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 The psoas major ( or ; from ) 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 other animals, this muscle is equ ...

.Tank (2005), p 93Gray (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 vertebra The lumbar vertebrae are located between the thoracic vertebrae and pelvis. They form the lower part of the back in humans, and the tail end of the back in quadrupeds. In humans, there are five lumbar vertebrae. The term is used to describe the ...

e. 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 The iliopectineal arch is a thickened band of fused iliac fascia and psoas fascia passing from the posterior aspect of the inguinal ligament anteriorly across the front of the femoral nerve to attach to the iliopubic eminence of the hip bone pos ...

.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.) * * {{Authority control Hip flexors Hip muscles Spine flexors Muscles of the lower limb