The embryological development of Jacobson's organ in Didelphys virginiana (Kerr).код для вставкиСкачать
THE EMBRYOLOGICAL DEVELOPMENT O F JACOBSON’S ORGAN I N DIDELPHYS VIRGINIANA ( KERR) ALICE M. RUSSELL Department of Biology, Rosemont College, Rosemont, Pennsylvania TWO FIGURES The observations reported in this paper were made as part of a program to complete information concerning Didelphys virginiana, undertaken by the Zoology Department of the University of Pennsylvania and The TiTristar Institute of Anatomy and Biology. The author wishes to express her gratitude to The Wistar Institute for permission to study its sets of slides, also to Dr. John McClain of Villanova College, and to Dr. Olin E. Nelsen for specimens of various ages for dissection. The vomeronasal organ of Jacobson lies on either side of the nasal septum, supported by curved plates of cartilage. This structure was described and figured as early as 1703 by Ruysch; however, it bears the name of Jacobson who described it in mammals in 1811. Many descriptions of Jacobson’s organ in the marsupials have been written from the standpoint of comparative antomy. There are a few brief notes on its embryogeny in the opossum, mentioning only “that it is formed by the invagination of the epithelium into the septum’’ (McCrady). The purpose of this brief paper is to describe the embryogeny and later development of Jacobson’s organ in Didelphys virginiana. The numbered stages mentioned below correspond to those used by McCrady in “The Embryology of the Opossum.” Stage 30 - is distinguished by the appearance of the oro-nasal groove. Stage 31 - The oro-nasal groove is converted into a tube. The frontal process has developed. Median and lateral nasal processes have grown forward and are fusing with the maxillary process to form the beginning of the snout. (McCrady.) Stage 32-One can distinguish the cartilage of the nasal septum. A shallow indentation of the epithelial lining of the nasal cavity, on the antero-lateral surface of the nasal septum marks the anlage of Jacobson’s organ. 149 150 ALICE M. RUSSELL Stage 33 - 34. The invagination becomes deeper and forms a diverticulum in the septum. Attached to the blind end of the sac one finds solid strands of tissue which stain deeply. Jacobson’s cartilage, or the cartilage of the vomero-nasal organ appears at this time as a bar anterior to the invaginating tissue. A small blood vessel lying parallel to the nasal septum becomes associated with Jacobson’s organ. Stage 35 - The diverticulum elongates. The lumen of its anterior portion enlarges and becomes crescentic, while its opening towards the nasal passage narrows. The epithelial lining of the mesial wall of the sac begins to differentiate into columnar epithelium. Birth occurs at the end of stage 35. Pouch young series have not been given stage names but are usually designated by crown-rump measurements. These were found to vary greatly from litter to litter, hence actual ages of the young will be indicated here. One and one-half-day pouch young. Jacobson’s organ is still a simple diverticulum. The epithelium of the mesial wall of the sac becomes high columnar epithelium. The cells along the lateral walls remain low, cuboid epithelium. Jacobson’s cartilage has become better developed, with the bars curving inward towards the nasal cavity. Eventually these curved bars completely encircle the anterior position of Jacobson’s organ, forming a cartilaginous cylinder named Jacobson’s capsule. Two-day-old pouch young. No difference from previous stage, Seven-day pouch yozing. At the cephalic end of the diverticulum the deeply staining solid strands of tissue seen in stage 34 have hollowed out to form one or two simple tubes lined with low epithelium. The opening of Jacobson’s organ into the nasal cavity becomes narrowed by the development of the palatine processes. Eventually its opening comes to lie at the nasal end of Stenson’s duct. S e v e n t o 15-day-old pouch young. These stages show the maximum development of Jacobson’s organ. Its lumen becomes much enlarged and bean-shaped. At its cephalic end it communicates with several tubes whose development was marked in the previous stage. These simple tubes have become much elongated and branched at the cephalic end, forming a group of glands known as Jacobson’s glands. Branches of the olfactory nerve pass through the cribriform plate and end either in Jacobson’s glands or in the high columnar epithelium of the mesial surface of the organ. The expansion of Jacobson’s organ, together wit11 the flaring of the supporting cartilaginous bars, produce a marked protuberance on the anterior portion of the nasal septum (figs. 1and‘2). EMBRYOOENY OF JACOBSON ’6 ORGAN 151 As the palatine processes fuse under the nasal septum, the openings of Jacobson’s organ on each side become further narrowed, or even totally closed. I n some groups of animals Jacobson’s organ opens directly into the nasal or oral cavity. I n Didelphys, however, Jacobson’s organ opens into the cephalic end of Stenson’s duct which forms the Fig. 1 Fifteen-day-old pouch young. ( A ) Cartilage of nasal septum. (B) Jacobson’s organ. (C) Cartilage of Jacobson’s organ. (D) Branch of the olfactory nerve. (E) Duct leading to numerous glands. ( F ) Glands of Jacobson’s organ. upper part of the incisive canal on each side, opening into the oral cavity in the vicinity of the median papilla. A IOg-day-oZd opossum. I n this specimen Jacobson’s organ is a large flat tube supplied at its cephalic end with numerous glands. It lies in a cylinder of cartilage lateral to the nasal septum on the floor of the nasal cavity. Its opening into Stenson’s duct may be completely closed. 152 ALICE M. RUSSELL Much of the voluminous literature on Jacobson’s organ is concerned with its evolutionary significance, or with the probable use of a structuke which is accessory to the nose. One of the most striking things about this organ is its essential similarity in all the groups in which it appears. “In all, Jacobson’s organ is alike - a tube lined with sensory epithelium lying in the rostra1 oral end of the septum nasi. Because it Fig. 2 Fifteen-day-old pouch young. Labels as in figure 1. ( G ) Stenson’s duct, or the naso-palatine canal. Note in these figures the protuberance on the wall of the nasal septum caused by the enlargement of Jacobson’s organ, and by the flaring of Jacobson’s cartilage. is associated constantly with the vomer bone it has been called the vomero-nasal organ. It is associated with glands (Jacobson’s glands) and is fed from above by branches of the olfactory nerve which enter the sensory epithelium. It opens either into Stenson’s duct or into the floor of the nasal cavity, either above, o r below, but always near Stenson’s duct. ” (Mihalkovics.) EMBRYOGENY O F JACOBSON’S ORGAN 153 SUMMARY 1. Jacobson’s organ arises as an invagination of epithelium into the nasal septum in stage 32. 2. The diverticulum thus formed continues cephalad, becomes associated with a series of tubes and glands. Cartilaginous bars surround it anteriorly. Branches of the olfactory nerve end in it. 3. The highest development of this organ is reached in 15-day-old pouch young. 4. In later stages it comes to lie in the nasal septum connected anteriorly to Stenson’s duct which opens by way of the incisive canal into the mouth cavity. LITERATURE CITED BAWDEN,H. HEATH 1901 Bibliography of the literature on the organ and sense of smell. J. Comp. Neur., vol. 2, pp. i-xl. 1920 Das organon vomeronasal Jacobsoni, ein Wassergeruchsorgan. Anat. BROMAN,IVAR Hefte, vol. 58, pp. 137-191. BROOM,R. 1895 On the organ of Jacobson in monotremata. J. Anat. and Physiol., vol. 30, pp. 70-80. HARVEY, R. 1882 Note on the organ of.Jacobson. Quart. J. Micros. Science; vol. 1882, pp. 50-52. MCCRADY,EDWARD,JR. 1938 The Embryology of the Opossum. American Anatomical Memoirs no. 16. The Wistar Institute of Anatomy and Biology, Philadelphia, Pa. MIHALKOVICS, VICTORVON 1898 Nasenhohle und Jacobsonsehes Organ. Anat. Hefte, Bd. 11, 8. 1-107. ROSE, C. 1893 o b e r das Jaeobson’sehe Organ von Wombat und Opossum. Anat. Anz. Bd. 8, S. 766-768. SMITE,G. ELLIOT1895 Jacobson’s organ and the olfactory bulb in Ornithorhynchus. Anat. Am., Bd. 11, S. 161-167. SYMINGTON, J. 1891 On the organ of Jacobson in the kangeroo and the rock Wallaby. J. Anat. and Physiol., vol. 26, pp. 371-374.