478 LABORATORY MANUAL OF HUMAN ANATOMY 



the arteries. From what larger sympathetic plexus are the 

 nerves of this plexus derived? 



Mesenteric Lymph-glands (Lymphoglaiidulae mesentericae). (Vide 



Fig. 249, and Toldt, Fig. 1083.) 



How large are these glands? Where are they most numer- 

 ous ? Do you find any along the intestinal margin of the mesen- 

 tery? Examine the lymph-nodes in the mesocolon (lymplio- 

 glandulae mesocolicae). What is the course and destination of 

 the lacteals ? 



Inferior Mesenteric Vessels and Nerves. 



Turn the loops of the small intestine to the right side of the 

 body cavity. Remove by blunt dissection the peritoneum of the 

 posterior abdominal wall and that passing from the posterior 

 abdominal wall upon the colon descendens and colon sigmoideum. 

 Study- 



(a) Inferior mesenteric artery (A. mesenterica inferior). (Vide Fig. 



250, and Spalteholz, Fig. 465.) 



(da) Left colic artery (A. colica sinistra). Determine with what 

 vessels this artery anastomoses above and below. Does it 

 form arcades before the intestinal branches are given off? 



(ab) Sigmoid arteries (Aa. sigmoideae} . 



(ac) Superior hemorrhoidal artery (A. haemorrhoidalis superior). 



This artery descends into the pelvis between the layers 

 of the pelvic mesocolon, and is found upon the posterior 

 surface of the rectum. Its distribution will be studied in 

 a later dissection. When it reaches the rectal ampulla it 

 divides into two branches which descend upon the sides of 

 the rectum as far as the anus. 



(b) Inferior mesenteric vein (V. mesenterica inferior). (Vide Spalte- 



holz, Fig. 497.) 



The beginning of this vein will be found later when the 

 dissection of the rectal wall is made. Two large lateral 

 tributaries will be found which run upon each side of the 

 rectum. They unite to form the 



(ba) Superior hemorrhoidal vein (V. haemorrhoidalis superior). 



An anastomosis is established in the rectal wall between the 

 systemic and portal circulation. Hemorrhoids often de- 

 velop as a result of disease of the liver or occlusion of the 

 portal vein. Why? 



(bb) Sigmoid veins (Vv. sigmoideae). 

 (be) Left colic vein (V. colica sinistra). 



What relation does the V. mesenterica inferior bear to 

 the artery? Into what large vein does it empty above? 

 Use models to study the relation of this vein to the pancreas 

 and the surrounding viscera. 



