368 



HOW FOOD IS PREPARED FOR BODY USE 



Note in the frog the glistening membrane (peritoneum) lining the 

 body cavity. A similar membrane is found in man. 



In man, the body cavity or space in which the internal organs rest 

 is divided into two parts by a wall of muscle, the diaphragm, which 

 separates the heart and lungs from the other internal organs. In the 

 frog no muscular diaphragm exists. Numerous blood vessels can be 

 found in the frog, especially in the walls of the food tube, which carry 

 the digested nutrients to other parts of the body. 



Notice the large, reddish brown organ covering most of the other 

 organs. This is the liver. Count the lobes or divisions of the liver 

 and compare the position and general structure with the liver of man 

 (use manikin). Lift up the middle lobe of the liver and find the gall 

 bladder, a greenish sac. This contains bile, a secretion from the liver. 

 Now compare with the manikin to see if you can locate where the bile 

 gets into the food tube. 



The food tube begins at the mouth, continues as a short, wide gullet 

 into the stomach (just under the liver). Compare these structures in 

 the frog with similar structures in man. The stomach of the frog 

 leads into a long coiled small intestine and thence into a very short 

 large intestine. The large intestine not only excretes the solid wastes of 

 the body, but it is also the reservoir for nitrogenous wastes. It thus differs 

 from a true large intestine and is called a cloaca. 



....gullet 

 ----liver-- 



A..gall blacCder. 

 -j--ston?ack-. 



pancreas. 



smctll 

 intestine 



■ L*\ :^\£mtSn:\ ;4 ■■■: I 



appendix 



aau^. 



Compare part by part, the digestive tract of the frog with that of man. Are there any structures 

 found in one and not in the other? 



