Body fluids Flashcards
What is the importance of water/body fluids
what are all cells acclimatized to? how is it a solvent? why is it important for body physiology? why is stable vol and compostion essential? what does it handle?
- All cells originated surrounded by water
- Without water there wouldn’t be diffusion
- All cells are acclimatized to water
- It is a solvent (through making and breaking of H bonds)
- it is a universal solvent
- It is important for body physiology
- It is a medium for metabolic processes
- life depends exclusively on chemical reactions that take place in aqueous medium
- stable volume and composition of the body fluids is essential for metabolism (homeostasis)
- It handles diffusion of nutrients and waste products
How are fluids controlled
organs that are involved in this?
2 ways water decreases with humans over time
Fluids need to be kept at a stable volume and composition
Organs involved in fluid control are: • kidneys • brain and cortex • aortic arch • adrenals
Water in elderly is lower
Water decreases as body fat increases
Clinical indications of changes in body fluid
of less body fluid? (3)
of more body fluid? (2)
Less body fluid
• very dry skin
• diarrhea
• low blood pressure
More body fluid
• high blood pressure
• kidney failure
How much water do we need
what is intake nirmally?
output?
Intake - 2300ml
• ingested fluids - 2100ml
• metabolism - 200ml
Output - 2300ml • urine - 1400ml • insensible loss through skin - 350ml • insensible loss through lungs - 350ml • faeces - 100ml • sweat - 100ml - sweat may increase to 6000ml leading to dehydration
Body Fluid Compartments - composition
how many compartments?
% of body weight?
positve and negative ions in them?
There are 3 body fluid compartments
• intracellular fluid
- 40% of body weight
- positive ions involve
- K+
- negative ions involve
- SO4 2-
- phosphates
- negative proteins
• extracellular fluid
- 20% of body weight
- positive ions involve
- Na+
- negative ions involve
- Cl-
- bicarbonates
• plasma - positive ions involve - Na+ - negative ions involve - Cl- • The positive and negative ions are important to nerve cells and heart muscle cells
Body Fluid Compartments - why
what is the intracellular fluid? interstitial? plasma?
what is the importance of all these compartments?
Intracellular fluid is the largest compartment
- trapped inside the cell and is very important for all the metabolic porcesses that happen inside the cell
Interstitial fluid
- water outside the cell which is imporrtant for bringing nurtition inside and out of the cell and taking waste products away
Plasma compartment
- brings nutrients + o2 from heart and gut towards the interstitial fluid which diffuse to ICF
Interstitial fluid + plasma = extra cellular fluid
Body fluid distribution
what is the 40 - 20 rule?
60% of body weight is water
40% of body weight is intracellular water
20% of body weight is extracellular water
40 - 20 rule
hence for 70kg man
42 L in circulatrion
28 is ICF and 14 is ECF
Composition of body fluids
what ions does intra have?
what about the other compartments?
Composition varies because each compartment has different ions;
Intracellular compartment has potassium and phosphates
Interstitium has sodium and chloride ions
Blood plasma contains sodium and chloride ions
Differences in permeability
capillary membrane?
plasma membrane?
explain why Na+ and cl- outside cell and K+ and phospjates inside cell
The capillary membrane allows most/all molecules through
Plasma membrane only allows specific molecules to pass through
Na+, Cl- is found outside cells, K+ and phosphate is found inside the cells; this is because Na-K pumps push out sodium and take in K+
How does fluid movement happen
what two main things does it depend upon?
describe the nature of barrier for cell membranes
describe the nature of barrier for capillary wall
• Depends on pressure
- ionic pressure
- osmotic pressure
• Depends on nature of barrier
- > cell membrane
- lipid bilayer with proteins
- impermeable to most ions and proteins; has pumps
- water is allowed to move freely
- osmotic pressure drives the movement of water
- > capillary wall
- endothelial cells, semi permeable pores
- only large molecules (e.g. proteins) can exert an osmotic pressure across it
- hydrostatic pressure drives movement of water
Diffusion and Osmosis
what are they?
• Diffusion
- movement of molecules from higher to lower concentration, due to random motion
• Osmosis
- net diffusion of water across selectively permeable membrane from a region of high concentration of water to a region of low concentration of water
Osmosis’ unit of measurement
what is osmole?
what does one mole of NaCl give?
what is osmolality?
what is osmolarity?
what is the osmolarity like between the 3 compartments?
• Osmole - a unit of measurement to describe the
concentration of solute particles
- 1 osmole = 1 mole = 6.02x1023 osmotically active particles
- Osmotically active particles are particles which produce pressure to move water
- 1 mole of NaCl will give 2 Osmoles of osmotically active particles (Na+ Cl-)
• Osmolality - Osmole/kg of water
• Osmolarity - Osmole/litre of water (changes with
temperature)
- the osmolarity is very similar in all 3
compartments
- may cause swelling or shrinking of cells if not balanced
Osmolarity is very similar across 3 regions
what does this mean?
Osmolarity is very similar across each of the 3 fluid compartments, and so water can move freely across both types of wall (cell membranes and capillary membranes)
Tonicity
define
what does it depend on?
define isoosmotic? isotonic?
moveemnt of water with tonicity and osmalarity?
effect of a solution [and solutes that cannot cross] on osmotic movement of water across cell membrane
- depends on active osmoles
- applies osmotic pressure
• Isoosmotic
- solutions that have the same osmolarity are known to be isoosmotic
• Isotonic
- solutions that have the same tonicity are known to be isotonic
• If two solutions differ with respect to tonicity irrespective of their osrnolarity, water movement
(osmosis) will occur from hypotonic to hypertonic solution, but if two solutions are isotonic to
each other, then there will be no osmosis between two solutions whatever may be their osmolarity status.
Van’t Hoff’s law
equation?
II = R x T x C
osmotic pressure = gas constant x temperature x concentration of solution
Pressure exerted by a solution across a semi-permeable membrane
