MEDIAL SIDE OF THE THIGH 



271 



obturator interims 



Quadratu 

 femoris 



at its insertion into the femur. It has a fleshy origin, from 

 the pectineal line of the pubis, and from the surface of the 

 hip bone anterior to it (Fig. 116). Some fibres are derived 

 also from the lacunar ligament. It descends obliquely, 

 laterally and backwards, and gains insertion into the back 

 of the femur, lateral to 

 the lesser trochanter, 

 and to a certain extent 

 also into the line which 

 leads from that promin- 

 ence towards the linea 

 aspera (Figs. 121, 122). 

 It is supplied by the 

 femoral nerve. The 

 pectineus adducts the 

 femur and rotates the 

 thigh laterally. It also 

 assists in flexion of the 

 hip joint. 



Dissection. De- 

 tach the pectineus from 

 its origin, and throw 

 it towards its insertion. 

 Whilst separating the 

 muscle from the pubis 

 the dissector must bear 

 in mind that in some 

 cases an accessory ob- 

 turator nerve descends 

 into the thigh, under 

 cover of its lateral 

 margin, and over the 

 pubis. Care must also 

 be taken not to injure 



(1) the anterior division 



of the obturator nerve which lies posterior to the muscle, or 



(2) the medial femoral circumflex artery which passes posteriorly 

 in contact with the lateral border of the muscle (Fig. 113). 



Nervus Obturatorius Accessorius. The accessory obturator nerve, 

 when present, arises within the abdomen either from the lumbar plexus or 

 from the obturator trunk near its origin (Fig. 124). In the thigh it gives 

 a branch to the hip joint and joins the anterior division of the obturator 

 nerve. It is very rare to find a twig given to the pectineus either by it or 

 by the trunk of the obturator nerve itself. 



Art. Circumflexa Femoris Medialis. The medial femoral 

 circumflex artery springs from the medial and posterior aspect 



FIG. 122. Posterior Aspect of Proximal 

 Portion of Femur, with the Attachments 

 of Muscles mapped out. 



