ABDOMEN. 233 



Hesselbach's triangle is of surgical importance because direct inguinal hernia 

 passes through it. (Fig. 165.) It is bounded internally by the rectus, externally by 

 the deep epigastric artery, below by Poupart's ligament. See, now, that the con- 

 joined tendon of the internal oblique and transversalis stretches across the inner 

 two-thirds of this triangle. Hence this tendon may become one of the coverings 

 of a direct inguinal hernia. 



1 . Points of surgical interest. 



The inguinal canal, since, physiologically, it transmits the male spermatic cord 

 and its homologue, the round ligament of the uterus ; since, pathologically, in- 

 guinal hernia and diseases of the cord are interrogated here. 



2. Importance of tlie umbilictts. 



This is a physiological cicatrix or scar, marking the aperture through which 

 passed the vessels that made up the umbilical cord, or funis, in the child before 

 birth. These vessels were the right and left hypogastric arteries (branches of the 

 internal iliacs) and the umbilical vein. The arteries took blood to the placenta 

 for aeration ; the vein returned this blood aerated. You will find internally in 

 adult dissections remains of these three vessels centering at the umbilicus. 



3 . Further importance of umbilicus. 



In both adult and child it may be the location of umbilical hernia. 



4. Give nerve-supply of the abdominal muscles. 



The six lower thoracic nerves, through their anterior primary divisions, 

 assisted by the ilio-hypogastric and ilio-inguinal nerves from the lumbar plexus. 

 They also supply the skin covering these muscles. 



5 . Give the blood-supply of the abdominal ivalls. 



This is both abundant and important, (i) The deep epigastric ; (2) the internal 

 mammary ; (3) the lumbar arteries ; (4) the intercostals ; (5) the deep circum- 

 flex iliac ; (6) the superficial circumflex iliac ; (7) the superficial epigastric. The 

 deep epigastric, a branch of the external iliac, anastomoses in the substance of 

 the rectus muscle with the superior epigastric branchof the internal mammary 

 artery, a branch of the subclavian artery. 



6. Function of abdominal muscles. 



(i) They protect from violence and temperature changes the organs in the 

 abdominal cavity ; (2) they assist internal organs to discharge their contents, in 

 that they excite peristalsis a physiological Crede ; (3) they, by their various 

 contractions, alter the relations between the thorax and abdomen ; (4) they are 

 strongly analogous to structures above the diaphragm. The external oblique is 

 analogous to the external intercostals ; the internal oblique to the internal inter- 

 costals ; the transversalis to the triangularis sterni ; the rectus to the sternum ; 

 the linese semilunares to the chondra, vertically ; the lineae transversae to the cos- 

 tal cartilages ; their nerve- and blood-supply are strongly analogous, while func- 

 tions conform to local demands and structure is modified accordingly. 



Important Attachments and Relations. Notice carefully the following, and 

 demonstrate on your dissection the following points : 



1. Each of the three broad muscles has (i) an outer muscular part, and (2) 

 an inner aponeurotic part ; the latter are inseparably united, the former may be 

 separated from each other. 



2. The conjoined aponeuroses of all three planiform muscles form the verti- 

 cal mid-line of the abdominal walls, known as linea alba abdominis. 



3. The two inner muscles are attached to the upper surface of Poupart's 

 ligament for about one-half the length of this (the outer one-half), and then leaving 

 the same arch over the spermatic cord, forming the roof of the inguinal canal, and 

 are inserted into the pubic crest and inner part of the ilio-pectineal line. 



4. Between the muscular parts of the internal oblique and transversalis 

 muscles is located a meagre plexus of nerves, from which the abdominal muscles 



16 



