forward while pushing the abdominal contents outward.
[10]
The psoas lies posterolateral to the lumbar
sympathetic ganglia
, and the needle tip will often pass through the psoas major during a lumbar sympathetic block.
The
genitofemoral nerve
is formed in the midsection of the psoas muscle by the union of branches from the anterior rami of L1 and L2 nerve roots. The nerve then courses inferiorly within the psoas muscle and finally "pierces" the muscle and emerges on the anterior surface of the psoas distally. The nerve then traverses the
retroperitoneum
, descending over the anterior surface of the psoas.
[11]
See also
[
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]
Notes
[
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]
This article incorporates text in the
public domain
from
page 467
of the 20th edition of
Gray's Anatomy
(1918)
- ^
a
b
c
Platzer (2004), p 234
- ^
Bojsen-Møller, Finn; Simonsen, Erik B.; Tranum-Jensen, Jørgen (2001).
Bevægeapparatets anatomi
[
Anatomy of the Locomotive Apparatus
] (in Danish) (12th ed.). pp. 261?266.
ISBN
978-87-628-0307-7
.
- ^
Gray's anatomy : the anatomical basis of clinical practice
. Standring, Susan (41st ed.). [Philadelphia]. 2016. p. 1324.e2.
ISBN
9780702052309
.
OCLC
920806541
.
{{
cite book
}}
: CS1 maint: location missing publisher (
link
) CS1 maint: others (
link
)
- ^
Hanson, P.; Magnusson, S. P.; Sorensen, H.; Simonsen, E. B. (1999).
"Anatomical differences in the psoas muscles in young black and white men"
.
Journal of Anatomy
.
194
(Pt 2): 303?307.
doi
:
10.1046/j.1469-7580.1999.19420303.x
.
PMC
1467925
.
PMID
10337963
.
- ^
Nunes, MT; Bianco, AC; Migala, A; Agostini, B; Hasselbach, W (1985).
"Thyroxine induced transformation in sarcoplasmic reticulum of rabbit soleus and psoas muscles"
.
Zeitschrift fur Naturforschung C
.
40
(9?10): 726?34.
doi
:
10.1515/znc-1985-9-1025
.
PMID
2934902
.
- ^
Arbanas, Juraj; Starcevic Klasan, Gordana; Nikolic, Marina; Jerkovic, Romana; Miljanovic, Ivo; Malnar, Daniela (2009).
"Fibre type composition of the human psoas major muscle with regard to the level of its origin"
.
Journal of Anatomy
.
215
(6): 636?41.
doi
:
10.1111/j.1469-7580.2009.01155.x
.
PMC
2796786
.
PMID
19930517
.
- ^
Earls, J., Myers, T (2010).
Fascial Release for Structural Balance
. Chchester, England: Lotus Publishing. p. 130.
ISBN
9781905367184
.
{{
cite book
}}
: CS1 maint: multiple names: authors list (
link
)
- ^
Thieme Atlas of Anatomy
(2006), p 422
- ^
Akuthota, et al.(2008). p 40
- ^
Corbo, & Splittgerber (2007).
Your Body, Your Responsibility
. Arizona: Wheatmark Inc, Amazon. p. 88.
- ^
Gupton, Marco; Varacallo, Matthew (2020).
"Anatomy, Abdomen and Pelvis, Genitofemoral Nerve"
.
StatPearls
. StatPearls Publishing.
PMID
28613484
. Retrieved
20 October
2020
.
References
[
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]
Additional images
[
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]
-
Position of psoas major muscle. Animation.
Hip bones
are shown in semi-transparent.
-
Horizontal disposition of the
peritoneum
in the lower part of the
abdomen
. Psoas major labeled at bottom left.
-
Diagram of a transverse section of the posterior abdominal wall, to show the disposition of the lumbodorsal fascia.
-
Muscles of the iliac and anterior femoral regions.
-
The lumbar plexus and its branches.
-
Psoas major muscle
-
Psoas major muscle
External links
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]