. The development of the chick; an introduction to embryology. Birds -- Embryology. ALIMENTARY TRACT AND ITS APPENDAGES 311 bends sharply to enter the descending Hmb of the second loop. This bend or duodeno-jejunal flexure (X, Fig. 179) is a relatively fixed point in the growth of the intestine, and marks the bound- ary between the duodenum and succeeding parts of the small intestine. The second loop descends deep into the umbilical cord, and the yolk-stalk is attached to its lowermost portion. A bilateral swelling at the upper end of its ascending limb is the primordiuni of the caecal process
. The development of the chick; an introduction to embryology. Birds -- Embryology. ALIMENTARY TRACT AND ITS APPENDAGES 311 bends sharply to enter the descending Hmb of the second loop. This bend or duodeno-jejunal flexure (X, Fig. 179) is a relatively fixed point in the growth of the intestine, and marks the bound- ary between the duodenum and succeeding parts of the small intestine. The second loop descends deep into the umbilical cord, and the yolk-stalk is attached to its lowermost portion. A bilateral swelling at the upper end of its ascending limb is the primordiuni of the caecal processes, and marks the anterior end of the large intestine, which passes in a slight curve to the cloaca. In the subsequent growth of the intestine the fixed point referred to above at the hinder end of the duodenum is held in its place, and the duodenal loop in front of it simply becomes longer. Fig. 180. — Viscera of a chick embryo of 17 days' incubation from the right side. (After Duval.) Am., Attachment of amnion to umbiHcal stalk. Li. r., 1., Right and left lobes of the hver. Pc, Pan- creas. U. St., Umbilical stalk. Other abbreviations same as Fig. 179. without forming secondary convolutions; the pancreas comes to lie in this loop. The second loop, on the other hand, forms numerous secondary convolutions (Fig. 180) which lie at first in the umbilical cord, but which are gradually retracted (seven- teenth to eighteenth day) into the abdominal cavity. The two intestinal caeca begin to grow out as finger-shaped processes from the swelling already referred to, about the seventh day, and rapidly attain considerable length. The large intestine elongates only about in proportion to the growth of the entire embryo. Having thus noted the general gross anatomy of the embry-. 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 original
Size: 1935px × 1291px
Photo credit: © Paul Fearn / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorlilliefrankrattray187, bookcentury1900, bookdecade1900
