Body fluids lecture 2 Flashcards
What percentage of males and females are solids and fluid? Why is it different?
females
-55% fluid
-45% solid
Males
-60% fluids
-40% solids
Of your total body fluid, what percentage are intracellular fluids and extracellular fluids?
2/3rds are intracellular fluids
1/3rd are extracellular fluids
Of your extracellular fluids what percentage of them are interstitial fluid and what % is blood plasma?
interstitial fluids make up 80%
plasma makes up 20%
Define intracellular fluid
the fluids within cells (the cytoplasm) (includes GI tract
Define extracellular fluid
the fluids between cells
Define interstitial fluid
fluid that surrounds cells of tissues, including synovial fluid, CSF, lymph plasma
Define blood plasma
fluid in blood vessels that RBC travel through, yellow fluid that is 90% water
How is osmotic balance maintained between different fluid compartments?
it is maintained through the continuous exchange of water through different compartments
Define transcellular fluid
fluid in CSF, Ocular fluid, G-I tract, it comes from the interstitial fluid
Is osmolality equivalent in all body fluids?
yes it is generally equal to maintaining homeostasis between solute concentrations and yes because the solvent is almost always water
Table all the ions in body fluid compartments in ISF and extracellular (ISF+PLASMA)
ions in ISF
Na- 10
K- 142
Ca- 0.1
Mg-1
Cl- 10
Hco3- 10
A-132
pH-7
osmolality-290
ions in ISF+plasma
Na- 143
K- 4
Ca- 1.5
Mg-1
Cl- 118
Hco3- 24
A-10
pH-7.4
osmolality-290
Is osmolality higher in inter or extracellular fluid?
the concentrations of the solutes needs to be the same to prevent net movement of water between the compartments- so osmolality is equal in all body fluid compartments
Draw a table of ions in the intracellular fluid, interstitial fluid and plasma
the main ions are K, Na, Cl, Hco3 and proteins
-interstitial and plasma the ion concentrations are all equal.
-The plasma has more proteins
-The intracellular compartment has higher protein and K concentrations
Do all ions express the same osmotic pressure?
no because different ions are different sizes
What is osmotic pressure?
osmotic pressure is the pressure created via the movement of solvent particles across membranes in order to equalise the concentration of solute particles on both sides
What process’ affect the total volume in each of the body fluid compartments?
filtration
reabsorption
diffusion
osmosis
Why is there continual change between the fluid compartments?
concentrations of ions change or proteins levels change or a variable is affected by a stimuli
What is the biggest source of water movement between the intracellular and interstitial fluid and what determines the direction of the movement?
osmosis is the biggest source of water movement between intracellular and interstitial fluid
Despite this movement is the volume of each compartment consistent?
yes
Define osmosis.
the movement of water from low solute concentrations to high solute high solute concentrations across a semi-permeable membrane
Draw a figure that shows osmosis
what is osmotic pressure
related to the number of water particles that move from a place of high to low concentration.
Osmotic pressure is the pressure that must be applied to oppose osmosis
the difference in concentration of the impermeable solute exerts an osmotic pressure
What does the amount of water movement depend on?
the concentration of the solutes at the 2 sides of the semi-permeable membrane
What happens if 2 chambers contain different concentrations of a solute what will the water do?
water will move to equalise the concentration
What can water movement be counterbalanced by?
by a physical pressure
What are and what is the difference between osmolarity and osmolality?
Osmolality-
total number of dissolved particles (ions of molecules or both) dissolved per kg of water
Osmolarity- total number of dissolved particles (ions of molecules or both) per litre of solution
-Molarity x number of particles per molecule once the particles dissolve
-for undissolved particles- 1 mole=1 osmole
for a fully disassociated solute (e.g NaCl)- 1 mole= 2 osmoles
for proteins- 1 moles= 1 osmole
Why is molarity easier to measure than molality?
because it is easier to measure the volume of a solution in a medical setting since it is harder to separate water from the body fluids plus the solutions are very diluted anyway
How do the properties of the membrane determine which solutes are osmotically active?
the membranes are semi-permeable so only let the selected solutes through
In the ECF what are the major osmolytes?
Na+ and Cl-
What is nearly impermeable to sodium ions?
the cell membrane
Where is water lost from?
the extracellular space causing things like dehydration
How is water replaced in the extracellular space?
from the inside of the cell; water moves from the intracellular space to the extracellular space due to the increase in Na+ concentration caused by dehydration outside the cell. this increases extracellular osmolality
What organ plays an important role in maintaining normal osmolality?
the kidney
What happens if extracellular Na+ increases and why?
water flows out of the cell via osmosis to equalise the concentration of solutes
How can osmosis cause problems?
during inflammation due to an increase in extravascular osmolality
-the capillary wall is freely permeable so not osmotically active
- it is however impermeable to plasma proteins
-is extravascular proteins build up they can exert an osmotic pressure
What is an isotonic solution?
solutions that do not make cells swell or shrink
- same osmolality than plasma
What is a hypotonic solution? What affect can this have on cell volume?
a solution that causes cellular swelling
Cells would have higher osmolality than plasma
what are colloid pressures?
an alteration of osmotic pressures due to changes of large molecule distribution
What are hypertonic solutions? What affect can this have on cell volume?
a solution that causes cellular shrinkage
- cell has low osmolality than plasma
How is water lost by the body?
through skin, lungs, urine and faeces
What does water in need to equate to?
water gain needs to equate to water loss
How is water gained by the body?
food drink and metabolism
