Pathology Flashcards
What composes the capillary wall?
A semipermeable barrier that influences the movement of fluids, nutrients, and waste products between the blood and interstitium
How do lipid soluble substances, large proteins, and small polar molecules move through the capillary wall?
1) Lipid soluble substances -> dissolve in membrane lipid bilayer
2) Large proteins -> transport within vesicles
3) Small polar molecules -> move by inter-endothelial pores (typically passive and in response to gradients)
How is water distribution between the plasma and interstitium determined?
Osmotic and hydrostatic pressure differentials
What are the 4 causes of edema?
- Increased intravascular hydrostatic pressure
- Decreased intravascular osmotic pressure
- Increased microvascular permeability
- Decreased lymphatic drainage
What can result from edema caused by increased intravascular hydrostatic pressure?
active increase -> hyperemia from inflammation
passive -> congestion
localized portion results in localized edema
heart failure -> generalized edema
What are common causes of intravascular hydrostatic pressure?
-Portal hypertension
-Pulmonary hypertension
-Localized venous obstruction
-Fluid overload
-Hyperemia
What can lead to edema from decreased intravascular osmotic pressure?
Decreased concentration of plasma proteins (albumin) leads to this. More fluid filtration and decreased absorption results
Generalized edema
Results from decreased albumin production or excessive albumin loss
What leads to sodium and water retention?
When renal function is compromised -> salt is retained
Water follows salt, more salt, more water retained leading to an increase in hydrostatic pressure and decreased colloid osmotic pressure
What cascade of events leads to increased microvascular permeability?
1) Initial microvascular reaction to inflammatory or immunologic stimuli
2) Localized release of mediators that cause vasodilation
3) Endothelial cells contract and widen gaps
4) Triggers release of IL-1, TNF, and interferon gamma
5) cytoskeletal rearrangement -> endothelial cell retraction
What causes increased vascular permeability?
Infectious agents
Immune mediated events (type III hypersensitivity)
Neovascularization
Anaphylaxis
Toxins
Metabolic abnormalities
What causes increased vascular permeability?
Infectious agents
Immune mediated events (type III hypersensitivity)
Neovascularization
Anaphylaxis
Toxins
Metabolic abnormalities
T/F edema resulting from decreased lymphatic drainage is localized to the area served by the affected lymphatic vessel
True
What can lead to decreased lymphatic drainage?
-Lymphatic obstruction
-Congenital lymphatic aplasia
-Intestinal lymphangiectasia
-Lymphangitis
What is the difference between Hyperemia and Congestion?
Hyperemia results from a greater arrival of blood to a tissue (increased inflow)
Congestion results from blood accumulating in a tissue due to an obstacle preventing its exit (decreased outflow)
What are the two types of hyperemia?
- Physiologic hyperemia
-tissue with increased metabolic activity
-stimulation of nerve centers that stimulate pressure - Pathologic hyperemia
-inflammatory process, caused by vasodilator substances released from affected tissues
What are the subsets of congestion?
1) Local congestion -> acute local and chronic local
2) Generalized congestion -> acute generalized and chronic generalized
What causes acute local congestion?
compression of veins in a portion of the body that is often the result of poor viscera position (intussusception, volvulus, etc.)
What causes chronic local congestion?
Results from gradual or partial obstruction of venous circulation in an area, allowing tissue to adapt to the lower blood supply
Caused by external pressure or obstruction inside the vein
Leads to cellular atrophy and proliferation of connective tissue
What causes acute generalized congestion?
Sudden obstruction of blood flow in the heart or lungs
Cardiac causes: degeneration and necrosis of myocardium (myocardial infarcts, hydro, hemoperricardium, suppurative pericarditis)
Pulmonary causes: pneumonia, embolism, thrombosis, hydrothorax, hemothorax, empyema
What causes chronic generalized congestion?
Results from chronic obstruction of blood flow in the heart or lungs, causing permanent alterations in various tissues and organs
Cardiac: Valvular stenosis and insufficiency, myocardial failure, cardiac anomalies, constrictive lesions of epi and pericardium
Pulmonary: Obliteration of capillaries, chronic alveolar emphysema, pneumonia, hydrothorax, hemothorax, empyema, compression of major pulmonary vessels
What results from right cardiac insufficiency?
Blood accumulates in great veins and liver
Subcutaneous fluid accumulates in ventral areas, extremities, and body cavities
Liver with increased reticular pattern (nutmeg liver)
What results from left cardiac insufficiency?
Accumulation of blood and increased hydrostatic pressure in the lung
Extravasated erythrocytes in alveoli and phagocytized by macrophages (cardiac failure cells)
What is cor pulmonale?
an alteration in the structure and function of the right ventricle of the heart caused by a primary disorder of the respiratory system. Pulmonary hypertension is often the link between lung dysfunction and the heart in cor pulmonale
What is hypostatic congestion?
pooling of blood in the ventral areas of the body due to gravity
