Welcome.
In this lecture, we will be learning about
the fluid, electrolyte, and acid base balance of the body.
So first let's look at the two main fluid compartments
found in our body.
This is going to be
where the most of our bodies water content is located.
We have the intracellular fluid compartment,
which is the fluid found inside of all of our body cells,
and accounts for two-thirds of the total body fluid.
The second compartment is the extracellular fluid compartment.
This fluid compartment can be further broken down
into two main types of fluid.
And this fluid compartment
consists of all of the fluid outside of our cells.
This accounts for one-third of our total body fluid.
The two body fluids found in our extracellular fluid compartment
include our plasma,
which is a component of our blood,
and the interstitial fluid.
This makes up about 12 liters of our total body fluid
and it's found in the spaces in between our cells.
Fluids such as the lymph,
cerebral spinal fluid,
the humors of the eye,
synovial fluid,
serious fluids,
and gastrointestinal secretions
are all considered a part of the interstitial fluid.
So if we were to break down our total body water count,
we would find that our body contains about 40 liters of water or fluid
and makes up about 60% of our total body weight.
If we divide this up into the different compartments,
we find that our intracellular fluids
are going to make up about 25 liters of our fluid content.
Whereas,
the extracellular fluid is going to make up the remaining 15.
If we divide that remaining 15 up
into the different types of extracellular fluid,
we find that the interstitial fluid
is going to have a volume of about 12 liters
while the plasma has the remaining 3 liters of volume.
So, what is our bodies fluids mostly made of?
The main component of our body fluids is water.
The reason why is because water is a universal solvent
and many different other constituents can dissolve in water.
Substances that are dissolved in water are referred to as solutes.
And water is the solvent.
We can classify solutes based on how they react in water.
We classify them as either nonelectrolytes or electrolytes.
Nonelectrolytes are going to mostly be organic molecules
and these are not going to dissociate or break apart
when they are placed in water.
Examples of nonelectrolytes include things like
glucose, creatinine, and urea.
Lipids is also an example of a nonelectrolyte.
But unlike these other examples,
it does not dissolve in water at all.
We also have electrolytes.
Electrolytes are going to dissociate into separate ions
when they are placed in water.
Examples of electrolytes include inorganic salts,
all of our acids and bases,
and also some of our proteins.
The electrolytes that break down into ions
are then able to conduct electrical currents.
This is especially important
for our electrically excitable cells in our body,
such as our neurons and our muscle cells.
Each of our fluids compartment
have distinctive patterns of electrolytes.
If we start with the extracellular fluid compartment,
we find that the electrolyte content is pretty much similar
all over the body,
except for in the plasma,
where we have a higher protein and lower chloride ion content.
Outside of this, however,
the major cation in our extracellular fluid
is going to be sodium ion.
The major anion, in our extracellular fluid
is going to be chloride ion.
In our intracellular fluid compartment.
This is going to actually contain mostly soluble proteins.
This is going to have a low sodium and chloride content.
And the major cation found inside of ourselves
is going to be potassium.
The major anion in ourselves is going to be phosphate ion.
When it comes to numbers,
electrolytes are going to be our most abundant solutes
in our body fluids
and are going to determine
most of our chemical and physical reactions.
When it comes to how much space they take up however,
the bulk of our dissolved solutes are going to be
proteins, phospholipids, cholesterol, and triglycerides.
These are going to take up about 90% of our plasma,
60% of our interstitial fluid,
and 97% of our intracellular fluid.