THE HISTOLOGY OF THE URINARY SYSTEM OF THE MINK, MUSTELA VISION M III-.— Thosis for the Deon. of M. S. MICHIGAN STATE UNIVERSITY Richard Edward Bosfrom 1966 .-.‘. _.- - A..— _-_-__- _- —— III]! III 1 ll IIIIIIIIIIIIIIIIIIIIIIII "‘ 3 1293 00688 6885 L I E R A R Y Michigan Stave , University Room USE om 2mm 1":‘1‘?87’ FEW-£97; (’Mwfl JUN; 4 ‘m M f (H! w .- ”V39. ,u.: 1 6 9 m2" 111E C I ‘.I' III! I. I I) I}; THE HISTOLOGY OF THE URINARY SYSTEM OF THE MINK, MUSTELA VISION By Richard Edward Bostrom A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Anatomy 1966 ACKNOWLEDGMENTS The author wishes to express his sincere gratitude to Dr. M. Lois Calhoun, Professor and Chairman of the Depart- ment of Anatomy, for her inspiration, supervision, patience, and guidance throughout the course of this study and during the preparation of this manuscript. I acknowledge and give thanks to Dr. Esther M. Smith and Dr. Al W. Stinson for their valuable suggestions and assistance, especially in the prepa- ration of the photomicrographs and for their efforts in reading and giving constructive criticism of the manuscript. Thanks are also extended to Dr. Richard A. Notzold for his fine suggestions and constructive criticism of the manuscript. Appreciation is extended to Dr. Esther H. Roege for her help and numerous valuable suggestions regarding histotechniques. Acknowledgment and thanks are given to the entire faculty and staff of the Anatomy Department and to my fellow graduate students and friends for their helpful suggestions and en- couragement throughout this course of study. Sincere thanks are appreciation are extended to Dr. Philip J. Schaible, Professor of Poultry Nutrition, Richard Aulerich, Mink Technician, Dr. Robert K. Ringer, Professor of Poultry Physiology, and Peter Steelman, Assis- tant Mink Technician, for their continuous encouragement, ii II II I \I . -I. \IIIII.v\IIL\\I.\IIIu’.\|I|I{.‘Il!jIIIIlll’n\llI III \II \I’ I.II helpful suggestions and assistance in obtaining specimens used for this study. I acknowledge and express my appreciation for the financial assistance extended to me by the Mink Research Foundation and the Biological Stain Commission. In conclusion, I particularly want to thank my wife, Kay, for her untiring assistance in typing, reading, and giving constructive criticism of the manuscript, and for her continuous encouragement and inspiration throughout the entire program. iii TABLE OF CONTENTS ACKNOWLEDGMENTS . . . . . . . . . . . . . . . . . . LIST OF TABLES LIST OF FIGURES INTRODUCTION MATERIALS AND METHODS . . . . . . . . . . . . . RESULTS AND DISCUSSION . Kidney Capsule Uriniferous Tubules Nephron Renal Corpuscle Proximal Convoluted Tubule . . . Loop of Henle . . . . . . . . . Distal Convoluted Tubule . . . . . Collecting Tubules Arched and Straight Collecting Ducts Papillary Ducts . . . . . . . Macula Densa . . . . . . . Juxtaglomerular Apparatus Ureter Tunica Mucosa Epithelium . . . . . . . . . . Lamina Propria . . . . . . . . . . . Tunica Muscularis Tunica Adventitia iv Page ii vi vii OO \O\O\.O GDCDNIONQQON 0‘s O\ I'\) H FJH [—1 I-’ I\) FJH R)M HFJ on» :‘l I]}\l‘l \II \‘III‘ Urinary Bladder Tunica Mucosa Epithelium . Lamina Propria Muscularis Mucosae Tunica Submucosa Tunica Muscularis Tunica Adventitia Female Urethra Tunica Mucosa . . Epithelium . Lamina PrOpria Male Urethra . Tunica Mucosa Epithelium Lamina PrOpria SUMMARY LITERATURE CITED Page 13 13 l3 15 l5 l6 l6 l6 l6 l7 l7 l7 17 18 19 22 I I III‘. \I \II‘I I ll;'lll'l||l’]].'l|l'l’ll|' ll'l LIST OF TABLES AND ILLUSTRATIONS Table 1. Specimens used in the study 2. Analysis of the normal ranch diet fed the animals used in this study . . . . . . 3. Summary of kidney measurements Illustrations 1. Areas of the urinary system from which tissues were selected for study vi Page 11 Figure 10. ll. 12. 13. IA. 15. 16. LIST OF FIGURES Kidney capsule . . . . . Reticular network of the kidney and its capsule . . . . . . . . . . Kidney cortex Kidney cortex . Branching arcuate artery near the cortico- medullary Junction . . . . . . . . . . Concentrations of lipid material in the prOXimal convoluted tubules and the thick descending limbs of Henle Lipid drOplets concentrated in the proxi- mal convoluted tubules and the thick descending limbs of Henle . . P. A. S. positive material in the epithelium covering the renal crest . . . . . . . P. A. 8. positive material in the epithelium lining the papillary ducts . . . . . . P.A.S. positive material in the epithelium lining the papillary ducts . . . . . . . Proximal ureter with surrounding fat tunic Dense reticular network in the lamina pro- pria and tunica submucosa of the ureter Arrangement of the muscular coats in the tunica muscularis of the proximal ureter Cross section of the middle of the ureter Cross section of the distal ureter . . Transitional epithelium of the ureter vii Page 25 27 29 29 31 33 35 35 37 37 39 Al A3 “5 47 A9 Figure Page 17. Transitional epithelium of the ureter . . 51 18. Reticular network of the bladder . . . . 53 19. Arrangement of the tunica muscularis of the bladder . . . . . . . . . . . . . . 53 20. Urinary bladder mucosa . . . . . . . . . 55 21. Transitional epithelium of the bladder. . 55 22. Bladder epithelium with surface cells about to be sloughed. . . . . . . . . . 57 23. Cross section of the outer bladder wall . 59 24. Cross section of the prostatic urethra. . 59 25. Prostatic duct opening into the urethral lumen . . . . . . . . . . . . . . . . 61 26. Cavernous spaces in the prostatic urethra 63 27. Elastic fibers in the lamina prOpria of the prostatic urethra . . . . . 63 28. Prostatic utriculus . . . . . . . . . . . 65 29. Cross section of the membranous urethra . 67 30. Mucosa of the membranous urethra . . . . 67 31. Epithelial lining of the membranous urethra . . . . . . . . . . . . . 69 32. Cross section of the membranous urethra showing the extensive network of elastic fibers . . . . . . . . . . . . 71 33. Cross section of the membranous urethra showing the extensive network of elastic fibers . . ... . . . . . . . . 71 34. Cross section of the proximal penile urethral mucosa . . . . . . . . . . . . 73 35. Epithelial lining of the proximal penile urethra . . . . . . . . . . . 73 36. Cross section of the penile urethra near the external urethral orifice . . . . . 75 viii Figure Page 37. Epithelial lining of the penile urethra near the extrenal urethral orifice . . . 75 38. Reticular network of the female urethra . 77 39. Cross section of the proximal female urethra . . . . . . . . . . . . . . . . 77 40. Female urethral epithelium . . . . . . . . 79 Al. Nests of serous glands in the submucosa and between the bands of the skeletal urethral muscle in the female urethra . 79 A2. Intraepithelial cysts in the female urethral epithelium . . . . . . . . . . 81 A3. Epithelial lining of the distal female urethra . . . . . . . . . . . . . . . . 81 ix INTRODUCTION From an economic standpoint, losses suffered due to urinary tract pathology such as urolithiasis (Nielson, 1956), urinary incontinence (Schaible e£_§l., 1962; Aulerich gt_§I., 1963), "Wet Belly" (Leoschke, 1962; Aulerich §£_ai., 1963), and Aleutian disease (Karstad and Pridham, 1962; Leader gt_al., 1963; Gershbein and Spencer, 196A; Thompson and Aliferis, 196A) are of extreme importance to the mink rancher. A thorough review of the literature indicated that there were no reports available on the normal histology of the urinary system of the mink. Because a previous know- ledge of the normal is essential in recognizing the abnormal, a histological study of the urinary tract of the normal mink (Mustela vision) was undertaken. MATERIALS AND METHODS The entire urinary systems of eight male and eight female clinically normal mink were supplied by the Michigan State University mink ranch (Table l). The animals, ranging in age from one month to two years, were fed a normal ranch diet (Table 2). Twelve of the animals were killed by cervical dis- location.l Their urinary tracts were dissected out and im— mediately placed in a 10% formalin solution buffered with sodium acetate or in Carnoy's fixative (Gridley, 1957). The tissues were kept in the fixative for A8 hours prior to em- bedding. Because of the extreme difficulty in preserving the cytological detail of the kidney, the urinary systems of the remaining four animals were fixed'with a perfusion of buffered formalin. This was accomplished by first anes- thetizing the animals with an intraperitoneal injection of 3% sodium pentabarbital (1 ml./kg. of body weight). After the animals were anesthetized, the carotid artery and the external Jugular vein were cannulated and the vascular sys- tem flushed via the carotid arterywith mammalian Ringer's solution. This was followed immediately with an infusion of buffered formalin. After infusion, the urinary tract was dissected out and placed in a solution of buffered for- malin for A8 hours. Table l.--Specimens used in the study. ‘7 Specimen Mink Age in Weight Color Number Number Months in Grams Sex Pattern l K 381 10 1,550 Male Dark 2 KP 181 12 1,u60 Male Pastel 3 K 371 12 1,850 Male Dark A KP 2 1A 950 Female Pastel 5 KP 52 2 A80 Female Pastel 6 K 26A 1A 815 Female Dark 7 K A70 1 155 Female Dark 8 L 70 2.5 705 Female Dark 9 KP 183 1A 1,600 Male Pastel 10 J8 322 2A 770 Female Sapphire 11 K 310 13 965 Female Dark 12 KP 707 12 1,800 Male Pastel 13 LP 272 7 785 Female Pastel 1A L 167 7 1,300 Male Dark 15 K 315 12 1,635 Male Dark 16 L 631 6 965 Male Dark Table 2.--Analysis of the ration fed to the Moisture Protein Ether extract Crude fiber Ca Ph Na K Trace minerals this study. 67.99% 10.81% 13.35% 5.69% .22% .23% .17% .1A% 1.AO% animals used in Just prior to embedding, the tissues were removed from the fixatives and trimmed to block size. Areas from which tissues were selected for study are shown in Illustra- tion 1. The tissues were dehydrated and cleared in four changes of dioxane (Bucher and Blakely, 1936) and infiltrated with Paraplast under a vacuum of 25 mm./Hg. at 58—6000. for a period of one to two hours. Unless otherwise indicated, sections were out 6-8 microns. Hematoxylin and eosin (Malewitz and Smith modifi- cation, 1955), Weigert and Van Gieson's connective tissue stain (Mallory, 19AA) and Periodic Acid-Schiff (Gridley, 1957) were used routinely. The following special techniques were also used: (1) A modified reticular tissue stain (Gridley, 1957; Lillie, 195A);(2) Alcian blue and nuclear fast red (Gridley, 1957) for acid mucopolysaccharides; (3) Crossmon's (1937) modification of Mallory's triple stain for connective tissue; and (A) Oil Red 0 (Mallory, 19AA) and Sudan Black B (Chieffele and Putt, 1951) for lipid material. The last two stains were used on frozen sections as most lipids are dissolved by the paraffin embedding technique. Illustration l.--Areas of the urinary system from which tissues were selected for study. ———kidney reter ladder rostatic urethra ladder membranous k:_7; urethra female urethra . penile ~__vagina urethra Areas selected for sectioning. .\\\\\\\\\\\\\\\\\\\‘ RESULTS AND DISCUSSION KIDNEY The mink kidney is bean-shaped and unipyramidal with the papillary ducts opening on a renal crest rather than a renal papilla. This is similar to the cat and dog kidney (Trautmann and Fiebiger, 1957). CAPSULE The capsule of the mink kidney is composed of an inner and an outer coat. The outer coat is much thicker and consists almost entirely of adipose tissue with a few blood vessels and nerves coursing through it (Figure l). The inner coat is primarily fibrous connective tissue inter- laced with reticular fibers, some of which penetrate the cortex of the kidney (Figure 1). No smooth muscle or elastic connective tissue is noted. This is similar to the inner one-layered tunica fibrosa of the cat kidney (Yadava and Calhoun, 1958). URINIFEROUS TUBLES Nephron Renal Corpuscle.--The renal corpuscles as well as the glomeruli are spherical and have an average transverse diameter of 115 and 95.5 microns, respectively. The parietal and visceral layers of Bowman's capsule, as in other animals, are lined with a layer of simple squamous epithelium. The intercapillary space contains a few reticular fibers and an occasional fibroblast. Proximal Convoluted Tubule.--The average transverse diameter and epithelial height of the proximal convoluted tubules are 39.9 and 11.3 microns, respectively. They are lined by a single layer of pyramidal and/or low columnar shaped cells with granular acidophilic cytOplasm (Figure 3). Numerous intracytoplasmic lipid droplets, which are Sudan Black B and Oil Red 0 positive, are present in the epithe- lium lining the proximal tubules and those of the thick descending limb of Henle as well (Figures 6 and 7). Similar lipid material has been reported in the cat kidney (Modell, 1933; Lobban, 1955; Stranack, 1962), in the dog kidney (Mac Nider, 19A5) and in the kidney of the lion, tiger, cheetah and ocelot (Hewer gt_al., 19A8). In most other animals and man this is considered pathologic. The basal portions of the cells lining the proximal convoluted tubules have a striated appearance due to the presence of numerous mito- chondria in the form of rods and filaments which line up perpendicular to the basement membrane. The apical surface of the epithelium has a prominent brush border which increases the surface area of the cells. Its mucopolysaccharide makeup is evidenced by its P.A.S. positive reaction (Figures A and 5). The nuclei are large and usually spherical, contain a promi- nent nucleolus and have a coarse chromatic network. Cell boun- daries are indistinct. Loop of Henle.-—The loop of Henle consists of a descending and an ascending portion connected by a sharp bend. It is divided into a thick and a thin segment. The epithelium lining the thick descending portion resembles that of the proximal convoluted tubule, and the epithelium of the thick ascending portion resembles that of the distal convoluted tubule. The thin segment has a diameter of l7.A microns which is smaller than either the proximal or the distal tubules. It is lined by simple squamous or low cuboidal epithelium. Spherical bulging nuclei give an ir- regular contour to the lumen ot these tubules (Figure 7). The nuclei have a distinct nuclear membrane, a nucleolus and a dense granular chromatin network. The cytoplasm is slightly eosinophilic. A brush border is not visible with the light microscope. Distal Convoluted Tubule.——The distal convoluted tubules have an average transverse diameter and epithelial height of 35.6 and 8.0 microns, respectively. They are lined by simple cuboidal epithelium. The cells have fine basal striations with faint borders. They are lower and smaller than those in the proximal tubules, so in a typical cross section more nuclei are seen. Their agranular cyto— plasm is slightly more eosinOphilic than that of the thin 100p of Henle. The nuclei are characterized by a prominent nucleolus, a dense chromatin network, and a distinct nuclear membrane. Lipid material is not evident in the distal con— voluted tubules (Figure 7). Collecting Tubules Arched and Straight Collecting Ducts.—-The arched and straight collecting ducts are difficult to separate histologically and will be discussed together. They have an average transverse diameter and epithelial height of 33.1 and 7.0 microns, respectively. Light, eosinophilic staining, low cuboidal cells with distinct cell boundaries characterize the epithelium lining these ducts. They con- tain spherical, basally placed nuclei with an indistinct nucleolus and dense chromatin networks that stain darkly with hematoxylin. Basal striations are not apparent, and a brush border is lacking. The cells of the straight col- lecting tubules contain a few P.A.S. positive, Alcian blue negative, intracytOplasmic granules. Papillary Ducts.--The papillary ducts have an average transverse diameter and epithelial height of 53.8 and 9.9 microns, respectively. The epithelial lining changes from cuboidal or low columnar at the origin of the ducts to high columnar and sometimes transitional as the ducts Open into the renal pelvis. The cells have distinct boundaries but lack basal striations and brush borders. The cytoplasm is colorless or slightly eosinophilic. P.A.S. positive, Alcian blue negative intracytOplasmic granules are present in many of the cells lining these ducts (Figures 9 and 10). They are often most prominent in the apical portion of the cells and may occasionally be seen in the lumen of the tubules. In some cases these granules are found in the cells 10 of the epithelium covering the renal crest (Figure 8). These granules are similar to those mentioned by Longley e§_al., (1963) in the collecting tubules of normal guinea pigs and those in the pelvic epithelium covering the pyramids in the normal human kidney by Tucker g§;al., (1959). Karstad (196A) reported similar granules in 23 out of A0 mink showing le- sions pathognomonic for Aleutian disease. These granules were also found in 8 out of 1A normal mink from the same study. MACULA DENSA The macula densa is a modification of that portion of the distal convoluted tubule that comes in contact with the Juxtaglomerular apparatus of the afferent arteriole (Figures 3 and A). This portion is lined by closely packed columnar shaped cells that lack distinct cell boundaries and basal striations. Visible granulation is lacking in the faintly acidOphilic cytoplasm. The closely packed spherical or oval nuclei are larger in this area and seem to have a greater affinity for hematoxylin. JUXTAGLOMERULAR APPARATUS The Juxtaglomerular apparatus is located near the vascular pole of the glomerulus where the afferent arteriole comes in contact with the macula densa of the distal convo- luted tubule. It consists of enlarged, slightly bas0philic, myoepithelioid cellsin.the tunica media of the afferent ll arteriole (Figure 3). A summary of the kidney measurements is shown in Table 3. Table 3.--Summary of kidney measurements. Microns Renal corpuscle 115.0 Glomerulus 95.5 Proximal convoluted tubule a. Cross sectional diameter 39.9 b. Epithelial height 11.3 A. Thin loop of Henle a. Cross sectional diameter 17.A b. Epithelial height A.6 5. Distal convoluted tubule a. Cross sectional diameter 35.6 b.' Epithelial height 8 0 6. Arched and straight collecting ducts a. Cross sectional diameter 33. b. Epithelial height 7 7. Papillary duct a. Cross sectional diameter 53.8 b. Epithelial height 9.9 URETER The wall of the ureter is generally divided into tunica mucosa, tunica submucosa, tunica muscularis, and tunica adventitia. In the following discussion, the mucosa and submucosa will be described together as there is no sharp demarcation between the two. 12 TUNICA MUCOSA Epithelium The epithelium is transitional and varies from 1 to 8 cell layers in thickness (Figures 16 and 17). It has a cross sectional diameter varying from 9 to 98 microns. This wide variation in cell layers and cross sectional diameters is primarily due to the different degrees of lumenal distention at the time of fixation. Elongated spindle-shaped cells with hyperchromatic nuclei and slightly more eosinOphilic cytOplasm than the remainder of the epi— thelium could occasionally be seen on the luminal border of the epithelium (Figures 15 and 16). P.A.S. positive material similar to that reported by Liu (1962) is present in the epi- thelial cytoplasm. Lamina Propria The lamina prOpria consists of loosely arranged collagenous connective tissue, blood vessels, lymphatics, nerves, diffuse lymphatic tissue, a few elastic fibers, and a supporting network of reticular fibers (Figure 12). The loose arrangement allows the epithelium to be thrown into longitudinal folds, and this folding is responsible for the characteristic stellate appearance of the lumen (Figure 15). There is an average of 6 major and minor folds in the proxi- mal segment of the ureter, 6 in the middle segment and 5 in the distal segment of the ureter. A capillary plexus is present just beneath the epithelium (Figure 16). This is 13 similar to the capillary plexus present in the ureters of ruminants (Calhoun, 1959). TUNICA MUSCULARIS The tunica muscularis of the ureter consists of an inner longitudinal, middle circular, and an outer longi- tudinal layer of smooth muscle. The inner longitudinal layer thins out and the outer longitudinal layer thickens near the bladder (Figures 13, 1A, and 15). The middle cir- cular layer maintains a relatively constant thickness the entire length of the ureter (Figures, 13, 1A, and 15). The dog, cat, pig, cow, sheep, goat and horse have a similar muscular arrangement (Calhoun, 1959). TUNICA ADVENTITIA A loosely arranged collagenous connective tissue rich in blood vessels, lymphatics, nerves and containing a few autonomic ganglia is characteristic of the adventitia throughout the length of the ureter (Figure 1A). This is surrounded by a thick tunic of fat which is supplied by a sparse vascular and nerve supply (Figure 11). URINARY BLADDER TUNICA MUCOSA Epithelium The transitional epithelium lining the urinary bladder varies from three to four cell layers in thickness and from 29 to A6 microns in cross sectional diameter. 1A As in the ureter, this wide variation is primarily due to the different degrees of luminal distention at the time of fixation. The surface epithelial cells often have a slightly, greater affinity for eosin than the rest of the epithelium, and this tends to give a cuticle-like appearance to the luminal border. The large, umbrella, cuboidal and pear- shaped cells have oval or spherical vesicular nuclei. They contain one or more nucleoli and have little affinity for hematoxylin (Figures 21 and 22). Occasional elongated spindle-shaped cells with hyperchromatic nuclei are also seen. The basal and intermediary layers consist of cuboidal and columnal cells with spherical or oval nuclei that have a thin nuclear membrane and a faint diffuse chromatin network. The cell boundaries are indistinct and the cytOplasm is slightly eosinOphilic. In a number of the areas, the sur- face cells are elongated and resemble the cornified cells in the stratum corneum of stratified squamous epithelium. In these areas and others, there seem to be a great many cells undergoing degenerative changes. Many of these cells have sloughed into the bladder lumen (Figure 22). This might pos- sibly be a factor in the high incidence of urinary calculi in mink as these sloughed cells could easily act as foci for the deposition of the various mineral salts making up the calculi. 15 Lamina PrOpria The lamina prOpria consists of a framework of re- ticular (Figure 18) and dense fibroelastic connective tissue interspersed with scattered lymphocytes, occasional solitary lymphoid nodules, numerous lymphatic and blood vessels and a few nerves. The blood vessels form a rich vascular bed just under the epithelium and occasionally appear to pene- trate its basal layer (Figures 20 and 21). Muscularis Mucosae Small scattered bundles of smooth muscle arranged in circular, longitudinal and oblique planes comprise the muscularis mucosae. It serves to separate the mucosa from the submucosa and probably helps account for the marked folding of the mucosa in the contracted bladder (Figure 19). TUNICA SUBMUCOSA Except for being somewhat thinner, loosely arranged and slightly less vascular, the submucosa is similar to the lamina prOpria. TUNICA MUSCULARIS The tunica muscularis consists of two thick layers of smooth muscle usually arranged in an inner circular and outer longitudinal manner (Figure 19). On occasion these layers seem to either spiral or cross and give the appear- ance of an inner circular, outer longitudinal layer in one place and an inner longitudinal, outer circular layer in 16 another area on the same section. The muscle layers are supplied by numerous blood vessels, lymphatics and nerves. A few intramural autonomic ganglia are present between the various muscle bundles (Figure 23). TUNICA ADVENTITIA Loosely and densely arranged collagenous connec- tive tissue, a few elastic fibers, numerous blood vessels, lymphatics, nerves and a few autonomic ganglia constitute the tunica adventitia. In some areas it is covered by a reflection of the peritoneum and, therefore, could be called a serosa (Figure 23). FEMALE URETHRA TUNICA MUCOSA Epithelium The lining of the female urethra varies from pre- dominantly transitional epithelium at its origin, mixtures of transitional, stratified and pseudostratified columnar, and stratified squamous in the mid-portions (Figure A0) to primarily stratified squamous at the external urethral ori- fice (Figure A3). A few intraepithelial nests of mucous cells are present in all segments and are especially numerous in the proximal and middle portions (Figure A0). Invagina- tions of the epithelium (lacunae of Morgagni) containing saccular outpocketings of mucous secreting cells penetrate the lamina prOpria and occasionally extend deeply into the l7 submucosa (Figure A2). The mucous cells in both the intra- epithelial nests and lacunae of Morgagni contain P.A.S. positive, Alcian blue negative, secretion granules located primarily in the apical portion of the cytoplasm. In some cases P.A.S. positiveexxflnophilic concretions resembling intraepithelial cysts could be seen distending the lumens of the tubules and glandular nests (Figure A2). Lamina Propria Fibroelastic and reticular connective tissue pene- trated by invaginations of the epithelium from the luminal surface and ducts from the serous intramural and extramural glands in the tunica muscularis surround the numerous venous sinuses of the lamina propria-submucosa (Figures 38, 39, and Al). The venous sinuses are most prominent in the proximal and midportions and diminish somewhat near the urethral orifice. MALE URETHRA TUNICA MUCOSA Epithelium The epithelium lining the origin of the prostatic urethra is two to four cell layers in thickness, primarily transitional in nature with some areas resembling pseudo- stratified columnar and stratified cuboidal epithelium. The large spherical to oval nuclei have a medium to heavy chromatin network, a prominent nucleolus, and a heavy 18 nuclear membrane. Cell boundaries are faint or indistinct. In most cases the basal cells are similar to those on the apical surface. However, a few of the surface cells are noted undergoing degenerative changes, suggesting that they are about to be sloughed. The prostatic portion of the proximal urethra is surrounded by the prostate gland which consists of multi- lobular mucous acini which empty via their ducts into the urethral lumen (Figures 2A and 25). The prostatic utriculus and the colliculus seminalis are evident in the middle of this area (Figure 28). The epithelium lining the membranous and penile urethra is similar to that in the proximal urethra except there is a greater prOportion of pseudostratified columnar and stratified columnar epithelium and a decrease in the amount of typical transitional epithelium (Figures 31 and 35). Near the urethral orifice the epithelium is lower and resembles stratified cuboidal epithelium (Figure 37). Lamina Propria The lamina prOpria of the male urethra consists of numerous venous sinuses surrounded by collagenous and reti- cular connective tissue. The venous sinuses of the prostatic and membranous urethra are less extensive than those in the penile urethra (Figures 26, 29, 3A and 361 In addition, the lamina prOpria of the male urethra contains numerous elastic fibers throughout its length (Figures 27, 32 and 33). SUMMARY Histologic studies were made on the entire urinary systems of eight male and eight female mink ranging in age from one month to two years. The mink kidney is unipyramidal. The capsule has a single layered tunica fibrosa. The renal corpuscles and glomeruli are spherical and have an average transverse diameter of 115 and 95.5 microns, respectively. The epi- thelium of the proximal convoluted tubules and thick des- cending limbs of Henle have an average transverse diameter and epithelial height of 39.9 and 11.3 microns respectively and contain numerous intracytoplasmic lipid droplets. A brush border is uniformly arranged along the luminal border of these cells. The macula densa and juxtaglomerular ap- paratus are similar to those of other species. The epithelium of the straight collecting ducts and papillary ducts contain varying numbers of P.A.S. positive, Alcian blue negative, intracytOplasmic granules which are often located in the apical portion of the cells. The ureter is lined by transitional epithelium. A capillary plexus is located in the lamina propria adjacent to the base of the epithelium. The tunica muscularis con- sists of an inner logitudinal, middle circular and outer l9 20 longitudinal layer of smooth muscle. The inner layer thins out and the outer layer thickens near the bladder. The tunica adventitia is surrounded by a thick tunic of fat. The urinary bladder is lined by transitional epi- thelium of varying thickness. A number of the surface cells have undergone degenerative changes and have sloughed into the bladder lumen. Numerous blood vessels form a rich vascular plexus just below the epithelium. Ossasionally some of these vessels could be seen penetrating the basal layers of the epithelium. Small, scattered, variously arranged bundles of smooth muscle comprise the muscularis mucosae. The tunica muscularis consists of two thick spiraling layers of smooth muscle. The epithelium lining the female urethra varies from transitional to stratified squamous. Intraepithelial nests of mucous cells, lacunae of Morgagni and intraepithe- lial cysts are present in variable numbers. The lamina propria-submucosa consists of numerous venous sinuses sur- rounded by fibroelastic and reticular connective tissue. The venous sinuses are most prominent in the proximal and midportions of the urethra. The epithelial lining of the male urethra is variable throughout its length. It is predominantly tran- sitional at its origin, variably transitional, stratified and pseudostratified columnar throughout the remainder, except near the urethral orifice where it resembles strati— fied cuboidal. 21 Other than the size differences between the very young and the adult animals and the differences between the male and female urethra, no obvious sex or age differences are noted. LITERATURE CITED Aulerich, R. J., Ringer, R. K., and Schaible, P. J.: Mink pelts affected with "Wet Belly." Quar. Bull. of Mich. Ag. Exp. Sta., AA, (l962):38A-39l. Aulerich, R. J., Schaible, P. J.,and Ringer, R. K.: Effect of time of pelting on the incidence of "Wet Belly." Quar. Bull. of Mich. Ag. Exp. Sta., A5, (1963): A39-AA3. Aulerich, R. J., Shelts, S., and Schaible, P. J.: Influence of dietary calcium levels on the incidence of urinary incontinence and "Wet Belly" in mink. Quar. Bull. of Mich. Ag. Exp. Sta., A5, (1963): AAA-AA9. Bucher, C. J., and Blakely, K. D.: The use of dioxane in the preparation of histologic sections by the paraffin method. Anat. Rec., 132, (1936):569-583. Calhoun, M. L: Comparative histology of the ureters of domestic animals. Anat. Rec., 133, (1959):365-366 (abstract). Chiffelle, T. L., and Putt, P. A.: Propylene and ethylene glycol as solvents for Sudan IV and Sudan Black B. Stain Tech., 26, (1951):51-56. Crossmon, G.: A modification of Mallory's connective tissue stain with a discussion of the principles involved. Anat. Rec., 69, (l937):33-38. Gershbein, L. L., and Spencer, K. L: Clinical studies in Aleutian disease of mink. Canadian J. Comp. Med. and Vet. Sci., 28, (196A):8-l2. Gridley, M. F.: Manual of Histologic and Special Staining Techniques. Armed Forces Institute of Pathology, Washington, D. C., 1957. Hewer, T. F., Mathews, L. H., and Malkin, T.: Lipuria in tigers. Proc. Zool. Soc., London, 58, (19A8): 326-328. 22 23 Karstad, L.: Viral plasmacytosis (Aleutian disease) in mink: IV. Cytoplasmic glycoprotein inclusions and their differentiation from the viral inclusions of dis- temper." Can. J. Comp. Med. and Vet. Sci., 28, (l96A):1A3—1A7. Karstad, L., and Pridham, T. J.: Aleutian disease of mink. 1. Evidence of its viral etiology. Can.J. Comp. Med. and Vet. Sci., 26, (l962):97—102. Leader, R. W., Wagner, B. M., Henson, J.,and Gorham, J.: Structural and histochemical observations of liver and kidney in Aleutian disease in mink. Amer. J. Path°3 A3, (1963)=33-53- Leoschke, W. L.: Studies on the "Wet Belly" disease of mink. Proc. Ind. Acad. Sci., 72, (l962):l36—318. Lillie, R. D.: Histologic Technique and Practical Histo- chemistry. McGraw-Hill Book Co., New York, 195A. Liu, H. C.: The comparative structure of the ureter. Amer. J. Anat., lll, (l962):l-15. Lobban, M. C.: Observations on intracellular lipid in the cat kidney. J. Anat., 89, (l955):92-99. Longley, J. B., Burtner, H. J., and Monis, B.: Mucous sub- stances of excretory organs: A comparative study. Ann. N. Y. Acad. of Sci., 106, (1963):A93-501. MacNider, W. B.: Occurrence of stainable lipoid material in renal epithelium of animals falling in different age groups. Proc. Soc. Exp. Biol. and Med., 58, (l9A5):326-328. Malewitz, T. D., and Smith, E. M: A nuclear stain employing dilute Harris hematoxylin. Stain Tech., 30,(l955): 311. Mallory, F. B.: Pathological Technique. W. B. Saunders Co., Philadelphia, 19AA. Modell, W.: Observations on lipoids in the renal tubule of the cat. Anat. Rec., 57, (l933):l3-27. Nielsen, I. M.: Urolithiasis in mink: pathology, bacteriology and experimental production. J. Urology, 75, (1956): 602. Schaible, P. J., Travis, H. F., and Shelts, G.: Urinary in- continence and "Wet Belly" in mink. Quar. Bull. of Mich. Ag. Exp. Sta., AA, (l962):A66—A83. Stranack, Thompson, 2A F.: Fat distribution in the kidney tubules of the Felidae. Proc. Zool. Soc. (London), 139, (1962): A75-A82. G. R., and Aliferis, P.: A clinical-pathological study of Aleutian mink disease: An experimental model for study of connective tissue disease. Arthritis Rheumatism, 7, (196A):52l-533. Trautmann, A., and Fiebiger, J.: Fundamentals of the His- Tucker, E. Yadava, R. tology of Domestic Animals. Translated and revised by Habel and Biberstein, Comstock Pub. Assoc., Ithaca, New York, 1957. , Lupton, C. H., and McManus, J. F. A.: A new in— clusion in the visceral epithelium of the renal pelvis. Cancer, 12, (1959):1052-1059. C. P., and Calhoun, M. L: Comparative histology of the kidney of domestic animals. Amer. J. Vet. Res., 19, (1958):958-968. 25 Figure l.—-Kidney Capsule 1. Outer adipose connective tissue portion of the kidney capsule. 2. Inner fibrous connective tissue portion of the kidney capsule. 3. Kidney cortex. Hematoxylin and eosin x 32 27 Figure 2.-—Reticular network of the kidney and its capsule. Gridley's modified reticular stain x 200 29 Figure 3.--Kidney cortex 1. Macula densa 2. Juxtaglomerular apparatus 3. Glomerulus A. Proximal convoluted tubule 5. Distal convoluted tubule Hematoxylin and eosin x 300 Figure A.--Kidney cortex 1. Macula densa 2. Brush border of the proximal convoluted tubule P.A.S. x A80 31 Figure 5.--Branching arcuate artery near the cortico—medullary junction of the kidney. 1. Arcuate artery 2. Arcuate vein 3. Proximal convoluted tubule with a prominent brush border P.A.S. x 200 33 Figure 6.--Concentrations of lipid material in the proximal convoluted tubules and thick descending limbs of Henle. The dark rim around the tubules is composed of 011 Red 0 positive lipid material. See next figure for higher power. 011 Red 0 x 32 1" ""~ 39"!) AI: ' 1'1"; -."~‘e‘é:"" '15 £6"? \ o" , a 53.3.4.) ..9 h" .n‘} ..:“ ,\ p.01 N. 351' {"R: “’:.\"\ 'a _-'\0‘ ;‘\ ‘a: h K.:“... 35 Figure 7.--Lipid droplets concentrated in the proximal con- voluted tubules and thick descending limbs of Henle. l. Proximal convoluted tubule Thick descending limb of Henle 3. Thin 100p of Henle 4. Thick ascending limb of Henle Oil Red 0 x 500 Figure 8.--P.A.S. positive material in the epithelium covering the renal crest. l. Epithelial covering the renal crest 2. Papillary ducts 3. Lumen of the renal pelvis P.A.S. x 800 37 Figure 9.-—P.A.S. positive intracytoplasmic granules in the epithelium lining the papillary ducts. l. Papillary duct P.A.S. x 320 Figure 10.--P.A.S. positive intracytoplasmic granules in the epithelium lining the papillary ducts. l. Papillary duct epithelium 2. P.A.S. positive granules P.A.S. x 800 #1“ . I) fin .wc. , .. ._ v MIUUIaflJW. J A \ .‘l. 39 Figure ll.--Proximal ureter with surrounding fat tunic. 1. Inner longitudinal smooth muscle layer 2. Middle circular smooth muscle layer 3. Outer longitudinal smooth muscle layer 4. Surrounding fat tunic Hematoxylin and eosin x 200 41 Figure l2.--Dense reticular network in the lamina propria submucosa of the ureter. Gridley‘s modified reticular stain x 300 ‘.. my ‘ C Q I 1g I 5 a L a" ....w . & k. I a .. 1. 43 Figure l3.--Muscular arrangement of the tunica muscularis in the proximal ureter. 1. Inner longitudinal muscle layer 2. Middle circular muscle layer 3. Outer longitudinal muscle layer u. Transitional epithelium Hematoxylin and eosin x 320 “5 Figure lH.--Cross section of the middle of the ureter showing the rich vascular plexus in the adventitia and the arrangement of the tunica muscularis. l. 2. 6. Lumen of the ureter Lamina propria-submucosa Inner longitudinal smooth muscle layer Middle circular smooth muscle layer Outer longitudinal smooth muscle layer Vascular plexus Hematoxylin and eosin x 200 147 Figure lS.-~Cross section of the distal ureter showing the marked thickening of the outer longitudinal muscle layer and the diminished inner longitu— dinal muscle layer 1. Inner longitudinal smooth muscle layer 2. Middle circular smooth muscle layer 3. Outer longitudinal smooth muscle layer Hematoxylin and eosin x 200 “9 Figure l6.--Transitional epithelium lining the ureter l. Transitional epithelium 2. Elongated spindle shaped cell with a hyperchromatic nucleus on the lumenal border 3. Capillary plexus Just below the epi- thelium in the lamina propria-submucosa Hematoxylin and eosin x 1025 51 Figure l7.--Transitional epithelium lining the ureter l. Elongated spindle shaped cell on the lumenal surface of the ureter Hematoxylin and eosin x 800 53 Figure 18.--Dense reticular network of the bladder l. Bladder lumen 2. Ureter Gridley's modified reticular stain x 32 Figure l9.--Cross section of the bladder wall showing the arrangement of the tunica muscularis. In other areas the reverse arrangement is often true. 1. Inner longitudinal smooth muscle layer 2. Outer circular smooth muscle layer 3. Muscularis mucosae Hematoxylin and eosin x 32 55 Figure 20.-—Urinary bladder mucosa l. Transitional epithelium 2. Vascular plexus in the lamina propria 3. Capillary indenting the epithelium Hematoxylin and eosin x 255 Figure 21.--Transitional epithelium of the bladder showing capillaries indenting its basal layers 1. Capillaries indenting the epithelium Hematoxylin and eosin x 637 57 Figure 22.—-Bladder epithelium with surface cells about to be sloughed Hexatoxylin and eosin x 50C 59 Figure 23.--Cross section of the outer bladder wall 1. Adventitia (serosa) 2. Tunica muscularis 3. Autonomic ganglion Hematoxylin and eosin x 75 Figure 2H.--Cross Section of the prostatic urethra l. Lumen of the prostatic urethrae 2. Ductus deferens Hematoxylin and eosin x 19.2 ; I". t ' I A . 1 'l he’ . 3‘ ‘3'. . ’0 V" '3' W "W‘ 3 - " ' 5% .’«_"'~"'""""“’ 61 Figure 25.—-Prostatic duct opening into the urethral lumen l. Prostatic duct 2. Urethral lumen Hematoxylin and eosin x 200 63 Figure 26.-~Cavernous spaces in the lamina prOpria of the prostatic urethra l. Cavernous spaces Hematoxylin and eosin x 200 Figure 27.--Elastic fibers in the lamina prOpria of the prostatic urethra 1. Elastic fibers Weigert VanGieson x 800 65 Figure 28.-—Prostatic utriculus opening on the colliculus seminalis of the prostatic urethra l. Prostatic utriculus 2. Colliculus seminalis Hematoxylin and eosin x 200 67 Figure 29.--Cross section of the membranous urethra l. Urethral lumen 2. Cavernous spaces 3. Skeletal urethral muscle Hematoxylin and eosin x 30 Figure 30.--Mucosa of the membranous urethra l. Urethral lumen Hematoxylin and eosin x 120 69 Figure 31.-—Epithelial lining of the membranous urethra Hematoxylin and eosin x 200 71 Figure 32.--Cross section of the membranous urethra showing the extensive network of elastic fibers in the lamina prOpria l. Lamina propria Weigert VanGieson x 30 Figure 33.-—Cross section of the membranous urethra showing the extensive network of elastic fibers in the lamina prOpria l. Lamina prOpria 2. Elastic fibers Weigert VanGieson x 480 73 Figure 34.--Cross section of the proximal penile urethral mucosa 1. Numerous venous sinuses in the lamina prOpria Hematoxylin and eosin x 200 Figure 35.--Epithelial lining of the proximal penile urethra l. Stratified columnar epithelium 2. Intraepithelial nest of mucous cells 3. Lacunae of Morgagni Hematoxylin and eosin x 500 75 Figure 36.--Cross section of the penile urethra near the external urethral orifice l. Os penis 2. Urethral lumen 3. Venous sinuses engorged with blood H. Nerve plexus Hematoxylin and eosin x 30 Figure 37.--Epithelial lining of the penile urethra near the external urethral orifice Hematoxylin and eosin x “80 77 Figure 38.--Cross section of the female urethra showing the dense reticular network in the lamina propria- submucosa l. Reticular fibers Gridley's modified reticular stain x 30 Figure 39.—-Cross section of the proximal female urethra l. Skeletal urethral muscle 2. Urethral lumen 3. Lacunae of Morgagni Hematoxylin and eosin x 30 79 Figure MO.--Female urethral epithelium (mid portion) 1. Lacunae of Morgagni 2. Intraepithelial nest of mucous glands Hematoxylin and eosin x 120 Figure ul.--Nests of serous glands located deep in the submucosa and between the bands of the skeletal urethral muscle of the female urethra l. Nests of serous glands 2. Skeletal urethral muscle 3. Submucosa Hematoxylin and eosin x 15“ 81 Figure u2.--Intraepithelial cysts in the female urethral epithelium l. Intraepithelial cyst 2. Lacunae of Morgagni 3. Nests of mucous cells Hematoxylin and eosin x 120 Figure N3.--Stratified sqamous epithelium lining the distal female urethra Hematoxylin and eosin x 300 ”11111111111111