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On the comparative histology of mammalian livers Rogers, Wilbur Stuart 1922

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ON THE COMPARATIVE HISTOLOGY OP MA1MALIAM LIVERS. by Wilbur Stuart Rogers. A Thesis submitted for the Degree of MASTER OP ARTS i n the De#artaent of BIOLOGY. -» THE UNIVERSITY OF BRITISH COLUMBIA APRIL - 1922. OK THE COMPARATIVE HISTOLOGY OF MAMMALIAN LIVERS INTRODUCTION. The work was undertaken with a view to determining the chief differences i n the c e l l u l a r structure of repres-entative mammalian l i v e r s - - carnivorous, omnivorous, and herbivorous. Those dealt with are the cat, the human , the pig| t the beef» the sheep and the rabbit* Specinane of p i g , be#f,and sheep were obtained i n a freshly k i l l e d condition from the P.Burns' a b a t t o i r ! the rabbit and cat came from ©tfcr Gtbe** l o c a l sources, and the human tissue was already available for study i n some sl i d e s belonging to the University, as were alsosome cat and rabbit sections. METHODS. The fresh tissues were washed i n saline solution to renege the exeess blood, out into small pieces% and placed in.JS*G-*. Fixing'Solution-for f o r t y - ^ eight-h.©.urs*,uThey were'.. ' then removed, washed and"run up" through progressively increasing a l c o h o l i c solutionsto dehydrate(six hours each)* From .Absolute alcohol, they were traaaferredto Xylene and In t h i s .gradually-Infiltratod-with. paraffin,, f i n a l l y — o b t a i n -ing them imbedded i n a s o l i d p a r a f f i n block. Paraffin sections of the tissue were now made with the microtome , with a uniform thicltewsss of ten microns, and these mounted with gum arable solution upon s l i d e s . These were allowed to dry , and the para f f i n dissolved out by means of Xylene , leaving the cut tissue, adhering to the surface of the s l i d e and ready f o r d i f f e r e n t i a l s t a i n i n g . ®b*tn an aqueous s t a i n was used, the b s l i d e was gradually''run down" through alcohol to water or to the required d i l u t i o n of alcohol, and a f t e r staining run up again through the more concentrated alcohol solutions to > (2) dehydrate again and then to Xylene to "clear" , being mounted i n Canada Balsam from t h i s . The chief stains used were Delafield's Haemotoxylin and EosIn, Methylene Blue and Eosin, China Blue , Bright Green i n Clove On , Safranin, and Cochineal ( the t r i t u r a t d insects.) Of these various stains , the best results were undoubtedly obtained with a 50% Cochineal solution, which brought out the varied tissue elesaents with remarkable" clearness.. Most of -.the-- descriptions . i n this... paper. are based upon- a-- study- -of Cochineal sections. . MftYQXiOQ*, ; • The embryonic l i v e r f i r s t appears as a two-lobed diverticulum or outgrowth,from the ventral wall of the fore-gut , w e l l back , near the point of junction with the yolk-sac. This outgrowth gradually extends into the mass of mesoderm!e tissue forming the septus transversura or primitive diaphragra, at the same tirae d i v i d i n g into i t s two character-i s t i c t i s s u e s ; — the anastomosing hepatic cordswith i n t e r -vening c a p i l l a r y sinuses, and the enveloping capsule with ramifications, extending from the periphery into the par-enchyma of the organ and eventually dividing i t into i t s anatomical units-the lobules . The hepatic tissue ramifies around the v i t e l l i n e veins forming a plexus of lacunarvessels which are i n close juxtaposition with the cords of hepatic c e l l s . In l a t e r embryonic l i f e , the v i t e l l i n e veins fuse to forn a single trunk and become otherwise modified to forn the portal vein. The v i t e i l i n e v e l n s , a f t e r leaving the hepatic plexus, fuse t to form the hepatic vein , oarrying a l l the venous blood of the l i v e r to the i n f e r i o r vena cava. The hepatic artery , (3) a branch of the coeliae plexus, ramifies through the connect-ive tissue elements of the l i v e r , d i s t r i b u t i n g nourishment to them but has no connection withthe hepatic c e l l s . The l i v e r undergoes r e l a t i v e l y much greater development pre-na t a l l y , being at one time equal i n weight to the entire embryo. At b i r t h , i n the human, i t s r a t i o to body weight i s one to eighteen , and at maturity one to t h i r t y - two. GROSS ANATOMY» ' , The l i v e r i s an i r r e g u l a r , usually five-lobed organ, situated,justbehlnd the diaphragm on the ri g h t side, I t s shape being largely determined by the orientation of the neighboring organs. I t is. covered externally by peritoneum, folds of t h i s membrane being formed as i t passes from the surface of the l i v e r to adjacent parts and forming four of the so-called ligaments holding the organ i n place. The proper coat i s a th i n but dense r e s i s t i n g fibrous membrane, adherent to the substance of the organ , but eas i l y detached and very closely united to the peritoneum. This membrane , at the transverse fi s s u r e , surrounds the hepatic duet, the por-t a l vein, and the hepatic artey, and penetrates into the substance of the organ i n the form of a sheath investing the vessels , and branching with them. This membrane , as i t ramifies i n the substance of the organ , i s called the Capsule of Glisson. I t i s these ramifications which divide the hepatic tissue into lobules."In man and the mammalia generally, these trabe-cular are rather t h i n , becoming more and more delicate as the vessels subdivide, and being e n t i r e l y l o s t before the vessels are distributed betweenthe lobules" MICROSCOPIC ANATOMY. (4) lach lobule Is sore or less thlnble - l i k e i n form with a minute tri b u t a r y of the hepatic vein running through i t s central axis. Around the periphery of the lobule are three or four small branches of the portal vein , which are connected with the central vein by means of innumerable small c a p i l l a r i e s , the oa p i l l i f o r r a sinusoids, with the hepatic c e l l s arranged i n cords around them. In elose concomitance with these three or four Interlobular veins are found branches of the hep-a t i c artery and b i l e ducts, these l a t t e r sending off innumer-able b i l e c a p i l l a r i e s into the hepatic cords of the adjacent lobules. ?he l i v e r c e l l s themselves are ovoid or i r r e g u l a r l y polygonal c e l l s with a considerable v a r i a t i o n i n size. The c c e l l s present,nuclei and often n u c l e o l i , and the cytoplasm contains small granules which give the tissue a very charact-e r i s t i c appearance. They may also contain more or less gly-cogen i n the form of granules surrounding the nu c l e i , but th i s l a t e r character varies over wide l i m i t s according to the condition of the animal when k i l l e d . Hog. The l i v e r of the hog i s e a s i l y differentiatedfrom that of the otber speeiraans by means of the large amount of conn-ective tissue surrounding the lobules ( Plate I) *Ms i s of rather rare occurrence but i s found also , i n the polar bear and camel, anteals of the greatest divergence of both habit and d i e t . That the hog, which has l i t t l e i n common with eit h e r of the above , should also have each of i t s lobules completely enclosed i n a connective tissue sheath , rather a adds to the enigma as to why such a condition should exist i p such widely varying types. The preparation of the material f o r staining has caused the hepatic tissue of the lobule to (8) shrink away r,# . i8,..Pl«o«s » from the peripheral capsule , leav-ing free spaces at the margin© of the lobule that are not normal. At the point of confluence of two or three lobules there Is a thickening of the connective tissue to form the " portal canal" in. which .the,-thin, walled i n t e r l o b u l a r vein, (of the portal system)..» the thiokwalled .nuscular. branch of fthe hepatic artery, and the in t e r l o b u l a r b i l e duet with i t s l i n i n g .of colnranar endotheliumare.-founfi i n close, apposition to one another ,. Of ...these ..t .the .vein .is by far. the ..larger, ... and Is store or less flattened, due to collapse o i i t s w a l l s , fhe r a d i a l structure of the oapillifo-rm sinusoids with the hepatie cords bordering, then,is r e a d i l y v i s i b l e . ' Dnder higher, .power * the. .hepatic,, .cells., are .seen as ovoid or polygonal bodies with t h e i r apposed surfaces f l a t -tened from mutual pressure(PlateII) ^ e y are almost a l l mononuclear with a d i s t i n c t nucleolus and a few eccentric granules i n the cytoplasm , Glycogen granules were not v i s i b l e even when s p e c i a l l y f or with a ohloroformio solution of Iodine , Under the immersion lens » very occasional.trian-g u l a r c e l l s with a single darkly staining nucleus,,,.were observed, i n the sinusoidal spaces of the lobule,. These were the " s t e l l a t e c e l l s of von Kuppfer, belonging , according to M l n o t , to the endothelial l i n i n g of the c a p i l l a r i e s of fehe portal, vein system. , Beef...... ''fhe' interlobular connective tissue i s here reduced to a a i n imam.,. being, only found epghea thing-, the Interlobular vein, hepatic artery and b i l e duct. (PlateIX I ) . These are found i n a very closely approximated condition, the vein as usual, being by f a r the largest. The lobules are arranged as d e f i n i t e (6) radiating cords , t h e i r boundaries being only determinable as the regions where the radiating cords of one lobule fuse with those of another , forming an intermediate region of in d e f i n i t e d i r e c t i o n , with a portal canal placed at two or three points around the periphery. The cords are rather loosely arranged , with frequent s t e l l a t e c e l l s occurring i n the interspaces, forming the nucleiof the c e l l s forming the endoplasmic l i n i n g og the c a p i l l i f o r r a sinusoids. (Plate 1 W ) The c e l l s themselves are oval rather than polygonal and are mostly mononuclear, thoufeh in certain areas , usually near the periphery of the lobule , there are a considerable number of b i n u c l e a r c e l l s . There also appear in the same region certain c e l l s with except-i o n a l l y large nuclei but these arenot ^amorous. The nuclei themselves are oval or occasionally crescentic with a deeper staining nuclear membrane , enclosing a d e f i n i t e nucleolus and several smaller chromatic granuleu . The cytoplasm has suspended i n i t l i g h t l y staining material , giving the whole a somewhat floceulent appearance. There i s not: Halting..,oeabran© t©\4h© hepatic- c e l l : ,.. the • boundaries .-' b#lnt'-more.'Or l i i s s t®d:i#ii»et ,. .though... there i s no ind i c a t i o n 1 any 'fusion securr.ing. • ;"ft» ©t»r»eterlstie Ment I f i e a t i o n points: are the compare -tir* tommmnm of the- hepatic .eorda (i.-ev- the., breadth «f ttm '©aptlitfora: sinusoids) and th#. Jjtrgii. ooaib«r -.©£• nuclei: .of Ton •Ktapffer's s t e l l a t e c e l l s . '•Sfa»ep There: here also an exceptionally <«nall amount' of ln.t«rl©telar connective' tissue- >• aa coapared with th«.h©gt only s u f f i c i e n t being present to bind the-, vein artery and b i l e (?) duet. Into a single sheathed portal canal . The lobate struct-ure i s less definable than i n any of the tissues examined ,e even the radiate appearance of the cap i l l i f o r r a sinusoids being : jftt times ti _ uncertain.* (Plate?!). The c e l l s appear imbedded in a dense r e t i c u l a r network, with the nuclei of s t e l l a t e c e l l s frequently v i s i b l e .Very frequent spaoes (Plate T f I I I ) , c i r c u l a r , and extending i n most cases completely through the sections, are probably spaces formerly occupied by hepatic c e l l s , which have shrunken through starvation and have f a l l e n out during the prepar-ative technique , leaving the cavity i n the"Gitterfasern w. ^he c e l l s are polygonal or spheroidal, with a darker stain-ing peripheral sone , and having no granules v i s i b l e in the cytoplasm, The nucleus i s usually single ,though occasional c e l l s are binuclear, and contains no regularnucleolus, but masy irregular scattered chromatic granules of varying sizes throughout the karyoplasm. Around the lumen of the central veins, numerous nuclei of connective tissue are v i s i b l e , radiating out for sone distance into the parenchymal tissue, and in soie places beang almost as numerous as the hepatic c e l l s . ^he numerous "holes " i n the tissue gives many of the c e l l s an appearance of enclosing a large fat granule within t h e i r cytoplasm. '''his i s due to cutting the r e t i c u l a r space of the c e l l at a different plane, thus giving apertures of varying 'sizes. " cat : Two different l i v e r s were used, the one in a normal condition , the o t h T of a starved cat k i l l e d by intravenous d i g i t a l i s Injection. Between these two specimans a marked ( g f t difference was found. Ttee r a d i a t i o n of the hepatic cords from the central vein i s noticeable, but the hepatic tissue of one lobule passes into that of another without v i s i b l e demarcation except for the presence of :.the i n t e r l o b u l a r vein , hepatic artery and b i l e Suet sheathed i n a small amount of connective tissue. (Plate Xt&XIY) w i t h the high power , the c e l l s are mostly polygonal or oval, with a single nucleus i n which i s a single darkly s t a i n -ing c i r c u l a r nucleolus, and a number of chromatic granules scattered through the whole mass.(Plat© XIXAXIII). At times, the nucleolus i s placed e c c e n t r i c a l l y and the chromatic gran-ules seem forced over to the opposite pole of the karyoplasa. The n u c l e i are very large compared with the amount of cyto-plasm, frequently the boundaries of the cytoplasm are rather I n d i s t i n c t as i n the beef, ^he s t e l l a t e c e l l s of Von Kupffer are almost e n t i r e l y absent. In the speciraan ©f l i v e r obtained frora the starved eat ,h the appearance of the tissue under low magnification resembled very much » that ©f the sheep. The same " riddled " aspect i s found with the nu c l e i of the hepatic c e l l s apparently i n tee i n t e r c e l l u l a r r e t i c u l a r network, " i t h the immersion lens the divergence frora normal ( i . e . the f e l i n e tissue spoken of above) i s not so marked , though a considerable resemblance to that of the sheep i s s t i l l apparent. The c e l l s seem rather shrunk-en i n outline and very few granules are seen i n the cytoplasm. I t i s known that i n any animal without food for any considerable period, there i s a great decrease i n the amount of stored glycogen, the granules gradually disappearing as emaciation (9) proceeds, and the c e l l s shrinking considerably i n s i z e . Shis being so, the explanation naturally suggests i t s e l f that, as in the case of the sheep , the * riddled" appearance i s due to i n t e r c e l l u l a r spaces i n the " Oitterfasern" formerly occupied by hjspatic c e l l s , but which have been unable to r e t a i n themselves i n the net on account of t h e i r shrunken condition. They have accordingly f a l l e n out i n the preparation of the 1 t i s s u e , leaving v i s i b l e cavLties of varying siz<-s , accord igg to the plane ofi section. Rabbit " The radiate arrangement of the hepatic cords around the central vein i s p l a i n l y d i scernible. Hather more interlobular connective tissue i s present than i n the eat, though thereis no approximation to the condition found i n the hog.(Plate XT* X V I t ) The vein artery and b i l e duct are found in close prox-imity to on^ another, in a sheath of connective tissue situated i n the interspace between two lobules , whose boundaries are also distinguished as the l i n e s of fusion of the rows of radiating cords fron adjacentcentral veins. The c e l l s of the rabbit are almost a l l binuclear, i n many sections examined , i n others , only a few of the c e l l s contain two n u c l e i . There seems no apparent? reason for t h i s peculiar-i t y , adjacent sections from the same organ often presenting I t " Irtate XVt). Thenuclei stain'rather darkly and contain chromatic granules scattered"in the karyoplassi usually near the periphery. The boundaries of the in d i v i d u a l c e l l s are quite "distinct,. the cytoplasm exhibiting numerous darker staining granules , connected i n most cas-s by an Indistinct fibrous net-work. The c e l l s themselves are very i r r e g u l a r l y polygonal, in shape with a considerable v a r i a t i o n i n s i z e . (10) The* 'Stellate c e l l s of "^ on ^upffer are not numerous but are p l a i n l y r i s i b l e in seetions stained with Methylene Slue . Human The histology of the human l i v e r has been worked out so thoroughly on account of I t s significance in medicine , that i t Is treated here only i n i t s comparative aspects . The anatomical basis of structure i . e . the lobule , i s precisely the same as i n the other tissues examined. The d i v i s i o n Into lobules i s very I n d i s t i n c t however, though complete lobular segregation may b*v found under certain pathological conditions. The portal canals occur as isolated areas around the periphery, one canal giving off eight to teninterlobular branches into the contiguous lobules usually two but sometimes three in number. The boundaries of the c e l l s In the tissues e^anined were, at times very i n d i s t i n c t and ran into one another almost with-out v i s i b l e demarcation, giving the whole, tissue a syncytial appearance. The number of c e l l s , present, were .In these cases, only, approximately determinable, by. the number of n i i e l e i . A few binuclear c e l l s were present ,.. but the.great,majority pa&s.es.s, but one nucleus. The .cytaplasm is^ f i n e l y granular.,showing, a more.or less d e f i n i t e outer and inner zone , The nucleus has a d e f i n i t e nuclear membrane and nucleolus. Von Kupffer'a S t e l l a c e l l s were absent with the stains used. A comparison, of .the r e l a t i v e si$©s of. the o e l l s of tbe di f f e r e n t tissues based upon a measurement of four represent-ative cells. In each tissue gave the following r e s u l t ; Hog 1?.2 micronsjBeef 16 micronsj Sheep 15.4 microns; c a t 15.2 microns; Rabbit 20.6 microns ; Human 19. microns. As may be seen from these figures, there seems no connection whatever either i l l ) between the size of the c e l l and the d i e t of the animal , or betweenthe siae of the c e l l and the siae of the animal. The amount of, glycogen stored i n the l i v e r at any one ti»e depends upon the condition of the animal. The l i v e r always contains more glycogen during digestion than i n fasting animals . A f t e r a few days of starvation the glycogen ateost or quite disappears from the l i v e r . This also occurs i n animals fed exclusively upon fats , an£ the quantity i s diminished by a purely protein diet as contrasted with a mixed one. Bernard has shown that glycogen i s invariably present i n the l i v e r s of healthy carnivorous animal® fed upon meat alone . Favy , working with dried dogs' found the following r e s u l t s a f t e r anirtal food 7.19*'; af t e r animal food with sugar 1^.15^ a f t e r a vegetable diet 17,23 $ . Thus the formation ©f glycogen i s favored by a free supply of carbohydrate. -1th the above facts i n mind , i t must be apparent , that any attempt to determine -he r e l a t i v e glycogen content of the l i v e r must be carried out under conditions where the diet can be c a r e f u l l y selected and regulated. -Jnee these conditions wee© not available , no determinations were made. It would sees l o g i c a l , however to i n f e r from the above figures that, other things being equal, a r e l a t i v e l y largeramount of glycogen -would be found i n an animal subsisting upon a purely herbi-vorous d i e t , than i n a earnIvor , with the oranivor possibly between these. comimim. (12) One may say that the differences i n the tissues examined are simply those of degree. The mechanism of carbohydrate metabolism i s carried out i n a precisely s i m i l a r manner by anatomical elements of i d e n t i c a l arrangement, but modified morphologically i n a more or less d e f i n i t e manner by various unknown environmentalinfluences acting upon the i r possessors. In concluding , I should l i k e to express ny appreciation of the advice and assistance tendered by Dr. C. McLean Fraser of the Zoology Department, and also my thanks to Messrs. B r a s s e l l and Douglas of the P. Burns Company of this c i t y , f or t h e i r assistance in procuring material. / / — - ---'/ BIBLIOGRAPHY. Textbook of Histology Lewis and Stohr Blaklston 1918 pp. 276-- 289 Textbook of Histology P i e r s o l Lippincott 1920 pp. Textbook of Histology Jordan 1920 Textbook of Histology Bohra and Davidoff Saunders 1904 pp. 289-- 298 Gompend of Anatomy Potter Blakiston 1915 pp. 336-- 343 Handbook of medicine Jack Livingstone 1916 pp. 113 Essentials of Medicine Emerson Lippincott 1916 pp. 129-- 130 I 41 P I ft T j= Vf { I I 7 ^ t Put-, * Ml $ \ mm (3 'I ATE XJK if 9 -

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