1 Body Fluid Compartments Free interactive Physio tools
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- Slide 1
- 1 Body Fluid Compartments Free interactive Physio tools
http://www.winona.edu/biology/adam_ip/home/
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- 2 Lecture outline I. Water compartments of the body
A.Intracellular B. Extracellular i. Interstitial ii. Plasma iii.
Transcellular II. Compare/contrast water compartments A. Size B.
composition C. Osmolality III. How do we have different
composition/ movement of solutes A. Different permeability B. Types
of transport across the membrane for solutes--Protein transporters
C. Review of Simple diffusion of solutes IV. Movement of water A.
Osmosis-movement across cell membranes due to unequal particles B.
Hydrostatic pressure- movement across capillaries V. Examples of
when water vs. solute moves VI. Definition of osmotic pressure A.
Examples of osmotic pressure differences in body fluid compartments
VII. Tonicity vs osmolality A. Examples of tonicity and
osmolality
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- Body Fluid Compartments Why do you need to understand body
fluid compartments and osmolarity calculations? Many of you will be
applying IV care for patients, and sometimes doctors make mistakes,
so you need to be able to catch these errors. Most medical
solutions are calculated in units that dont require a periodic
table of elements, but if someone miscalculates a solution, and you
inject it, and the patient crashes, you are just as liable, and you
will be sued. 3
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- 4 Water Water makes up 60% of our body weight Divide this into
two compartments Intracellular water Extracellular water
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- 5 Compartments Intracellular Fluid (60% Body Wt) Extracellular
Fluid Interstitial fluid (the water immediately outside cells,
between and around cells) (30%) Plasma fluid (the water inside
blood vessels, but not in blood cells) (9%) Transcellular fluid
(the water enclosed in chambers lined by epithelial membranes) (1%)
These are stomach epithelial cells Lumen of stomach * * * *
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- Body Fluid Compartments If you manipulate one body fluid
compartment, it has an effect on another compartment. Body fluid
compartments have different sizes and volumes, and different
compositions. Although the volume and substances dissolved in the
fluid of one compartment is different than another compartment,
each compartment has the same number of particles dissolved in the
water. 6
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- Body Fluid Compartments Therefore, size and composition (what
particles are dissolved in the water) does not have an effect on
the number of particles dissolved in the water of each compartment.
If you could count every particle dissolved in the water of that
compartment, you would see that in all the compartments there are
the same number of particles: 300 million particles per liter,
expressed as 300 million osmoles or 300 mili-osmoles. It could also
be described as having an osmolarity of 300. 7
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- Body Fluid Compartments That means that there are 300 million
particles (or 300 milliosmoles, abbreviated 300 mOsm) dissolved in
each liter of water in each compartment. If one compartment has
more particles than another one next to it, and if those particles
cannot reach equal numbers on their own because the cell membrane
blocks their passage, water will try to dilute the compartment with
the higher number of particles until they are at the same number of
particles per liter. Water always moves across the compartments
because cell membranes always allow water to pass. 8
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- 9 Body Fluids compartments Different compositions (different
amounts of individual particles). For example, one coffee cup has 1
teaspoon of instant coffee and 2 teaspoons of sugar, another cup
has 2 teaspoons of coffee and 1 teaspoon of sugar. Different
volumes (one coffee cup holds 8 oz, another holds 16 oz) Same
osmolalities (total number of particles) When you evaporate away
the liquid in both coffee cups and count each coffee grain and each
sugar grain, there are 300 million total grains per liter in both
cups. 0.3 Osmolal = 300 mOsmolal ( actually closer to 280mOsmolal)
IntracellularInterstitialPlasma
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- Diffusion If the plasma becomes diluted to 260 mOsm, and the
cells next to a blood vessel are still at 300 mOsm, the cells now
have more particles. By a law of physics, all particles want to
move from an area of high concentration to an area of low
concentrationThat is why perfume will diffuse out of the bottle and
fill up the room if you leave the top off. Therefore, since the
particles in the cells are 300 mOsm and the particles in the blood
vessel are 260 mOsm, which way do the particles want to move? The
particles in the cells will want to move into the plasma. However,
the cell membranes will not allow them to pass, so they are stuck
inside the cell. The next force of nature that will kick in is
water diffusion. Water also wants to move from its area of high
concentration to an area of low concentration. 10
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- Diffusion If I have 2 identical cups with the same amount of
water, and I add 20 teaspoons of lemonade to one cup and 10
teaspoons of lemonade to the other cup, which cup is more
concentrated with lemonade? The one with the most particles (20
teaspoons). Which one is more concentrated with water? The one with
the fewest particles (10 teaspoons). If these two solutions were in
body fluid compartments that were next to each other, and if the
particles cannot move from their area of high concentration to low
concentration, then water will move from its area of high
concentration (which was the more watery cup; the one that had only
10 teaspoons of lemonade) to its area of low concentration (the cup
with low WATER concentration was the one with 20 teaspoons of
lemonade). That is the same thing as saying that particles suck
water. 11
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- Diffusion What will move, in order to dilute the cells? Water.
Why? Because particles suck! In the case where the plasma has 260
mOsm (260 particles per liter) and the nearby cells have 300 mOsm
(300 particles per liter), will the cells will draw the water into
themselves, or will the plasma draw water into the blood vessel?
The compartment with more particles (the cells) will suck the water
in. Therefore, water will move from the plasma to the adjacent
cells. What will that do to the cells? They will lyse (rupture).
When would that ever happen in real life? 12
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- Diffusion When would that ever happen in real life? January 12
th, 2007, A 28 year-old mother of three from Sacramento decides to
go on a radio program to compete in a contest called, Hold your Wee
for a Wii. They offered a prize to the person who could drink the
most water in two hours without going to the bathroom. During this
contest, she drank 6 liters in 2 hours (3 liters an hour). The
maximum the kidney can filter is 1 liter an hour. After the
contest, she called her co-workers to say she wasnt coming to work
because her head hurt so badly. Later she is found dead. 13
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- Diffusion She was OVER hydrated, so the original 300 particles
per liter in her plasma were now at 300 particles per 2 liters,
since the excess water increased her blood volume. That means there
were only 150 particles per liter, so overall, there were now fewer
particles in the plasma than in the adjacent cells. Therefore, the
adjacent cells had more particles, and they sucked in the water.
Her brain cells also sucked up the water until they ruptured and
exploded in her skull. 14
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- Overhydration Drinking too much water changes the extracellular
osmolality. When the plasma is too dilute (too much water, too few
solutes), water will leave the bloodstream to enter the tissues,
where there are more solutes (solutes SUCK!). Water will enter the
tissues (intracellular body fluid compartment), including the
brain. The excess water will cause the brain to swell. 15
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- Overhydration Thus, we learn that if a person is over-
hydrated, the plasma will be diluted below 300 mOsm, but the cells
still have 300 mOsm in particles. So, the cells will draw in more
water from the plasma and the cells will enlarge and rupture. She
should have been given an IV that was hypertonic (greater than 300
mOsm) to balance out the number of particles in the plasma so it
matched the number of particles in the cells. 16
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- Dehydration The opposite is true for someone who is dehydrated.
Since the original number of particles was 300 million particles
per liter, and then the patient became dehydrated, they would now
have 300 million particles per half a liter (since they lost plasma
volume due to dehydration), so their plasma is actually at 600 mOsm
per liter. Therefore, if a patient is mildly dehydrated, you will
give an IV that was hypotonic (less than 300 mOsm, be careful of
the drip rate) to balance out the number of particles per liter
within the plasma and within the adjacent cells. This has the same
effect as having the patient drink some water, but the iv will work
faster. 17
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- Dehydration If a doctor accidentally tells you to give a mildly
dehydrated patient an IV solution that is hypertonic (greater than
300mOsm), the plasma will have more particles than the cells, and
the cells will have the water sucked out of them, which also causes
death. Hypertonic solutions are only okay for an overhydrated
person, or a dehydrated person who has lost particles, such as from
blood or electrolyte loss after surgery. Understanding body fluid
compartments is important! 18
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- Sources of water intake/output 19 Water intake must equal water
output 2500 ml
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- Thirst mechanism for regulating water intake 20 Na+ acts as a
powerful water magnet, but the kidney and brain hormones can
regulate water independently of Na+. Drinking water satisfies
thirst before the water is absorbed because the mouth, throat, and
stomach sensors provide feedback signals that inhibit the thirst
center in the brain.
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- Types of Dehydration Isotonic fluid deficit Hypotonic fluid
deficit Hypertonic fluid deficit 21
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- Isotonic fluid deficit Type of Loss: solute and water loss
proportional, no change in plasma volume, serum sodium level is
decreased to 125-150 mEq/L. The cause of the fluid loss is GI fluid
loss (vomiting or diarhea), urine loss and decreased oral intake.
Clinical signs: poor skin turgor; cold, dry dusky skin; sunken
eyes; dry mucous membranes; depressed fontanelles in babies; rapid
pulse; low B/P; irritability or lethargy Fluid Replacement
Guidelines: Initially, a bolus of 0.9% sodium chloride or Ringer's
lactate is given followed by 5% Dextrose in water and 0.45% sodium
chloride. Half of the deficit should be replaced in the first 8
hours and the remaining half over the next 16 hours 22
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- Hypotonic fluid deficit Type of Loss: More solute is lost than
water. Plasma volume moves from the ECF to the ICF. Serum sodium
levels are decreased below 125 mEq/L. The cause of the fluid loss
is often a GI fluid loss with hypotonic oral intake. Clinical
Signs: Include very poor skin turgor; cold, clammy, dusky skin;
sunken eyes; slightly dry mucous membranes; depressed fontanelles
in babies; rapid pulse; very low blood pressure; lethargy; coma;
seizures Fluid Replacement Guidelines: Initially a bolus of 0.9%
sodium chloride or Ringer's Lactate followed by 5% Dextrose in
water and 0.9% sodium chloride. If the patient is severely
symptomatic 3% sodium chloride at 4mL/kg should be given over 10
minutes with close monitoring. Half of the fluid deficit should be
replaced in the first 8 hours and the remaining half over the next
16 hours. 23
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- Hypertonic fluid deficit Type of Loss: There is greater water
loss than solute loss. Volume moves from the ICF to the ECF. Sodium
levels are maintained at over 150 mEq/L. The cause is GI fluid loss
with hypertonic oral intake, diabetes insipidus, fever and
hyperventilation. Clinical Signs: Include fair skin turgor; cold,
thick and doughy skin; sunken eyes; parched mouth; depressed
fontanelles in babies; a moderately rapid pulse; moderately low
blood pressure; hyperirritability; high-pitched crying in babies;
seizures. Fluid Replacement Guidelines: 5% Dextrose in water and
0.225% or 0.45% sodium chloride. If the patient is hypertensive
0.9% sodium chloride or Ringer's lactate should be given at a rate
of 20mL/kg over one hour. Fluid replacement should be given slow
and gradual over 48 hours. 2 to 3 mEq/kg of potassium should be
given per 24 hours. At least 2 mEq/L/hour of sodium should also be
included in the IV fluids that are used. 24
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- Patient Case 1 Patient recovering from bacterial infection has
been suffering with diarrhea. He has not been able to eat or drink
anything. Low BP=70/40, High Pulse-110bpm. Do you give an iv
solution that is hyper, hypo, or isotonic? Why? 25
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- Patient Case 1 Give Isotonic solution (ringers solution). The
person has a high pulse rate and low blood pressure. Since the
person is severely dehydrated, but the water loss and particle loss
are equal (diarrhea or vomiting) you do not want to overhydrate the
cells with a hypotonic solution and you don't want to make the
dehydration worse by giving him a hypertonic solution, thus you
give him an isotonic solution. 26
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- Patient Case 2 Patient, age 24, has been suffering from food
poisoning with vomiting and diarrhea. He has been drinking a lot of
plain water, not Gaitoraid or Pedialite. Skin and mucous membranes
are dry, and he's complaining of a headache. Heart rate is normal,
but he has high BP=200/120. Do you give an iv solution that is
hyper, hypo, or isotonic? Why? 27
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- Patient Case 2 The person has hypotonic dehydration, so give a
hypertonic solution. He has excess solute loss from GI distress,
while replacing it with plain water. His plasma fluid has more
water than particles, water moves from the plasma to the
interstitial space, and then into the cells. This can lead to
shock. The headache is from the brain cells swelling from the
excess water they have absorbed. He should have replaced the
electrolytes by drinking something like Gaitoraid or Pedialite.
28
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- Patient Case 3 A 35 year old patient recovering from food
poisoning has been vomiting and eating only Saltine crackers. She
has a moderately rapid pulse and moderately low blood pressure Do
you give an iv solution that is hyper, hypo, or isotonic? Why?
29
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- Patient Case 3 She has a hypertonic fluid deficit, so she needs
a hypotonic solution. The salty crackers replaced the sodium lost
from GI distress, but the salt replacement exceeded the water
replacement, so her plasma is hypertonic. 30
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- Body Weight in Water There are 100 trillion cells in your body,
25% of them are red blood cells (RBCs). Dead RBCs are the reason
why your pee is yellow and your poop is brown! You will understand
why, later in the semester. About 60% of your body weight is from
water. How can you calculate your water weight? For every 2.2
pounds, you are 1 kg in weight. Take your weight in pounds and
divide by 2.2. Then multiply that number by 0.6 to see how much
water is in your body. Water makes up 60% of our body weight 70 kg
man X 0.6 = 42 kg = 42 L of water is in his body How much of your
own weight is water? If you weigh 150 lbs: 150 lbs/ 2.2 = 68 kg 68
x 0.6 = 40.8 Liters 31
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- Body Fluid Compartments The total amount of water in your body
is divided into two compartments Intracellular water is inside of
your cells. Most of your water is here (60%). Extracellular water
is outside of your cells. There are three types. Interstitial fluid
(the water immediately outside cells, between and around cells)
(30%) Plasma fluid (the water inside blood vessels, but not in
blood cells) (9%) Transcellular fluid (the water enclosed in
chambers lined by epithelial membranes, including the GI tract and
synovial joints) (1%) 32
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- Composition of Compartments All compartments are not the same
size. Which is the biggest? Intracellular Whats the smallest?
Trancellular The inside of each cell is low sodium and calcium, and
high in potassium and proteins (there are four times as many
proteins in cells than there are in plasma). Outside of cells (in
the plasma) are high in sodium and calcium, low in potassium and
proteins. Sodium has the highest extracellular fluid to
intracellular fluid concentration ratio for most mammalian cells.
33
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- Homeostasis of Osmolarity As stated, if you could count all the
solutes (particles) inside and outside of the cell, they are the
same number (300 mOsm). Why does it need to be that way? All
particles pull water to them, whether the particle is glucose,
calcium, a protein, salt, etc. We dont want a net gain or loss of
fluid across the cell membrane or the cell will shrink or burst.
Not all compartments have the same volume liquid, but they all have
the same number of particles per liter. 34
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- Cell membranes are semi-permeable If the numbers of particles
are always the same, how can we have higher numbers of potassium
ions inside of the cell compared to the outside of the cell? Wont
the potassium ions want to move down their concentration gradient
towards equilibrium? Yes, they will want to, but the cell membranes
are designed to be semi-permeable (they will only let certain
substances come into and go out of the cell). The cell membranes
prevent potassium (and other particles) from crossing. 35
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- Diffusion If you have a cell immersed in pure water, will it
shrink or burst? The particle concentration is higher in the cell
than in pure water, so the particles want to leave the cell and
enter the pure water. However, they cannot do that because they are
blocked in by the cell membrane. That means there are more
particles on the inside of the cell than in the pure water.
Particles suck, so pure water will get sucked into the cell until
the cell bursts. In theory, if the substance we are talking about
was a particle that can cross the cell membrane whenever it wants
to, it would simply diffuse across the cell membrane until it
reached equilibrium, so the cell would not burst. 36
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- 37 What particles can cross the cell membrane? Gases (O2, CO2)
Lipids and lipid-loving (hydrophobic or lipophilic) substances,
such as alcohol
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- 38 Functions of Membrane- Selective Permeability and Transport
Selectively permeable- allows some substances to pass between
intracellular and extracellular fluids Only small uncharged
molecules or fat soluble molecules can pass through membrane
without help. They get through by one of two types of ways: Passive
transport means that energy (ATP) is not needed to get a particular
substance across the cell membrane. Active transport means that ATP
is used.
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- 39 Membrane Function There are three types of Passive
Transport: 1) Simple Diffusion 2) Facilitated Diffusion 3) Osmosis
All of these involve particles crossing from high to low
concentration. Osmosis is diffusion of WATER across a CELL
MEMBRANE.
http://www.northland.cc.mn.us/biology/BIOLOGY1111/animations/passive1.swf
Osmosis only happens if the solute is permeable across the cell
membrane!
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- Permeability A water-hating (hydrophobic) substance can cross a
cell membrane. A very small water-loving (hydrophilic) substance
can also cross, such as gasses or a water molecule itself. However,
a larger water-loving molecule needs a special protein channel in
the cell membrane to help it to cross. If it does not require
energy (ATP), it is called facilitated diffusion (facilitated means
helping). If it requires ATP, it is crossing by an active transport
mechanism. 40
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- Facilitated diffusion Facilitated diffusion is when an ion
wants to travel down its concentration gradient, but there is a
channel in the cell membrane that opens and closes by a protein
which enlarges or shrinks to open or block the channel (remember,
this is still passive transport, so it does not need ATP). 41
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- Three types of Passive Transport: Simple Diffusion Facilitated
Diffusion Osmosis 42
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- Active Transport Active Transport is when a substance needs to
move against its concentration gradient (it is moved from an area
of low concentration on one side of the cell membrane to an area of
high concentration on the other side of the cell membrane). It
accomplishes this because a protein embedded in the cell membrane
grabs onto the substance and drags it across the cell membrane
(this requires ATP). 43
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- Active Transport There are three main types of active
transport: Ion Pumps Cotransport Endocytosis Because these are
active transport mechanisms, ATP is used. 44
http://www.northland.cc.mn.us/biology/BIOLOGY1111/animations/active1.swf
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- Transport of Water There are two ways that water can move:
Osmosis Hydrostatic pressure 45
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- Hydrostatic vs. Osmotic Pressure Hydrostatic pressure is water
being pushed out by some force. If there is a lot of water in the
blood vessel, it will get pushed out, causing edema in the tissues.
Osmotic pressure is water moving from its area of high
concentration to its area of low concentration. If there are too
many particles in the plasma, water will be sucked into the blood
vessel, causing the blood pressure to elevate. 46
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- Hydrostatic Pressure Fluid is forced out of systemic
capillaries at the arteriolar end because the hydrostatic pressure
of the blood is greater than the osmotic pressure of the intestinal
fluid. 47
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- 48 Movement of water Always passive Pores (called aquaporins)
in the cell membrane serve as conduits (conducting channel) Osmosis
Water wants to move from its area of high concentration (less
particles in the water) to its area of low concentration (more
particles in the water). When it crosses a cell membrane to do
this, it is called osmosis. In a solution, water is called the
solvent and the particles are called the solutes. Hydrostatic
pressure This is the pressure of the fluid exerted on the vessels,
or container. If you squeezed on this bottle to get the water to
shoot out, what kind of pressure would this simulate?
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- Hydrostatic Pressure Squeeze a water bottle to shoot the water
out, this is hydrostatic pressure. Hydrostatic pressure is the
pressure of the water exerting on the blood vessel wall. If you
push harder, the water will shoot farther. The hydrostatic pressure
of water being filled in a balloon will exceed the capacity of the
balloon and pop. That is how water moves between cells and into
cells so that plasma becomes interstitial fluid. The plasma leaks
out between the cells that make up the capillaries. If you have a
swollen ankle and apply an ace wrap, you are applying hydrostatic
pressure to force interstitial fluid back into the plasma.
Hydrostatic pressure is not the movement across a cell membrane.
That is osmosis. 49
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- Osmosis Osmosis is movement of water across the cell membrane.
Osmosis will occur when there is a difference of particle
concentration on each side of a cell membrane. Osmotic pressure can
be measured. If there is more water on one side of a membrane than
the other side of the membrane, the water will move down its
concentration gradient. This occurs when there are more particles
on one side of the membrane than the other, but the particles are
not free to diffuse across until they reach equilibrium. 50
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- Dialysis Tubing Demonstration Dialysis tubing is a flexible
tube that looks like plastic sausage tubes, but they are
semipermeable like a real cell membrane. Dialysis tubing is used in
laboratory demonstrations about osmosis because it is not permeable
to glucose but water can cross it. It helps you learn about the
body because glucose also cannot get across the bodys cell
membranes, but water can. 51
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- 52 In another laboratory demonstration, water will move past a
sheet of dialysis tubing in a column until it reaches a certain
column height. It does not continue to climb higher and higher in
the column indefinitely, because gravity will be exerting forces on
it too (hydrostatic pressure). Eventually, the water will reach a
certain height and then stop.
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- 53 The point at which water stops moving is when the
hydrostatic pressure caused by the gravity is equal to the osmotic
pressure of the water trying to get into the tube. If we did this
experiment in outer space, all of the water would cross over the
membrane and the column would rise until all the water is gone.
Gravity Osmotic pressure
- Slide 54
- Movement of Water in the GI Tract Imagine that you take some
aspirin and wash it down with water. If the aspirin particles can
get across the cell membrane of your intestinal tract, there will
be no net gain or loss of water in the compartment. But if you eat
a bunch of cellulose (fiber), it cannot cross a cell membrane.
There will be more particles in the GI tract lumen, so the GI lumen
will suck water from the nearby cells into the intestinal lumen.
That is how laxatives work! A laxative will cause the osmolality of
the GI tube to be increased, so water will move from the
surrounding cells into the GI lumen. If they extract fluid from the
body in excess, they may cause dehydration. 54
- Slide 55
- Hydrostatic Pressure Osmotic pressure is the amount of
hydrostatic pressure required to stop osmosis from moving water
from high to low concentration across a cell membrane. Osmotic
pressure is attributed to the osmolarity of a solution. The
solution with the highest number of particles will have the highest
hydrostatic pressure. 55
- Slide 56
- 56 Membrane Function Osmosis is movement of water to an area
with more solutes This happens when the cell membrane is permeable
to water but not solute direction of osmosis is determined by
differences in total solute concentrations Hypo-osmotic (few
particles) Hyper-osmotic (many particles) Water always moves! Watch
your body fluid compartments In what direction will osmosis go?
What side of the tube is hypo-osmotic? Which side is hyper-osmotic?
When would osmosis stop? What if we were in space?
- Slide 57
- 57 Review: Implications of Concentration and Osmolality
Differences Across Membranes First, lets focus on a solute that can
move across the membrane. Lets say these green particles are
aspirin molecules in the stomach. How would these molecules move
across the body fluid compartments? Diffusion- random movement of
particles from high to low Plasma GI tract
- Slide 58
- 58 Review: Implications of Concentration and Osmolality
Differences Across Membranes Now, lets say youve eaten fiber
(cellulose) You cant absorb it! There are more particles in one
body fluid compartment What will happen? Water movement Osmosis
Hydrostatic pressure This is the basis for how diuretics and
laxatives work! Plasma GI tract
- Slide 59
- 59 Osmotic Pressure Osmosis occurs when water moves from a
solution w/ fewer particles to one with more particles because the
particles cant move across the membrane! Remember particles suck
(....the water). Osmotic pressure is the amount of pressure
required to stop osmosis from happening (hydrostatic pressure).
Water is likely to enter a solution that contains lots of particles
that are impermeable across a membrane thus the solution is said to
have a high osmotic pressure!
- Slide 60
- 60 Osmotic Pressure: the amount of hydrostatic pressure (force
of fluid exerted on the vessel wall) required to counter osmosis
Osmotic pressure is attributed to the osmolarity of a solution
Figure 4-10; Guyton & Hall Isosmotic - has same osmolarity as
body fluids (same number of particles, or 300 mOsm) Hyperosmotic -
higher osmolarity than body fluids Hyposmotic- lower osmolarity
than body fluids
- Slide 61
- Osmotic Pressure In a U-shaped tube separated by a membrane,
water moves to the side with more particles (Particles suck). If a
compartment has a high number of particles that cannot cross the
cell membrane, water will move from the area with fewer particles
to the area with more particles. Osmotic pressure is the amount of
hydrostatic pressure you need to apply to stop the water from
moving (from the top of the tube where the particles are highest).
61
- Slide 62
- What will happen to a cell placed in the following solutions?
Isosmotic (300 mOsm): no net gain or loss of water. Hyperosmotic
(600 mOsm): particles suck, so solution will suck the water from
the cell, which will shrink. Hyposmotic (100 mOsm): particles suck,
so cell will suck water from the solution and burst. 62
- Slide 63
- Diffusion The above example assumes that the particles in the
cell cannot diffuse out, which is usually the case. However, there
are particles (such as urea) that can cross a membrane. Urea will
diffuse out of one compartment and into another, down its
concentration gradient. As it does so, water will also be diffusing
back and forth down its own concentration gradient, but overall,
there is no net gain or loss of water in a compartment when
particles are able to diffuse across the membrane. 63
- Slide 64
- 64 Example with Diabetes Increased sugar in the blood
Relatively less water due to increased solute concentration
Describe the movement of water when the mOsmolal changes! (It flows
into the plasma) Intercellular fluid Interstitial space S Plasma S
S S S 304mOsm 300 Water flow
- Slide 65
- Example with Diabetes When you eat, sugars are absorbed into
plasma. Normally, insulin transports these sugars into the cells,
but in a diabetic with no insulin, the sugars stay in high
concentration in the plasma. That raises the plasma above 300 mOsm,
while the interstitial fluid is still at 300. Where will water go?
Water will move from the interstitial fluid into the plasma. Now,
the interstitial space has less water, but the same number of
particles, so it may be at 300 particles per HALF a liter, instead
of 300 particles per liter. To calculate the number of particles
per liter, multiply by 2 and you will see that the interstitial
space has actually become 600 mOsm. 65
- Slide 66
- 66 Example with Diabetes Water flows into the blood vessel
until the osmolarity in the blood vessel decreases to 300 mOsm
(normal). However, the interstitial space now has less water, but
the same number of particles, so it may be at 300 particles per
HALF a liter, instead of 300 particles per liter, which is the same
as saying it has become 600 mOsm. Where will water go now?
Intercellular fluid Interstitial space S S Plasma SS S 300mOsm 300
600 Water flow Water will then go from the cells or blood vessels
into the interstitial space and the person gets dehydrated.
- Slide 67
- Polydipsea The condition where a person drinks a lot of water
because they are thirsty is called polydipsea, and is
characteristic of a person with diabetes. 67
- Slide 68
- 68 Test yourself- by picking which one of these is correct What
is the proper sequence of events in diabetes mellitus? a)Cells lose
water to ECF via osmosis; ECF osmotic pressure rises; Solute
concentrations increase in ECF. b)Solute concentrations increase in
ECF; Cells lose water to ECF via osmosis; ECF osmotic pressure
rises c)Solute concentrations increase in ECF; ECF osmotic pressure
rises; cells lose water to ECF via osmosis d)Water is lost from the
ECF; Solute concentrations increase in ECF; ECF osmotic pressure
rises; Cells lose water to ECF via osmosis. What if the question
described an athlete who was dehydrated?
- Slide 69
- 69 Same thing occurs with a dehydrated athlete There is less
water in the plasma, so the mOsm there is higher than normal (304
mOsm). Water flows into the blood vessel until the osmolarity in
the blood vessel decreases to 300 mOsm (normal). However, the
interstitial space now has less water, but the same number of
particles, so it may be at 300 particles per HALF a liter, instead
of 300 particles per liter, which is the same as saying it has
become 600 mOsm. Where will water go now? Intercellular fluid
Interstitial space S S Plasma SS S 304mOsm 300 Water flow Water
will again go from the cells into the interstitial space. The blood
volume becomes normal but the person is thirsty. If the condition
lasts for too long, blood volume (and blood pressure) will go
down.
- Slide 70
- 70 Note this poor childs swollen distended belly. This
condition is called ascites. It occurs from lack of dietary
protein. Alcoholics and elderly people also may lack dietary
protein. Used with permission given by A. Imholtz
http://academic.pg.cc.md.us/~aimholtz/ Kwashiorkor- disease of
deposed child (no longer suckled). Occurs in economically
disadvantaged countries that use cornmeal as their primary food
source Corn has no protein Edema (interstitial accumulation of
fluid) is caused by low levels of plasma proteins (particles in the
blood!). In Kwashiorkor, the plasma osmotic pressure is low
compared to the transcellular osmotic pressure That means the
plasma has more water, less particles than normal. The fluid moves
from the plasma into the interstitial space and then into an area
of low resistance, which is the abdominal cavity.
- Slide 71
- Example with Malnourishment We need all of our essential amino
acids, and problems can occur if you are deficient in only one
amino acid. All compartments, including the plasma, should be 300
mOsm. There are many plasma proteins; the most abundant is albumin,
which is made in the liver. If your diet is deficient in an amino
acid, the liver cannot make enough plasma proteins. If albumin
numbers decline, particles in the plasma decrease. 71
- Slide 72
- Example with Malnourishment Plasma decreases to 200 mOsm. Other
compartments will suck the water from the plasma and edema will
result. Therefore, lack of dietary protein causes a low mOsm in the
blood plasma. Since there are more particles in the interstitial
space, water will move from the plasma to the interstitial
compartment. 72
- Slide 73
- Ascites The peritoneal cavity is the space outside of the
digestive organs and under the skin and fat. It is an area of low
resistance; there is not much there to hold back something that is
pressing from the inside. The fluid goes from the plasma into the
peritoneal compartment (outside of the GI organs, deep to the
skin), and the belly becomes distended with fluid (the condition is
called ascites). It is not to be confused with a full stomach;
ascites is characteristic of malnutrition and other diseases. Edema
(excess interstitial fluid) also occurs in legs, since there is no
pressure there to keep it in. Ascites is not just a problem of poor
countries. Other people who often get ascites are alcoholics and
the elderly who dont eat their protein. When malnourished, the body
will break down the proteins in the muscles to get what is needed
elsewhere. Alcoholics drink their diet; the liver becomes so
scarred that it cant make proteins. 73
- Slide 74
- Acites Bile is made in the liver and excreted into the
digestive tract by the bile duct. Ascites puts pressure on the bile
duct, causing portal hypertension. This blockage prevents the
release of bilirubin, so this yellow pigment enters the tissues,
turning the skin yellow, especially the white parts of the eyes.
This yellow appearance of the skin is called jaundice. When excess
bilirubin enters the brain, it causes nerve cell death. This is why
alcoholics still seem drunk when they are sober. Bilirubin is the
result of RBC death. Parts of the RBC can be recycled (such as the
iron), but the bilirubin (part of hemoglobin) needs to be
eliminated. Bilirubin is what causes the color of urine and feces.
74
- Slide 75
- 75 Our book refers to tonicity more than osmolality....are they
interchangeable? NO!!!!!!! Tonicity refers to the number of
particles per kg of water in each of two compartments, where the
membrane that separates them is impermeable to the particles.
Differences in tonicity between the two compartments always leads
to water moving from one compartment to the other. Osmolality
refers to the number of particles- regardless of permeability Some
solutes (primarily urea) are freely permeable to cell membranes
(exhibit passive transport). A hyperosmotic solution may cause only
transient shifts in the body under steady-state conditions. Figure
25-5; Guyton and Hall
- Slide 76
- Urea is Permeable Why is it important to understand this about
urea? Because urea is reabsorbed in the early stage of kidney
filtration, and then excreted in the later stage. During the early
stage, it does not cause water to be reabsorbed with it, so the
kidneys are free to excrete the excess water. 76
- Slide 77
- Tonicity vs. Osmolality Tonicity and osmolality are not the
same word. Tonicity refers to the number of particles in 1kg of
water. Will there be a shift of water across the cell membrane?
Most of the time, particles dont move so the water does. If this
was always the case, tonicity and osmolality are the same number.
But substances, such as urea, can move across a cell membrane, so
there is only a transient shift in water. In these cases, the
resulting osmolality and tonicity are different. 77
- Slide 78
- 78 For example: 300mmol/L sucrose isosmotic to our bodily
fluids! 300mmol/Kg sucrose 300mmol/kg sucrose is also isotonic- no
change in cell volume Its osmolality is also its effective
osmolality (tonicity).
- Slide 79
- Place a cell in isotonic solution: There are equal particles
and no net gain or loss of water. This solution is considered to be
Isotonic and isosmotic. 79
- Slide 80
- 80 What about 600mOsmolal Sucrose? Hyper-osmotic Hypertonic
Water will move out of the cell. Place a cell in hypertonic
solution: The cell will shrink. This solution is hypertonic and
hyperosmotic.
- Slide 81
- 81 What about 200mOsmolal Sucrose? Hypo-osmotic Hypotonic Water
will move into the cell. Place a cell in hypotonic solution: The
cell will swell. This solution is hypotonic and hypo- osmotic.
- Slide 82
- 82 Lets see what happens with urea 400mmol/Kg urea
Hyper-osmotic Isotonic (long-term)
- Slide 83
- Difference between tonicity and osmolarity Not all hyperosmotic
solutions are hypertonic. If you place a cell in a solution with
400 mOsm of urea, the urea (a particle) will move into the cell
until it equalizes. The water will transiently shift from the
solution to the cell until it equalizes, with no net gain or loss
of water from the cell. The cell will not shrink, nor will it
swell. This solution is hyperosmotic but isotonic. Urea is
important for proper kidney function, so it needs to be able to
cross a membrane. 83
- Slide 84
- Study Tip: How to remember what a cell does in hypertonic
water? Hypertonic has an e in it. Make the letter e with your body.
See how you have to curl up and shrink to make this letter? A cell
will curl up and shrink in hypertonic solution. How to remember
what a cell does in hypotonic water? Hypotonic has an o in it. Make
the letter o with your arms over your head. See how you have made
yourself bigger? A cell will swell up in hypotonic solution.
84
- Slide 85
- Interactive Physio 85 Free interactive Physio tools
http://www.winona.edu/biology/adam_ip/home/ Click On: Fluids and
Electrolytes Intro to Body Fluids Pages 4-8 13-15 20 22