Pathology Week 9 E Flashcards
Define effusion
The escape of blood or other bodily fluid into a cavity or tissue
The fluid that has escaped
Define oedema
An effusion of serous fluid into the:
- tissue spaces (interstitial spaces)
- body cavities
The presence of excess fluid in the interstitial spaces of the body
Define anasarca:
Severe and generalised oedema with profound subcutaneous tissue swelling
Define transudate:
A collection of fluid that has formed after passing through a membrane, pore or interstice
Define exudate
Fluid that has exuded out of a tissue or its capillaries due to injury or inflammation
What are the types of local oedema?
Inflammatory oedema
Allergic oedema
Venous obstruction
Lymphatic obstruction
What is capillary hydrostatic pressure? At which end of the system is it highest?
The pressure of fluid within a capillary
Highest at the arterial end than the venous end
What is average capillary hydrostatic pressure in arterial end?
35mmHg
What is average capillary hydrostatic pressure in the venous end?
15mmHg
What is the purpose of higher capillary hydrostatic pressure at the arterial end?
It forces fluid into the interstitial space from the capillaries in the arterial end
What is capillary osmotic pressure? Where does it tend to draw water?
Is the pressure exerted by the flow of water through the capillary wall (i.e. semipermeable membranes)
Occurs between regions with different concentrations of solute.
Tends to draw water into the capillary
What is average capillary osmotic pressure?
28mmHg
What are the only solutes which do not pass freely between the plasma and the interstitium?
Proteins in the plasma
What is the most abundant plasma protein? How much of the capillary colloid pressure does it make up?
Albumin
21.8mmHg
What is interstitial osmotic pressure?
A small amount of protein is present in the interstitium. This protein draws water out of the capillary and into the interstitial space.
What is the average interstitial osmotic pressure?
8mmHg
What is interstitial hydrostatic pressure?
May be positive or negative:
- When its positive it forces fluid into the capillary
- When its negative it forces fluid into the interstitium
What is the average interstitial hydrostatic pressure in loose connective tissue?
3mmHg
Define interstitial fluid in terms of comparison to plasma and where it comes from
It is derived from capillariesIt has solutes that are similar to plasma except for the protein content
What is the lymphatic system and what is its purpose?
Is it a system of fine lymphatic channels throughout the body passing via lymph nodes to the thoracic duct.They collect fluid from the interstitial spaces and pass it back to the venous system to be filtered and excreted
What are the causes of oedema?
Raised capillary hydrostatic pressure (e.g. Na+ retention)
Reduced plasma osmotic pressure (conditions reducing serum albumin)
Endothelial damage (inflammation)
Impaired lymphatic drainage (eg obstruction)
What causes capillary hydrostatic pressure? What kind of oedema is it?
Cardiac failure:
- Right ventricle failure (Systemic/generalised oedema)
- Left ventricle failure (pulmonary oedema)
- Congestive heart failure (both Rv and Lv)
Local venous obstruction:-DVT
- External compression
- Superior vena cava obstruction
Constrictive pericarditis
It is usually a protein poor transudate
What causes raised capillary pressure?
Excessive loss of albumin (renal failure with albumin lost across glomerulus.
Hepatic disease - inadequate albumin synthesis
Malnutrition - inadequate albumin synthesis
Where is albumin made?
The liver
What is the main cause of increased tissue hydrostatic pressure?What can also cause it?
Lymphatic obstruction
Tumours
Neoplasia
Inflammation
- parasites
- fibrosis
- congenital abnormality
Post surgical
Post irradiation
What are the types of local oedema?
Inflammatory oedema
Allergic oedema
Venous obstruction
Lymphatic obstruction
What is inflammatory oedema?
Caused by increased capillary permeability and increased hydrostatic pressure as a result of local vasodilation
What is allergic oedema?
Acute allergic reactions stimulate the release of vasoactive substances that cause increased capillary permeability and arteriolar dilation.
What is venous obstruction?
Depends on the extent of the collateral circulation
Can be caused by
- thrombosis
- increased hydrostatic pressure and
capillary rupture
What are the causes of generalised oedema?
Decreased oncotic pressure
Increase vascular permeability to proteins
Increased hydrostatic pressure
Obstruction to lymph flow
Inappropriate renal sodium and water retention
What causes decreased oncotic pressure?
Nephrotic syndrome
Cirrhosis
Malnutrition
What causes increased vascular permeability to proteins leading to generalised oedema?
Angioneurotic oedema (usually allergic)
What causes increased hydrostatic pressure leading to generalised oedema?
Congestive heart failure
Cirrhosis
What causes an obstruction to lymph flow which can cause generalised oedema?
Congestive heart failure
What can cause inappropriate renal sodium and water retention?
Renal failure
Nephrotic syndrome
What are the types of generalised oedema?
Cardiac oedema
Oedema of hypoproteinaemia
Renal oedema
Pulmonary oedema
Describe the process of congestive heart failure
Right ventricular output is reduced
= decreased cardiac output
= decreased renal perfusion
=triggers renin-aldosterone-angiotensin axis
=Na+ and water retention
=OEDEMA
How is renal oedema usually caused?
Nephrotic syndrome, albumin is lost through the kidneys
In pulmonary oedema, what does the oedema often relate to?
Often relates to the increase in pulmonary artery pressure and decrease in lymphatic drainage.
