Avian Histopathology avian Histopathology Histopathology Learning Module 1 – Learning Component 1...
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Avian Histopathology Learning Module 1 – Learning Component 1 Introduction, Terms, and Language of Pathology
Transcript of Avian Histopathology avian Histopathology Histopathology Learning Module 1 – Learning Component 1...
Avian Histopathology
Learning Module 1 – Learning Component 1Introduction, Terms, and Language of
Pathology
Presenter
Presentation Notes
This is the first learning component – Learning Component 1 in Learning Module 1. This learning component presents some differences between birds and mammals and reviews the terms and language of pathology.
Bird Facts
• 9300 Species of Birds– >22,000 Sub-Species– 166 Families
• 27 Orders
• Wide Variations– Size– Behavior– Diet– Flight
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There are many species of birds and they vary greatly. For example, think about the differences between a hummingbird and an ostrich.
Birds Are Not Mammals
• Differences in Anatomy– Beaks– Feathers– Accessory Structures– Lungs and Air Sacs
• Pneumatic Bones– Crop, Proventriculus, Gizzard– Ceca
• Not present in all avian species
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Presentation Notes
Birds have characteristic features that make them distinct from mammals. Some important features unique to birds include beaks, feathers, lungs and air sacs, a digestive tract that includes crop, proventriculus, gizzard, and ceca. Not all species of birds have ceca.
Avian Histopathology
• Basic Responses of Avian Tissues to Injury– More Similarities Across Avian Species than
Differences– Faster Response Times than Mammals
• Inflammation– Hours not Days– Days not Weeks
• Basic Patterns are Similar to Mammals– Language of Pathology Does Not Change
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Presentation Notes
Avian tissues respond to injury in basic ways that have many similarities to the responses found in mammals. The basic terminology or language of pathology that you have already learned is applicable to avian histopathology. Differences in response time are important. Think hours, not days, and days, not weeks for lesion development in birds compared to mammals. Remember also that all avian cells are nucleated, including erythrocytes and thrombocytes, so avian tissues tend to look more cellular under the microscope than mammalian tissues.
Language of Pathology
• Disturbances of Circulation include:– Congestion
• Usually of little help in making a disease Dx– Hemorrhage– Thrombosis
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The terminology for disturbances of circulation is basically the same for birds as for mammals. Bird thrombocytes are nucleated, have significant phagocytic ability, and are relatively less important in the initial blood clotting process than are mammalian thrombocytes. Thrombocytes in birds are the major phagocytic cell within the blood vessels.
Language of Pathology
• Inflammation• Fibrin• Platelets• Heterophils
– Heterophilic – Not Purulent Inflammation
• Eosinophils• Lymphoid cells• Macrophages or Histiocytes• Fibroblasts and Collagen• Giant Cells
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Presentation Notes
Heterophils are the bird’s equivalent of mammalian neutrophils, but differ from neutrophils in having fewer proteolytic enzymes in their granules while retaining abilities to be highly efficient at phagocytosis and bacterial killing. We use the term heterophilic inflammation – not purulent inflammation in avian histopathology. Read the sections assigned in the 3rd edition of Avian Histopathology about heterophils and these other cell types. Birds respond with giant cells to the caseous necrosis generated by the death of heterophils. A giant cell granulomatous response in birds occurs because heterophil enzymes don’t liquefy the dead cells, thus granulomas must not be automatically considered to be due to fungi, parasites, or some other foreign body. These other “things” also cause granulomatous inflammation.
Terms
• Apoptosis• Necrosis:
– Caseous most common• Hypertrophy• Hyperplasia• Metaplasia• Neoplasia• Atrophy
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Presentation Notes
Apoptosis and necrosis are terms that are used to refer to cell death. Apoptosis being programmed or normal cell death and necrosis being a lesion. Caseous necrosis is so common in birds because of the lack of certain proteolytic enzymes in the granules of heterophils. The rest of the terms on this slide refer to disturbances of growth. If you don’t remember their meanings, please refer to Avian Histopathology, 3rd ed. or any textbook on pathology.
Patterns of Injury
• Relation to Normal Histology• Focal• Multifocal• Diffuse• Expanded• Collapsed• Intralesional
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Presentation Notes
Patterns of injury are important to determine as we identify the responses to injury (disturbances of circulation, inflammation, cell death, disturbances of growth). We will illustrate the terms using specific digital images and you will practice their use as you examine and identify changes in the virtual slides assigned. Lesions and/or features should be stated in relation to normal histologic structure for each respective organ.
“Things”
• Parasites• Fungi• Foreign Material• Mineral• Urates• Pigments• Fat
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Things are features of interest or importance that provide diagnostic clues as to the nature and cause of the lesions. These “things (features) will be illustrated in digital images and you will gain experience in recognizing them as you work with the assigned virtual slides.
“Things”
• Bacteria• Viral Footprints
– I/N Inclusions– I/C Inclusions
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Bacteria and footprints of viral infection (inclusion bodies) may be present and are described as being intralesional. Not all bacterial or viral infections result in visible organisms or footprints, but, when present, are important. Bacteria may be visible due to growth after death (post-mortem) and must be differentiated from bacteria associated with lesions.
Hemorrhage Example
• Pheasants– 24-25 Weeks– 26,000 in Flock– Mortality Increased Over Past Month– “Birds Just Lay Down and Die”
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This is a case example in which hemorrhage was a significant gross and microscopic lesion. Hemorrhage resulted from systemic infection with Pasteurella. The lesions found had to be differentiated from those caused by viral infections including exotic Newcastle disease, and avian influenza.
Gross Lesions in Crop
A B
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The image on the left (A) shows the crop exposed at the thoracic inlet. Note the large amount of fresh blood. The image on the right (B) shows the mucosal surface of the crop with several focal areas of hemorrhage. One area of hemorrhage in the base of an ulcer is identified by the red arrow.
Crop and Proventriculus
A B
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Image A Shows hemorrhage in the mucosa of the crop. These lesions are multifocal. Image B shows multiple coalescing (multifocal to diffuse) hemorrhages in the mucosa of the proventriculus. Ulcers are multifocal in both organs and associated with the hemorrhage.
Liver, Spleen, and Serosa
A B
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The liver on the left (A) has multiple small white foci that are focal areas of necrosis. The spleen and serosa in the right image (B) have multifocal hemorrhages. These are small and are termed petechiae (petechial hemorrhages).
Proventriculus
A B
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Image A is a low power image of the esophageal-proventricular junction. This region, outlined by the rectangular box, has a large collection of lymphocytes arranged in nodular and diffuse patterns. Collection of lymphocytes in this esopheageal-proventricular region is normal. Hemorrhage is diffuse within this region. A proventricular submucosal gland is identified with the circle. Image B is a higher magnification of A showing the diffuse hemorrhage and blood vessels (circles) filled with blood (congestion).
Proventriculus – Higher Magnification
A B
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Higher magnification of the blood vessels (A) shows accumulation of platelets and development of fibrin thrombi. Image B shows the platelets (black arrows) and clumps of bacteria (box) within the lumen of a vessel
Thrombosis and Platelets
• Example is from Broiler Breeders• Increased Mortality and Drop in Egg
Production• Swollen Kidneys
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This case involved broiler breeders with increased mortality in the flock and shows platelets and fibrin thrombi in kidneys.
Platelets
A
B C
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The top image (A) shows a kidney with a fibrin thrombus in a blood vessel (circle). Other lesions are visible and include dilated tubules, expansion of interstitial tissue and accumulations of heterophils. Image B is a higher magnification of the vessel and image C is an even higher magnification that shows platelets (arrow – the small dark cells) and the eosinophilic material that is fibrin.
A B
C D
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Another region within the kidney shows a more well- developed thrombus. Images A-D are progressively higher magnifications that show the small darkly-stained platelets within this thrombus.
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