Body fluid compartments- Week 1 Flashcards
What are the ways the body looses water?
-insensible losses
-sweat
-feces
-kidneys
How much water is ingested in a day?
2100ml/day
how much water is synthesized by the body via oxidation of carbs?
200mL/day
What is the total water intake in a day?
2300ml/day
How much water is lost from evaporation during the day? (insensible water loss)
700mL/day
What is the most important means by which the body maintains a balance between water intake and output (and electrolytes)?
Controlling the rate the kidneys excrete these substances.
What is transcellular fluid?
The Compartment contains fluid in synovial, peritoneal, pericardial, CSF, and intraocular spaces
Considered a specialized type of extracellular fluid
Constitute 1-2L
In a 70kg man, what percentage of body weight is water?
60% or 42L
- dependent on age, gender and obesity
As a person gets older, the percentage of total body weight:
DECREASES
d/t increase fat
Is the protein level higher in the plasma or interstitial fluid?
plasma
(d/t low membrane permeability)
Is the capillary membrane separating the interstitial and plasma permeable or impermeable?
highly permeable
What separates the intracellular fluid from the extracellular fluid?
cell membrane
Is the cell membrane permeable or impermeable?
highly permeable to water NOT electrolytes= semipermeable
What is the composition of the extracellular fluid regulated by?
Kidneys
What is the Gibbs-Donnan Equilibrium?
When 2 solutions containing ions are separated by a membrane that is permeable to some ions and not to others, and electrochemical equilibrium is established
electrical and chemical energies on either side of the membrane are equal and opposite of eachother
Bc of the Gibbs donnan effect positively charges ions (cations) are slightly greater where?
PLASMA
-plasma proteins, sodium and potassium
Anions are higher where?
Interstitial fluid
What is the compartment volume measurement?
The principle of conservation of mass.
The total mass of a substance after dispersion in the fluid compartment will be the same as the total mass injected into the compartment
What determines the distribution of fluid between the intracellular and extracellular compartments? (across the cell membrane)
the osmotic effect of small solutes
Na+ and Cl-
What determines fluid distribution between interstitial and plasma compartments? (across the capillary membrane)
balance of hydrostatic and colloid osmotic forces across the capillary membrane
What is the rate of osmosis?
the rate of diffusion of water
What is a Mole?
defining specific quantity of molecules
What is an osmole?
of particles in a solution
What is osmolality?
Osmoles / kg of water
What is osmolarity?
Osmoles / liter of solution
What is osmotic pressure?
amount of pressure required to PREVENT osmosis
Molecules that disassociate when dissolved into a solution have more:
osmotic effect
What is Van’t Hoff’s Law?
Once can calculate the potential osmotic pressure of a solution, assuming that the cell membrane is impermeable to that solute.
What electrolytes determine the osmolarity of the extracellular fluid?
Sodium and Chloride
What electrolytes determine the osmolarity of the intracellular fluid?
Potassium
Whats the total osmolarity of each compartment?
300 mOsm/L
What is the effect if isotonic saline is added to the extracellular compartment?
the only effect is an increase in extracellular fluid volume
If a hypertonic solution is added to the extracellular fluid what is the effect?
Increased extracellular osmolarity, fluid leaves cells to increase extracellular fluid.
Decreased intracellular volume, rise in osmolarity in both compartments
If hypotonic solution is added to extracellular fluid what happens?
Water diffuses into the cells, and intravascular volume increases.
What causes Hyponatremia?
Excess water
Loss of sodium
Diarrhea & vomiting
diuretic abuse
addison’s disease
excess water retention (ADH)
What causes hypernatremia?
Loss of water
excess sodium
lack of ADH
DI
dehydration
Aldosterone secretion
What happens of plasma sodium concentration falls below 115-120 mmol/L?
-brain swelling
-seizure
-coma
-perm. brain damage
-death
a rapid reduction in plasma sodium concentration can cause brain cell edema and neurological symptoms- headache, nausea, lethargy, disorientation
Primary loss of water from extracellular fluid results in?
-Hypernatremia
-dehydration
what kind of urine is excreted in central diabetes insipidus?
dilute urine
What level of sodium willl you see symptoms related to hypernatremia?
158-160 mmol/L
what are the effects of hypernatremia?
increased thirst, and secretion of antidiuretic hormone
how would you correct hypernatremia?
hypo-osmotic sodium chloride or dextrose solutions
where does edema occur?
EXTRACELLULAR FLUID COMPARTMENT
when would you see intracellular edema?
-inflammation has a direct effect on increasing cell membrane permeability
-depression of cellular metabolic function
-lack of nutrition to the cell
-decreased blood flow: reduced o2 and nutrient supply
-ionic pumps of the cell membrane require oxidative metabolism (ATP) to remove intracellular sodium
What causes extracellular edema?
1.) abnormal leakage from plasma
2.) lymphatic failure to return fluids to blood
-lymphatic blockage
What causes an abnormal leakage from plasma?
-increase capillary filtration
-increased capillary hydrostatic pressure
-decreased plasma colloid osmotic pressure
what causes increased capillary pressure?
1.) excessive kidney retention of sodium and water
2.) high venous pressure and venous constriction
3.) decreased arteriolar resistance
What causes decreased plasma protein concentration?
-loss of proteins in the urine (nephrotic syndrome)**
-loss of protein from denuded skin areas
-failure to produce proteins
What causes increase capillary permeability?
-immune system reactions (histamine release)
-toxins
-bacterial infections
-vitamin deficiency (esp. vit C deficiency)
-prolonged ischemia
-burns
What causes a blockage of lymph return?
-cancer
-infections (filaria nematodes)
-surgery
-congenital absence or abnormality of lymphatic vessels
What causes edema in heart failure?
blood flow to kidneys is reduced = secretion of renin–> angiotensin 2–> aldosterone= additional salt and water by kidneys
summary of causes of extracellular edema:
1.) increased capillary pressure
2.) decreased plasma proteins
3.) increased capillary permeability
4.) blockage of lymphatic return
What are the 3 main factors that prevent edema?
1.) low interstitial compliance (-3mmhg)
2.) ability to increase lymphatic drainage
3.) “wash down” of interstitial fluid proteins (as lymphatic flow increases proteins are washed away)
6 major functions of the kidneys:
1.) maintenance of extracellular volume and composition
2.) blood pressure regulation (long and intermediate term)
3.) excretion of toxins and metabolites
4.) maintenance of acid-base
5.) hormone production (erythropoietin, calcitriol, prostaglandins)
6.) blood glucose homeostasis
Why do we have kidneys?
-regulation of fluid volume and body fluid composition
-excretion of metabolic waste and foreign chemicals
-secretion of certain hormones
what is the hilus?
vertical cleft where ureter and vein and artery enter/exit
lies at L1
What is the total safety factor against edema?
17mmHg (3, 7, 7)
capillary pressure can double before significant edema occurs
where do the kidneys lie?
paravertebral gutters, behind the peritoneum, with the right slightly lower d/t liver
What is the functional unit of the kidney?
nephron
Where does plasma filtration occur?
glomerulus
what is the juxtaglomerular responsible for?
concentration of urine
what percentage of the cardiac output does the kidney receive?
22% (1100ml/min)
oxygen consumption in the kidney varies directly with:
active transport of Na+
where does the highest metabolism take place in the kidney?
renal cortex
on a per gram basis______
renal blood flow is the highest of any organ
makes up .4% of body weight - most highly perfused major organs in body
14mL/L kidney
60ml/L muscle
140ml/l hearty
what are the cortical nephrons?
short loops of henle extend to outer medulla, glomeruli in outer cortex
- MORE
What are the juxtamedullary nephrons?
loops of henle extend deep into the medulla, glomeruli near the corticomedullary border, larger glomeruli, higher GFR
-PLAY A BIG ROLE IN CONCENTRATING URINE
- kidney cannot regenerate new nephrones
what is the glomerulus?
-high-pressure capillary bed
-the site of blood filtration
what is the bowman’s capsule?
-funnel-like structure “beginning of nephron”
each nephron has its own_____ _____ ____
independent blood supply (renal arterioles and veins)
what is considered the beginning of the nephron?
bowman’s capsule
