psoas minor 



psoas major 



artery and vein 

 iliacus 



pectineus 



adductor longus et brevis 



gracilis 



adductor magnus 



and 

 semimembranosus 



semimembranosus 



gastrocnemius 

 popliteus 



gracilis 



Figure M-9. Ventral (inner) musculature of the hip of the cot. A, hip in medial view with body 

 wall opened to expose the iliacus and psoas muscles; B, deeper layer. 



be made up of a psoas major arising from the under side of 

 the vertebral muscles. Medial to the major is the psoas 

 minor tapering posteriorly to a long tendon which inserts 

 on the ilium, below the head of the femur. From the mar- 

 gin of the pelvis behind and above the insertion of the 

 minor, another muscle, the iliacus arises. Its belly extends 

 posteriorly and laterally, wrapped partly around the psoas 

 major, to insert in common with the psoas major. Section 

 of the bellies of the pectineus and adductor longus reveals 

 the obturator externus. This muscle arises around the mar- 

 gins of the obturator fenestra; its belly tapers to a tendon 

 which inserts on the femur, behind the neck, in common 

 with the obturator internus. 



The intrinsic muscles of the thigh are the vastus lateralis, 

 vastus medialis, and vastus intermedius. These arise from 

 the surface of the femur and insert on the knee region with 

 the extrinsic muscles. 



The shank musculature is separable into an anterior 

 (dorsal) division and a posterior (ventral) division (Figure 

 14-10). The superficial layer of the posterior muscles in- 

 cludes the two heads of the gastrocnemius, lateral and 

 medial, and the distally separated plantaris. Below this 

 outer layer is a spindle-shaped muscle, the soleus, which 

 inserts with the outer muscles. Medial to the proximal end 

 of the soleus is the popliteus, which inserts along the bula. 



Below the soleus and lateral to the popliteus are the flexor 

 hallucis, and flexor digitorum longus, in that order. 



The anterior muscles are the outer (and medial) tibialis 

 anterior and below this the extensor digitorum longus. On 

 the lateral aspect of the tibia is a series of three peronaeus 

 muscles: the longus, tertius, and brevis in a proximal to 

 distal order. 



The muscles of the foot and the insertions of the shank 

 muscles, the flexors and extensors of the digits, resemble 

 those of the hand. 



General observations In describing limb muscles a number 

 of basic terms of functional connotation are encountered. 

 The contraction of a muscle is related to responses in 

 antagonistic and complementary muscles and results in the 

 movement of one, or more, skeletal unit in relation to 

 another, or others. The resultant actions are described by 

 the terms defined in Table 14-1. 



As is apparent from the examples given and the previous 

 description, these terms are commonly used in the naming 

 of the muscles. The shape of a muscle (deltoides), the 

 number of parts or heads (biceps), as well as the origin and 

 insertion of a muscle (coccygeofemoralis), have also been 

 utilized in forming names. 



430 



THE MUSCULAR SYSTEM 



