THE THIGH 247 



third of the thigh distal to the inguinal ligament. It 

 possesses a roof or anterior boundary ; a floor or posterior 

 boundary ; a medial boundary ; and a lateral boundary ; 

 a base, which is situated proximally at the junction of the 

 thigh with the abdomen ; and an apex, which lies distally 

 at the junction of the proximal and middle thirds of the 

 thigh (Fig. 1 12). 



The lateral boundary is formed by the medial border of 

 the sartorius muscle as it runs distally and medially across the 

 thigh from the anterior superior spine of the ilium, and, more 

 deeply in the distal part of the triangle, by the medial border 

 of the rectus femoris. The medial boundary is constituted by 

 the prominent medial border of the adductor longus, and 

 the two muscles meet below at the front of the apex of the 

 triangle. The anterior boundary, or roof, is formed by the 

 iliac part of the fascia lata and the cribriform fascia. It is 

 perforated by the structures which pass through the fascia 

 cribrosa (see p. 229), by the lumbo-inguinal nerve, and the 

 intermediate cutaneous nerve of the thigh, and it is covered 

 by the superficial fascia and skin. The posterior boundary, 

 or floor, slopes backwards from the medial and lateral 

 boundaries ; the triangle is, therefore, triangular in section as 

 well as in superficial outline. The medial part of the floor is 

 constituted mainly by the anterior surfaces of the adductor 

 longus and the pectineus, but, if an interval exists between 

 the adjacent borders of those two muscles, a part of the 

 anterior surface of the adductor brevis also appears in the 

 medial part of the floor. The lateral part of the floor is 

 formed by the anterior surfaces of the iliacus and the 

 psoas major. The medial femoral circumflex artery passes 

 through the floor, between the adjacent borders of the psoas 

 and the pectineus, and the profunda artery leaves the 

 triangle by passing behind the upper margin of the adductor 

 longus, close to the femur ; it is accompanied by the profunda 

 vein. The apex is bounded medially by the adductor longus, 

 laterally by the vastus medialis, and anteriorly by the sartorius ; 

 through it the femoral vessels, accompanied by the saphenous 

 nerve, pass from the femoral triangle into the adductor canal. 

 The base is situated at the junction of the thigh with the 

 abdomen ; it is bounded, superficially, by the inguinal 

 ligament ; medially, by the lacunar ligament ; laterally, by the 

 anterior border of the ilium ; and posteriorly, by the pectineus, 



