Week 1 Renal Flashcards
Water is added to the body by two major sources?
(1) it is ingested in the form of liquids or water in food, which together normally add about 2100 ml/day to the body fluids
(2) it is synthesized in the body by oxidation of carbohydrates, adding about 200 ml/day. These mechanisms provide a total water intake of about 2300 ml/day.
Breakdown of the body fluid compartments?
60/40/20/16/4
Plasma & interstitial (extracellular) fluids are similar in composition?
Highly permeable capillary membrane
Protein level > in plasma because of low membrane permeability
Intracellular Fluid
Separated by cell membrane
Highly permeable to water not electrolytes (semi-permeable)
What is the Gibbs Donnan Equilibrium
-when two solutions are separated by a membrane that is permeable to some ions but is not to others an electrochemical equilibrium is established
-electrical and chemical energies on either side of the membrane are equal and opposite to each other
Conservation of mass principle
the total mass of a substance after dispersion in the fluid compartment will be the same as the total mass injected into the compartment.
If none of the substance leaks out of the compartment, the total mass of substance in the compartment (Volume B × Concentration B) will equal the total mass of the substance injected
Describe the fluid exchange and osmotic equilibrium
-Distribution of fluid between intracellular & extracellular compartments determined by osmotic effect of small solutes.
-Electrolytes or small ions (i.e.: sodium & chloride) determine distribution of fluids across the semi-permeable cell membrane
-Osmotic factors cause fluids to shift between compartments
What is the rate of osmosis?
The rate of diffusion of water is called the are of osmosis
What is the osmolality?
Osmoles / kg of water
What is osmolarity?
Osmoles / liter of solution
What is osmosis?
-the net diffusion of water across a selective membrane
-high water concentration to low water concentration
What is osmotic pressure?
-refers to the amount of pressure required to prevent osmosis
-Pressure applied in opposite direction of osmosis
Total osmolarity of both the interstitial fluid and plasma, and intracellular fluid?
Total osmolarity of each compartment @ 300 mOsm/L
Net effect of an isotonic solution?
increase in extracellular fluid volume
Net effect of a hypertonic solution?
an increase in extracellular volume (greater than the volume of fluid added), a decrease in intracellular volume, and a rise in osmolarity in both compartments
Net effect of a hypotonic solution?
Both the intracellular and the extracellular volumes are increased by the addition of hypotonic fluid, although the intracellular volume increases to a greater extent.
What is hyponatremia and what are some conditions that can cause it?
Hyponatremia: excess water and loss of sodium
Conditions that can cause:
-diarrhea and vomiting
-diuretic abuse
-Addisons disease (decreased secretion of the hormone aldosterone, impairs the ability of the kidneys to reabsorb sodium and can cause a modest degree of hyponatremia)
-excess water retention (ADH)
Causes of Hypernatremia?
-inability to secrete antidiuretic hormone, which is needed for the kidneys to conserve water. As a result of lack of antidiuretic hormone, the kidneys excrete large amounts of dilute urine (a disorder referred to as“central” diabetes insipidus
-kidneys cannot respond to antidiuretic hormone, causing a type of“nephrogenic” diabetes insipidus.
Two general causes of extracellular edema?
- Abnormal leakage from plasma
-Excessive capillary filtration rate
-Filtration dependent on permeability & surface area of capillary
-Starling factors: hydrostatic pressure & colloid osmotic pressure
-Histamine release- anaphylaxis - Lymphatic failure to return fluids to blood
-Lymphatic blockage preventing return of proteins to plasma
-Increased interstitial colloid osmotic pressure
-Cancer, surgery, infection (filaria nematodes)
Abnormal leakage from plasma overview?
Increased capillary filtration coefficient
Increased capillary hydrostatic pressure
Decreased plasma colloid osmotic pressure
Calcium channel blockers primarily arterial dilate compared to venous dilation which can cause edema
Edema caused by heart failure?
Blood flow to the kidneys is reduced and this reduced blood flow stimulates secretion of renin, causing increased formation of angiotensin II and increased secretion of aldosterone, both of which cause additional salt and water retention by the kidneys
Other causes of extracellular edema?
-Increased capillary pressure
Retention of sodium & water
High venous pressure
-Decreased arteriole resistance
Decreased plasma proteins
Loss of proteins
Failure to produce proteins
-Increased capillary permeability
Immune reactions
Infection & toxins
Burns & ischemia
-Blockage of lymphatic return
Safety factors that prevent edema?
- The safety factor caused by low tissue compliance in the negative pressure range is about 3 mm Hg.
- The safety factor caused by increased lymph flow is about 7 mm Hg.
- The safety factor caused by washdown of proteins from the interstitial spaces is about 7 mm Hg.
Therefore, the total safety factor against edema is about 17 mm Hg.
What percentage of cardiac output is the kidneys?
22% (1100ml/min)
What is the nephron?
Functional unit of the kidney
What are cortical nephrons
Short loops of Henle, extend to outer medulla
Outnumber juxtamedullary nephrons ~7:1
What are Juxtamedullary nephrons?
Extend deep into medulla with long loops of Henle
Play a big role in concentrating urine
Few juxtamedullary nephrons
Which nephrons comprise the largest percentage in the human kidney?
cortical nephrons
Interstitial space compliance is _____________ as a defense mechanism against edema.
low
The osmolarity of plasma is primarily due to?
80%: Sodium and chloride
Parts of the loop of henle?
consists of a thin descending limb
a thin ascending limb
a thick ascending limb
What percent of nephrons are juxtamedullary?
15%
The relative amounts of extracellular fluid distributed between the plasma and interstitial spaces are determined mainly by the balance of?
sodium and chloride
The greatest blood flow per gram of tissue goes to which organ?
kidney
Which value below is closest to normal serum osmolarity?
300
