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Edema (Macroscopic appearance (Swelling: fluid accumulation, Heavier,…
Edema
Causes
Decreased oncotic pressure
Starvation/ Extensive hepatic injury: x formation of blood protein
Oncotic P drops from 30 mmHg to 20mmHg
Haemorrhage: loss of blood protein: parasitism,gastric ulcer
Arterial (45mmHg) and venous (15mmHg) blood P remains as normal resting state
Arterial end:
blood P (45mmHg) overcome oncotic P (20mmHg),
fluid forced into tissue at rate of 25mmHg
Venous end
: blood P (15mmHg) cannot entirely overcome oncotic P (20mmHg).
Fluid leaving tissue at 5 mmHg
Fluid
accumulates
in tissue at rate of
20mmHg
Increased tissue P force fluid into lymph vessels
When fail to drain,
edema occurs
Increased hydrostatic pressure
General/Local congestion
Obstruction in heart/lung (general) or vein (local)
Increased venous blood P
Oncotic P (30mmHg) and arterial P (45mmHg) normal
Venous P increased 20mmHg
Arterial end:
Blood P (45mmHg) overcomes oncotic P (30mmHg),
fluid escape at 15mmHg rate
Venous end
: Blood P (20mmHg) partially overcome oncotic P (30mmg), fluid
returns from tissue at 10mmHg rate
Fluids
accumulates in tissue at rate 5mmHg
If failure to drained by lymph vessel,
edema occurs
Increased permeability of capillary endothelum
Blood protein escape, reduced oncotic pressure
Inflammation, injuries: histamine
Mechanism same wt Decreased Oncotic P (dashed line of capillary)
Obstruction of lymphatic vessels
Tumour, cysts, abscesses, thrombi, bandages
Parasite: presence or inflammation
Unable to remove fluid
Oncotic P reduced to 25mmHg
Blood P remain normal, arterial (45mmHg), venous (15mmHg)
Arterial end
: Blood P (45mmHg) overcome oncotic P (25mmHg),
fluid escape to tissue at 20mmHg
Venous end
: Blood P (15mmHg) partially overcome oncotic P (25mmHg), f
luid returns at rate 10mmHg
Fluid accumulates in tissue rate 10mmHg
Obstruction of lymph vessel
, fluid not removed, edema
Macroscopic appearance
Swelling: fluid accumulation
Heavier
Lower T: less vascularate
Pale: compressed capillaries
Fluid flow when incised
Fibrosis
Pitting on pressure: fluid move away then return
Excessive fluid accumulated in the intercellular space or body cavity