MUSCLES OF HIP 455 



In most of the limbed vertebrates these two groups of muscles are represented, but they 

 present marked specific variations in the different forms. Primitively, the iiiacus group lies 

 on the proximal portion of the lateral surface of the ilium. 



(a) Anterior Group 

 (Figs. 406, 411) 



The fan-shaped iiiacus muscle arises from the ihac fossa. The fusiform psoas 

 major muscle arises from the sides of the last thoracic and of the lumbar vertebrae 

 and extends along the medial margin of the iiiacus muscle. The two muscles are 

 inserted by a common tendon into the lesser trochanter of the femur. Together 

 they constitute the ilio-psoas muscle. The small, flat, fusiform psoas minor lies 

 on the medial surface of the psoas major and extends from the twelfth thoracic 

 vertebra to the ilio-pectineal eminence. The ilio-psoas flexes the thigh at the hip 

 and the pelvis on the trunk. The psoas minor aids in flexing the pelvis. 



The iho-psoas muscle arises in the human embryo from a blastema which at first surrounds 

 the femoral nerve and later extends proximally over the ilium (iiiacus) and toward the lumbar 

 vertebrae (psoas). The iiiacus is phylogenetically the more primitive. In the shoulder it is 

 probably represented by the infraspinatus. The psoas minor is much better developed in many 

 of the lower mammals than in man. 



FASCIA 



The fasciae and the relations of these muscles are shown in figs. 384 and 407. 



The ihac and psoas muscles are covered by a dense fascia which is but slightly adherent 

 to the underlying muscles. It is best developed in the pelvic region, where it extends from the 

 iliac crest and iho-lumbar ligament to the iliac portion of the Unea arcuata and is called the iliac 

 fascia. Superiorly it is continued over the psoas muscle as the psoas fascia and is attached 

 medially to the sacrum and the lumbar region of the spinal column. Laterally it unites with 

 the lumbar fascia and superiorly it is strengthened to form the medial lumbo-costal arch (fig. 

 391). Infiriorly the ilio-pectineal fascia extends over the iho-psoas muscle to its femoral inser- 

 tion. It is firmly united on each side of the muscle to the capsule of the hip-joint and to the 

 femur. As it passes beneath the inguinal ligament it is united to this by tendinous processes. 

 Beyond the ligament it is less dense than in the pelvic region. 



MUSCLES 



The psoas major (figs. 406, 411). — Origin. — (1) By a series of thick fasciculi from the inter- 

 vertebral discs between the twelfth thoracic and the fifth lumbar vertebra, from the adjacent 

 parts of the bodies of these vertebrae and from tendinous arches which bridge over the middle 

 of the sides of the first four lumbar vertebrae; and (2) by a series of more slender fascicuh from 

 the lower borders and ventral surfaces of the transverse processes of the lumbar vertebrae. 



Structure and insertion. — From these origins parallel fibre-bundles descend nearly vertically 

 and give rise to a fusiform muscle which lies at the side of the vertebral bodies and extends along 

 the border of the true pelvis toward its insertion. A tendon arises deep in the muscle near 

 the last lumbar vertebra, and becomes free on its dorso-lateral surface slightly above the inguinal 

 (Poupart's) ligament. On the medial side the attachment of fibre-bundles continues to the 

 insertion of the muscle into the small trochanter. The iiiacus muscle is attached to the lateral 

 side of the tendon from near the ilio-pectineal eminence downward. 



Nerve-supply. — Delicate branches pass into the psoas muscle from the trunks wliich unite 

 to form the femoral (anterior crural) nerve, i. e., from the fom-th, third, second, and often the 

 first lumbar nerves. 



The iiiacus (figs. 406, 411). — Origin. — (1) From the iliac crest, the ilio-lumbar ligament, 

 and the greater part of the iliac fossa, the anterior sacro-iliac ligaments, and often from the 

 sacrum, and (2) from the ventral border of the ilium between the two anterior spines. 



Structure and insertion. — -From these areas of origin the fibre-bundles pass to be inserted — 

 (1) in a penniform manner on the lateral surface of the tendon which emerges from the psoas 

 above the inguinal (Poupart's) ligament, and (2) directly on the femur immediately distal to the 

 small trochanter. The lateral portion of the muscle arise from the ventral border of the ilium 

 and is adherent to the direct tendon of the rectus femoris and the capsule of the hip-joint. It is 

 sometimes more or less isolated (w. iiiacus minor, ilio-capsulo-trochantericus, etc.). 



Nerve-supply. — Nerve branches, often united in a plexiform manner, arise from the femoral 

 (anterior crural) nerve and pass across the surface of the iiiacus muscle about midway between 

 the crest of the ilium and the combined ilio-psoas tendon. Special nerve branches are usually 

 likewise distributed from the main trunk of the femoral nerve to the fleshy portion of the muscle 

 which extends over the acetabulum and the head of the femur. 



Relations. — The psoas major lies lateral to the lumbar vertebrae and in front of the quad- 

 ratus lumborum and intertransverse muscles. The psoas minor passes downward.across its ventral 

 surface. Both psoas muscles are crossed by the crura of the diaphragm. The kidney with its 

 adipose capsule lies lateral to them opposite the first two lumbar vertebrae. For the rest, their 

 fascia is covered ventro-laterally by retro-intestinal and retro-peritoneal tissue in which the 

 vena cava inferior runs in front of them on the right side, the inferior mesenteric vein in front 

 of them on the left side, and the ureter, the spermatic or ovarian, and the renal and colic vessels 

 on each side. The external iliac artery hes medial to the psoas major in the pelvis, and beyond 

 the inguinal (Poupart's) ligament the femoral artery Hes ventral to it. The lumbar plexus arises 



