This dissertation has been microfilmed exactly as received HAYES, Thomas G., 1936- THE EMBRYONIC DEVELOPMENT OF THE ELLIPSOID SHEATH AS IT OCCURS IN THE DOG SPLEEN. The Ohio State University, Ph.D., 1965 Anatomy University Microfilms, Inc,, Ann Arbor, Michigan THE EMBRYONIC DEVELOPMENT OF THE ELLIPSOID SHEATH AS IT OCCURS IN THE DOG SPLEEN DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Thomas G. Hayes, B.A., A.M ******* The Ohio State University 1965 Approved by Adviser Sl Department of Anatomy ACKNOWLEDGMENTS The author wishes to express his sincere appreciation and indebtedness to his adviser, Dr. John A. Eglitis, for his guidance, his interest, and his stimulation throughout the present investigation. The example he has displayed as a teacher and scientist will never be forgotten. To the faculty and members of the Department of Anatomy for their many kindnesses shown during the course of his graduate studies, he is indebted. To his wonderful parents who helped make this goal possible, he is extremely grateful. ii VITA July 3, 1936 Born - Canonsburg, Pennsylvania 1958 ...... B.A. / Washington and Jefferson College, Washington, Pennsylvania 1958-1960. Teaching Assistant, Department of Biology, Western Reserve University, Cleveland, Ohio 1960 ................... M.A., Western Reserve University, Cleveland, Ohio 1961-1962. , . Teaching Assistant, Department of Anatomy, The Ohio State University, Columbus, Ohio 1963 ....................... Assistant Instructor, Department of Anatomy, The Ohio State University, Columbus, Ohio 1964-1965. N.I.H. Fellow. Predoctoral Fellowship awarded from the National Institutes of Health, Bethesda, Maryland 1965 ...... Instructor, Department of Anatomy, The Ohio State University, Columbus, Ohio FIELDS OF STUDY Major Field: Histology Studies in Gross Anatomy. Professor Linden F. Edwards Studies in Histology. Professors John A. Eglitis and G. A. Ackerman Studies in Neuroanatomy. Professor James L. Hall Studies in Embryology. Professor John Weston iii CONTENTS Page ACKNOWLEDGMENTS............................................................................... ii VITA ............................................................................................................... iii ILLUSTRATIONS................................ v INTRODUCTION ........................................................................................ 1 MATERIALS AND M ETHODS..................................................................... 8 OBSERVATIONS AND RESULTS.................................... 11 I. 35-Day Embryonic Dog S pleen................................ 11 II. 40-Day Embryonic Dog S p leen................................ 13 III. 45-Day Embryonic Dog S p leen................................ 15 IV. 5 5-Day Embryonic Dog S p lee n................................ 17 V. Adult Racoon and Woodchuck S p leen................... s 18 DISCUSSION................................................................................................. 25 SUMMARY AND CONCLUSIONS............................................................ 37 BIBLIOGRAPHY............................................................................................ 39 iv ILLUSTRATIONS Plate Page I 35-Day Embryonic Dog S pleen.......................................... 44 II 35-Day Embryonic Dog S p leen............................................. 46 III 40-Day Embryonic Dog S pleen............................................. 48 IV 40-Day Embryonic Dog S p leen............................................. 50 V 40-Day Embryonic Dog S p leen............................................. 52 VI 45-Day Embryonic Dog S p leen............................................. 54 VII 45-Day Embryonic Dog Spleen............................................. 56 VIII 55-D ay Embryonic Dog S p l e e n............................................. 58 IX 55-Day Embryonic Dog S p leen............................................. 60 X 55-Day Embryonic Dog S p leen............................................. 62 XI 55-Day Embryonic Dog S pleen............................................. 64 XII Adult Racoon Spleen.................................................................. 66 XIII Adult Racoon Spleen.................................................................. 68 XIV Adult Racoon Spleen.................................................................. 70 XV Adult Racoon and Dog Spleen............................................... 72 XVI Adult Racoon Spleen.................................................................. 74 XVII Adult Woodchuck Spleen........................................................ 76 XVIII Adult Woodchuck Spleen........................................................ 78 XIX Adult Woodchuck Spleen........................................................ 80 v INTRODUCTION AND HISTORICAL REVIEW The present investigation was undertaken in order to determine the possible origin of the so-called ellipsoid or Schweigger-Seidel sheath (48) as it occurs in the dog spleen. In addition to the basic problem cited above, a purely histo­ logical description of the adult racoon (Procyon lotor) and woodchuck (Marmota monax) spleens will be presented. Since the spleens of these two animals have not been adequately described in the literature, it is hoped that this presentation will add additional information to our com­ parative knowledge of the mammalian spleen. Anyone who has studied the spleen is well aware of the pre­ vailing controversies concerning the internal vasculature of this organ. This is particularly true of the so-called sheathed arteries. The vasculature of the spleen is unique in that it not only deter­ mines the distribution and inter-relationship of both the red and white pulp tissue but also determines the structural plan of the spleen as a whole. The arteries tend to be associated with the white pulp tissue; the veins form an intimate relationship with the red pulp tissue. The arteries enter the spleen at the hilus and follow the larger trabeculae into the organ as the trabecular arteries. When the latter vessel reaches a diameter of 0.2 mm., it leaves the trabeculae and enters the splenic parenchyma as the white pulp or central artery. The central artery while coursing through the follicle gives off capillary branches to all of the white pulp. Upon reaching a diameter of 50 micron. , the central arte­ ries lose their investment of white pulp and enter the red pulp. As the central artery enters the red pulp tissue, it arborizes into three to five long, straight, branches which, because of their resemblance to fine brushes, were called penicilli. The penicilli, in turn, are divisible into three successive segments: the red pulp artery, the ellipsoid artery, and the terminal capillary. The first segment, the red pulp artery, is the longest. This vessel courses within the red pulp tissue, finally dividing into two to three divisions. Each division, in turn, is provided with a spindle-shaped thickening, the ellipsoid sheath; this segment is the sheathed artery. The latter vessel gives rise to two to three branches as the terminal capillaries whose exact manner of ter­ mination is still disputed among investigators of the splenic vasculature. The ellipsoid sheath that surrounds the segment of the peni- cillar artery consists of an aggregation of reticular cells and reticular fibers arranged about the capillary vessel. The latter vessel is referred to in the literature as the Schweigger-Seidel sheath capillary, sheath artery, and the ellipsoid artery. An ellipsoid or sheath artery was first noted by Billroth (1857) (4) in the spleens of birds. He described them as iusiform-shaped bodies occurring along the terminal arteries. Six years later, Schweigger- Seidel (1863) (48) gave a more accurate description of similar bodies that he observed in the pig spleen, calling them "hfllsenarterien." He also described these structures in the dog, cow, cat, and man but failed to identify them in the horse spleen which he studied. These structures, that bear his name, were proposed by him to be organ filters of the blood. The first comprehensive work on these fusiform bodies was carried out by Muller (1865) (37), who described them in various rep­ tiles, fishes, birds, and mammals. He is responsible for coining the term "ellipsoid." Muller observed that the ellipsoids are well developed in birds and carnivores but are rudimentary in man and rodents. The ellipsoids were described as endothelial lined channels consisting of a mass of protoplasm representing an adventitial thickening of the axial vessel. They served as a point of termination for the splenic nerves. Kyber (1870) (23) maintained that the ellipsoid was a loosened adventitia infiltrated with lymphocytes resembling the splenic follicle in structure. The above investigator was the first to deny any communi­ cation existing between the capillary lumen and the sheath proper. Bannwarth (1891) (2), having described the sheath in the cat spleen, considered it as a growth center for the splenic pulp, serving its principal function during the embryonic period. In 1894, Whiting (62) conducted a comparative study of the ellipsoid sheath. He observed that the ellipsoids are composed of a homogenous ground substance containing a few lymphocytes. He main­ tained that the ellipsoids contain smooth muscle fibers that formed an essential constitutent of the sheath. This latter view was held by