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ORGAN SYSTEMS OF MAN 



fat ( fatty acids and glycerol ) , however, pass 

 through the mucosa and at once recombine 

 into large fat molecules which are slowly 

 taken up by the lacteals. The lacteals join 

 with the lymphatic system and eventually 

 pass into the general circulation. The end 

 result is that all food products eventually 

 reach the blood stream, where they are dis- 

 tributed to all parts of the body. Once the 

 food is in the blood or lymph, the next task 

 is to bring about its distribution to all parts 

 of the body and to provide oxygen so that 

 it can be burned to release energy, which is 

 the ultimate goal. 



FOOD 



Now that we have seen how food passes 

 through the digestive tract and is digested, 

 we shall discuss briefly the kinds of food 

 necessary for the continued health of a hu- 

 man being. 



Food must provide the body with the 

 proper amounts and kinds of substances 

 from which it can synthesize its own parts. 

 Just as the carpenter or mason must have 

 lumber, bricks, cement, and other materials, 

 so must the body have its building mate- 

 rials. The digestive process breaks down the 

 large, complex molecules to small or, sim- 

 pler ones that can be rebuilt into the spe- 

 cific molecules needed for human proto- 

 plasm. The process of reconstruction will be 

 taken up later. What concerns us now is the 

 kinds of food which, when reduced to the 

 simple state, will provide all of the essential 

 materials in sufficient quantities to build 

 and maintain the body. Returning to the 

 house analogy, if the carpenter does not 

 have enough lumber and nails, or the mason 

 enough bricks and cement, they will be 

 forced to cut corners and produce a house 

 that will not function as it should. Simi- 

 larly, food must contain all of the essential 

 substances if the body is to be properly con- 

 structed. Food must also supply a source of 

 energy to maintain the body at a constant 

 temperature and to permit movement. 



Therefore, food must imclude oxidizable 

 materials, or materials that can be con- 

 verted into substances that will burn. Let us 

 consider the kinds of food that contain 

 these two types of materials. 



Foods for building 



The simplest of these are the inorganic 

 salts. The analysis of any animal will reveal 

 a considerable amount of iron, calcium, 

 phosphorus, and other minerals. Moreover, 

 the animal body excretes minerals every 

 day, in man about 30 grams. This means 

 that the animal must get these from some- 

 where and, of course, the only source is 

 through the food supply. 



The minerals that are most apt to be de- 

 ficient in human diet are calcium, iron, and 

 iodine. Calcium is essential for building 

 bone and should be maintained at a high 

 concentration in the diets of children and 

 pregnant women. The old adage that a 

 woman loses a tooth with each child may 

 have some truth in it because the demands 

 of the fetus for calcium are great and cal- 

 cium can come only from the mother's 

 blood. If her diet is deficient in calcium, her 

 teeth may be sacrificed to obtain the vital el- 

 ement. Although calcium is present in small 

 amounts in vegetables and cereals, it is par- 

 ticularly rich in milk — hence, the constant 

 urge for an adequate supply of this food 

 for children. Iron is necessary for the forma- 

 tion of hemoglobin, the chief constituent of 

 the red corpuscles, and a low iron diet will 

 result in anemia. Meats and eggs are rich in 

 iron, as well as many kinds of fruits and 

 vegetables, and ordinarily, under normal 

 circumstances, it is not necessary to supple- 

 ment the diet for this mineral. Iodine is 

 required for the proper functioning of the 

 thyroid gland, as was pointed out earlier. 

 Near and at the seashore, and in regions 

 covered by the sea in past geological time, 

 this element is in adequate supply in the 

 water and food grown in the region. Sea 

 food in particular is always rich in it. In 

 other areas, however, particularly those 



