420 



THE MUSCULAE SYSTEM. 



OBTURATOR 

 INTERNUS 



Nerve-Supply. The semitendinosus is supplied by two branches from the nerve to the 

 hamstring muscles (L. 5. S. 1. 2.) 



Actions. A flexor of the knee, a medial rotator of the tibia, and an extensor of the hip. 



M. Semimembranosus. The semimembranosus arises by a tendon from the 



superior and lateral facet on the ischial 

 tuberosity (Figs. 366, p. 412, and 374, 

 p. 419). In the proximal third of the 

 thigh the tendon gives place to a 

 rounded fleshy belly, which lies an- 

 terior to the ischial portions of the 

 biceps and semitendinosus muscles. 



Becoming tendinous, at the back 

 of the knee, it is inserted into the 



QUADRATUS horizontal groove on the postero- 

 medial aspect of the medial condyle 



sciatic nerve f the tibia (Figs. 376, below, and 

 384, p. 428). A bursa lies deep to 

 the tendon at its insertion. It has 

 three additional membranous inser- 

 tions : (1) a fascial band extends 

 distally and medially to join the 

 posterior border of the tibial collateral 

 ligament of the knee-joint; (2) an- 

 other fascial band extends distally 



GRACILISI 



ADDUCTOR MAGNUS 



SEMITENDINOSUS. 



EXTERNUS 



GLUT x. us 



MAXIMUS 



ADDUCTOR 

 MAGNUS 



BICEPS (long 

 head) 



SEYIIMEMBRANOSUf 



SARTORIUS TENDON 



BICEPS (short 

 head) 



Tibial nerve 



BICEPS TENDON 



(with common 

 peroneal 

 nerve) 

 PLANTARIS 



GASTRO- 

 CNEMIUS 



FIG. 375. THE MUSCLES ON THE POSTERIOR 

 ASPECT OF THE RIGHT THIGH. 



imembran- 

 i (insertion 



Ligamentum 



patellae (insertion) 



Popliteua (insertion) 

 Attachment of 

 tibial collateral 

 ligament 



Gracilis (insertion) 



Semitendinosus 

 (insertion) 



FIG. 376. MUSCLE- ATTACHMENTS TO THE MEDIAL 

 SURFACE OF THE PROXIMAL PART OF THE 

 RIGHT TIBIA. 



and laterally, forms the fascia covering the popliteus muscle (popliteus fascia), and 

 is attached to the oblique line of the tibia ; and (3) a third strong band extends 

 proximally and laterally to the back of the lateral condyle of the femur, forming 

 the oblique popliteal ligament of the knee-joint. 



