Body Fluid Balance And Oedema Flashcards
(25 cards)
Define fluid balance
The process by which the body maintains an equilibrium between fluid intake and output
Mechanism of fluid intake
Drinking
Ingestion
Mechanism of fluid intake
Drinking
Ingestion of food containing water
Metabolic water (produce as a byproduct of cellular respiration and metabolic process
Mechanisms of fluid loss
Urinary loss
Sweating
Respiratory loss (water vapor lost through breathing)
Fecal loss (some water is lost through stool, particularly if diarrhea is present)
Insensible loss (Invisible water loss through skin evaporation)
Fluid surrounds cells in tissues
Interstitial fluid
Function of interstitial fluid
Plays a crucial role in nutrient exchange
Waste removal
Interstitial fluid is formed through
The movement of water
Ions
Small molecules across capillary walls
Fluid filtration across a capillary wall depends on
The nature of the capillary wall
The forces acting on fluid filtration =starling forces
2 main starling forces
- hydrostatic pressure (pushes fluid out of capillaries into the interstitial space)
2.oncotic pressure (exerted by plasma proteins, it pulls fluids back into the capillaries)
2 main starling forces
- hydrostatic pressure (pushes fluid out of capillaries into the interstitial space)
2.oncotic pressure (exerted by plasma proteins, it pulls fluids back into the capillaries)
2 kinds of hydrostatic pressure
Capillary hydrostatic pressure (pressure exerted by blood within Capillaries)
Interstitial fluid hydrostatic pressure (pressure exerted by the interstitial fluid outside capillaries)
2 kinds of oncotic pressure (colloid osmotic pressure)
Capillary oncotic pressure (due to plasma proteins in blood)
Interstitial fluid oncotic pressure (due to proteins in the interstitial fluid)
Net filtration
=(CHP+IFOP)-(COP+IFHP)
A positive value favours _________
- value favours_________
Filtration
Reabsorption
The heart pumps blood with a pressure
So, in general, _______
Plasma protein content is higher inside capillaries
So, in general ,_____________
CHP>IFHP
COP>IFOP
NFP at venous end
CHP is low
HP<OP
fluid is reabsorbed
NFP at arterial end
CHP is high
HP>OP
fluid filters out
Define Odema
Accumulation of excess fluid in the interstitial space
2 types of oedema
Generalized oedema (oedema of whole body /anasarca)
Localized oedema:oedema of part of the body
Causes of oedema 5
- Increased capillary hydrostatic pressure
- decreased plasma oncotic pressure
- lymphatic obstruction
- Increased capillary permeability
- Sodium and water retention
Explain how increased capillary hydrostatic pressure causes oedema
Give common causes and clinical examples
Elevated pressure within capillaries forces more fluid out into interstitial spaces
Common causes
Heart failure:reduced cardiac output leads to blood backing, up in veins
Deep vein thrombosis (DVT):blood clots obstruct venous return
Clinical examples
Peripheral oedema in lower limbs
Pulmonary oedema in heart failure
Decreased plasma oncotic pressure
Mechanism ?
Common causes?
Clinical examples?
Lower levels of plasma proteins (mainly albumin)reduce the osmotic pull that retains fluid within blood vessels
Common causes
Hypoalbuminemia:due to liver disease, malnutrition,
or nephrotic syndrome
Liver cirrhosis:impaired synthesis of albumin
Nephrotic syndrome Excessive loss of proteins in urine
Clinical examples
Generalized anasarca
Ascites in liver disease
Lymphatic obstruction
Mechanism?
M:Blockage or damage to lymphatic vessels impairs the removal of interstitial fluid
CC:Surgical removal of lymph nodes:especially in cancer treatments
Infections:such as filariasis
Truma of radiation therapy can damage lymphatic pathways
Increased capillary permeability
M?
CC?
CE?
M:Inflammatory processes or injuries make capillaries more leaky, allowing proteins and fluids to escape
CC:inflammation due to infections,autoimmune diseases, allergic reactions
Infection:such as cellulitis
Truma of burns:damage to capillary walls
Toxins and Venoms:Can disrupt capillary integrity
CE:localised swelling and redness
Acute Inflammatory responses
