The psoas minor muscle ( or ; from ) is a long, slender
skeletal muscle
Skeletal muscle (commonly referred to as muscle) is one of the three types of vertebrate muscle tissue, the others being cardiac muscle and smooth muscle. They are part of the somatic nervous system, voluntary muscular system and typically are a ...
.
When present, it is located anterior to the
psoas major muscle.
[Tank (2005), p 93][Gray (2008), p 1372]
Structure
The psoas minor muscle originates from the vertical
fascicles inserted on the last
thoracic
The thorax (: thoraces or thoraxes) or chest is a part of the anatomy of mammals and other tetrapod animals located between the neck and the abdomen.
In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main ...
and first
lumbar vertebrae. From there, it passes down onto the medial border of the psoas major, and is inserted to the
innominate line and the
iliopectineal eminence. Additionally, it attaches to and stretches the deep surface of the
iliac fascia
The iliac fascia (or Abernethy's fascia) is the fascia overlying the iliacus muscle.
Superiorly and laterally, the iliac fascia is attached to the inner aspect of the iliac crest; inferiorly and laterally, it extends into the thigh to unite with ...
and occasionally its lowermost fibers reach the
inguinal ligament
The inguinal ligament (), also known as Poupart's ligament or groin ligament, is a band running from the pubic tubercle to the anterior superior iliac spine. It forms the base of the inguinal canal through which an indirect inguinal hernia may ...
.
[Bendavid (2001), p 58] It is posteriolateral to the
iliopsoas muscle. Variations occur, however, and the insertion on the iliopubic eminence sometimes radiates into the
iliopectineal arch.
[Platzer (2004), p 234]
The psoas minor muscle receives oxygenated blood from the four
lumbar arteries (inferior to the subcostal artery) and the lumbar branch of the
iliolumbar artery.
Innervation
The psoas minor muscle is
innervated by direct branches of the
lumbar spinal nerves.
Variation
The psoas minor muscle is considered inconstant and is often absent, only being present in about 40% of human specimens studied.
[Mcg Farias (1 Jan. 2012). Morphological and morphometric analysis of Psoas Minor Muscle in cadavers. ResearchGate. Retrieved from https://www.researchgate.net/publication/280236296_Morphological_and_morphometric_analysis_of_Psoas_Minor_Muscle_in_cadavers] It has an average length of about 24 cm, of which about 7.1 cm is muscle tissue and about 17 cm is tendon.
Function
The psoas minor is a weak flexor of the lumbar vertebral column.
Other animals
The psoas minor muscle is present in other
mammals
A mammal () is a vertebrate animal of the class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three middle e ...
, such as
horses
The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 milli ...
.
In horses, it may be palpated during
rectal exams to check for causes of
back pain
Back pain (Latin: ''dorsalgia'') is pain felt in the back. It may be classified as neck pain (cervical), middle back pain (thoracic), lower back pain (lumbar) or coccydynia (tailbone or sacral pain) based on the segment affected. The lumbar area ...
.
Additional images
File:Gray236.png, Right hip bone, internal surface
File:Gray245.png, Right femur, posterior surface
File:Slide4nn.JPG, Psoas minor muscle
File:Slide9pp.JPG, Psoas minor muscle
File:Slide6ppp.JPG, Psoas minor muscle
Notes
References
*
* (ISBN for the Americas 1-58890-159-9.)
*
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{{Authority control
Hip flexors
Hip muscles
Spine flexors
Muscles of the lower limb