Fluid Balance Flashcards
Intracellular fluid (ICF)
Collective volume of water inside all of the cells. Accounts for 2/3 of total body weight (TBW)
Extracellular fluid (ECF)
Fluid in the interstitial space and blood plasma outside of the cells (1/3 TBW)
Functions of the kidney
- Regulates body fluid volume and osmolality
- Regulates electrolytes
- Regulates acid-bases
- Excretes metabolic products
- Secretes hormones, vit D
Plasma (intravascular fluid)
Fluid portion of the blood and makes up 1/4 of ECF
Interstitial fluid
Fluid in the tissues, closely resembles ion concentration of plasma, but lacks proteins. Eventually returns to the venous system (makes up 3/4 of ECF)
What is a typical daily water output
2 to 3 liters through urine, feces and perspiration
What is a typical daily intake of water
~2.5L. 300-500 is metabolic water intake. Any water lost due to extreme sweating needs to be replaced on top of 2.5L
What is water balance regulated by
Thirst (increase in plasma osmolality) and ADH hormone
What does ADH do
stimulates water conservation at the nephron
Where is ADH released from
the hypothalamus (pituitary gland). Occurs when plasma osmolality exceeds a set-point or person is thirsty
Third spacing
When ECF moves into a space between the skin and fascia (outside the interstitial space) “third space”
What other way is the third space referred to
non-functional compartment because the fluid is unavailable for use with the intravascular system
What is an example of third spacing
Ascites
Interstitial edema
Different from 3rd spacing. Is caused from large volume of fluid in the circulatory system. Is functional because it can be used by circulatory system still
What is an example of interstitial edema
lymphedema
Osmosis
Net movement of solvent (water) through semipermeable membrane to area of higher solute concentration (NaCl) and lower water concentration
Osmolarity
The total amount of solute in a solution (per L)
Tonicity
The ability of a solute to cross a membrane. Based on pressure gradiant of two solutions (which way things will flow)
Isotonic
A solution that has the same concentration of solutes both inside and outside the cell
Hypertonic
Solute concentration is higher outside the cell, water flows out, cell shrinks
Hypotonic
Solute concentration is higher inside the cell, water flows in, cells bursts
Which ion is the most abundant EC solute
Na+
Which ion has the most effect on ECV
Na+, because water follows it and will increase ECV if there is a high Na+ outside the cell
What regulates Na+
The kidney, Na+ is reabsorbed along the nephron, depending on EC tonicity
Which ion is found almost exclusively in IC fluid
Potassium
What is the role of K+
Helps maintain membrane resting potential, aids in cell membrane excitability. Heart conduction and nerve transmission
How is K+ regulated
Excreted mostly at distal tubule of nephron (with Na+). Aldosterone, acidosis/alkalosis,
Where is Ca+ predominantly located
IC in bone
What is the role of Ca+
Bone formation, membrane excitability, coagulation
How is Ca+ regulated
By parathyroid home stimulates calcitonin from bone. Reabsorbed at kidney
Where are the Ca+ regulation sites
Kidney, GI, Bone
What is the concentration level of H+ like in the body
Very low concentrations
High H+ means
Acidic
Low H+ means
Alkaline (basic)
Where is H+ regulated
By buffer systems in the kidney and lungs
How is H+ regulated
IC pH, aldosterone, and K+ concentrations. Also breath it off or it turns into HCO3 in kidney or is excreted
How is H+ removed
It is excreted or recycled as HC03
What is the function of Cl-
Help keeps things electrically neutral by working with Na
Where is Cl- controlled
At the nephron with Na+. If body needs more salt, it will reabsorb the Cl- with Na+. If body has too much, the cl- will be excreted. passive process.