362 



Action in- 

 voluntary. 



Take away 

 greater part 

 of the 

 diaphragm. 



Clean aorta, 

 vena cava, 

 and 

 branches ; 



also iliac 

 vessels. 



Dissect 

 muscles ; 



psoas and 

 nerves of 

 lumbar 

 plexus, 



Suadratus 

 imborum, 



and iliacus. 



Extent of 

 abdominal 

 aorta. 



surface 

 marking. 



Relations 



DISSECTION OF THE ABDOMEN. 



be rendered smaller, and that tube compressed ; but the other 

 openings for the vena cava and aorta, having tendinous surroundings, 

 are not materially changed. The possible sphincter action of the 

 fibres around the cesophageal opening is most likely to secure 

 closure of that part against the gastric contents when the 

 descending diaphragm, in its contraction, presses upon the stomach. 



The action of the diaphragm is commonly involuntary, but it is 

 perfectly under the control of the will. 



Dissection. After the diaphragm has been learnt the ribs that 

 support it on each side may be cut through it' the thorax has been 

 sufficiently dissected, and the loose pieces of bone with the fore part 

 of the diaphragm may be taken away, to facilitate the dissection of 

 the deeper vessels and muscles. But the posterior third of the 

 diaphragm, with its pillars and arches, should be left ; and the 

 vessels ramifying on it should be followed back to their origin. 



The large vessels of the abdomen, viz., the aorta and the vena 

 cava, are to be cleaned by removing the fat, the remains of the 

 sympathetic plexuses, and the lymphatic glands ; and their branches 

 are to be followed to the diaphragm, to the right kidney and supra- 

 renal body, and to the ovary, or to the inguinal canal for the testicle, 

 as the case may be. In like manner the large iliac branches of the 

 aorta and cava are to be laid bare as far as Poupart's ligament. The 

 ureter and the spermatic vessels are to be cleaned as they cross the 

 iliac artery ; and on the same vessel, near the thigh, branches of a 

 small nerve (genito-crural) are to be sought. 



The muscles are to be laid bare on the left side, but on the right 

 side the fascia covering them is to be shown. 



The psocis muscle, the most internal, lies on the side of the spine, 

 with the small psoas (if present) superficial to it. On its surface, 

 and in the fat external to it, the following branches of the lumbar 

 plexus will be found : The genito-crural nerve lies on the front. 

 Four nerves issue at the outer border, the ilio-hypogastric and 

 ilio-inguinal near the top, the external cutaneous about the centre, 

 and the large anterior crural at the lower part (fig. 138 and fig. 140, 

 p. 373). Along the inner border of the psoas the gangliated cord of 

 the sympathetic is to be sought, with a chain of lumbar lymphatic 

 glands ; and lower down the obturator nerve may be recognised 

 entering the cavity of the pelvis. External to the psoas is the 

 quadratus lumborum, and crossing the latter near the last rib is the 

 last dorsal nerve, with an artery. In the hollow of the hip-bone is 

 the iliacus muscle, which unites below with the large psoas. 



The ABDOMINAL AORTA (fig. 138, (6) extends from the lower part 

 of the last dorsal vertebra to about the middle of the body of the 

 fourth lumbar vertebra, where it divides into the common iliac 

 arteries. Its commencement is between the pillars of the diaphragm ; 

 and its termination is placed opposite a spot below and slightly to 

 the left of the umbilicus, and nearly on a level with the highest 

 point of the iliac crest. 



The chief relations of the vessel to surrounding parts have been 



