Histology Atlas : Normal structure of Salmonids by anil amin

I N T E R NAT I O NAL E D I T I O N

Histology Atlas Normal structure of Salmonids

A colour atlas --- English, German, French and Spanish legends

A. B. Amin and

L.Mortensen, T.Poppe

Histology Atlas NORMAL STRUCTURE OF SALMONIDS

This project has been partly supported by â&#x20AC;&#x153;Landsdelsutvalget for Nord-Norge og Namdalen.â&#x20AC;?

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I N T E R NAT I O NAL E D I T I O N

Histology Atlas Normal structure of Salmonids

A colour atlas --- English, German, French and Spanish legends

A. B. Amin and

L.Mortensen, T.Poppe Illustrations

J. E. Bronder Legends translated by: French Eivind Carlsen Jakob Larsen

German Mikail Schuster Till Uhlig

Akvapatologisk Laboratorium AS BODĂ&#x2DC; - NORWAY 1992 IV

Spanish Sergio Haro Iciar Martinez

Anil B. Amin Scientiﬁc director, Akvapatologisk laboratorium AS, Bodø Consultant, Patologisk Anatomisk Laboratorium, Nordland Sentralsykehus Bodø Liisa Mortensen Consultant, Akvapatologisk laboratorium AS, Bodø Mikrobiologisk avdeling, Nordland Sentralsykehus Bodø Trygve T. Poppe Norges Veterinærhøgskole Oslo

PREFACE It takes thorough knowledge to breed fish successfully. Every step in the process of managing a biological production must be mastered if success is to be achieved qualitatively and economically. Serious outbreaks of diseases, unfortunately, has been a common problem for most fish farmers. The occurrence of diseases are mainly due to lack of adequate knowledge and control in different stages of biological production. Most of the diseases are results of complex interaction between various etiological factors, and an assessment of a given disease often requires the use of many different diagnostic tools. One of these is histopathology. The study of microscopic structure of various tissues of the body is called histology.The individual tissue has a characteristic structure which is related to the function of the organ and the organism as a whole. The knowledge of this normal structure is therefore necessary to appreciate the changes in the disease state at the microscopic level (histopathology). This book intends to introduce the reader to tissue morphology of fish using salmonids as a model. Other species are mentioned briefly to highlight essential morphological differences between related species. It is not possible to be proficient in histopathology in one semester.lt is a maturation process, where the data base of biological knowledge needs to be enriched by experience. This atlas is not ment to be read as an ordinary textbook, but rather to be used at the microscope to compare the slides with the figures and text in the book. The text has been kept short so that the essential histological features can be quickly assimilated by the students. Glossary is included at the end of each chapter for benefit of the beginners. In some

places physiology is briefly mentioned for better understanding of morphological and functional correlation. Readers are, however, urged to consult standard textbooks of physiology. Most of the microphotographs show tissue sections stained by Hematoxylin and Eosin. This is the standard stain, and every histologist has to learn this method thoroughly. Other stains are only applied to demonstrate special tissue characteristics. Magnification factors of tissue sections have purposely not been given. Such ciphers do not mean much by themselves, and we feel that students of histology rather should become proficient in estimating the size of tissue components and cells by applying the built in micrometers in the tissues, namely the red and white blood cells. Recently a method based on the use of an external micrometer has been published, and this method is described in Appendix III by kind permission of the author and the publisher. Orientation of most of the gross photographs is facilitated by placement of in lower the left comer. In order to make this atlas readily usable at the international level, the legends are presented in four languages, viz. English, German, French and Spanish. Writing this book has been a challenge, as we have tried to help the greenhorns in biology as well as the veterinarians who might feel that a brush up of knowledge is in place. We do not intend to cover any curriculum list. We know that our potential readers will display quite a wide spectrum of expectations and expertise, and therefore we appreciate any kind of criticism, both positive and negative,that might be given. We have enjoyed making this book, and we do hope that our readers will find it useful.

In Memory of My Father Late Dr. B. M. Amin My First Teacher in Pathology A.B.A.

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ACKNOWLEDGEMENTS The authors wish to thank all who have contributed in preparation of this atlas. We wish to acknowledge the generous and unfailing encouragement given by Professor Malcom Jobling, University of Tromse. Histotechnologists have played an important role “behind the screen” in the gestational phase of this atlas. We are deeply indebted to our chief histotechnologist Taru Amin for her inordinate care and much tried patience in preparing histological sections of high quality suitable for microphotography. We would also like to mention Parvez Massey and the rest of the histology staff at the Nordland Central hospital for the help they have offered. We are particularly grateful to our colleague Jan Erik Bronder who painstakingly and meticulously prepared the illustrations to bridge the gap between the text and microphotographs. We are grateful to Ivar Fjellanger and Raymond Mortensen who examined the manuscript critically and came forward with valuable suggestions. Our thanks to Gro Sørmo and Hilde Fumnes for their secreterial help in preparation of the manuscript. Special thanks are also due to Âshild Eftevâg for help in the French part of the manuscript. We were fortunate in having colleagues Eivind Carlsen,Jakob Larsen, Mikael Schuster, Till Uhlig, Sergio Ham and Iciar Martinez around us who willingly offered their help in preparing multilingual legends. We and our readers will be grateful to them. For the preparation of the book’s index, software consultant Muni Bandlamoori offered his valuable service. We wish Offset Nord AS and Brandt Repro AS, to know how grateful we are for their skill and help. No words can express the understanding of our families whose time has been invested in preparation of this book and who patiently supported our engagement in this project.

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Contents PREFACE .................................................................................................. VI ACKNOWLEDGEMENTS ...................................................................... VIII 1.0. CELLS AND SUPPORTIVE TISSUE ................................................12

1.1. TISSUES AND ORGANS ............................................................................. 12

2.0. RESPIRATORY SYSTEM ..................................................................33 3.0. SKIN AND SCALES...........................................................................43

3.1. SKIN.............................................................................................................. 43 3.2. SCALES ........................................................................................................ 44

4.0. CARDIOVASCULAR SYSTEM .........................................................54

4.1. THE HEART.................................................................................................. 54 4.2. ARTERIES AND VEINS ................................................................................ 55 4.3. LYMPHATIC SYSTEM .................................................................................. 56

5.0 HEMATOPOIETIC TISSUE.................................................................66

5.1. HEMATOPOIETIC KIDNEY.......................................................................... 66 5.2. SPLEEN ........................................................................................................ 66 5.3. THYMUS GLAND ......................................................................................... 66 5.4. RETICULOENDOTHELIAL SYSTEM .......................................................... 67

6.0. BLOOD AND LYMPH ........................................................................73

6.1. ERYTHROCYTES ........................................................................................ 73 6.2. LEUKOCYTES.............................................................................................. 74 6.3. THROMBOCYTES ....................................................................................... 74

7.0. DIGESTIVE SYSTEM ........................................................................79

7.1. GASTROINTESTINAL TRACT..................................................................... 79 7.2. LIVER............................................................................................................ 81 7.3. PANCREAS .................................................................................................. 81 7.4. SWIM BLADDER .......................................................................................... 82

8.0. THE KIDNEYS..................................................................................100 8.1. RETICULOENDOTHELIAL PART .............................................................. 100 8.2. ENDOCRINE PART .................................................................................... 100 8.3. EXCRETORY PART ................................................................................... 100

9.0. ENDOCRINE SYSTEM ...................................................................109

9.1. PITUITARY GLAND ................................................................................... 109 9.2. THYROID ................................................................................................... 110 9.3. THE PINEAL ORGAN................................................................................ 110 9.4. ENDOCRINE ORGANS IN THE KIDNEYS ...............................................111 9.5. ULTIMOBRANCHIALGLAND .................................................................... 112 9.6. UROPHYSIS.............................................................................................. 112 9.7. SACCUS VASCULOSUS .......................................................................... 112 9.8. ISLETS OF LANGERHANS ...................................................................... 112 9.9. PSEUDOBRANCH .................................................................................... 112 9.10. GONADS .................................................................................................. 113 9.11. THYMUS ................................................................................................... 113 9.12. GASTROINTESTINALHORMONES ........................................................ 113

10.0. GONADS ......................................................................................132

10.1. THE TESTES ............................................................................................ 132 10.2. THE OVARIES ......................................................................................... 132

11.0. NERVOUS SYSTEM .....................................................................142

11.1. STRUCTURE ............................................................................................ 142 11.2. CENTRAL NERVOUSSYSTEM ............................................................... 143

12.0. SENSORY ORGANS .....................................................................154

12.1. THE EYE .................................................................................................. 154 12.2. OLFACTORY TISSUE .............................................................................. 155 12.3. GUSTATORY TISSUE .............................................................................. 155 12.4. LABYRINTH ANDAUDITORY TISSUE .................................................... 155 12.5. LATERAL LINE TISSUE ........................................................................... 156 12.6. PINEAL ORGAN ....................................................................................... 156

APPENDIX I : ........................................................................................170 LABORATORY METHODS IN HISTOLOGY ..................................................................170

APPENDIX II : .......................................................................................173 STAINING METHODS .....................................................................................................173

APPENDIX III : ......................................................................................181 TECHNIQUE FOR MEASUING STRUCTURES IN HISTOLOGICAL SECTIONS .......181

Contents XI

1.0. CELLS AND SUPPORTIVE TISSUE All tissues are made up of cells. Each cell consists of a cell membrane, cytoplasm and one or several nuclei.

depending on the cell type. In a living organism there is a continuous cell division to replace the dead cells and to promote growth of the organism.

The cell membrane is selectively permeable for different types of chemical substances depending on the function of the cell.

All the cells in an organism have the same chromosomes, so that each cell has the potential to develop into a specialized cell. This is true also for the fertilized egg, which, as the egg develops divides into individual cells which ultimately specialize for different functions. This is called specialization of the cells and it is probable that one part of the chromosome becomes active at the time of transfer of information from mother cell to the daughter cell. In this way, various types of cells, tissue and organs are built up.

The cell contains a nucleus which is enclosed in a nuclear membrane. The nucleus controls the function of the cell and contains all the genetic information necessary for cell division and function. This genetic information is localized within the chromosomes in the nucleus. The cytoplasm, which is a jellylike substance, constitutes the major part of the cell. In the cytoplasm, various types of secretory and excretory processes are undertaken. Various structures like mitochondria, endoplasmic reticulum etc. are found in the cytoplasm, as shown in ill. 1.1.

1.1. TISSUES AND ORGANS Cohesive aggregations of similarly specialized cells constitute tissues and more complex assemblies of the tissues form organs. A group of organs related to each other and functioning together constitutes an organ system e.g. the digestive system. In many tissues different types of chemical substances are found between the cells forming what is known as ground substance or matrix.

The life span of a cell varies from days to months,

In highly developed animals the body is made up of different types of cells and tissues: A: Epithelial cells B: Supportive and connective tissue, which is divided into 1) connective tissue and elastic tissue 2) fat tissue 3) cartilage and bone tissue C: Muscle tissue ill.1.1 Cell a) cell membrane, b) cytoplasm c) mitochondrium, d) endoplasmic reticulum (rough), e) smooth endoplasmic reticulum, f) Golgi apparatus, g) vacuoles, h) nuclear membrane, i) chromatin, j) nucleolus

D: Nerve tissue E: Fluid (blood) and bloodforming cells

Different types of epithelial cells and their functions are demonstrated in ill. 1.2. and table 1.1.

A: EPITHELIAL CELLS (FIG. 1.1.,1.2., 1.3.) The functions of epithelial cells are - to form a protective surface layer (epithelial layer) - to form glands with secretory and/or excretory functions - to form sensory tissues.

Squamous epithelium

Columnar epithelium with mucous cells.

Columnar epithelium with cilia.

PseudostratiďŹ ed columnar epithelium

StratiďŹ esd squamous epithelium

Umbrella cells Transitional epithelium

///. 1.2. Epithelial cells a) mucous cells, b) epithelial cells, c) cilia, d) basal layer 13

Table 1.1. Different types of epithelial cells and their function

CELL TYPES

FUNCTION

I: COVERING EPITHELIAL CELLS - single layer of

squamous epithelium cells - stratiďŹ ed squamous epithelium

LOCALIZATION

external and internal

eg. peri- and

coverings of organs

endocardium of the heart

protection and covering

eg. epidermis (skin), oral mucosa

II: COVERING EPITHELIAL CELLS eg. epithelial cells of - simple columnar-/cubic

secretory/

intestinal mucosa,

epithelial cells

excretory

kidney tubules.

- simple columnar epithelial

protection

eg. nasal cavity,

sensory

auditory canal

cells with cilia

III: GLANDULAR TISSUE - columnar epithelial cells

eg. glands in secretory

or glands formed

excretory

stomach, intestine and pancreas

by one to several layers of columnar-/cubic epithelial cells

IV: SENSORY CELLS - simple or multiple

sensory

auditory organ, lateral line structure and taste buds

layers (stratified columnar epithelial cells with/without cilia)

B: CONNECTIVE AND SUPPORTIVE TISSUES In the body there are many types of supportive tissues, like ﬁbrous and elastic tissue, fat, cartilage and bony tissue. Supportive tissues bind the cells together to form organs. They also support the organ in its proper place and ﬁll up empty space.

2) Fat tissue (Fig.1.5, ill. 1.3.) Fat tissue is composed of fat cells, in which cytoplasm is full of fat. This fat pushes the nucleus towards the periphery against the cell membrane. In routinely processed histology sections, fat is removed by alcohol, and fat cells therefore appear as having vacuoles in their cytoplasm.

1) Fibrous tissue and elastic tissue (Fig.1.4,ill.1.3.) Fibrous tissue is composed of spindle shaped cells which are called fibroblasts. Fibroblasts have oval nuclei with sharply pointed ends. Fibroblasts form fibre rich substance, collagen tissue, which have supportive functions in various organs. The elastic tissue consists of cells with oval nuclei and sharp pointed ends, but appear different from fibrous tissue in that fibres of elastic tissue are wavy and stain blue with hematoxylin and eosin (HE stain), which is the routine stain used in histology.

3) Cartilage and bone tissue (Fig. 1.6, 1.7) Cartilage tissue consists of cartilage cells (chondrocytes) and collagen or elastic tissue in a ﬁrm matrix. Depending on the type of ﬁbres dominating the matrix, the cartilage can be named, as shown in ill. 1.4 and table 1.2.

Hyaline cartilage a) chondrocytes b) Hyaline matrix

Elastic cartilage a) chondrocytes b) elastic tissue

ill. 1.3. Connective tissue a) fat cells, b) fibroblast cells, c) elastic fibres, d) macrophages, e) blood vessels with blood cells Fibrous tissue and elastic tissue, together with fat tissue, have the function of covering and protecting other tissue (e.g. around the heart and the intestine), or as binding and supportive elements in various organs and tissues. (e.g. between skin and underlying muscles and between groups of muscle fibres).

Fibrous cartilage a) chondrocytes b) ﬁbroblasts

ill.1.4 Cartilage tissue

Table 1.2. Different types of cartilage and their characteristics CARTILAGE TYPE

COMPOSITION

Hyaline

Firm matrix with few collagen ﬁbres

Elastic

Firm matrix with elastic Fibres

Fibrous

Firm matrix rich in collagen ﬁbres

Bone tissue is composed of bone cells (osteocytes) and collagen ﬁbres in hard matrix as shown in ill. 1.5. The matrix is composed of collagen tissue and inorganic salts rich in calcium and phosphates and gives bone its unique mechanical properties.

C: MUSCLE TISSUE Muscle cells have the capacity to contract, resulting in movements of various parts of the body. It is composed of muscle ﬁbres organized in groups held together by connective tissue forming myotomes. There are three types of muscle tissue: 1) Smooth muscle 2) Striated skeletal muscle 3) Striated heart muscle 1) Smooth muscles (ﬁg. 1.8) Smooth muscles are composed of spindle shaped cells, and have a central oval nucleus with rounded ends (cigar shaped), as shown in ill. 1.6. - They are found in the stomach, intestinal tract and in larger blood vessels. - They work continuosly, but slowly. Smooth muscle cells can increase in size (hypertrophy) and number (hyperplasia).

ill. 1.6. Smooth muscles a) nucleus, b) spindle shaped muscle ﬁbre, c) nerve ﬁbre

ill.1.5 Bone tissue a) interstitial tissue, b) Haversian canal, c) periosteum

2) Striated skeletal muscle (ﬁg-1.9,1.10,1.11, 1.12,1.13) In comparison to cells in other tissues, the ﬁbres in striated muscles are larger and possess many peripherally located nuclei, as shown i ill. 1.7. In longitudinal sections alternating dark and light bands, which represents the regularly organized proteins actin and myosin, may be seen.

Skeletal muscles are grouped together forming myotomes along the length of the whole body. These muscles are under control of the will (voluntary muscles). In fish there are two types of skeletal muscles, red and white muscles. The red muscles are arranged as a triangular band under the skin along the lateral line. The red muscle fibres are shorter and have a smaller diameter than the white muscle fibres. Red muscle also have higher lipid content and many mitochondria in their cytoplasm. The two types of muscle fibres are used in different swimming activity: -

the white fibres are used in certain strong movements (flight and fight) the red muscle fibres are used in long term quiet movements (normal swimming)

ill. 1.8. Cross striated cardiac muscles a) nucleus, b) cross striations, c) nerve ﬁber D) NERVE TISSUE Nerve tissue is composed of nerve cells (neurons) and supporting cells (neuroglia). Neurons are the structural and functional unit of the nervous system.

ill. 1.7. Cross striated skeletal muscle a) nucleus, b) cross striations, c) nerve fibre 3) Striated heart muscle (fig. 1.14) This type of muscle fibres are differentiated from skeletal muscles by their branching structure. These muscle fibres do not run parallel and therefore both longitudinal and transverse sections of fibres are seen in sections. Another difference is the location of nuclei. These are localized at regular intervals in the center of the fibre instead of at the periphery. Heart muscle fibres are oriented end to end and form a branching network as shown in ill. 1.8. The heart muscle is involuntary (not under control of will).

ill. 1.9. Nerve cell a) nucleus, b) dendrites, c) axon, d) myelin layer, e) nerve ﬁbre, f) Schwann cell nucleus

Neurons: The longer cytoplasmic process of the neurone, called the axon, conducts the nerve impulse away from cell body. The short cytoplasmic process, called dendrites, conducts nerve impulse to the cell body by making contacts with neighbouring neural cells. Neurons are classiﬁed according to the number of dendritic processes from the cytoplasm. - unipolar neurons with one dendrite - bipolar neurons with two dendrites - multipolar neurons with more than two dendrites Neuroglia cells form the supportive elements of the nervous system. Neuroglia cells are classiﬁed according to their structure and are of three types: 1: Ependymal cell: columnar epithelial cells, which cover the inner surface of ventricular cavities of the brain. 2: Astrocytes: cells with many long cytoplasmic extentions which often end on capillaries.

3: Oligodendroglial cells: small cells with few cytoplasmic extentions. E) BODY FLUIDS (BLOOD AND SECRETORY MATERIAL) AND BLOOD FORMING CELLS Blood consists of liquid with organic and inorganic molecules and cells. The ﬂuid portion of blood when not coagulated is called plasma. On coagulation, fibrin and various coagulation factors are removed from plasma and the remainder of the liquid portion is called serum. Three types of cells are found in the blood: - leucocytes (white blood cells) - erythrocytes (red blood cells) - thrombocytes (blood platelets/spindle shaped cells) These cells are described in chapter VI.

REFERENCES: GLOSSARY: Eosin: dye which stains cytoplasm red.

Kehler, Andreas. 1977. Anatomi og Fysiologi. Bind I. Nyt Nordisk Forlag. Arnold Busck, Copenhagen: 17 - 58.

Hematoxylin: dye which stains nuclei blue.

Wheater, P.R., H.G. Burkitt, and V.G. Daniels. 1979. Functional histology. Churchill Livingstone, Nottingham.

Histology: study of the living tissue (is used mainly for microscopic anatomy). Hyalin: structureless (glass like). Chromatin: stainable substance in cell nuclei, consisting mainly of DNA (hereditary substance). Chromosome: composed of hereditary substance, linear thread of DNA Peripheral: outermost, away from central point. Permeable: capable of going through a membrane. 18

FIG. 1.1. EPITHELIAL CELLS IN EPIDERMIS a) Squamous epithelial cells b) Mucous cells c) Scale

ABB. 1.1. EPITHELZELLEN IN DER EPIDERMIS a) Plattenepithelzellen b) Schleimzellen c) Schuppe

FIG. 1.1. CÉLULAS EPITELIAUS DE LA EPIDERMIS a) Células epiteliales planas b) Células espinosas c) Cornea

FIG.1.1.L’ÉPIDERME a) Epithélium pavimenteux stratiﬁé b) Cellules muqueses c) Écaille

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FIG. 1.2. EPITHELIAL CELLS IN EPIDERMIS (PAS STAINING) a) Squamous epithelial cells b) Mucous cells

ABB. 1.2. EPITHELZELLEN IN DER EPIDERMIS (PAS-FÄRBUNG) a) Plattenepithelzellen b) Schleimzellen

FIG. 1.2. CÉLULAS EPITELIALES DELA EPIDERMIS (TINICON DE PAS) a) Células epiteliales planas b) Células mucosas

FIG. 1.2. L’ÉPIDERME (COLORATION PAS) a) Epithélium pavimenteux stratiﬁé b) Cellules muqueuses

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FIG. 1.3.EPITHELIAL CELLS IN BILE DUCT (ON RIGHT) a) Columnar epithelial cell b) Smooth muscle ﬁbres

ABB. 1.3.EPITHELZELLEN IM GALLENGANG (RECHTS) a) Zylinderepithelzellen b) Glatte Muskulatur

FIG. 1.3.CÉLULAS EPITELIALES EN EL CONDUCTO COLÉDOCO (DERECHA) a) Células epiteliales en columna b) Tejido muscular lisa

FIG. 1.3.LES CELLULES DE REVETEMENT DES VOIES BILIAIRES (À DROITE) a) Epithélium cylindrique simple b) Musculeuse ﬁbres lisses

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FIG. 1.4. CONNECTIVE TISSUE (MASSON TRICHROME STAIN) a) Connective tissue b) Cross striated muscle ﬁbre

ABB. 1.4. BINDEGEWEBE (MASSON TRICHROM-FÄRBUNG) a) Bindegewebe b) Quergestreifte Muskelfaser

FIG. 1.4. TEJIDO CONJUNCTIVO (TINCIÓN DE MASSON TRIKROM) a) Tejido connective b) Fibra muscular estriada

FIG. 1.4. LE TISSU CONJONCTIF (COLORATION MASSON) a) Tissu conjonctif b) Fibres musculaires striés

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