founded by Richard Nickel, August Schu Volume 1:

Eugen Seiferle

I

the Domestic by Richard Nickel, August Schummer, Eugen Seiferl le (prob. published 1 ewein, and Marl-W. Volume 2 : The Viscera of the Domestic Mammals by August Schummer, Ric ard Nickel, and Wolfgang Otto Sack, 2nd revised Ed. 1979 Volume 3 : The Circulatory System, the Skin, and the Cutaneous

Volume 4 :

Volume 5: alter C. Siller

Verlag Paul Parey Berlin Hamburga

by August Schumer, He Bemd Vollmerhaus, and Translation alter G. Siller and Peter A. L. Wight

With 439 illustrations, 173 in colour

Verlag Paul Parey

Springer - Verlag New York - Heidelberg

Berlin

This volume is m authorized translation of R . Nickel, A. Schummer, E. Sciferle (Ed.), Lehrhuch der Anatomie der Haustiere (The Anatomy of the Domestrc Animals), Volume 3: Krelclaufsystem, Ha.ut und Ha,utorgane (The Circuhtory System, thc Skin, a n d the Cutaneords Organs of the Domestic Mammals) by A. Schummer, FI. Wilkens. D. Vollmerhaus, and K.-El. Habermchl, O 1976. Verlag Paul Parcy, Bcrl~nand Hamhurg, Germany. Richard Nickel t, Dr. med. vet., Professor and Hcad of thc Department of Anatomy, Tieraerztliche Hochschule Hanovcr, D 3000 Hanovcr, Germany August Schummer t, Dr. mcd. vct., Professor and Hcad of thc Dcpartmcn; of Veterinary Anatomy, Jus~us-Liebig-Univcrsitaet Gicssen. D-6300 Giessen, Germany Eugen Scifcrle, Dr. med. vet.. D r . med. vct. h. c., Professor and Head of thc Department of Veterinary Anatomy, Universitaet Zurich, CH-8057 Zurich, Switzerland Helmut Wilkens, D r . med. vet., Professor and Head of rhe Department of Anatomy, Tieracrzrliche Hochschule Hanover, D-3000 Hanovcr. Germany Berrid Vollmerhaus, Dr. med. vet., Professor and Hcad of thc Department of Veterinary Anatomy, Ludwig-Mauimilians-Universitaet Munich, D-8000 Munich, Gcrmany Karl-Heinz Habcrmehl, Dr. mcd. vet., Professor and Head of the Department of Veterinary Anatomy, Justus-Liebig-Universitaet Giessen, D-6300 Giessen, Germany Walter G . Siller, Dr. med. vet., Ph. D.. M.R.C.V.S., F.R.C. Path., F.R.S.E., Universry of Edinburgh Pcter A. L. Wight, F.R.C.V.S., Ph. D., D.V.S.M., F.R.C. Path., F.R.S.E., University of Edinburgh S y n o p i s of thc English cdition: The Anatomy of the Domestic Animals : H Wille. Volumc 1: Locomotor System of the Domestx Mammals. By R. Nickcl, A. Schummer, E. Seiferle, J. Frewcin, and K . Translation from the German. Approx. 540 pages, with about 517 illustrations in the tcxt and on 11 colour plates. In preparation Volume 2: The Viscera ofthe Domest~c Mammals. By A. Schummer, R. Nickel, and W. 0.Sack. 2nd revised edition. Translated and revised- from the 4th German edition. 1979. 446 pagcs, with a total of 559 illustrations in the text and on 13 colour plates Volumc 3: The Circrdatory System, the Skin, a n d the Cutancom Organs of the Domestic Mammals. By A. Schummer, H . Wikens, B. Vollmerhaus, and K.-H. HaLcrmehl. Translated from thc German by W. G. Sillcr and P. A. L. Wighr. 1981. 630 pages, with a total of 439 illustrations, 173 in coloulVolume 4: Nervous System, Sensory Organs, Endocrine Glands of the Domestic Mammals. By E. Seiferle. T ~ a n s h t i o n from the German. Approx. 442 pagcs, with a total of about 253 illustrations, abour 95 in colour, in the text and on 10 colour plates. In Volume 5: Anatomy of the Domcstic Birds. By A. Schummer. Translated from the German by W. G . Siller and P. A. I.. Wight. 1977. 214 pagcs, with 141 illustrations in the text and on 7 colour plates Synopsis of the German edition: Lehrhuch der Anatomie der Hardstiere Volumc I: Bewegungsappamt. By R. Nickel, A. Schummer, E. Seiferle, J. Frewein, and K.-H. Wille. 4th revised edition. 1977. 560 pages, with a total of 517 illustrations in the text and on 11 colour plates Volume 11: Eingeweide. By A. Schummcr and R. Nickel. 4th edition. 1979. 446 pages, with a total of 559 illustrations in the text and on 13 colour plates Volume 111: Kreislatdfsystem, Haut rrnd Hautorgane. By A. Schummcr, H . Wilkens. B. Vollmerhaus, and K.-H. Habcrmehl. 1976. 662 pages, with a total of 439 illustrations, 172 in colour Volume IV: Nervensyrtem, Sinncsorgane, Endokrine Druien. By E. Seiferle. 1975. 442 pages, with a total of 250 illustrations, 95 in colour in the text and on 10 colour plates Volume V: Anatomie der Harrsvogel. By A. Schummer. 1973. 215 paEes, with a total of 141 illustrations in the text and on 7 colour . platesA

C1P-Kurztitelaufnahme der Deutschen Bibliothek Nickel, Richard: The anatomy of the domestic animals / founded by Richard Nickel, August Schummer, and Eugcn Seiferle. - Bcrlin ; Hamburg : Parcy Dt. Ausg. u.d.T.: Nickcl, Richard: Lehrbuch der Anatomie der Haustiere. - Vol. 2 u. 5 erschiencn nicht als Teil d. Gesarntwerks N E : Schummer, August: ; Sciferle, Eugen: systcm, rhe skin and Vol. 3. + Thc c~rculatory the cutaneous organs of thc donir\tic ~m:lmmnls T h e circulatory system, t h e skin a n d the cutaneous organs of the domestic mammals / by August Schummer . . . Transl. by Walter George Sillcr and Peter Albcrt Laing Wight. - Berlin ; Hamburg : Parcy, 1981. (The anatomy of the domestic animals / foundcd by Richard Nickel, August Schummer, and Eugen Seiferle ; Vol. 3) ISBN 3-489-556184 NE: Schummer, August [Mitverf.]

Cover dcsinn: Christian Honie, D-5450 Neuwicd/Rhein. Germanv This work is subject to copyright. All rights are reserved, whcrher the whole o r part of the matcrial is concerncd, specifically those rights of translation, reprinting, rc-use of illustrations, rccitation, broadcasting, reproduction by photocopying machine o r similar means, and storagc in data banks. Under $ 54,l of the Gcrman Copyright L.aw where single copies arc made for other than privatc use, a fee is payable to thc publisher according t o S 54,2 of the Gcrman Copyright Law. The amounr of the fee is to be determined by agreement with the publisher. Q 1981 by Verlag Paul Parey, Bcrlin and Hamburg, D-1000 Bcrlin 61, Germany Printed in Gcrmany by Felgentreff & Goehcl Buch- und 0ffsct:druckcrei G m b H & Co. KG, D-1000 Berlin 61, Germany Binding by Liiderirz & Bauer, D-1000 Bcrlin 61, Gcrmany ISBN 3489-55618-6 Vcl-lag Paul Parcy, Berlin and Hamburg ISBN 0-387-91193-6 Springer-Verlag, New York. Publishcd simultaneously by Springer-Verlag New York for distribution in the United Statcs and its possessions, Canada and Mexico.

Dedicated to the memory of

Richard Nickel (1905-1964), Dr. med. vet. habil., Dip1.-Landwirt, Professor of Veterinary Anatomy, Histology and Embryology at Hanover 1948-1964

tors9 prefaceThe publication of this translated volume provides English versions of three of the five books which comprise the "Lehrbuch der Anatomie der Haustiere". Some revision was necessary in the English edition of the second volume largely to adapt the nomenclature, but this was not required in the present book in which terms listed in the Nomina Anatornica Veterinaria were used in the original German text. This is, therefore, an unrevised, unabridged translation which follows faithfully the German text. As in the English version of Volume V, translated by ourselves, the Latin terminology is used the first time a name occurs but subsequently the Englisch equivalent is generally substituted. It should be pointed out that some of thc breeds of farm animals mentioncd may not be well known outside their native Central Europe, but descriptions of many of them can be found in Mason, I. L. (1951) "A world dictionary of breeds, types and varieties of livestock," Commonwealth Agricultural Bureau, Eneland. " In the chapter o n the lymphatic organs, many references will be found to meat inspection and thc German legal requirements for the examination of lymph nodes in the abatoir. We were in some doubt whether thcse should be omitted from the English edition becausc obviously legislat~onis not identical in all countries. However. it was decided to retain them because thev mav be found useful as a general , ,, guide but it must be remembered that they are based on the German regulations. It is our pleasant duty to acltnowledge the invaluable advice on the integument given by D r . W. M. Stokoe of the Department of Anatomy, Faculty of Veterinary Medicine, University of Edinburgh, and Dr. M. L. Ryder of the Agricultural Research Council's Animal Breeding Research Organisation, Edinburgh. We would also like to thank Mrs. Kathleen Wight for the accurate preparation of the typescript. Finally, w e must thank D r . F. Georgi and his staff at the publishing house Paul Parey, Berlin, for their patience and friendly consideration.L ,

Edinburgh, March, 1981.

W. G . Siller and P. A. L. Wight.

e German

E

The publication of volume I11 completes the five-volume Textbook of Anatomy of Domestic Animals. The authors of the chapter on the blood vascular system are Professor A . Schummer of Giessen (blood vessels - general considerations, blood and heart) and Professor H. Wilkens of Hanovcr (blood vessels - arterial and venous systems). Thc section on the lymphatic system was compiled by Pr?fessor B. Vollmerhaus of Munich and that o n the skin and cutaneous organs was written by Professor K.-H. Habermehl of Giessen. D r . W. Munster of Hanovcr also contributed to the section on arteries and vans. This summarizes the general content of volume I11 in which the individual species of animals are treated according to the same basic principle as in the prcvious volumes. The introductory chapter discusses the cardiovascular system in a general way because the clinical

VIIT

Preface to the German Edition

a thorough knowledge of the entire system. The formation, composition, function and destruction of the blood are dealt with and this is followed by a discourse on the structure and function of the blood vessels, including their nervous and hormonal control. The description of the heart follows the same scheme, the f m t part dealing with fundamental cardiac anatomv applicable to all mammals whde subsequently consideration is given to specles . -peculiarities and the comparative characteristics of the organ. In describing the origin, course and topography of the blood vessels it was important to it~clude all ~ e r t i n e n tderail and yet avoid too lengthy' a text. This could only be achieved by a comparative presentation of the vessels of all species, region by region. This chosen method also scrvcd to emphasize the fact that in each region the organization and distribution of the blood vessels is basically similar in all species, thus allowing rules of nomenclature to be established for individual blood vcssels. Once this fundamental concept is understood, it is possible to extract all the desired information about any one species from the descriptive text and illustrations. The principle is used throughout except in the blood vessels of the foot where, because of the obvious differences in the structure of the extremities, it is necessary to give a detailed description for each species of animal. The discussion on the function of the lymphatic system is appropriate to the importance of this subjcct, because much current research on it is of great medical interest. For this reason it seemed advisable to record the present (1975) state of our knowledge in this field, although we are well awarethat theories are more quickly outdated in this area than in other medical disciplines. In accord with the general p r ~ n c ~ p a l the book, the systematic dcscription of the lymphatic organs in the various of spe~ieshas been compiled so as to provide both basic knowledge and information of value in veterinarv practice. The fundamental descriptions of Baum and his students and the more recent investigations of other authors proved of great servlce In compiling this chapter. Numcrous valuable illustrations from older monographs, long out of print, were reproduced by kind permission of Springer Verlag. As bcfits the importance of the carnivores, pig and ruminants, these species are dealt with more liberally in rhe chapter on skin and the cutaneous organs than has been the custom in previoustextbooks of anatomy. Particular stress is placed on the account of special skin glands which are of great importance as scent, marker and signal glands in conspecific cornrnunication. We had numerous collaborators in the Institutes of Veterinary Anatomy in the Universities of Giessen and Munich and of the. Veterinary School of Hanover and we thank them all for their valuable,:a .

diagnosis of pathological conditions depends on

assistance.

O u r thanks go to Mrs. V. Gube of Giessen for illustrating tlie chaptcrs on the heart and skin and! cutaneous organs, which she accomplished with the artistic skill, understanding and insight for which she is wcll known. We also thank Mrs. S . Pletscher of Zurich for some illustrations in the section on the hoof. Dr. K.-H. Wille of Giessen provided expert criticism and correction of these chapters and, last but not least, we are grateful to the secretary of the Institute a[ Giessen, Miss H. Seip, for the careful preparation of the ~ypescript. We thank Mrs. R. Rochner, Mr. W. Heinemann and Mr. G. Kapitzke of Hanover for the careful graphic work and exelnplary artistic illustrations to the chapters on the blood vascular system and the skin and cutaneous organs. We thank M.-L. Meinecke for the conscientious typing and Mrs. G. Voigt and many other members of the institute for their help. We are grateful to Professor Dr. Wissdorf for his valuable and stimulating cooperation. We are indcbtcd in Munich to Mrs. L. Kiirner for the drawings, to Dr. H . Roos, Dr. B. Hossenfeldner, Dr. H. Waibl and Dr. H . E. Konig for their valuable help in preparing the list of contents and the index and for proof-reading. Our thanks also go to Mrs. A. Speiser and Miss Ch. Drechsler for typing the manuscript. It is largely due to thc constant and personal interest of Dr. Priedrich Ccorgi, a proprietor of the publishing house, that this third volume, and, indeed, the whole project, was so satisfactorily completed. He had great patience and understood the problems which confronted the authors. O u r special thanks are likewise extended to Mr. E. Topschowsky, manager of the publishing house, whose vast experience spanning many decades, contributed considerably to the outstandingly high standard of tlie book. We hope that this third volume will be as well received as those which preceded it.

Giessen, Hanover, Munich Summer 1976

August Schummer, Karl-Heinz Ilabermehl, Helmut Wilkens, Bernd Vollmerhaus

ContentsOrgans

Page

of the circulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bloodvascular system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Blood (A. Schummer. Giessen) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Blood plasma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Alood cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Erythrocytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Leucocytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Granulocytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Monocytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lymphocytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . Thrnmbocytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Organs of the haematopoiesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Development of blood cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Blood vessels, structure and function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Veins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Capillaries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arteriovenous anastomoses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nutrition of the vessel wall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Innervation of the blood vessels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hormones acting on the blood vessels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Heart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pericardium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conformation of the heart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Position of the heart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Tissue components of the heart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The skeleton of the heart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Architecture of the heart musculature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The chambers of the heart and their internal structure . . . . . . . . . . . . . . . . . . . . . . . . . . . .The atria of the heart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Right atrium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Left atrium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The ventricles o f the heart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Right ventricle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Left ventricle

11 1 2 2 2

4

........................................................

Excitation and conducting system of the heart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Innervation of the heart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Blood vessels of the heart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Veins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Structure and special organization of the blood vessels of the heart . . . . . . . . . . . . . . Lymph vessels of the heart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Species characteristic of the heart, general considerations . . . . . . . . . . . . . . . . . . . . . . . . . Size, weight and measurements of the heart, general consideration . . . . . . . . . . . . . . . . . The heart of the dog and the cat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Interior of the ventricles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Size and weight of the dog's heart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Position of the heart in the dog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Heart of the cat, size and weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Blood vessels of the heart of the dog and cat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Veins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Heart of the pig . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Internal structure of the ventricles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Size and weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Position of the heart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Blood vessels of the heart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Veins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Heart of the ox . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Internal structure of the ventricles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Size and weight of the heart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Heart of the sheep and goat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Internal structure of the ventricles (sheep) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Size, weight and position . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Blood vessels of the hearts of ruminants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arteries of the heart of the ox . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Veins of the heart of the ox . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Heart of the horse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Internal structure of the ventricles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Size and weight of the heart Posltlon of the heart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Blood vessels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Veins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Species-diagnostic features of the hearts of domestic ma~nmals. . . . . . . . . . . . . . . . . . . . . Dog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pig . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sheep and goat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ox ................................................................... Horse

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Arteries (arteriae) (H. Wilkens in collaboration with W . Miinster, Hanover) . . . . . . . . . . .Truncus pulmonalis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Aorta . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Contents Arcus aortae and truncus b r a ~ h i o c c ~ h a l i c u . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . s Arteries nf the pectoral limb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Comparative topography and nomenclature of the blood vessels of the autopodium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Deep vessels of the metapodium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Superficial vessels of the metapodium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Vessels of the acropodium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arteries of the forefoot of carnivores . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arteries of the forefoot of the pig . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arteries of the forefoot of ruminants

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Arteries of the forefoot of the horse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arteries of the head and neck . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Aorta thoracica . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Visceral arteries of the thoracic aorta . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Aorta abdommalls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arteries of the pelvic limb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arteries of the hindfoot of carnivores . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arteries of the hindfoot of the pig . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arteries of the hindfoot of ruminants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arteries of the hindfoot of the horse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arteries of the pelvic and tail regions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Visceral arteries of the abdominal aorta . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Visceral arteries of the internal iliac and internal pudendal interna . . . . . . . . . Venae pulmonales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Vena cava cranialis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

.............................................................. Veins of the pectoral limb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Veins of the forefoot of carnivores . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Veins of the forefoot of the pig . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Veins of the forefoot of ruminants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Veins of the torefoot of thc horse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Veins of the head and neck . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Vena cava caudalis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Veins of the pelvic limb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Veins of the hindfoot of carnivores . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Veins of the hindfoot of the pig . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Veins of the hindfoot of ruminants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Veins of the hindfoot of the horse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Veins of the pelvic and tail regions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Visceral veins of the caudal vena cava . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Visceral veins of the internal iliac and internal pudendal veins . . . . . . . . . . . . . . . . . . . Lymphatic system (B . Vollmerhaus. Munich) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lymphatic organs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Vena azygos Phylogenesis of lymphatic organs Im~nune system ..............

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Contents Structure and function of lymphatic organs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fixed cells of the lymphatic organs . . . . . . . . . . . . ; . . . . . . . . . . . . . . . . . . . . . . . . . . . . Frce cells of the lymphatic organs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Classification of organs of the immune system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Peripheral lymphatic organs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lymphatic tissue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Tonsils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lymph nodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Haemolymph nodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Spleen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Thymus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ontogenesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Microscopic structure and function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Macroscopic description of the thymus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Thymus of carnivores . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Thymus of the ~ i g. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Thymus of ruminants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Thymus of the horse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lymphatic vessel system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . General considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Phylogenesis of lymphatic vessels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ontogenesis of lymph vessels and nodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Structure and function of lymphatic vessels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lymph capillaries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Extravascular circulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lymph formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lymph vessels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Special arrangement of lymph capillaries and lymph vessels in various organs . . Lymph collecting vessels and lymphovenous anastomoses . . . . . . . . . . . . . . . . . . . . . Systematic and topography of lymph vessels and lymph nodes . . . . . . . . . . . . . . . . . . . . . General considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Comparative description of the lymph vessel system . . . . . . . . . . . . . . . . . . . . . . . . . . Lymph vessel system of the head . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Outflow of lymph from the head . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lymph vessel system of the neck . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lymph vessel system of the forelimb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Outflow of lymph from the forelimb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lymph vessel system of the chest wall and thoracic organs . . . . . . . . . . . . . . . . . . Ductus thoracicus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lymph vessel system of the dorsal abdominal wall and the abdominal viscera . . Cisterna chyli . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lymph vessel system of the lateral and ventral abdominal wall. the pelvis. the pelvic viscera and the pelvic limb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Outflow of lymph from che pelvis and pelvic limb . . . . . . . . . . . . . . . . . . . . . . Concluding remarks on comparative aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . Lymph nodes of the dog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lymph collecting ducts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Contents Lymph nodes of the cat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lymph collecting ducts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lymph nodes of the pig . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lymph collecting ducts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lymphnodesoftheox . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lymph collecting ducts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lymph nodes of the goat and sheep . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lymph collecting ducts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lymph nodes of the horse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lymph collecting ducts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Skin and cutaneous organs (K..H. Habermehl, Giessen) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C o m m o n integument. integurnentum c o m m u n e . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . General a n d comparative considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Phylogenesis of skin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ontogenesis of the skin and its appendages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Subcutis. telasubcutanea . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Corium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Epidermis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hairs. pili . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Outer hair (Capilli) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wool hair (Underwool. pili lanei) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Long or horse hairs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

.......................................................... Tactile hairs (pili tactiles) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arrangement of the hair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hair colour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hair replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Skin glands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sebaceous glands (glandulae sebaceae) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sweet glands (glandulae sudoriferae) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Blood supply to the skin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nerve supply to the skin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Specialized structures of t h e skin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . General skin modification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Localized special glandular apparatus (cutaneous scent glands) . . . . . . . . . . . . . . . . . . . . . Perioral glands. glandulae circumorale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Infraorbital organ. sinus infraorbitalis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H o r n gland. glandula cornualis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ceruminous glands. glandulae ceruminosae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mental organ. organum mentale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Carpal organ. organum carpale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Metatarsal glandular organs. organa metatarsalia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Interdigital sinus. sinus interdigitalis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Tail gland. organum caudae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Subcaudal gland. glandula subcaudalis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Anal sac. sinus paranalis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Circumanal glands. glandulae circumanales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Bristles (setae)

XIV

Contents Inguinal sinuses. sinus inguinalis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Preputial glands. glandulae praeputiales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Preputial diverticulum. diverticulum praeputiale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mammary gland. mamma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ontogenesis of the mammary gland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . General and comparative considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mammogenesis and lactopoiesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Specific hairless skin organs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ontogenesis of the specific hairless skin organs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . General and comparative considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Digital organ. organum digitale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hoof . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Claw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The horn of ruminants. cornu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The skin and its appendages of carnivores . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Skin of the dog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Skin of the cat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mammary gland of the dog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mammary gland of the cat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Digital organ of carnivores . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Skin and cutaneous organs of the pig . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Skin of the pig . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mammary gland of the pig . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Digital organ of the pig . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Blood vessels of the digital organ of the pig . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arterics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Veins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Skin a n d cutaneous organs of ruminants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Skin of the ox . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Skin of the goat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Skin of the sheep . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mammary gland of the cow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Blood vessels of the udder of the cow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Veins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lymph vessels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nerves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mammary gland of the sheep . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Blood vessels of the udder of small ruminants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Veins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Digital organ of the ox . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . General considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Subcutis of the claw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cerium of the claw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Contents

Epidermis of the claw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Digital organ of the small ruminants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Blood vessels of the digital organ of ruminants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Veins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Skin and cutaneous organs of t h e horse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

........................................................... ................................................. Blood vessels of the mammary gland of the horse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Veins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The digital organ of the horse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . General considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Skin of the horse Mammary gland of the horse Subcutis of the hoof . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Corium of the hoof . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Epidermis of the hoof . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Differences between the hoofs of the fore- and hind-limbs . . . . . . . . . . . . . . . . . . . . . Histological structure of the horn tubules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chestnuts and ergots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Blood vessels of the digital organ of the horse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arteries Veins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Source of non-original illustrationsFig. 1: Schcunert, A , , and A. Trautmann, Lehrbuch der Vererinar-Physiologic, 5"' ed., Paul Parcy, Berlin and Hamburg. 1965. n Fig. 2: GI-au, H., and I?. Walter, GrundriR der Histologie und v ~ r ~ l e i c h e n d crnikroskopischen Anatomie der Haussaugetierc, Paul Pal-ey, Berlin and Hambul-g, 1967. Fig. 3: Staubesand, J., in M.Ratschow, Angiologic, ed. by Heberer/Rau/Schoop, 2 n d ed., Thicme, Stuttgart, 1974. Figs 24, 136-119, 140-143: Ackcr-knecht, E., in Ellcnbergrr/Bau~n, Handhuch dcr vergleichcnden An;atomie der H a u s t ~ e r e ,I8'" cd., Spr-inget-, Berlin, 1943. F i g d C , 76, 83, 84, 93: 135, 166, 211, 367, 368, 375. 413, 429: Zietzschn~ann, O . , in EllenbergerIBaum, Handbuch der vergleichcndcn Anatomie der Hmstiere, I S t h ed., Springel, :Berlin 191.3. Figs 65, 66, 197: Ellenbet-ger, W., and H. Bautn, H a n d b u c h dcr vergleichendcn Anatomic d c r Haustierc, 17"' ed., Springer, Berlin, 1932. Figs 103, 104, 110, 114, 123, 124, 249, 419, 421-423, 428, 433: Mat-tin, P.,1.chrhuch der Anatomie der Hausticre, vol. 11, L n d cd., by Schickhardr and Ebnct-, Stuttgnl-t, 1915. Fig. 206: Schmaltz, R . , Atlas der Amatomic des Pferdes, pal-t 2 : Topographische Myelogie, j t h e d . , Schoctz, Berlin, 1939. Fig. 222 A: Grau, H. in KrollingIGrau, Lehrhucli del- Histologie und ~ e r ~ l e i c h e n d e n mikrnsltopischen Anatomie der Haustiere, 10'li ed., Paul Pat-ey, Bel-lin and Hamburg, 1960. Fig. 232: Tondury, G., and St. Kubik, Zul- Ontoge~lesedes lymphatischcn Systcms. I n : Handhuch dcr allgemeincn Pathologie, vol. 3 , part 6, Springer. Berlin. Heidelherg, N e w Yol-k, 1972. Fig. 234: L.cak, L. V . and J. F. Bul-ke, in L. V. Leak, T h e Fine Structure and Function of the 1.ympbaric Vascula~ S y s r ~ m In: Handhuch der all~cmeinen . Pathologie, vol. 3, part 6, Springcr, Bcrlin. Hcidelberg, N e w York, 1972. Fig. 235 A: Sushlto, A . A , . in . Wcntzel, Normale Anatornie des LymphgefaC\systcmz. In: Handbuch der allgcmcincn Patholosic, vol. 3 , part 6, Springer. Ecrlin, Heidelberg, N e w York, 1972.

Fis. 235 B: Rampmeicr, 0 . F. in J. Wenzel, Normale Anatomie clcs Lymphgefiifisystems. In: Handhuch derallgemeinen Pathologie, vol. 3, part 6 , Springcl-, Berlin, Heidelberg, N c w Yor-lc, 1972. Fig. 236: Courticc, F. C . , The Chemistry of L y m p h . In: Handbuch der allgemeincn Pathologie. vol. 3, part 6 , Springcr, Bel-lh, Hcidelbcr-g, N e w Yorlt, 1972. Fig. 238: Casley-Smith, 7. R.. in: N c w Trcnds in Basic Lymphology, ed. by Collcttc/Janter/Scliofeniels, Rirlthauser, Basel, 1967. Figs 240 A , 253, 256, 282-294: Baum, H., and H . Grau, Das Lympl~gef'aflsystern dcs Schwcines, Paul Parcy, Rcrlin, 1938. Figs -744, 245, 262~-273: Baum, H., Das LytnpIigefiiRsymm dcs Hundcs, Hil-schwald, Berlin, 1918. Figs 246, 255, 257, 321-335: Baum, H., Das Lyrnphgci,ifisystcm des Pfcrdes, Springer, Berlin, 1928. Figs2250, 251, 258, 259, 296-309: Baum, H., D a s LymphgefdRsyacelrr des Rindes, Hil-schwald, Bcrlin, 1912. Figs 280, 281 : Zietzschmann, O . , in S c h i i n b e r ~ I Z i c t z s c b ~ l ~ ~Tiel-arztliche F l e i s c h u n t c r s ~ c h u l i ~ ed., Paul ann, Parey, Bcrlin and Hamburg, 1958. Figs 159, 396, 398: Mnl-tin, P . , and W. Schaudel-, I chrhuch dcl- Anatonlie der Hausticre, vol. 3 , 3"' Scliicltliardt and Ehner, Sruttgart, 1938. ed., b y

O t h c r illustrations have been reproduced fi-om distcrtations and journals which arc lisrcd in the bibliography at thc cud of tlic book.

List of Abbreviations( I n t h e plural fol-m t h e litst letter of t h e a b b w u i a t i o n is d u p l i c a ~ e d )a. art. can. cad. com. cran. dext. dist. dors. duct. est. fiss. for. gd. gJ(d ). 111C. inf.= = = =

= == =

== =

= = = = ==

arteria articulatio canalis caudalis coinmunls cranialis dexter distalis dorsalis ductus extcrnus fiswra foramen ganglion glandula incisura inferior

int. lam. lat. Ic. lig. In. lob. m. mand. max. med. min. 11. nl. palm. plant. post.

= = = =

== = = = = ==

== =

= =

internus lamina lateralis lymphoccntrum lignmentum Iymphonodus lobus ~nusculus ~nandibularis maxillaris medialis minor nervus nodus lprnphaticus pallnaris plantaris posterior

pot.

= processus

prof. propr. prox. r. 1-cg. rostr.S.

= profundus= proprius

S111. str. sup. supf. transv. trunc. tub. v. ventr.

= proximalis = ramus - reglo = I-ostralis = seu, sive = sinister = stratum = supcrior = superficialis = transversus = truncus = tuberculuin = vena = ventralis

Text references to figuresThese appear in parenthesis in the text, mostly thus: ( 3 6 / a ) . T h c number before the ohlique line refers t o the illustration; the symbol in italics following rhc oblique refers t o n labeled part in that illustration. Thcrefore, notation ( 3 6 / a ) , for instance, refers t o structure a in figurc 3 6 . T h e notation ( 3 6 , 3 7 , 3 8 / b ) rcfcrs to structure b in all three figurcs 3 6 , 37 and 38. Vi'hen thc italicized indcx applies t o several illustrations, then all the preceding figure iluinber-s are separated h y commas thus ( 3 6 , 3 7 , 3 8 l b ) ; if, on the other hand thc italicized indices apply only t o somc figures, thcn thc figul-c numbel-s are separated by sc~nicolonsas, for instance (54; 6 0 , 6 1 / a ) . This I-efers to figure 54 a n d str-uctul-ea in figures 60 and 6 1 .

The organs of the circulation (angiologia) h c l u d e the bloodvascular system and the lymphatic systcm. The bloodvascular system (systema cardiovasculare) consists of the heart, its central organ, and the blood vessels among which w e differentiate thc arteries, rullning centrifugally fronl the heart, and the veins which are directed towards the heart. T h e arterial and venous networks are connected by the capillaries. The blood circulating within these vessels, thc organs of blood formation (haematopoiesid and. the organs responsible for the breakdown of the blood cells are also part of the bloodvascular system. The lymphatic system (systema lymphaticurn) is composed of the lymph and the lymph vessels, the Iattcr generally accompanying the veins. Another important component of this system is the lymphoreticular tissue which varies in structure and appearance and is widely distributed throughout the body.

The functioils of the blood circulating within the vascular system include supplying the cells and tissues of the body with the nutrients required for their maintenance and function, removing break-down products and conveying them to the organs of excretion and transporting surplus metabolites t o the storage organs. Further functions are regulation of water and electrolyte metabolism, involvement in the maintenance of body temperature and assisting the body's defence against foreign substances and pathogenic organisms. A n essential prerequisite for the fulfilment of these duties is the correct functional construction of the system as a whole and its appropriate relationship with the other organs. Very high demands are made o n the efficiency of the circulation, and especially the heart, in warmblooded animals. In the transition t o a terrestrial existence numerous changcs in life pattern took place as the animals adapted t o their new environment and these led to an intensification of metabolism. An illcrease in the oxygen requirement was mainly involved and this was achieved b y a transition to pure pulmonary respiration which necessitated the division of the heart and the circulation into two "halves". Both anatomically and. functionally, therefore, the heart of birds and mammals is divided into t w o (double heart) consisting of an arterial part which carries oxygenated blood and a venous part in which the blood is rich in carbon dioxide. The left (arterial) and the right (venous) halves of the heart each conskt of an atrium and a vefltricle and they supply completely separated vascular systems known as the systemic o r large circulation and the pmlmonary or small circulation respectively.

looThe blood conslsts of blood plasma, a viscous fluid possessing the ability t o coagulate, the blood cells and the blood platelets, the latter being formed elcments which are non-cellular in nature.

Blood plasma, Rlood cclls. El-ythl-ocytcs

Blood plasmaThe blood plasma is an aqueous solution of blood proteins, such as fibrinogen, albumin, various and blood sugar. The inorganic substances contained in the blood plasma cnsure the types of maintenance of the cl~emico-physical r o ~ e r t i ofs the blood and they include, amongst others, sodium, ~ c potassium, calcium and magnesium ions. As bicarbonate and phosphate salts they have a buffering effect, taking up, for instance, the carbon dioxide and lactic acid liberated by the cissues and so keeping the reaction of the blood at thc requisite slightly alkaline level. Other components of blood plasma are lipids in fine suspension. The plasma serves as a carrier of nutrients, taken up during digestion, for the supply of the body's cells and tissues. Similarly it carries vitamins, hormones and enzymes. It contains products of intermediary metabolism which are break-down ~ r o d u c t s that have to be eliminated fi-om the body. As part of the defence mechanism, the plasma contains enzymes, such as proteinases or peptidases, and antigens, antibodies and antitoxins for the neutralization of foreign protein and bacterial toxins. The blood remains fluid while within the circulation but it clots when it leaves the vessels. Blood coagulation, a vital protective mechanism, depends on the ability of the fluid fibrinogen contained in the plasma t o become transformed by the interaction of thrombin, into a delicate elastic network of fibrin. This complex process, initiated by the breakdown of thombocytcs, is, according to modern theories, dependent on the interaction of nearly thirty different factors. 117 the patl~ological condition of thrombosis blood coagulation can also take place in the unopcned blood vessel, when its inner lining, which in the healthy state prevents coagulation, bears lesions which bring about the formation of thrombi. Blood collected in a container will clot unless some anticoagulant substance has becn added. The coagulation time varies considerably among the different species. In birds it is only 1-2 minutes, the pig 10-15 minutes and the horse 15-20 minutes. When blood coagulates, a clot of fibrin and sedimented blood cells forms at the bottom of the vessel, the supernatent being the clear, yellowish, fibrin-free blood serum which contains antibodies and is thus employed in serum therapy. Mention should also be made of the sedimentation rate of the erythrocytes. If blood which has been prevented from clotting is allowed to stand in a test tube, the blood cells will settle out after some time. The duration of this process is termed the sedimentation rate. In certain diseases this rate may deviate from the values established for the respective species under physiological conditions, the reason For this presumably being the altered composition of the blood plasma.

(1 and table) The blood cells or corpuscular elements of the blood derwed from cells are listed according t o frequency as follows: 1 . the red blood corpuscles (erythrocytes), 2. white blood cells or corpuscles (leucocytcs) and 3. platelets (thrombocytes) (1). Blood films are used in haematology to examine the ~ n o r ~ h o l o g ~ , number, size and reaction to chemical substances such as dyes, of the blood cells. A very thin film of freshly drawn blood is spread onto a slide so that the individual blood cells lie side by side in a single layer t o facilitate recognition. The tinctorial differentlation of the different types of cells and their intracellular structures is carried out with a mixture of neutral, acid and basic dyes. Special facilities are required to examine the cells in the living state, for which purpose the blood is greatly diluted with an isotonic fluid. The blood cells are counted with the aid of a haemocytometer.

ErythrocytesIn the domest~c mammals the red blood corpuscles (erytbrocytes) of the blood are circular, b~concave and anucleate discs. Tylopods (e.g. camels, llamas, etc.) have erythrocytes which are anucleate but oval. The diameters of the erythrocytes differ in the various species of domestic mammals. In the dog, for instance, they are 7.3 p m in diameter but in the goat they measure only 4.1 p m (see table). The thickness of the erythrocytes, measured at the edge of the disc, also varies between 2.1 p m in the horse and 1.5 p m in the goat. The same disparity between species is found in the number of red cells per cubic mill~meter of blood and their numbers are influenced furthcr by breed, sex, age, husbandry, nutrition,

Erythrocytesneutrophd granulocyfe (stab cell) horse eryfhrocyfe horse neutmphd granulocyte mth segmented nucleus cat horse

eosinoph,l granulocyte horse

eosmoph~lgranulocyte ox

eosinoph~lgranulocyte ca i

basophil granulocyt~ horse monoc te

performance and various other factors. An individual erythrocyte is yellowish-green and o d y thc concentration of large numbers is responsible for the rcd colour of the blood. T h e red blood cells are elastic and consequently their shape may be temporarily altered, a property which ~ e r m i t s them to pass through capillaries whose lumen is narrower than the diameter of the erythrocytes. In mammals the most striking characteristic of the mature erythrocyte is the absence of a cell nucleus (all other vertebrates have nucleated, oval erythrocytes). Because of the absence of a nucleus their life is relatively short, being about 120 days. I t has been shown by electronmicroscopy that they have a semipermeable cell membrane consisting o f three layers. T h e y therefore exhibit a characteristic behaviour in media of different molar concentrations. In an isotonic solution, such as physiological saline, they maintain their normal form because tlic same osmotic tension is present both inside and outside the cell. In hypertonic media, however, the cell loses water and shrivels t o the shape of a thorn-apple, while in hypotonic solutions they swell, rupture and release their contents. T h e latter process is known as (osmotic) haemolysis, the fluid medium taking o n a red paint-like appearance. After haemolysis the erythrocyte cell membranes can bc demonstrated as pale ghosts. The cytoplasm of the red blood corpuscle consjsts of various proteins and lipids. A special cytoplaslnic structure in the form of a nctwork of delicate grai~ules,the substan~ia~etic~.lofilamensosa, can be demonstrated with specific staining methods only in the incompletely matured cells known as reticulocytes o r proerythrocytes. Functionally the most important component of the erythrocyte is the red pigment haemoglobin which is concerned with oxygen transport. I t consists of a protein component, globin, and the iron-containing pigment haem. Haemoglobin has the ability to bind oxygen in a readily dissociable form during its passage through the lung, as a result of which it is converted t o bright-red oxyhaemoglobin. Subsequently the oxygen is given off to the tissue cells and, due to this reduction of the oxyhaemoglo-

4

Lcucocytes, Granulocytes

bin, the colour of the blood becomes dark red. This function of the erythrocytes is dircctly dependent 011 their haemoglobin content, which content can be measured by various methods. The removal of carbon dioxide from the cells and tissues and its elimination in the lung is accomplished nlainly by binding to alkaline salts of the blood plasma and these also easily dissociate. 111order that the blood may perform its numerous functions it must, in the first place, be present in sufficient amount. Its total volume, which can bc assessed by various methods, amounts to 6-8% of the body weight. The percentage of the blood volume occupied by the red blood cells is equally important; this is referred to as the haeinatocrit value and is dependent o n the total number and size of the erythrocytes and on the plasma volume. Determination of the number of blood cells and the relative proportion of the various blood cells to onc another is also of great importance (see table). Red blood corpuscles can show various abnormal features such as differcnt staining affinity; hyperchromasia if the haemoglobin content is too great and hypochronzasia if it is too small. Abnormalities in size arc termed anisocytosis, in shapepoikilocytosis and in number hypererytbrocytosis (normal state in neonates) or oligoerythrocytosis (in anaemia). Information regarding these, as well as other tnorphological, quantitative and qualitative values, provides an important diagnostic aid for the clinician, especially in diseases of the haemopoietic system but also in numerous other illnesses.

Unlike the red blood corpuscles, the white blood cells (leucocytes) are colourless, round and nucleated. Ccrtain characteristics, such as differing cell size, nuclear shape, cytoplasmic inclusions and different tinctorial properties make it possible to classify three genetically and functionally seperate types of leucocytes. These are the polymorphonuclear granulocytes, the lymphocytes and the monocytes. The number of white blood corpuscles, between 4,000 and 24,000 per mm3 of blood, is far less than the number of erythrocytes which are about 500 to 1,500 times as numerous. One of the most striking characteristics of the leucocytes is their amoeboid movement and their consequent ability to leave or enter the capillary by migrating through its wall. In so doing the granulocytes considerably alter the shape of both their cytoplasm and nucleus.

GranulocytesThe granulocytes (1) develop, like erythrocytes, in the red bone marrow. They have a diameter of 10-15 p m and thus exceed the red blood cell in size and volun~e (1:7). During the immature stage their nucleus is unsegmented, rod or "S"-shaped, whereas the nucleus of the mature cells is polymorphic, with a degree of segmentation which depends on the age of the cell. Granulocytes have particularly well-developed amoeboid movement. They leave the capillaries in response to chemotactic stimuli (leucodiapedesis) and collect in areas of vascular damage or loci of bacterial accumulation wherc they phagocytose and incorporate cell fragments or bacteria and subject them to enzymic digestion. Because of this phagocytic activity, the granulocytes represent a significant part of thc complex defense mechanism of the body. Despitc their importance they only survive in the circulating blood for 1-11/, days. As already mentioned, we differentiate between granulocytes with rod-shaped and those with segmented nuclei. An increase in the cells with rod-shaped nuclei indicates the appearance of immature forms and these provide the clinician with important indications about the progress of ccrtain diseases. By means of special stains, which consist of a mixture of neutral, acid and basic dyes, it is possible to distinguish three groups of granulocytes. This is because the granules contained in their cytoplasm have a different pH-dependent affinity for these dyes. The delicate granules of one group stain with both the basic (blue) and acid (red) dyes, being thus coloured violet and these cells are termed the neutrophil granulocytes. The coarse granules of the second type, the acidophil o r eosinophil grant~locytes, stain selectively with the acid, red dye (e.g. eosin). Making up only 2 - 1 5 s of the total granulocytes, they are far less comlnon than the neutrophils which, depending on the species, amount to 40-75s of the white blood cells. The basophil granulocytes, sometimes referred to as blood mast cells, comprise only 0.5-1 % of the total leucocytc count. As their name indicates. their coarse granules react with the basic component of the stain (e.g. haematoxylin or methylene blue) which colours them dark blue or neta achromatic all^ dark violet. The light-blue-stained nucleus of the basophils is more or less completely covered by the granules.

Monocytes, Lympl~ocytes,Thronibocytes Monocytes The monocytes are large cells 10-15 pm in diameter and they have a round o r kidney-shaped nucleus and ample cytoplasm. They, too, display amoeboid movement and their phagocytic activity is well developed. They are therefore termed rnacvophages. Special staining methods will demonstrate delicate granules in their cytoplasm. Their number varies, according to species, from a minimum of 2 %-3% to a maximum of 4%-10% of the total leucocytes. Thcre is doubt about their origin but is seems likcly that they can develop from the reticulum of the red bone marrow as well as from thc reticulum of the lymphatic organs.

The lymphocytes (1) constitute the second large group of white blood cells. They differ morphologically, functionally and genetically from the granulocytes. Their number per 41 of blood varies considerably between species and also shows considerable individual and age variation but it ranges between a mininlum of 20% and a maximum of 70% of the leucocytes. It is possible to differentiate two forms with the light microscope. By far the most common, comprising about 9070, are the small lymphocytes, the remainder being the large ~ymphocytes. The small lymphocytes measure about 6.5 ! m A and are therefore of similar size to the erytl~rocytes.They are, however, spherical in structure and possess a relatively large, chromatin-rich nucleus which is surrounded by a narrow border of cytoplasm. They are not able to phagocytose and their amoeboid movement is less than that of the granulocytes. The large 1ym.phocytcs have a diameter of 10-15 lrm. Their nucleus is looser in structure and surrounded by a broader rim of cytoplasm in which isolated granules can be deinonstrated with the aid of special stains. The lymphocytes originate in the bone marrow, in the cortex of the thymus and in the germinal centres of peripheral lymphatic organs. Accounts of thcir differentiation'into immune cells may be found in textbooks of histology.

ThrombocytesThe thrombocytes ( I ) , also known as blood platelets, have a diameter of 2 4 p m and are approximately round or spindle-shaped, Dctermination of the number of platelets requires special methods hecause they quickly disintegrate after leaving the circulation; there are said to be 200,000-800,000 per /il of circulating blood. Blood cell i ~ u m b e r s t h e most important domestic mammals1 of Erythrocytes Species Num bcr Diamcter N u ~ bcr n 1nill.Ip1 pin thousand per lrl NeutroFhils Leucocytes Percentage distribution Eosinophils Basophds

ProJnbOcytes Number millions Lympho- Mono- per p l cytes cytes-

Dog Cat Pig Ox Sheep Goat Horse

' After Eder: Das Blut. In: Schcunert/Trapt~nann,Lehrbuch der 7Jeterinir-Physiologje,6th Ed. 1976.'" S c r also chaprcr "lymphatic system".

6

Organs of haematopoiesis, Development of blood cells

These anucleate structures consist o f a stainable groundsubstance, the hyalomer, and a centrally situated granulomer which consists of a number of granules. T h e thrombocytes are the product of the bone marrow giant cells, the megakaryocytes, from which they arise by budding-off of cytoplasmic excrescences. When their cytoplasm has been used-up in this manner the megakaryocytes die. T h e function of the throlnbocytes is to liberate prothrombin, when they break up, froin which chrombin then develops. This in turn converts the fibrinogen o f the blood plasma into fibrin which stops the flow of blood.

ans of haematoIn the embryo both the earliest forination of blood and the ~ r i m a r y anlage for blood vessels occur in the mesoderm of the yolk sac. A t this site the mesenchymal stem cells of the blood give rise first t o the haennocytoblasts. T h e latter are capable of ~ e r p e t u a l division and from them originate, amongst other cells, the primitive haemoglobi~l-containing erythroblasts. As blood cell formation (haematopoiesis) ceases in the yolk sac, it is taken over by the mesenchymal component of the liver anluge, where not only primitive erythroblasts but also granulocytes and megakaryocytes develop. Subsequently the spleen becomes a site of blood cell formation. As development of the foetus advances these organs cease t o form blood cells and haematopoiesis is taken over by the red bone marrow (medulla ossium rubra) which continues t o maintain the supply of myeloid cells, that is the erythrocytes, granulocytes, monocytes and thrombocytes, throughout life. This process of continually renewing the blood cells continues in the adult. T h e bone marrhw is situated in the marrow cavity and in the spaces of the spongy substance of the bones. Despite its scattered distribution the bone marrow, which is under huinoral and neurovegetative control, is a functional unit. While in the growing individual the bone marrow is responsible for increasing the absolute number o f blood cells, its function in the adult is t o maintain the normal quality and quantity of the blood cells. F o r this reason the marrow cavity of y o u n g animals consists almost entirely of bloodforming red marrow, whereas in the adult the latter is confined t o the spongiosa of the short and flat bones and the ends o f long bones while about half the marrow organ is converted into yellow o r fatt-7 marrow (medulla ossium

flava) .T h e b o n e m a r r o w consist of reticular connective tissue, the cells of which form a delicate meshwork within the marrow cavity permeated b y numerous thin-walled blood vessels which arise from the wasa nutritia. T h e blood passes from the arterial capillaries through funnel-shaped connections into the ramifications of the venous sinuses ( 2 / F ) . T h e specially constructed, extremely thin endothelial wall of these sinuses allows the easy entrance of young blood cells. Within the intercellular spaces of the reticular tissue one can find all the immature and adult stages of blood cells formed by the active red bone marrow. T h e red bone marrow is not only an organ of liaeniatopoiesis b u t also an important component of that complex defence mechanism of the body which is collectively referred t o as the reticuloendo~helial system (REX). Both the reticulum cells and the vascular endothelia of the marrow are competent in phagocytosis. T h e y can take up and deal with particles and substances originating from within o r outwith the body and they participate in the formation of antibodies. However, macrophages and plasma cells arising from the reticulum cells are capable of similar ful~ctions. Formation of the fat marrow is also a function of the reticulum cell which, by storing lipids, assumes the appearance of a typical adipose cell. T h e fat m a r r o w is a reserve fat depot which is utilised in prolonged fasting and in the course of serious illness. I t then becomes changed into what is termed gelatinous marrow.

Development of blood cellsT h e erytlarocytes g o through a number of ~ n t e r i n e d ~ a stages in the course of thew developinent. te

Erythropo~eszscommences during embryonic development when ret~culumcells are transformed into haemocytoblasts. These glve rise t o the erythrocyte stem cells, thcproerythroblasts W ~ t h formation the o f haernoglobin the latter change into macroblasts (eryth~oblats)which have a nucleus of loosestructure. T h e erytlil-oblasts decrease in slze, their mlcleus bccoines dense and the tinctorla1 behaviour of

Blood vesscls, structure and function

7

the cytoplasm is altered as they change into normoblasts. The normoblasts are still able to divide. The transition from the normoblast to the anuclear erythrocyte is completed by the extrusion, o r more rarely the brealr-down, of the nucleus. Nucleated erythrocytes can be observcd in the circulation for short periods after, for instance, severe loss of blood o r during diseases which are associated with an increased turnover of red blood corpuscles. The stem cells of the granulocytes are also derived from the h a e m o ~ ~ t o b l a s t s ; they are the myeloblasts which have spherical nuclei and basophilic cytoplasm. The next intermediate stage is the promyeloyte and this is followed by the myelocyte which contains granulcs of spccific staining reaction. The cells arising from the myclocytes show striking changes in their nuclei. At first the nucleus is rounded but it then becomes indented and thus characterises these cells as metamyelocytes or immature forins. With further transformation of the nucleus the cell enters the circulation as the rod-shaped form of the granulocyte which has been discussed earlier. The final stage in the development of the polymorphonuclear granulocyte (1) is attained when the nucleus segments into several connected limbs. The thrombocytes originate, as has already been described, by budding from the megakaryocytes of the bone marrow. The latter, which may measure up to 5 0 p m in diameter when mature, develop Megakaryoblasts originate from the through several intermediate stages from the n~e~akaryoblast.

haemo ytoblasts. A proportion of monocytes develop in the bone marrow by an essentially similar route, since they mature through one intermediate stage from the n7onoblasts which also originate from the haemocyroblasts. The remaining monocytes develop from the reticulum cells of the lymphatic organs. The plasma cells of the bone marrow and of the peripheral lymphoid organs are reactive forms of the reticulum cells. Antigens, such as bacterial brealr-down products, stimulate the development of these immunoglobulin-producing cells. The lymphocytes belong to the lymphatic series of blood cells. Because of their origin in the mcsenchymal connective tissue they possess throughout life a multipotentiality which gives them the power to differentiate as necessity dictates. Proliferation and differentiation to immuno-competent cells takes place in all lymphoid organs.

Blood vessels, structure and function(2-4) If one compares the total blood volun~e the body to the capacity of the blood vascular system, it is of obvious that not all the organs and body regions can be supplied all the time with a constant amount of blood. If we further consider that substantial amounts of blood can be t e m ~ o r a r i l v retained in various organs which act as blood reservoirs, it is evident that the peripheral circulation must posscss a mechanism bv which the blood flow can be regulated. This mechanism is able. in balanced u interrelatio~~ship with the central organ, the heart, to supply the various organs with the appropriate amount of blood required to perform their specific functions. This thesis is supported firstly by the morphological demonstration of numerous s~ecialised structures in different regions of the vascular tree and, secondly, by their interpretation on a haemodynamic basis. From the heart arise the arteries (2/A; 4/black) which spread throughout the body, ever decreasing in size until the very narrow arterioles or precapillary arteries 2/B) terminate in innumerable capillaries ( l E ) which form an extensive vascular bed. Thence the blood is released into the narrow venules o r postcapillary veins ( / C ) . The precapillary arteries, the capillaries and the postcapillary veins form what is sometin3es known as the terminal circulatzon; here the exchange takes place between blood and tissues or cells of all those substances which are required for their multifarious functions. The venules, following on from the capillaries, carry the blood into the venous side of thc circulation. This consists of the veins which progressively increase in lumen diameter and which eventually carry the blood back to the heart ( 2 / 0 ; 4/long lines). The walls of the vessels, excluding those of the terminal circulation, consist of three layers: the tunica interna s. intima (2/a, b, c), the t m i c a media (/d) and the t m i c a externa (/e, f). It should bc noted that the vessels show quantitative, qualitative and structural differences in response to the different mechanical demands made on them and the special functions thcy have t o perform in the different regions of the body. This applies especially to the structure of the tunica media of the arteries and partly also to that of the veins.

-

Arteries

Arteries( 2 / A; 4 )T w o structural types of arteries can be recognised even o n gross examination. The first type includes the vessels near the heart, the aorta and its cranially-directed branches as well as the pulmonary trunk and its large branches which enter the lungs. T h e o ell ow colour of all these vessels and their extreme distensibility are due to the large amounts of elastic fibres and membranes present in the media ( 2 / d ) . These are, therefore, elastic arteries. Towards the periphery these elastic arteries gradually merge into the second type which are reddish o r white, thick-walled muscular arteries. The intima (/a, b, c) of both types of arteries consists of endothelium ( l a ) , a single layer of flat, rhomboid cells which lies u p o n an elastic membrane known as the lamina elastica interna (lc). Between these t w o layers there is sparse collagenous tissue representing the lamina subendothelialis ( l b ) . T h e lamina elastica interna of the elastic arteries gradually merges with the concentrically layered elastic membranes which form the basic ground structure of the media ( l d ) . The elastic larnellae are connected to the muscle cells which regulate the tension of the arterial wall. The significance t o the circulation as a whole of the structure o f the media of these arteries can best be demonstrated using the aorta as an example. Blood which has been pumped into the aorta under systolic pressure puts the media under elastic tension, whereby some of the power produced by the heart is temporarily retained as potential energy. During the diastolic pause this is changed into kinetic energy by the contraction of the vessel wall s o that the blood expelled f r o m the heart in rhythmic strokes is transported to the periphery in a much more even stream. T h e function o f the aorta, and the succeeding arteries of elastic type, may thus be compared with that of an expansion chamber. T h e arteries of muscular type act as distributing vessels and have the task of carrying the blood to the appropriate organs. As they d o so, the pressure of the blood causes their walls to stretch in both longitudinal and circular directions. Depending o n the relationship between the arteries and their surrounding tissues there is, especially in the region of the limbs, considerable stretching in the longitudinal direction. The muscular arteries respond to these pressure changes by the organisation of the various tissues in the media and the tunica externa. There is usually a well-developed internal elastic lamina (2/c) followed by a media ( l d ) largely composed of smooth muscle. The vascular lumen is surrounded by tracts of muscle tissue which contain different amounts of elastic fibres and which are arranged in spiral layers orientated in various directions and variable gradients. The media, being able to respond t o this transverse tension, is therefore in a position to adapt to changing demands by constricting o r dilating the lumen and s o regulating the blood pressure within the arterial system and maintaining it within physiological limits. If, due to degenerative changes o r hardening of the arterial wall, this constantly-active regulatory mechanism is lost, then permanent hypertension may follow with a danger of rupture of the brittle arteries. T h e variable longitudinal tension and distension of the arterial wall are taken u p by the tunica exteyna which is made u p of a lamina clastica externa and tunica adventitia. T h e tunica externa (le, f)consists of collagenous and elastic fibres which are interwoven and crossed in helical fashion. Furthermore, the tunica externa ensures that the arteries arc built into their surroundings in a functionally correct manner. There are some organs, such as the brain and the kidneys, which have s o high and constant a requirement for oxygen that they need a blood supply independent of other circulatory fluctuations. O t h e r organs, like the gastrointestinal tract, lung and slreletal musculature are supplied with a variable amount of blood depending o n their clianging degrees of activity. In order t o prevent excessive demands being made o n the heart and to obtain the most economical use of the available volume of blood, the circulatory system is able t o provide certain areas with a preferential supply and others with less blood whenever this is necessary. Although arteries o f all sizes can reduce the diameter of their lumina to a certain extent, they cannot completely occlude them, and consequently there are other blood vessels which participate in the regulation of blood flow to the organs. These are the arterioles orprecapillaries which are an important component of the terminal circulation ( 2 / B ) . Their lumina are often no wider than those of the capillaries following them. Since their media consists of but a single layer of muscle fibres and the elastica interna is broken u p into a netwol-lr of fibrcs, they can completely close their lumina thus achieving an alternative method of controlling the blood stream. Blood stream regulating structures of another type occur, their occlusive mechanism being characterised by the presence of swellings o r cushions of longitudinal muscles o r cpithclioid muscle cells which

Arteries

9

bulge the intima into the lumen during contraction and thus bring about their complete closure.'' Thcse special structurcs occur in the skin, lungs, erectile tissue and in certain other organs.

:'The Gcrlnan

term Drosselarterien (rhrocrlc aricrics)

describes their mode of acrion

Veins

Veins( 2 / D; 4 )T h e Venous side o f the circulation has the function of returning t o the heart a continuous stream of blood which has lost more than 8 0 % o f its systolic pressure through the flow-resistance of the arteries, arterioles and capillaries. A completely differcnt haemodynamic function is demanded from the venous systctn than f r o m the arterial sidc of the circulation. This is achieved by the general make-up of the veins and their specialized structures and, in ~ a r t i c u l a r by the topography and specialized function of certain , parts of the venous system. Firstly it should be pointed o u t that the number of veins is much greater than the number of arteries because the latter are often accompanied b y two, o r even more, collateval veins. Furthermore, their number is increased, especially in the skin, by veins and collateral vessels w i t h which there is n o accompanying artery. Added t o this the lumina of the veins are always wider than those o f their accompanying arteries and in many sites thcy form networks s o that the potential volume of the venous system is much greater than that of the arterial counterpart. In this connection o n e must stress that the spleen, liver, lungs and skin are able to store large amounts of blood and then return it t o the circulation when required. T h e necessity t o shunt blood into venous branches, comparable with railway-sidings,