T3- Fluid + Electrolytes Part 1 Flashcards
How much of our body weight is composed of water?
50-60%
What stuff other than water makes up our body?
Primarily proteins, followed by lipids, minerals, carbohydrates, and miscellaneous.
How is the composition of weight broken down in a male vs a female?
A male has around 33% intracellular fluid, 21.5% interstitial fluid, 4.5% plasma, and 2% other.
In a female, 27% is intracellular, 18% interstitial fluid, 4.5% plasma, and 1.5% other.
Females have 50% of their body weight in solids, whereas males have 40%.
How does our body water change as we age?
For females, total body water, ICF, and ECF fluid all decrease.
For males, total body water and ECF decrease. ICF stays about the same.
What two organs are barely made of water?
Skeleton (bone 22%)
Adipose tissue (10%)
What two organs/things in our body are made almost entirely of water?
Blood (83%)
Kidneys (82.7%)
How much of our total body water is intracellular fluid?
2/3 of our body water.
How is ECF broken down into its components?
25% is plasma, inside the blood vessels.
74-75% is interstitial fluid, outside of the body’s cells.
1% is transcellular compartment, such as the CSF, joint spaces, GI/GU tracts and the 3 main body cavities.
What does a body fluid contain?
Electrolytes (NaCl)
Ions (cations + anions)
Non-electrolytes (glucose, urea, ethanol)
What is the predominant cation found in the ECF?
Sodium
What is the predominant cation found in the ICF?
Potassium
What is the predominant anion found in the ECF?
Chloride
What is the predominant anion found in the ICF?
Hydrogen phosphate.
What are the 3 primary cations found in the ICF?
Potassium, Sodium, Magnesium
Define diffusion.
Movement of particles along a concentration gradient, from higher to lower conentration.
Define osmosis.
Movement of water across a semipermeable membrane. (aka not all solutes can cross)
Define osmotic pressure.
The pressure water creates as it moves across a semipermeable membrane.
Specifically, it is the hydrostatic pressure needed to counter the movement of water across the membrane.
Define osmolality/osmolarity.
Osmolarity is # of solutes per L of solvent.
Osmolality is # of solutes per kg of solvent.
The greater the number, the greater the osmotic activity/pull, which draws water from one side of a membrane to another.
What is plasma osmolality?
Posm
It is the ratio of plasma solutes to water.
Plasma solutes are mainly NaCl and sodium bicarb.
Normal: 275-290 Posm.
Walmart version: 2x serum sodium!!!!!
Note: Glucose and urea account for about 5% of osmotic pressure.
What can cause rare changes in Posm?
Alcohol and acetones!
What are plasma and ECF osmolality generally the same as?
ICF
Cell membranes are mostly permeable to water, so equilibrium is established.
What is Urine osmolality?
of solutes per unit of water in urine.
Higher Uosm = concentrated urine.
What is the effect of ADH on Uosm?
Increases it.
We secrete ADH when we need to retain water, so increased ADH would concentrate our urine, making the Uosm high. We would secrete ADH when our Posm is high, since we want more water to dilute our Posm.
High Posm => increased ADH => increased Uosm
What is normal Uosm? How does it change if I am dehydrated?
500-800 mOsm/kg.
12-14 hrs of restricted fluid intake can increase it to 850.
Clinically dehydration can increase it to 1000.