456 



THE HUMAN BODY 



stomach, along the mesentery. This innervation extends through- 

 out the small intestine and the ascending and transverse colons. 

 The descending colon has its thoracico-lumbar innervation by way 

 of the hypogastric nerve which extends to the hypogastric plexus 

 in the lower portion of the abdominal cavity and ramifies thence 

 over the descending colon and rectum. The opposing autonomic 

 innervation for this region is derived from the sacral part of the 

 system. The nervus erigens is the path from the sacral part of the 



FIG. 132. The under surface of the liver, d, right, and s, left lobe; Vh, hepatic 

 vein; Vp, portal vein; Vc, vena cava inferior; Dch, common bile-duct; DC, cystic 

 duct; Dh, hepatic duct; Vf, gall-bladder. 



spinal cord to the hypogastric plexus. Thence the distribution 

 is the same as for the thoracico-lumber autonomies. 



The intestines are provided, in addition, with an intrinsic inner- 

 vation consisting of two nervous networks or plexuses lying, one 

 between the mucosa and the muscular coat, the plexus of Meissner, 

 and the other between the circular and longitudinal muscle layers, 

 the plexus of Auerbach. 



The Liver. Besides the secretions formed by the glands em- 

 bedded in its walls, the small intestine receives those of two large 

 glands, the liver and the pancreas, which lie in the abdominal 

 cavity. The ducts of both open by a common aperture into the 

 duodenum about 10 centimeters (4 inches) from the pylorus. 



