622 THE BLOOD-VASCULAR SYSTEM 



and at the termination of the artery lies a little to its medial side. The tibial 

 (internal popliteal) nerve is superficial to both artery and vein. As it enters the 

 space it is well to the lateral side of the vessels, but as it descends it gradually 

 approaches them, crosses behind them, and at the lower part of the space lies to 

 their medial side. The artery in the whole of its course is deeply placed and 

 covered by a considerable amount of fat and cellular tissue. 



Relations (fig. 498). — In front, the artery lies successively on the popliteal surface of the 

 femur (from which it is separated by a httle fat and sometimes one or two small glands); on the 

 posterior ligament of the knee; on the hinder edge of the articular surface of the head of the tibia; 

 and on the popliteus muscle. From the latter muscle it is separated by the expansion from the 

 semi-membranosus which covers the muscle, and is attached to the popliteal line on the tibia. 



Behind, the arterj' is covered, above by the semi-membranosus; in the centre of the space by 

 the skin, superficial and deep fascia; and below, by the medial head of the gastrocnemius. The 

 popliteal vein is behind it in the whole of its course. The tibial (internal popliteal) nerve crosses 

 behind it obHquely, from the lateral to the medial side, about the centre of the space. As the 

 artery divides into the anterior and posterior tibial, it is crossed by the aponeurotic arch of the 

 soleus which stretches between the tibial and fibular origins of that muscle. 



To the medial side are the semi-membranosus above, and the medial head of the gastrocne- 

 mius and the tibial (internal pophteal) nerve below. 



To the lateral side are the biceps and the tibial (internal popliteal) nerve above, and the 

 lateral head of the gastrocnemius and the plantaris below. 



Branches of the Popliteal Artery 



The branches of the popliteal include the following: — ^(1) the sural; (2) the 

 articular; and (3) the terminal. 



(1) The sural arteries [aa. surales] arise irregularly from the popliteal and 

 supply the muscles of the calf, sending branches upward to the muscles bound- 

 ing the upper part of the popliteal space. From the sural arteries also arise 

 the superficial sural or cutaneous branches which pass downward between the 

 two heads of the gastrocnemius, and, perforating the deep fascia, supply the skin 

 and fascia of the calf. A branch, usually of moderate size, accompanies the small 

 saphenous vein, and is sometimes called the posterior saphenous artery. 



(2) The articular, five in number, are divided into two superior (medial and 

 lateral), two inferior (medial and lateral), and the middle or azygos. The 

 superior and inferior come off transversely in pairs from either side of the popliteal, 

 the superior above, the inferior below the joint. Winding round the bones to 

 the front of the knee, they form — by anastomosing with each other and with the 

 genu suprema (anastomotica magna), the termination of the profunda, the descend- 

 ing branch of the lateral circumflex, and the anterior tibial recurrent — a super- 

 ficial and deep arterial rete (fig. 499). The superficial anastomosis or rete lies 

 between the skin and fascia round about the patella (patellar rete), which it 

 supplies, the larger branches entering it from above. The deep anastomosis or 

 articular rete [rete articularis genu] lies on the surface of the bones around the 

 articular surfaces of the femur and tibia, supplying branches to the contiguous 

 bones and to the joints. The middle articular is a single short trunk coming 

 off from the deep surface of the popliteal artery. It at once passes through the 

 posterior ligament into the joint. 



(a) The superior lateral articular artery [a. genu superior laterahs], the larger of the two 

 superior articular branches, runs in a lateral direction above the lateral head of the gastrocne- 

 mius, and, passing beneath tlie biceps and througli the lateral intermuscular septum and vastus 

 lateralis, enters the substance of the vastus intermedins (crureus), and anastomoses, above with 

 the descending branch of the lateral circumflex, below with the inferior lateral articular, and 

 across the front of tlio femur with the superior medial articular, the genu suprema (anastomot- 

 ica magna), and termination of the profunda, forming with them, as already described, the 

 deep articular rete. Branches are given off to the patella, to the upper and lateral part of the 

 joint, to the boiK;, and to the contiguous muscles. 



(h) The superior medial articular artery [a. genu superior mcdialis] (fig. 499) runs medially 

 just al)Ove the medial iieud of the gastrocncniius, beneath the semi-membranosus, and, after 

 perforating the ten<ion of the a(ldu(!tor nntgnus, enters the substance of the vastus medialis. 

 ilerf! it anastomo.ses witli the deep branch of the genu suprema (anastomotica magna) and ter- 

 mination of the profunda al)ovc, with the inferior medial articular below, and with the superior 

 lateral articular acro.ss the front of the fenun-. It supplies small branches to the contiguous 

 muscles, to the femur, to t lie patella, and to the joint. 



(c) The inferior medial articular artery [a. genu inferior medialis], the larger of the two in- 

 ferior articular arteries, passes in an obliquely medial direction across the ])()])liteus, below the 

 medial condyle (tuberosity) of the tibia and beneath tlie tibial collateral ligament to the front and 



