658 A MANUAL OF ANATOMY 



For the posterior aponeurosis of the muscle, see p. 765. 



Conjoined Tendon. — This is the tendon which gives a common 

 insertion to the Poupart fibres of the internal oblique and trans- 

 versalis abdominis muscles. It is inserted into (i) the front of the 

 pubic crest, and (2) the pectineal portion of the ilio-pectineal line 

 for I inch. The tendon is formed principally by the transversalis 

 abdominis, which extends for i inch along the ilio-pectineal line, 

 whilst the internal oblique only extends along that line for 

 I inch. 



Relations — Supeirficial. — The structures in front of the conjoined tendon, 

 from the middle line outwards, are as follows : the lower part of the in- 

 ternal pillar of the external abdominal ring ; the triangular fascia ; the insertion 

 of the cremaster ; Gimbernat's ligament ; the inner part of Poupart's ligament ; 

 and the spermatic cord. Deep. — The fascia transversalis. 



The conjoined tendon varies greatly in development, and in many cases 

 is hardly distinguishable. As a rule, it covers the inner two-thirds of the 

 floor of Hesselbach's triangle, where it lies behind the inner two-thirds of 

 the inguinal canal and has the spermatic cord, or the round ligament of the 

 uterus, as a superficial relation. It also lies directly behind the external 

 abdominal ring, and so strengthens what would otherwise be a weak part of 

 the abdominal wall. In some cases the conjoined tendon is divisible into 

 two parts, the outer being known as the ligament of Hesselbach, and the 

 inner as the ligament of Henle. 



ReQected Tendon of Cooper. — In normal circumstances the conjoined 

 tendon is limited to the first inch of the pectineal portion of the ilio-pectineal 

 line. Sometimes, however, the anterior aponeurosis of the transversalis 

 abdominis is prolonged outwards beyond the normal limit of the conjoined 

 tendon, in the form of a thin semilunar expansion which extends as far as 

 the inner and lower parts of the internal abdominal ring, and is attached 

 inferiorly to the deep crural arch. This semilunar expansion of the con- 

 joined tendon is known as the reflected tendon of Cooper. Its concavity is 

 directed outwards, and, when present, it covers the outer third of the floor 

 of Hesselbach's triangle, where it lies behind the spermatic cord, and is 

 closely connected with the subjacent fascia transversalis, to which it imparts 

 strength. 



An inspection of the external oblique, internal oblique, and 

 transversalis abdominis muscles shows that they cross each other 

 at different angles, the external oblique passing downwards and 

 forwards, the internal oblique upwards and forwards (these two 

 muscles thus crossing like the limbs of the letter X), and the trans- 

 versalis horizontally forwards. They thus form an intricate 

 lattice-work which renders the abdominal wall very strong, and 

 is a powerful safeguard against hernial protrusions. 



Rectus Abdominis — Origin. — This muscle arises by two heads, 

 both of which are tendinous. The external head, broad and flat, 

 arises from the pubic crest, and the internal head, narrow and some- 

 what round, from the fibrous structures in front of the symphysis 

 pubis, where it is closely connected with its fellow of the opposite 

 side. The two heads join about i inch above the symphysis 

 pubis. 



Insertion. — By means of three flat slijjs, which are at first fleshy 

 and subsequently tendinous, into the anterior surfaces of the fifth, 

 sixth, and seventh costal cartilages. The most internal slip is 



