Haemolymphatic and Alimentary Pathology Flashcards
What does the bone marrow normally look like at post mortem?
In normal adult animals, the marrow is low cellularity and dominated by fat with a thin rim of active marrow peripherally.
What is Haematopoiesis?
Haematopoiesis concerns the development of erythrocytes, thrombocytes, granulocytes (neutrophils, eosinophils and basophils), monocytes and lymphocytes. All these cell lines complete some or all of their development in the bone marrow. When there is demand for haematopoeisis, extramedullary haematopoiesis can occur in other organs (spleen and liver).
What is hyperplasia of bone marrow?
In Functional hyperplasia there is an increased cellularity of the marrow because of increased production by the haematopoetic cells. Fatty white marrow is converted to cellular red areas beginning in the endosteal zone. Hyperplasia may be in response to a fall in the number of peripheral cells or to an increased demand in inflammatory conditions.
What is the name for the bone marrow itself becoming inflamed?
Myelitis
What is involution of bone marrow?
Involution may be due to many causes such as plant and chemical poisons, radiation, bacterial toxins, ageing and viral diseases, causing hypoplasia or aplasia in one or more cell lines. Marrow fat is relatively resistant to lipolysis but in severe starvation it becomes watery, translucent and pink.
What is Anaemia and how does it occur?
Anaemia can result from either an increased rate of destruction or loss of RBCs, or alternatively from a decreased rate of production (non -regenerative). The signs of anaemia are referable to reduced oxygen supply to the tissues. May be Haemorrhagic, haemolytic.
What are the major pathological features of Anaemia?
Pallor: Due to reduction in haemoglobin
Pulmonary oedema: Depends on the severity of the anaemia
Cardiac changes: If anaemia is chronic, myocardium is flabby, friable and pale.
Liver changes - periacinar hepatic necrosis if acute anaemia.
Spleen - Varies according to cause and course of disease e.g acute haemorrhagic (contracted); acute haemolytic (enlarged and meaty).
Muscle - In chronic anaemia, muscles pale in proportion to loss of myohaemoglobin.
Describe nodular hyperplasia of the spleen
Very common in old dogs - producing demarcated encapsulated swellings. The spleen will have a nodular enlargement and firm consistency. The tissue comprises hyperplastic foci of lymphoid cells or mixed lymphoid cells with areas of EMH.
Describe Primary haemangioma and haemangiosarcoma
Common neoplasms of older dogs (especially large breeds). They are frequently large with areas of haemorrhage and necrosis and may rupture spontaneously or due to palpation causing life threatening intra abdominal haemorrhage. Metastases to lungs and wider are frequent with haemangiosarcoma.
When is contraction of the spleen seen?
Can be marked in association with catecholamine release, shock (e.g hypovolaemia, cardiogenic).
Describe splenic Rupture?
Quite common in the dog (RTA). It may be fatal or additional splenic fragments may form in the surrounding tissues. Congenital accessory splenic fragments may also be found in the omentum.
What are siderofibrotic plaques? (gamna-gandy bodies)
Common lesions in older dogs - yellow, dry encrustations on the capsule - probably sites of previous local haemorrhage with subsequent deposits of Fe, Ca and fibrosis.
What is Haemosiderosis?
RBC breakdown - formation of haemosiderin and some haemosiderin will therefore normally be found in spleen. Excessive amounts can occur e.g in haemolytic anaemia, chronic heart failure.
Describe Infarcts of the Spleen
These tend to occur in the more peripheral zones of the spleen where perfusion is poorer or in diseases which cause vasculitis.
What is the definition of lymphadenopathy?
A regional or generalised lymph node enlargement of unknown/unspecified cause.
What is lymph node hyperplasia?
Hyperplasia of B and or T cell compartments secondary to immunological reactions/infections.
What is lymphadenitis?
It can result when an infectious agent is present in the lymph node - e.g equine strangles. May be accompanied by lymphangitis.
What is anthracosis of the lymph nodes?
Seen as black discolouration of the medulla of the bronchial nodes of dogs in industrial areas.
Why is melanin pigment sometimes seen in lymph nodes?
It can be seen in association with pigmentary incontinence - pigment is taken by macrophages to draining lymph nodes.
When would degeneration of the thymus occur?
Lymphocytolysis can occur in association with a number of viral diseases e.g canine distemper virus, equine herpes virus 1. The thymus is composed of both lymphoid and epithelial tissue, thymic involution is part of the normal ageing process.
Describe common Neoplasms of the thymus
Thymic lymphosarcoma - cats, young cattle and dogs. Signs relate to the space occupying effect of the tumour.
Thymoma - less common, generally slow growing and rarely metastasise. They may be predominantly lymphocytic, predominantly epithelial or mixed.
Where is stratified squamous epithelium found in the alimentary tract?
Lines the mouth, oesophagus, the non-glandular part of the stomach in the pig and horse, the fore-stomachs of ruminants and the anus. This is keratinised in ruminants, the horse and the pig.
Which epithelium lines the stomach/abomasum through to large intestine?
Simple columnar glandular epithelium. This consists of a single layer of cells overlying the lamina propria. in the stomach the glandular epithelium is composed of simple tubular glands with five cell types; Stem cells at the neck, mucous neck cells, parietal cells, chief cells and neuroendocrine cells.
What lines the large intestine?
The large intestine, caecum and colon is lined by a thick layer of glandular mucous epithelium containing many mucus secreting goblet cells. No villi are present in the large intestine. The large intestine absorbs more water and secretes fewer enzymes than the small intestine.
Describe the secretions of the alimentary tract and their functions.
Saliva - flushing effect and antibacterial components, e.g lysozyme, secretory IgA. Mucus - inhibits contact with mucosa, protects surface. Acid - parietal cells in stomach. Digestive enzymes - salivary amylase, pepsin from gastric chief cells, pancreatic and small intestinal enzymes. Bile secretions - kill some pathogens.
Describe the Epithelial defence mechanisms of the alimentary tract?
forms mucosal barrier; tight junctions between epithelial cells prevent entry of macromolecules and pathogens but allow ions and water to diffuse through. Stratified squamous epithelium: multilayered, relatively high cell turnover, may have a keratinised surface layer at some sites.
What is the function of the commensal flora of the alimentary tract?
Act as barrier to pathogens - they secrete volatile fatty acids and compete with pathogens for nutrients. They are essential for digestion in herbivores. Any disequilibrium of microflora can lead to disease.
What are the cell mediated and humoral defences in the alimentary tract?
Lamina propria contains macrophages, B and T lymphocytes, plasma cells, mast cells. Epithelium - intraepithelial lymphocytes. Lymphoid aggregates - peyer’s patches, gut associated lymphoid tissue. Antibody production (IgA), regional lymph nodes, omental macrophages.
hat is a diphtheritic membrane?
Composed of fibrin and necrotic material; secondary bacterial invasion.
What is erosion?
Loss of superficial Mucosa
What is an ulcer?
Loss of deep mucosa.
Describe Erosion and ulcer in mucosa lined by stratified squamous epithelium.
Erosion - Loss of partial thickness of epithelium. Ulcer - full thickness epithelial defect in which there is loss of the entire epithelium down to or deeper than the basement membrane.
Describe erosion and ulcer in mucosa lined by simple glandular epithelium.
Erosion: loss of epithelium and partial thickness loss of lamina propria. Ulcer: full thickness mucosal defect in which there is loss of epithelium and the entire lamina propria, sometimes extending into the submucosa.
What are vesicles?
Vesicle formation is a common response to systemic viral infections that target stratified squamous epithelial cells. It is also seen at mucocutaneous junctions in autoimmune diseases and as a response to thermal injuries. Hydropic degeneration occurs in cells, which swell and undergo necrosis, leaving a fluid filled space (vesicle).
What is brachygnathia?
Short maxilla/mandible
What is prognathia?
Abnormal prolongation of maxilla/mandible
Describe cleft palate/palatoschisis
Inadequate growth of palatine shelves leaves a central defect. Communication of nasal and oral cavities may result in aspiration pneumonia and problems with suckling. Affects hard and/or soft palate.
What is a hare lip/cheiloschisis?
Absence of part of lip rostral to nasal septum.
What is Stomatitis?
Inflammation of the membranes of the oral cavity
What is glossitis?
Inflammation of the tongue.
What is wooden tongue?
Granulomatous inflammation caused by actinobacillosis - actinobacillus lignieresii, a chronic lesion of bacterial origin.
What is lumpy jaw?
A chronic lesion of fungal origin - caused by actinomycosis - actinomyces bovis in cattle. The mandible becomes enlarged due to chronic osteomyelitis.
Describe Calf diphtheria
Caused by Fusobacterium necrophorum, necrosis predominates with coagulative necrosis and surrounding granulation tissue affecting the gingival and oral mucosa.
Describe some examples of disease which cause oral ulceration?
Feline calicivirus and feline herpesvirus infections. Mucosal disease caused by bovine viral diarrhoea virus in which ulceration of the oral cavity, muzzle and more distal alimentary tract occur. Immune mediated diseases - autoantibodies directed against epithelial cell surface antigens e.g pemphigus vulgaris.
Describe an example of a disease with papular lesions.
Proliferative papular lesions e.g contagious pustular dermatitis (orf) in sheep and oats, with firm raised papules and pustules on lips and oral mucosa. There is hydropic degeneration, mixed inflammatory cell infiltration and secondary bacterial invasion.
Describe two common examples of Epithelial Neoplasia’s In the oral cavity.
Papillomas - are benign epithelial tumours with raised, sometimes cauliflower like lesions on the lips and oral mucosa. There is a thick squamous epithelium over a branching Pedunculated fibrous stroma. Squamous cell carcinomas - are malignant epithelial tumours common in cats, often on the ventrolateral tongue. They are locally invasive. Composed of elevated firm white plaques.
What is a melanoma?
A tumour of pigment producing melanocytes. Most common oral neoplasm in dog and nearly always malignant in the oral cavity. They grow rapidly and are not always pigmented. (amelanotic melanoma). Oval or spindle shaped melanocytes with variable melanin content.
What are Epilus?
A group of benign neoplasms of periodontal origin affecting gingivae. Particularly in brachycephalic dog breeds. They are firm lesions on gums, surrounding teeth, especially in carnassial/canine region. Dense collagenous and sometimes ossified tissue covered with stratified squamous epithelium which descends into dermis in cords.
What is segmental aplasia?
Rare failure of fusion. Band of fibrous tissue where distal oesophagus should be.
What is Achalasia?
failure of cardiac sphincter to open.
What is mega-oesophagus and what are its possible causes?
Dilated oesophagus lack peristalsis, accumulates ingesta due to underlying neuromuscular disorder but lower oesophageal sphincter is usually normal. May be idiopathic - developmental disorder of vagus nerve/motor nucleus. Acquired - neurological - dysautonomias (grass sickness), myasthenia gravis. Acquired - muscular - myodegeneration (nutritional myopathy).
Describe potential Obstructions of the oesophagus.
Intraluminal- Foreign body e.g root veg. Most likely at cardiac sphincter, thoracic inlet. May cause inflammation, necrosis, ulceration and perforation. Bloat in ruminants. Stricture on healing.
Intramural - within the wall - inflammatory lesion, -abscess, granulation, neoplasm - narrowing.
Extrinsic - vascular ring anomaly - persistent right aortic arch constricts oesophagus and leads to megaoesophagus cranially. Also pressure from abscess, haematoma, neoplasm.
Describe the possible causes of inflammation of the oesophagus (oesophagitis).
Reflux oesophagitis - damage from gastric acid due to gastro oesophageal reflux or vomiting. This results in erosion of epithelium which may progress to ulcers.
Infectious agents - e.g actinobacillosis, feline calicivirus.
Describe possible neoplasia’s of the Oesophagus.
Papillomatosis in cattle - bovine papillomavirus type 4. (transforms to squamous cell carcinoma with bracken fern toxins)
Squamous cell carcinoma - in cat especially
Leiomyoma - benign tumour of smooth muscle
Describe primary and secondary ruminal tympany
failure to expel fermentation gases. Primary ‘frothy bloat’ is due to formation of stable foam in the rumen - due to ingestion of excess high protein or high concentrate/low roughage diet. Secondary - mechanical/functional obstruction of oesophagus - accumulation of gas. Rumen distended with gas/feed. Blood is dark and clots poorly. Congestion, oedema and subcutaneous haemorrhage of head and neck tissues.
What is ruminal acidosis?
Caused by grain overload - excess carbohydrate - increased gram positive cocci - increased volatile fatty acid and lactic acid production - drop in pH <5 = acidosis. Gross PM findings - porridge like contents, ruminitis may develop and allow thromboemboli to travel to the liver - hepatic abscessation. may be Focal erosions/ ulcerations.
What is traumatic reticulitis?
Ingestion of sharp objects e.g wire/nails - can either fall to the floor of the reticulum - insignificant or contractions force foreign body into wall. Mild suppurative or granulomatous reticulitis/peritonitis. Foreign body may penetrate cranial wall - encouraged by rumen contractions - acute peritonitis, local fibrous adhesions. Progresses through diaphragm. Inflammatory process around reticulum may also lead to vagus indigestion and ruminal stasis.
What is ruminitis?
bacterial or mycotic ruminitis - fusobacterium necrophorum or fungi - opportunist pathogens which take advantage of acidotic lesions and other disturbances of rumen flora. Multiple dark red areas of swollen papillae. Coagulative necrosis of papillae, marked neutrophil infiltrate, sero fibrinous exudate. Thromboembolic spread to form areas of coagulative necrosis and abscesses in the liver.
Describe neoplasia’s of the ruminant forestmachs
Papillomatosis - bovine papillomavirus type 4 - usually Pedunculated structures in the reticulum/rumen of cattle. Squamous cell carcinoma - thought to develop from Papillomas in cattle in associated with ingested carcinogens in bracken fern.
Describe potential causes of obstruction in the glandular stomach/abomasum.
Foreign body/functional obstruction - bones, stones, hair/wool balls, plant material, neurologic causes include dysautonomia, end stage liver disease, vagal indigestion. Pyloric stenosis - dog, foal, - congenital hypertrophy of pyloric muscle causes delayed gastric emptying and persistent vomiting/regurgitation. Acquired following healed ulcers.
Describe how the abomasum can become displaced
Ventral and to left of rumen (LDA) - dairy cattle
To right of rumen (less common)- Constriction of blood vessels and trauma to vagus nerve resulting in Abomasal distension with blood stained fluid and gas, congested mucosa, infarction. May rupture - peritonitis, shock, death.
What is gastric dilatation and volvulus? (GDV)
Occurs in large deep chested dogs and pigs. Aetiology is obscure but usually exercise post feeding/aerophagia. Stomach is distended with as, causing increased pressure on thoracic viscera and blood vessels. Stomach and spleen rotate on long axis and occlude oesophagus and venous return - congestion, oedema and necrosis of gastric mucosa. May rupture.
What is haemorrhagic gastritis/abomasitis?
Can be caused by clostridial diseases eg clostridium septicum in sheep - acute abomasitis with red, thickened, necrotic haemorrhagic mucosa. Coagulative necrosis of mucosa and deeper structures with fibrin, oedema, haemorrhage and sometimes emphysema.
What causes hypertrophic gastritis/abomasitis
Chronic hypertrophic gastritis in dogs - thought to be due to chronic retention of gastric fluid and bile reflux. Marked mucosal thickening and convolution of rugae. There is marked epithelial hyperplasia, loss of parietal/chief cells, dilatation of mucous glands and mixed inflammatory cell infiltrates in the lamina propria.
