University of Mosul – College of Vet. Med. Dep. of Path. & Pol. Dis. Systemic Pathology lectures for third class students by Prof.Dr.S.O.Youkhana
DIGESTIVE SYSTEM
Mouth and pharynx :-
Inflammation of the mouth is called stomatitis , Inflammation of the pharynx is called pharyngitis , Inflammation of the lips is called cheilitis , Inflammation of the gum is called gingivitis , Inflammation of the tongue is called glossitis , inflammation of the tonsil is called tonsilitis .
Causes of stomatitis :-
1 – Physical causes such as trauma , sharp objects , ect……
2 – chemical substances such as caustic alkalis , corrosive acids and their salts .
3 – Irritants.
4 – Microorganisms such as bacteria , viruses , parasites , fungi ……
Stomatitis may be primary or secondary , it may be local or diffuse . various types of stomatitis are classified according to the character of the exudate it may be : catarrhal , vesicular , ulcerative and of necrotic type .
1 – Catarrhal stomatitis :- It may be primary or secondary .
Macroscopic appearance :- the mouth mucous membrane is congested swollen with mucous exudates specially in the soft palate , the lesion may be focal or diffuse . Small cysts may seen due to occlusion of the mouth mucous glands . Microscopically there is superficial desquamation of the epithelium , the exudates consist of leukocytes , desequmated epithelial cells on the mucosa .
2 – Vesicular stomatitis :- It is usually associated with the viral diseases such as FMD , Infecious viral stomatitis , Mucosal disease , Rinder pest .
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Macroscopic appearance :- Vesicles are seen in the mucous membrane of the lips , tongue , gum , dental pad and hard palate , their size vary from 1-2 mm they are filled with clear serous exudate as a result of hydropic degeneration of the epithelium . If these vesicles ruptured they leaved eroded surfaces .
3 – Ulcerative stomatitis :- The lesion extend to submucosal layers deep ulcers appear with hyperemia and hemorrhage .
4 – necrotic stomatitis :- cused by sever mechanical , chemical , thermal and /or other infectious agents which cause necrosis of mucous membrane of the oral cavity . The most common cause is Fusiformis necrophorus , the disease is called in calves calf diphtheria .
The lesion may be focal or diffuse consist of casious necrosis of the mouth mucous membrane with white to yellow in color . In some cases fibrinous exudate may cover the lesion so it called sometimes fibrinous stomatitis or diphtheritic stomatitis . Microscopically coagulative necrosis is seen in the beginning of the disease then causes necrosis in the underlining mucosa . Neutrophils are the principle cellular constituent of the exudates .
Glossitis :- Inflammation of the tongue . It is commonly occurred in the viral diseases of the mouth e.g. FMD. The lesion appeared as vesicles in the periphery of the tongue , these vesicles contained serous fluid it may be ruptured then lead to red erosions covered by brownish scabs , it occur in blue tongue in sheep , wooden tongue in cattle . In chronic cases granulomatous lesion may seen with connective tissue and suppuration may be seen in the center of the lesion , in these cases contain sulphur granules which are bacterial colonies and this will predispose to producing tumor of the tongue .
Gingivitis :- superficial inflammation of the gum, it is commonly seen in dogs . In chronic cases the lesion extend deeper to submucosal layer causing suppuration of the gum and lead to osteomyelitis .
Systemic Pathology Digestive system Prof.Dr.S.O.Youkhana
TEETH
Teeth diseases are common in animals , it may include anomalies , growth disturbances such as dysplasia , hyperplasia , sharp teeth , attrition of enamel , fracture of teeth is common and lead to alveolar perostitis . Dental hypoplasia affect permanent teeth due to acute infections of the enamel . The most causes are toxins like flurosis , which colored the teeth greenish , decrease in calcification give the teeth chalky coloration . Necrosis of the teeth occurred because of the acids , bacteria , infections which lead to pulpitis .
SALIVARY GLANDS
Inflammation of salivary glands is rare in domestic animals . it is associated with diseases of the mouth . Obstruction of salivary gland ducts occur by forgin bodies , litheiasis specially seen in paroted and submaxillary salivary gland in horses which lead to appearance of retention cysts .
PHARYNX
Inflammation of the pharynx is called pharyngitis . It is usually associated with stomatitis the pharynx appeared as congested and swollen . Tonsilitis may occur together with pharyngitis . The inflammation may be catarrhal and seen mostly in septicemic diseases which cause necrosis of the pharynx with edema and hemorrhage in the submucosal layer , this lesion is mostly seen in anthrax .Neoplasms of the mouth :- Epulis is fibroma of the gum ,osteoclastoma , melanoma is seen in dogs , canine viral papilloma and squamous cell carcinoma occurred in tonque the and tonsils.
ESOPHAGUS
Esophageal obstruction is very common in domestic animals . The causes are variable , it may be as a result of hypoplasia of the esophagus , impaction by
Systemic Pathology Digestive system Prof.Dr.S.O.Youkhana
foreign bodies , pressur from outside like abscesses or tumor masses . Achalasia is common in dogs . Perforation of esophagus is common in animals caused by mechanical factors from the exterior like traumatic injuries . Rupture of the esophagus is usually associated with obstruction . Dilatation of the esophagus may be a result of congenital anomaly or it may be acquired occurred as a result of stenosis and it is of two types :-
1 – Ectasia :- is uniform , spindle or cylindrical shaped dilatation it may be due to stenosis .
2 – Diverticulum :- is one-sided sacculated dilatation , it may be due to traction by cicatrical tissue on the outside of the esophagus .
Disturbances in circulation of esophagus :- Hyperemia occur as a result of inflammation , edema of the submucosa is common .
Disturbances in growth of esophagus :- Aplasia and hypoplasia are common , hyperplasia is common as a result of hyperkeratosis , hypertrophy is seen in horses , metaplasia of the mucosa of esophagus occurred due to deficiency in vitamin A in chickens , the cells of the glands of esophageal mucosa changed from columinar type to stratified squamous type .
Esophagitis :- Is inflammation of esophagus . It is of the following types :-
1 – Catarrhal esophagitis :- It is very common in animals , occurred as a result of mild injuries of the esophageal mucosa , the principle constituent of the exudates is mucous.
2 – Fibrinous esophagitis :- It is uncommon and seen in chicken with thallium sulphate poisoning .
Systemic Pathology Digestive system Prof.Dr.S.O.Youkhana
3 – Suppurative esophagitis :- It is usually secondary to mechanical injuries indused by sharp foreign bodies passing through the esophagus or in the area were the esophageal obstruction has occurred .
4 - Necrotic esophagitis :- It is observed in all domestic animals . The esophagus may be entirely necrotic and consist of dry tan diphtheritic membrane . Linear ulcers may seen in esophageal mucosa . The lesions are most sever in the distal third of the esophagus .
5 – Gangrenous esophagitis :- Occurred when the injuries in the wall of esophagus were invaded by saprophytic organisms , it is mostly seen in areas of esophageal obstruction .
Parasitic esophagitis :- Hypoderma bovis , lineatum larvae are commonly observed in esophageal submucosa appear as white in color and resemble grains of rice . Spirocerca lupi in dogs , Cysticercus bovis and ovis are also seen in musculature of esophagus .
Neoplasms of esophagus :- Are rare in animals . Papilloma and fibrosarcoma in cattle , malignant connective tissue tumors are seen in dogs induced by Spirocerca lupi parasite and mostly affect the distal part of esophagus .
RUMENITIS
Rumenitis :- Inflammation of rumen . Rumenitis in cattle is traumatic or non-traumatic in origin. The traumatic type is caused by various types of foreign bodies which are ingested by cattle . The non-traumatic type is caused by infectious agents ( microorganisms ) . Rumenitis is characterized by acute inflammatory reaction of mucosa and submucosa , foci of necrosis up to 5cm. in diameter . In chronic cases the villi may lost in areas up to 20 cm. thickened mucosa and submucosa due to fibroplasias .
Neoplasms of rumen :- papillomas of mucous membrane are common also carcinoma .
Systemic Pathology Digestive system Prof.Dr.S.O.Youkhana
STOMACH
Gastritis :- Is inflammation of the stomach . gastritis occur in all species of domestic animals it may be primary or secondary . Gastritis is classified according to the following types :-
1 – Catarrhal gastritis :- caused by bacteria , parasites or other infectious agents , traumatic injuries . it may be acute or chronic the inflammatory exudates is mucous .
2 – Fibrinous gastritis :- caused by more sever irritant , the exudates is fibrinous in nature .
3 – Hemorrhagic gastritis :- caused by very sever irritant , the principle constituent of exudate is red blood cells .
4 – Suppurative gastritis :- caused by pyogenic microorganisms , the principle constituent of exudate is neutrophils .
5 – Necrotic gastritis :- It is common and very sever , it may be focal or diffuse . The focal type is very common and appear in the form of ulcer .
GASTRIC ULCERS
Gastric ulcer arise from ( causes ) :-
1 – Local circulatory disturbances e.g. hemorrhages .
2 – traumatic injuries of stomach epithelium e.g. coarse feed .
3 – Digestive action of gastric juce upon the injured tissue .
Gastric ulcers are variable in size , round or irregular in shape and are variable in their depth ranged from mild mucosal changes to complete perforation of the mucosal layers . They are developed rapidly ( 3 – 4 ) days , complete perforation
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may occur from 6 – 7 days . Most ulcers heal slowly by formation of granulation tissue .
Parasitic gastritis :- It is very common in domestic animals , and is usually of the chronic catarrhal type . Haemonchus contortus is the most important gastric parasite occur in abomasum of sheep , goat and cattle . ostertagia ostertagi is common in cattle .
Neoplasms :- Lymphosarcoma of abomasum , adenocarcinoma , leiomyoma and papilloma .
INTESTINE
Physical influences of intestine :-
1 – Perforations :- perforations of intestinal wall may be from external or from internal . Rapid penetration induce wound with hemorrhage .
2 – rupture of intestine :- rupture of intestine may be due to trauma , distention or dilatation of the jejunum and ileum.
3 – Volvulus :- Is rotation of intestine on the long axis of the mesentry occur in the horse due to many causes such as vascular disturbances , over filling of portion of intestine with gas or ingesta and increase in the perstaltic movement of the intestine .
4 – Torsion :- Usually occur in colon . The left dorsal part turn laterally or medially around the left ventral part . Torsion occur in cecum also , the tortion part undergo acute local passive hyperemia with hemorrhage , gangrene and mostly cause death .
5 – Intussuscption :- Telescoping of section of intestine in to following portion , the most causes are circulatory disturbances and increase in the perstaltic movement of intestine . The intussuscpted part undergo passive hyperemia ,
edema , hemorrhage and necrosis become swollen with red to bluish red in color.
Systemic Pathology Digestive system Prof.Dr.S.O.Youkhana
6 – hernia :- It is common in domestic animals , the causes are defect in the anatomy of natural body openings in the abdominal wall . The body openings not closed completely to retain the viscera . Hernia may be congenital or acquired . The acquired hernia are result of mechanical injuries and it may be reducible or irreducible .
7 – Obstruction of the intestine :- Causes of intestinal obstruction are :-
a- Factors from outside of intestine which compress the lumen such as enlarged lymph node , tumors , abscesses , adhesions , parasites and impaction with ingesta or feces .
b- Factors located within the lumen which cause obstruction such as foreign bodies , mass of parasites , tumors , hematocysts and chronic inflammation .
c- Torsion and volvulus of the intestine .
8 – Impaction of the intestine :- Is accumulation of excessive amount of ingesta in portion of intestinal tract . Accumulation of feces obstruct the lumen cause death of the animal .
9 – Dilatation :- Acute tympanic dilatation caused by abomasal fermentation of ingesta and/or swallowing large quantities of air seen in horses , the intestine may rupture or the abdominal enlargement cause rupture of the diaphragm or ventral abdominal wall .
Systemic Pathology Digestive system Prof.Dr.S.O.Youkhana
CIRCULATORY DISTURBANCES OF INTESTINE
1 – Active hyperemia :- Seen in enteritis and in inflammatory reactions of intestine , physiological active hyperemia associated with process of digestion .
2 – Passive hyperemia :- Seen in hernia , torsion and Intussuscption . The color of the intestine is dark blue or brownish – red in color . Chronic passive hyperemia due to more gradual obstruction to the flow of the blood in intestinal tract .
3 – Thrombosis :- Thrombosis of intestinal arteries is very common in horses due to Strongylus vulgaris larvae . Anterior mesenteric artery endothelium is injured , thrombosis undergo organization , fibrosis and scar formation of the wall of the vessel .
4 – Embolism :- The embolus usually lodged in colic and cecal arteries , the results depend weather the closure is partial or complete , sudden or gradual .
5 – Hemorrhage :- Hemorrhage of intestine mostly occur in acute inflammation , septicemic diseases and mechanical injuries . The type of hemorrhage may be petechial , echymotic or linear . The blood from hemorrhage which occur in anterior portion of intestinal tract partially digested and the intestinal content become brown to black in color , while in the posterior portion of the intestinal tract the blood is bright-red in color .
6 – Edema :- edema of the wall of intestine is very common in heavy parasitic infection of animals as a result of hypoprotenemia .
ENTERITIS
Enteritis :- Is inflammation of the intestine , duodenitis is inflammation of the duodenum , jejunitis is inflammation of the jejunum , ileitis is inflammation of the ileum , cecitis is inflammation of the cecum , colitis is inflammation of the
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colon . Enteritis is classified according to the character of the exudate in to the following types :-1 – Catarrhal enteritis :- It is either acute or chronic .
a- Acute catarrhal enteritis :- Is the mildest type of intestinal inflammation , the principle constituent of the exudate is mucous . The most causes are mild irritants , chemicals , coarse feed , foreign bodies , parasites ……. Ect .
b- Chronic atarrhal enteritis :- Is persisting inflammation of intestine inducing permanent tissue alteration characterized by deposition of connective tissue and infiltration of macrophages . It followed acute catarrhal enteritis that persist for long period of time , it is always associated with parasitic infection . The diameter of intestine is increased , the wall is thickened the mucous has yellow-white coloration and covered by layer of mucous . Microscopically the epithelium undergo mucous degeneration with inflammatory cell infiltration mainly neutrophils , lymphocytes and macrophages . If the cause is parasitic eosinophils may present in large numbers .
2 – Suppurative enteritis :- The principle constituent of the exudate is pus and neutrophils , caused by pyogenic organisms .
3 – Fibrinous enteritis :- The principle constituent of the exudate is fibrin . It is always serous and end with death of infected animal . The causes are chemical agents , bacteria such as E. coli , Salmnella . It is characterized by present of sheets of fibrin on intestinal mucous membrane . The amount of fibrin depend upon the severity of the irritant. The affected mucosa is hyperemic , edematous . The intestinal content are fluid mixed with fibrin . The small intestine are more affected than large intestine . Microscopically , the inflammatory exudate consist from fibrin network , desquamated epithelial cells and neutrophils. Hyperemia and edema are seen . If very sever irritant when there is necrosis of epithelium and the underlying tissues of the intestine the layer of fibrin and necrotic tissue is
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called diphtheritic membrane and the condition is called diphtheritic enteritis or fibrinonecrotic enteritis .4 – Hemorrhagic enteritis :- The principle constituent of the exudate are red blood cells . It caused by very intense irritant , chemical , bacterial , parasitic …… ect.
5 – Necrotic enteritis :- The principle alteration is necrosis of the intestinal epithelium and underlining tissue . It is caused by sever chemical , bacterial , viral or parasitic agents . Macroscopic appearance the intestinal alteration consist of sever inflammation in which portion or entire intestinal mucous membrane undergo necrosis . The necrotic area may extend to underlining mucosa and submucosa . The necrotic surface is covered with a layer of fibrin . Microscopically , vascular and cellular alterations associated with inflammation are present . Necrosis of epithelium , mucosa , and submucosa .
Neoplasms of intestine :- They are not common as in human , sarcoma , carcinoma , lipoma of the mesntry , leiomyomas , lymphangioma , adenoma of mucous glands are seen in large intestine of cattle .
PERITONEUM
Peritonitis :- Inflammation of the peritoneum . It may be local or general and it is classified as suppurative , serofibrinous or hemorrhagic peritonitis . The most common causes of peritonitis in domestic animals are bacteria and their toxins such as streptococcus , staphylococcus , clostridial spp. And corynebacterium pyogens . The mode of infection occur via the followings :-
1- By surgical incision through the abdominal wall .
2- Perforation of intestinal wall , stomach and uterus .
3- Direct contact from the adjacent organs .
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4- Via the blood stream ( hematogenus ) .
Tuberculous peritonitis ( pearly disease ) is very common in cattle it called pearly due to the presence of tubercle gray mass on the peritoneal surface .
LIVER
Hepatic injury and inflammation :-The high metabolic activity of liver cells ( hepatocytes ) renders them very susceptible to any metabolic disturbances that lead to cellular degeneration and necrosis .
Patterns of hepatocellular degeneration and necrosis :-
Degeneration and/or necrosis of hepatic cells occurs in one of the three following morphologic patterns :-
1- Random hepatocellular degeneration and/or necrosis:- This type of pattern is characterized by presence of either single – cell necrosis through the liver parenchyma or multifocal aggregates of necrotic hepatocytes . These areas are scattered randomly through out the liver . This type of pattern is typical of many infectious agents including bacteria , viruses and certain protozoa like toxoplasma gondii which reach the liver hematogenously . The gross lesions are discrete pale of less often dark red foci that are delinated from the adjacent parenchyma . The size of these foci ranged from tiny ( 1mm ) to several centimeters.
2- Zonal hepatocellular degeneration and/or necrosis:- This type of pattern affects hepatocytes within defined areas of the hepatic lobule . The zones are centrilobular , midzonal ( between centrilobular and periportal areas ) or
Systemic Pathology Digestive system Prof.Dr.S.O.Youkhana
periportal areas . It occur typically in case of sever anemia and phosphorus poisoning .3- Massive necrosis :- In this pattern all hepatocytes within the affected lobules are necrotic . Microscopically the affected areas consist of blood filled spaces within a connective tissue stroma and later the necrotic hepatocytes lyse without regeneration .
Response of liver to injury :- The liver cells response to injury by the following mechanisms :-
1- Regeneration . 2- Fibrosis . 3- Hyperplasia of the bile duct .
End stage liver or cirrhosis :-
End stage liver or cirrhosis is characterized by the loss of normal hepatic architecture due to nodular regeneration of hepatic parenchyma combined with fibrosis and biliary duct hyperplasia .
Causes of end stage liver or cirrhosis :-
1- Chronic toxic insult ( toxic plants , drugs ………. Ect ) .
2- Chronic extrahepatic biliary obstruction and cholestasis lead to extensive portal fibrosis .
3- Chronic infections of liver or biliary tract .
4- Chronic passive congestion lead to fibrosis around the central vein .
Hepatitis :- Is inflammation of liver parenchyma .
Cholangitis :- Is inflammation of biliary ducts .
Cholangiohepatitis :- Is inflammation of biliary ducts and hepatic parenchyma .
Systemic Pathology Digestive system Prof.Dr.S.O.Youkhana
The routes of liver infection are hematogenous , direct penetration and ascending from biliary system .
Acute hepatitis :- Acute hepatitis is characterized by infiltration of inflammatory cells mainly neutrophils , lymphocytes and plasma cells particularly if the infectious agent is present .
Chronic hepatitis :- Chronic hepatitis results when there is continued inflammation due to persistence of an antigenic stimulus . It is characterized by fibrosis and accumulation of mononuclear inflammatory cells . Focal lesions such as abscesses or granulomas may developed . Sever chronic hepatitis usually lead to end stage liver .
GALL BLADDER
Cholecystitis :- Is inflammation of gall bladder . It may be acute or chronic . The most causes are viral infections such as infectious canine hepatitis and fibrinous choleycystitis in calves with acute salmonellosis .
Cholelithiasis ( gall stones ) :- Gall stones are usually of no clinical significance until they obstruct the biliary passages .
Hepatic neoplasia :- The most common tumors of hepatocytes are hepatocellular adenoma and hepatocellular carcinoma .
PANCREAS
Pancreatitis :- Inflammation of pancreas . It is of two types :-
1- Acute pancreatitis :- Is common in dogs , it occur due to released of activated pancreatic enzymes in to the pancreatic parenchyma and adjacent tissues , these activated enzymes particularly phospholipase and elastase digest pancreatic tissue which result in release of inflammatory mediators and then attract inflammatory cells . Acute pancreatitis usually occur in dogs after heavy meal of
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fat . The inflammation is characterized by infiltration of leukocytes in the affected tissue , rapidly followed by initial tissue necrosis .2- Chronic pancreatitis :- Chronic pancreatitis usually accompanied by fibrosis and parenchymal atrophy . It occur in all species of animals as a result of obstruction of the pancreatic ducts , it is most common in dogs . It is characterized by fibrosis as a result of progressive destruction of the pancreatic tissue by repeated mild episodes of acute pancreatic necrosis and pancreatitis . The pancreas has poor regenerative capacity and response to injury by fibrosis and loss of glandular tissue .
Pancreatic neoplasia :- Pancreatic adenoma and pancreatic carcinoma .