The psoas minor muscle ( or ; from grc, ψόᾱ, psóā, muscles of the loins) is a long, slender

skeletal muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of m ...

. When present, it is located anterior to the

psoas major muscle The psoas major ( or ; from grc, ψόᾱ, psóā, 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 il ...

.Tank (2005), p 93Gray (2008), p 1372

Structure

The psoas minor muscle originates from the vertical

fascicle Fascicle or ''fasciculus'' may refer to: Anatomy and histology * Muscle fascicle, a bundle of skeletal muscle fibers * Nerve fascicle, a bundle of axons (nerve fibers) ** Superior longitudinal fasciculus *** Arcuate fasciculus ** Gracile fasc ...

s inserted on the last

thoracic The thorax or chest is a part of the anatomy of humans, 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 divisions of the crea ...

and first

lumbar vertebra The lumbar vertebrae are, in human anatomy, the five vertebrae between the rib cage and the pelvis. They are the largest segments of the vertebral column and are characterized by the absence of the foramen transversarium within the transverse ...

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 a fascia in the region of the ilium of the pelvis. It has the following connections: * ''laterally'', to the whole length of the inner lip of the iliac crest. * ''medially'', to the linea terminalis of ...

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 The iliolumbar artery is the first branch of the posterior trunk of the internal iliac artery. Structure The iliolumbar artery is the first branch of the posterior trunk of the internal iliac artery. It turns upward behind the obturator nerve and ...

Innervation

The psoas minor muscle is

innervated A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system. A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the e ...

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 Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur o ...

, 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 million ...

. In horses, it may be palpated during rectal exams to check for causes of

back pain Back pain 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 is the most common ...

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