Cell Injury and Diseases

Study Notes

Cell Injury

Definition: A sequence of events (biochemical and morphologic) upon exposure of the cell to injurious agents.
Causes:
Injurious agents
Excess fat in diet
Viral hepatitis

Types of Cell Injury

Reversible cell injury (Degeneration)
Irreversible cell injury (Cell Death)

Reversible Cell Injury

Definition: Characterized by accumulation of excess water or fat in cells.
Microscopic picture:
- Cellular swelling (cloudy swelling and hydropic swelling)
- Accumulation of water in the cell (small amount)
- Cytoplasm: fine granules
Organs affected:
- Liver
- Kidney
- Heart
Clinical Picture:
- Liver: no significant change
- Kidney: proteinuria
- Heart: dilatation
Fate:
- Can recover with removal of injurious agent
- Persistence of injurious agent leads to irreversible cell injury

Irreversible Cell Injury (Cell Death)

Definition: Death of large groups of cells or tissues within the living body.
Causes:
- Injurious agents
Microscopic picture:
- Nuclear changes
- Cytoplasmic changes
Fate:
- Cell death

Bilharziasis (Schistosomiasis)

Chronic, specific, granulomatous infection caused by Schistosoma species, endemic in Egypt
Life cycle and pathogenesis:
- Acute schistosomiasis: severe febrile illness, peak after 2 months
  - Early stage: TH1 cells dominate, producing IFN-γ, stimulating macrophages to secrete cytokines TNF, IL-1, and IL-6, leading to fever
- Chronic schistosomiasis: dominant TH2 response, although TH1 cells persist
  - Parasite egg proteins stimulate mast cells to produce IL-4, leading to TH2 differentiation
  - Both TH1 and TH2 cells contribute to granuloma formation around eggs

Bilharzial Lesions

Lesions produced by Cercaria:
- Acute allergic dermatitis at skin penetration sites
- Gross picture: maculopapular skin rash
- Microscopic picture: dilated capillaries, neutrophils, eosinophils, and macrophages
Lesions produced by adult worms:
- Dead worms: severe inflammation, necrosis, and thrombophlebitis
- Living worms: brown bilharzial pigment in liver, spleen, and other tissues
Lesions produced by ova:
- Recurrent bleeding due to injury by ova spines, leading to anemia
- Trapped ova: sensitization of T lymphocytes, leading to inflammatory response and granuloma formation

Bilharzial Antigens

From worms or ova, causing hyperplasia of lymphoid and reticuloendothelial cells

Liver Bilharziasis

Common in patients with intestinal bilharziasis
Portal tracts show major changes:
- Ova are carried as emboli through the portal vein and trapped in small and large portal tracts
- Granulomas form, leading to fibrosis
Dead worms: trapped in venules, leading to thrombophlebitis
Angiomatoids: dilated capillaries in fibrotic portal tracts, representing dilated collateral channels between branches of the hepatic artery and portal veins
Hepatic lobules: minimal lesions, preserved architecture, and minimal steatosis
Fine bilharzial periportal fibrosis:
- Gross picture: normal-sized liver with finely granular surface and dark brown cut surface
- Microscopic picture: portal tracts show ova, granulomatous inflammation, and fibrosis
Coarse bilharzial periportal fibrosis:
- Gross picture: reduced liver size, firm with irregular surface, and dark brown cut surface
- Microscopic picture: portal tracts show ova, granulomatous inflammation, and fibrosis

Effects and Complications

1. Portal Hypertension:
- Pathogenesis: portal fibrosis leads to compression of portal veins, and angiomatoids convey high pressure of the hepatic artery to the portal veins
- Effects: splenomegaly, ascites, and opening of porto-systemic venous collaterals
1. Portal Vein Thrombosis: may occur due to vascular stasis
1. Mild disturbances of liver functions: lowering of plasma proteins
1. Ascites: due to portal hypertension and lowering of plasma proteins
1. Ammonia Encephalopathy: hepatic portal fibrosis allows ammonia to escape through open porto-systemic collaterals, leading to encephalopathy and coma
Causes of death in hepatic bilharziasis:
1. Bleeding (hematemesis)
2. Superimposed chronic viral hepatitis (relatively common) leading to cirrhosis and liver failure

Description

This quiz covers the different types of cell injury, their causes, and effects on various organs such as the liver, heart, kidney, and muscles. It also touches on related diseases like viral hepatitis.