THE DIGESTIVE SYSTEM 1/3 



THE LACTEALS 



The lacteals are minute vessels that commence in the 

 villi of the small intestine. They pass between the layers 

 of the mesentery to small glands, which they enter. The 

 first range of glands collects many small vessels, and trans- 

 mit a few larger branches to a second range of glands ; and, 

 finally, after passing through several successive ranges of 

 these glandular bodies, the lacteals, diminished in number 

 and increased in size, proceed to the enlarged portion of the 

 thoracic duct, into which they open. They are more 

 numerous in the upper portion of the small intestine. 



The absorption of digested materials is accomplished by 

 the lymphatics or lacteals of the intestines which form part 

 of this great system. The absorption takes place in the 

 villi, which are part of the mucous coat of the small in- 

 testine. Passing through the epithelial layer, the lymph 

 comes at once in contact with the capillaries of the vascular 

 network. 



Lymphatic absorbent vessels are found in every part 

 of the body in the glandular system, muscular organs, 

 and mucous membranes. The lymph is a colorless or 

 slightly yellowish, transparent liquid. 



The lymphatic vessels of the intestines originate in the 1 

 substance of the villi. They form plexuses, and continue 

 to build up in size and diminish in number until they 

 finally terminate in a saccular dilatation called the 

 receptaculum chyli, which is the beginning of the thoracic 

 duct. 



The products of digestion, which are taken up by the 

 blood-vessels and lymphatics of the intestines, pass by 

 two different routes into the general circulation. The 

 blood of the portal system, containing albuminose, sugar, 

 and molecular fat, is carried at once to the liver, where 

 it traverses the capillary vessels of this organ before 

 reaching the ascending vena cava and right side of the 



