. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. 3H Biology of the Vertebrates. about equal lengths of the remainder of the small intestine, are not distinctly marked off. The jejunum is richer in blood vessels as well as having a some- what thicker wall and wider lumen than the ileum. The characteristic modification of the lining of the mammalian small in- testine is the presence of innumerable tiny thickset velvety projections, or villi, which enormously increase, in a mini- mum of space, the absorbing
. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. 3H Biology of the Vertebrates. about equal lengths of the remainder of the small intestine, are not distinctly marked off. The jejunum is richer in blood vessels as well as having a some- what thicker wall and wider lumen than the ileum. The characteristic modification of the lining of the mammalian small in- testine is the presence of innumerable tiny thickset velvety projections, or villi, which enormously increase, in a mini- mum of space, the absorbing surface ex- posed to the dissolved food. In fact these are the definite organs of absorption. Each villus consists of a thimble-like projection whose thin wall of cells en- closes a capillary loop and a micro- scopic lacteal, or terminal element of the intestinal lymphatics (Fig. 260). Fat that has been reduced to lower terms in the intestine passes into the lacteals and thence to the lymphatics, eventually emptying into the venous system by way of the thoracic duct. Digested proteins and carbohydrates are collected by the venous capillaries of the villi and carried to the liver by way of the portal vein. In the ileum particularly, the forest of microscopic villi is frequently interrupted by irregular bare patches from half an inch to three or four inches in extent, which show like worn places in the nap of a Brussels carpet. These "intestinal ton- sils," or Peyer's patches (Fig. 261), are lymphoid in character. It is important to remember that in typhoid fever the chief lesions occur in these areas. Smaller lymph nodes are also interspersed among the villi. Fig. 260. Diagram of a villus and a gland, or crypt, of Lieberkiihn. Peter's Lft patch ^^Mmm Li/mph nocWe. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the or
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Keywords: ., bookcentury1900, booksubjectanatomycomparative, booksubjectverte
