By William J. Krause
A renewed curiosity is starting to emerge spotting the possibility of marsupials as detailed versions for biomedical examine. due to their abbreviated interval of intrauterine improvement, marsupials are available versions with which to review the early improvement of mammalian organ platforms. The North American opossum (Didelphis virginiana) has acquired extra medical scrutiny than the other marsupial thus far. the aim of volumes I and II is twofold. the 1st aim is to attract jointly and in brief summarize the morphologal occasions and assisting quantitative facts interested in the histogenesis/organogenesis of many of the organ platforms during this specific species. the second one target is to supply an creation into the literature with reference to the biology of Didelphis virginiana and to assemble jointly a number of experiences that experience involved in this species. quantity I summarizes gametes and fertilization, blastocyst formation and early organogenesis, fetal membranes and placentation, parturition and migration to the pouch, normal postnatal progress and improvement, and histogenesis/organogenesis of the integument, musculoskeletal process, cardiovascular process, blood and blood forming organs, lymphatic organs, frightened process, eye, and ear. quantity II summarizes the histogenesis/organogenesis of the breathing approach, digestive approach, urinary method, male reproductive procedure, girl reproductive approach, and classical endocrine system.
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Additional resources for A Review of Histogenesis/Organogenesis in the Developing North American Opossum (Didelphis virginiana)
The mesonephric duct (D), the Miillerian duct (U), developing gonad (G), metanephros (N), and adrenal gland (A) also are shown. x65 (Krause et a1. 1979a) b A section through the length of a mesonephros from a newborn opossum. The renal corpuscles (C) are restricted in distribution to the medial region of the mesonephros. The mesonephric duct (arrow) is shown at the right of the photomicrograph. x40 (Krause et a1. 1979a) Mitochondria often show some orientation parallel to the long axis of the cell.
Endocrine cells immunoreactive for insulin occupy the central region of the islets. Development of the opossum pancreas occurs almost entirely during the postnatal period and the general pattern of development for both endocrine and exocrine components is typical of that reported in other mammals. 1 Pronephros The pronephros of Didelphis initially appears early during the ninth prenatal day and reaches the peak of its development at about the middle of the tenth day of embryonic life. It lies between the seventh and tenth somites and consists of five to six solid epithelial tubules that are continuous, both with the coelomic epithelium and the mesonephric (wolffian) duct (McCrady 1938).
It is believed that the regions of variable electron density indicate the presence of different substances within a given secretory granule. The opossum duodenal glands secrete mucin-type glycoproteins rich in O-linked carbohydrates (Schumacher and Krause 1995). It is thought that such mucus glycoproteins contribute to selective barrier functions and lubrication of the mucosa lining the proximal small intestine. Although the submucosal (Meissner's) plexus has been detailed in the adult intestinal tract (Christensen and Rick 1985), little if any information is available concerning this plexus in the developing opossum.