Question

Explain in detail the mechanisms of fluid exchange between capillaries and the interstitium. Then, define edema, and use cause-and-effect arguments, explain how each of the following conditions cause edema. Be sure to explain the underlying mechanism causing the edema.

• Lymphatic filariasis (elephanaiasis) and parasitic infection with a type of nematode.

• Surgical removal of lymphatic collecting vessels and lymph nodes. For example in cancer treatment.

• Pregnancy. Specically: gestational edema due to the pressure of uterus on the IVC and common iliac veins.

• Inflammation (histamine, cytokines)

• Liver failure (could be due to any of the following: hepatitis, cirrhosis, cancer)

• Renal disease (specifically glomerular nephritis) • Renal failure (complete failure)

• Heart failure (specifically: weakened right ventricle)

• Heart Failure (specifically: weakened left ventricle)

Answer 1

This has a figure and a flow chart,fig shows exchange mechanism or factors responsible for fluid movement across capillary wall,and flowchart shows mechanisms of systemic edema in heart failure,renal failure,malnutrition,hepatic failure,and nephrotic syndrome.

Edema_it is the abnormal and excessive accumulation of free fluid in iterstitial tissue and serous cavity.edema in body cavities is called effusion.

Under normal circumstances ,the tendency of vascular hydrostatic presdure to push water and salts out of capillaries into the interstitial space is nearly balanced by tendency of plasma colloid osmotic presdure to pull water and salt back into vessels. There is usually a small net movement of fluid into interstitium, but this drains into lymphatic vessels and ultimately returns to the blood stream via the thorasic duct , keeping the yissues dry.Elevated hydrostatic pressure or diminished colloid osmotic pressure disrupts this balance and results in increased movement of fluid out of vessels.If the net rate of fluid movement exceeds the rate of lymphatic drainage ,fluid accumulates.within the tissues_edena,within body cavity_effusion. Pregnency edema is physiological condition can be due to pressure on IVC leading to increased hydrostatic presdure, If much increased then eclampsia can be considered.

Edema fluids may be inflammatory (exudates)or non inflammatory(transudates).Exudates(protein rich)due to increased vascular permeability so that proteins move into interstitium,caused by inflamnatory mediators like histamine,cytokines(usually localised to one or a few tissues but in systemic inflammatory states like sepsis_produce widespread endothelial injury hence generalized edema).Transudates_protein poor_common in many diseases like heart failure,renal,liver failure and severe malnutrition conditions.

Trauma(surgical removal),fibrosis,invasive tumors and infectious agents can all disrupts lymphatic vessels and impair clearence of interstitial fluid,resulting in lymphedema in affected body part.

In parasitic filaruasis,nenatode induces obstructive fibrosis of lymphatic channel and lymph nodes. This may result in edema of extternal genitalia abd lower limbs that is so massive that can be called as elephantiasis.Severe edema of upper extrimity may also complicate surgical removal and irradiation of breast and associated axilary lymphnodes in patiebnts with breast cancer.

Left ventricular failure, increased left atrial pressure_increased pulmonary pressure in capillaries leads to pulmonary edema and pleural effusion.The lungs are 2_3 times their normal weight and sectioning yields frothy blood tinged fluid_mixture air,edema and extravaseted rbcs.Pulmonary edema can also occour with renal failure, ARDS, pulmonary inflammation or infection.

Right ventricular failure leads to increased right atrial pressure wich leads to pedal edema.