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Fluids, Electrolytes & Acid–Base Balance · Chapter 2 of 7
Her fluid has moved somewhere it should not be. This chapter builds the rules that decide where waterThe universal solvent essential for life. goes — electrolytes and the flask that shows which ones dissociate, milliequivalents, the bar graph of three compartments, osmolarityA measure of solute concentration in fluid; affects fluid movement between compartments. versus osmolality, tonicityThe ability of a solution to affect the water balance in a cell. and the red cell, fluid shifts, two and a half litres a day in and out, thirst and ADH on the collecting ductA duct in the nephron that collects urine from multiple nephrons and adjusts water reabsorption. — and reads the simulator’s marathon runner, the hot-tub patient and the beer-and-pretzels night as the same rule run three ways.
The question you will answer
Water goes where the solute is. Which compartment did her water leave, which did it flood — and does that alone tell you whether salt is to blame?
Opener · Three Tanks · about 1¾ minutes
The opener is the same narrated animation you will watch in Scene 1.
Watch the opener first. It sets the question; the chapter answers it.
1
Read the chart
Patient chart · Stina
2025 · age 50
Exam
Edema of both ankles; no ascites; lungs clear. Mucous membranes moist; no thirst; urineThe liquid waste excreted by the kidneys. pale.
Labs
Sodium 138 mEq/L; potassium(K⁺): Major ICF cation; essential for muscle and nerve function. 4.9; chloride 108; glucoseA simple sugar that is the main source of energy for cells. 92; BUN 24. Serum osmolality (calculated) 286 mOsm/kg — normal. Urine specific gravityA measure of urine concentration that compares the density of urine to water. 1.018.
Intake / output
Drinks about 2 L a day; urine volume normal; no vomiting or diarrhea; no diuretic.
For contrast
The simulator’s Yuki, 24, collapsed at mile 23 after water at every station: sodium(Na⁺): Major ECF cation; important for fluid balance, nerve function. 122, osmolality 248, confused. Treated with 3% saline, slowly.
Told
“Try cutting back on salt.”
Chart clues this module: 1 · The ankles · 2 · this chapter
Before you go on · your prediction
Normal sodium, normal osmolality, no thirst, pale urine — and three litres of extra fluid in her tissues. The water…
Open the one you lean toward. Nothing is recorded and nothing is revealed — you come back to it at the end.
Came from too much salt: sodium rose, water followed, the tissues filled
Ask what her sodium concentration and osmolality are, and what “water follows salt” would have done to them. Watch the red cell in the three flasks.
Came from too much water: she is diluted, and her cells are swelling like the runner’s
Ask what a diluted plasmaThe liquid component of blood. does to the sodium number and to the brain, and compare her 138 with Yuki’s 122.
Shifted out of the plasma into the interstitial space with its osmolarity unchanged — a boundary problem, not a dilution problem
Ask what can move water across a capillary wall without changing the concentration on either side. Then ask which tank got bigger and which got smaller, and what the kidney does when the plasma tank shrinks.
From Stina’s diary
2
The story
Three short movements: the case, the anatomyThe study of the structure of the human body. and physiologyThe study of how the body functions., then the tie back to Stina. Each links to the scene where you’ll see it move.
I · Normal numbers, wrong tank
Her sodium is 138 and her calculated osmolality 286 — dead normal. She is not thirsty, her urine is pale and her mucous membranes are moist. And three litres of water are sitting in her ankles. If she had eaten too much salt, her sodium and osmolality would have risen and water would have followed it into every compartment, including her cellsThe basic structural and functional units of life.. If she had drunk too much water, her sodium would have fallen, like the simulator’s marathon runner whose sodium of 122 swelled her brain at mile 23. Neither happened. Her water did not change concentration. It changed tanks — left the plasma and stayed in the interstitial space — which is a different kind of problem, with a different lever.
See it move: Scene 1 · Three Tanks · Scene 3 · Water Follows Salt: the Fluid Shift
II · Electrolytes, osmolarity, tonicity
A salt dropped in water dissociates, and the lecture’s flask shows three outcomes: a non-electrolyte like glucose or alcohol stays whole; a weak electrolyte splits partly; sodium chloride splits completely. Ions make the body electrical — a thought, the lecture says, is just electricity moving — and are measured in milliequivalents per litre, a count of charges. The bar graph of the three compartments is the map: potassium high inside cells, with phosphate and protein; sodium and chloride high outside, in plasma and interstitial fluidThe fluid surrounding cells within tissues. alike; bicarbonate(HCO₃⁻) – A crucial buffer in blood that helps maintain pH balance; formed when carbon dioxide react similar in both; protein high in plasma and low in the interstitial fluid — the one difference Chapter 3 will spend. The sodium–potassium pump, three out and two in per ATPThe energy currency of cells used for muscle contraction., keeps the gradient. Osmolarity counts particles per litre of solutionA homogeneous mixture of two or more substances.; osmolality per kilogram of water — fruit per litre of punch versus fruit per kilogram of juice — and the lab reports osmolality; plasma runs 285–295. Tonicity is a comparison: a red cell crenates in a hypertonicA solution with a higher solute concentration than the inside of a cell, causing water to leave the solution, holds in an isotonicA solution with the same solute concentration as the inside of a cell, maintaining equilibrium. one, swells and bursts in a hypotonic one — Amy’s cue, show the red-cell slide. Water follows solute, and because sodium is nine-tenths of the extracellular solute, sodium sets extracellular volume: the body holds concentration by moving water, a fluid shift, not by moving salt. About two and a half litres a day come in by drink, food and metabolismThe sum of all chemical reactions in the body. — a cup of it metabolic waterWater produced from cellular respiration. from your mitochondria — and go out by urine, skinThe body’s largest organ, providing protection and regulation., lungs and fecesSolid waste material formed in the large intestine and expelled through the anus., with an obligatory half-litre of urine: you have to flush. Thirst comes from osmoreceptorsHypothalamic cells detecting blood osmolarity to regulate ADH., baroreceptors and a dry mouthThe opening of the digestive tract where food enters and mastication begins., and it is an emotion people ignore. ADH, from the hypothalamusA small but vital brain region controlling hormones, temperature, and autonomic functions. via the posterior pituitary, puts aquaporins into the collecting duct and concentrates the urine; alcohol switches it off, which is why the notes’ cocktail party — salty hors d’oeuvres and drinks — raises osmolality two ways at once.
See it move: Scene 2 · Osmolarity, Osmolality, Tonicity — and the Red Cell · Scene 3 · Water Follows Salt: the Fluid Shift · Scene 4 · In and Out: Two and a Half Litres a Day · Scene 5 · ADH and the Collecting Duct
III · Three disorders, one rule
The notes’ three disorders of water balance are the same rule run three ways. Dehydration: water lost from the extracellular fluid(ECF) Fluid outside cells, including plasma and interstitial fluid. raises its osmolality and pulls water out of the cells, which shrink — the hot-tub patient, the Sahara runner — and the fix is water, slowly. Hypotonic hydration, water intoxication: too much water dilutes the extracellular fluid and water floods into cells, which swell, and the brain, which has nowhere to swell, pays first — Yuki at mile 23, headache, confusion, a sodium of 122 — and the fix is a solute-rich IV that pulls the water back out. Edema: fluid accumulates between the cells, not inside them, with the concentrations unchanged, because something at the capillary wall has changed — permeability, a blocked lymphatic, a high venous pressureThe force exerted by gases in the respiratory system, affecting airflow and gas exchange., or a plasma that has lost the protein that pulls water home. Her numbers put her in the third category and nowhere near the first two. The lever is at the capillary, and the next chapter turns it.
See it move: Scene 3 · Water Follows Salt: the Fluid Shift · Scene 5 · ADH and the Collecting Duct
3
Watch · explore · think · check
5 scenes. Each one has a short animation or a slide, something to explore, a true/false spot-check of your thinking, and a quick check. Every scene gives you an evidence card for your board.
How to read the scenes
- Animation (dark teal) — a short animated explainer, one idea each
- Slide (dark teal) — a still to study: a micrograph, a diagram or a map
- Explore (purple) — something to push on while you watch
- Game (purple) — a quick challenge
- Think (gold) — reason it out, then spot-check yourself with a few true/false questions; not graded
- Check (gold) — a quick H5P that scores itself
Scene 1 of 5
Three Tanks
Pour out the cells; bathe the tissues; fill the vessels.
Animation · in production · 1 min 50 s
Three Tanks
The three compartments as tanks with pipes: plasma ↔ interstitial ↔ cells; plasma alone opens to the outside (gut, lungs, kidney). A salt dropped in the plasma tank dissociates (the flask: non-, weak, strong electrolyte); mEq/L as charges per litre. The bar graph: K⁺ and phosphate and protein inside; Na⁺ and Cl⁻ outside; protein high in plasma, low in the IF. The Na⁺/K⁺ pump keeping the gradient (3 out, 2 in). A fluid shift: water moving between tanks to hold concentration steady.
Prefer the full lecture? Introduction (original video on the site)
Game
Which compartment?
Build the lecture’s bar graph before it draws: set the bars for six solutes in three compartments, then find the one that matters at a capillary.
Text description of this game
Step 1: six cards, one each for sodium, potassium, chloride, bicarbonate, phosphate and protein. For each, set the intracellular (ICF) bar high or low, and choose the interstitial (IF) and plasma bars: both high, both moderate, both low, or plasma much higher than IF. After you commit, the lecture’s graph draws, with approximate values in mEq/L for ICF, IF and plasma: sodium 14, 140, 142; potassium 140, 4, 4; chloride 4, 108, 104; bicarbonate 10, 28, 24; phosphate 75, 2, 2; protein 40, 2, 16. Step 2: choose the one solute whose bar differs between plasma and IF: sodium, chloride, bicarbonate or protein. Step 3: choose what that difference does at a capillary: pulls water from the IF into the plasma, does nothing because protein is a tiny share of osmolality, pushes water out of the plasma, or draws water into cells. Step 4: four flasks of water. Predict whether table salt, carbonic acid, glucose and alcohol split completely, split partly or stay whole, and how many particles one molecule makes; the flasks show the result after you commit. Every answer appears only after you commit, with a short explanation.
Think · not graded
Plasma and interstitial fluid have the same sodium and the same bicarbonate and are separated by a wall that water crosses freely. What is the one solute that is different on the two sides — and why must that one be the whole story of a capillary’s pull?
Spot-check your thinking: true or false?
Check · Single Choice
Toward which side does water move across a semipermeable membrane?
Evidence card 1
Add it to your evidence board
Same salt on both sides of the capillary wall; one solute differs — protein — and the pull belongs to it.
Scene 2 of 5
Osmolarity, Osmolality, Tonicity — and the Red Cell
Fruit per litre of punch, fruit per kilo of juice, and a cell in three flasks.
Slide · a still to study
Three Words, One Red Cell
Three words
- Osmolarity: solute particles per litre of solution (mOsm/L), the number printed on an IV bag.
- Osmolality: particles per kilogram of water (mOsm/kg), what the lab measures. Plasma is 275–295.
- Tonicity: a comparison that counts only particles that cannot cross the membrane. Urea crosses, so it adds to osmolality but not to tonicity.
One red cell
- Hypertonic: water leaves; the cell shrinks and crenates.
- Isotonic: no net movementA fundamental property of life involving motion of the body or its parts.; the cell keeps its shape.
- Hypotonic: water enters; the cell swells and can burst.
The bags
- Normal saline (308) and lactated Ringer’s (273) are isotonic and stay in the ECF.
- Half-normal saline (154) is hypotonic; 3% saline (1,026) is hypertonic.
- D5W reads 252 in the bag, but once the glucose is used it is free water: the D5W trap.
The lab measures osmolality; the bag prints osmolarity; the cell only cares about tonicity.
Prefer the full lecture? ECF Osmolarity (original video on the site)
Explore
Hang the bag
Hang each bag from the site’s IV-fluid table and predict what a red cell in the patient’s blood does, and where the litre ends up. Then treat four patients and one more.
Text description of this explore
Step 1: a wall of eight IV bags from the site’s IV-fluid table, each feeding a dish that holds a red cell from the patient’s blood: 0.9% NaCl (normal saline, 308 mOsm/L), lactated Ringer’s (273), 0.45% NaCl (half-normal saline, 154), 0.225% NaCl (quarter-normal saline, 77), 3% NaCl (1,026), D5W (5% dextrose in water, 252), D5NS (5% dextrose in normal saline, 560) and 5% albumin (about 310). For each bag, predict the red cell an hour after the litre runs in (shrinks and crenates, holds its shape, or swells and may burst) and where the litre goes (stays in the vessels, spreads to the IF, or goes into the cells too). After you commit, each dish shows the cell and each card explains why. Step 2: four patients from the site’s simulator: Yuki (sodium 122 after water at every marathon station), Mei (sodium 151, potassium 2.8 after three days of vomiting), Jamal (sodium 128 after sweating all day on water only) and Hassan (potassium 7.2 with peaked T waves). For each, choose the right treatment (3% NaCl slowly; ½NS with potassium slowly; an oral electrolyte drink; or calcium gluconate, insulin with glucose and a resin) and the one bag that would hurt (D5W, ¼NS, 3% NaCl, or ½NS with added potassium). Step 3: one litre of normal saline into Stina, whose albumin is 2.4 g/dL; choose where most of it is an hour later. The last answer links to the site’s IV-fluid table.
Think · not graded
Normal saline is isotonic and contains no protein. If you hung a litre of it on Stina, predict where it would be an hour later — and say why “isotonic” is not the same as “stays in the vessel”.
Spot-check your thinking: true or false?
Check · Fill in the Blanks
Fill in the rules that move water between compartments.
Evidence card 2
Add it to your evidence board
Tonicity is what the cell feels; a bag with no protein in it cannot stay in a vessel that has lost its own.
Scene 3 of 5
Water Follows Salt: the Fluid Shift
The body moves water, not sodium.
Animation · in production · 1 min 50 s
Water Follows Salt
A salty meal: sodium content up, concentration held — the body adds water (thirst, ADH) and the plasma balloon swells, seeps into the IF, and the cells keep their size. Dehydration: ECF loses water, osmolality rises, water leaves cells, cells shrink (hot tub; the Sahara). Hypotonic hydration: ECF diluted, water enters cells, the brain swells (Yuki). Beer and pretzels: alcohol switches off ADH (dilute urine) while the pretzels add solute — osmolality up two ways. Then Stina: sodium 138, osmolality 286, and three litres in the wrong tank — no shift of concentration at all.
Prefer the full lecture? ECF Osmolarity (original video on the site)
Explore
Three nights, three shifts
Three evenings on one body. Predict what each does to osmolality, the cells and the urine before it runs. Then set Stina’s sodium and look for an osmotic shift that could fill her ankles.
Text description of this explore
Step 1: three tanks, cells (ICF), IF and plasma, beside a body cell and a urine cup. Choose one of three nights: pretzels with water; pretzels with beer; or a litre of plain water every hour for four hours. Before each run, predict one of four outcomes: osmolality held near normal with the ECF growing, cells unchanged and dark scant urine; osmolality up with water leaving shrinking cells and pale plentiful urine; osmolality down with water entering swelling cells and pale plentiful urine; or osmolality up with shrinking cells and dark scant urine. Running the night moves the tanks, resizes the cell, colours the urine and lists ECF osmolality, the water shift, the cell, ADH and the urine. Step 2: three boxes, a cell, the IF and the plasma, separated by the cell membrane and the capillary wall, with a sodium slider from 118 to 160 and buttons for Stina (138), Yuki (122) and Mei (151). Predict where an osmotic shift moves water: into the cells, out of the cells, nowhere, or out of the plasma into the IF only; the readout gives the estimated osmolality and the shift at each wall. Step 3: decide what filled Stina’s ankles.
Think · not graded
The lecture says the body manages concentration by moving water, not salt. If that is true, what would a patient who ate too much salt look like on labs — and what does Stina’s normal sodium and osmolality rule out before you touch the salt shaker?
Spot-check your thinking: true or false?
Check · Multiple Choice
What happens to water distribution when plasma sodium falls?
Evidence card 3
Add it to your evidence board
Her concentration never moved; an osmotic shift is ruled out before the salt shaker is touched.
Scene 4 of 5
In and Out: Two and a Half Litres a Day
A soda bottle and a bit — and half a litre you have to flush.
Slide · a still to study
Water Balance
In, about 2.5 L a day
- Drinks: most of it.
- Food: much of what we eat is water.
- Metabolism: cellular respirationThe process of gas exchange, including ventilation, external and internal respiration. makes about 0.2–0.3 L.
Out, about 2.5 L a day
- Urine: about 1.5 L, the only output the body adjusts.
- Skin: insensible loss and sweat.
- Lungs: water vapour in every breath.
- Feces: a little.
Two rules
- Obligatory loss: the kidney must excrete the day’s solutes and needs at least about 0.5 L of urine to do it.
- Thirst: osmoreceptors in the hypothalamus and baroreceptors in the aorta and carotids drive it, but it lags behind need and fades with age.
Water output depends on water and on sodium.
Even on a day you drink nothing, you make a cup of water and must flush half a litre.
Prefer the full lecture? Water Management (original video on the site)
Game
Balance the day
Deal the day’s cards onto a two-column ledger, predict the scale at midnight, and find the day the kidney cannot balance.
Text description of this game
Step 1: six cards: three coffees, a run in July, a salty dinner, a bout of diarrhea, a night of beer and eight hours of sleep. For each, decide whether it writes in the intake column, the output column or both, and which line it changes: drink, food, sweat, skin and lungs, feces or urine. Step 2: a ledger and a body on a scale. Deal three cards with three menus, or load Day A (three coffees, a salty dinner, eight hours of sleep), Day B (a run in July, a bout of diarrhea, eight hours of sleep) or Day C (a night of beer, three coffees, eight hours of sleep). Every day also brings about 1 L of ordinary drinks, 1 L of water from food and metabolism, 0.7 L through skin and lungs and 0.1 L in feces. Predict the scale at midnight: up half a kilo or more, within half a kilo, or down half a kilo or more. The total lists each line, the urine the kidney chose (never below its 0.5 L floor) and the weight change. Step 3: why the kidney could not balance one of the days. Step 4: which card raises ADH most and which switches it off.
Think · not graded
The kidney must excrete the day’s solutes in at least half a litre of urine. On a day Stina eats a salty meal and her leaking kidney retains sodium, what happens to that minimum — and why does “drink less salt” make a little sense after all, without being the answer?
Spot-check your thinking: true or false?
Check · Drag and Drop
Sort the routes of water intake and output.
Evidence card 4
Add it to your evidence board
The books balance by water in and water out; her books are balanced — the water is simply in the wrong tank.
Scene 5 of 5
ADH and the Collecting Duct
Aquaporins on a slide, and the two ways to go wrong.
Animation · in production · 1 min 50 s
ADH and the Collecting Duct
Osmolality up or volume down → hypothalamus → posterior pituitary releases ADH → the collecting duct’s cuboidal cells move aquaporins to their apical surface → water reabsorbed, urine concentrated. ADH down → aquaporins withdrawn → dilute urine. Low BP (burns, fever, sweating, vomiting, diarrhea) also triggers it, “not a primary response”. On slide 210: the collecting ducts as wide tubes of pale cuboidal cells with crisp borders — the cells that hold the aquaporins. Then the two failures: dehydrationA condition in which fluid loss exceeds intake, leading to a decrease in total body water. (cells shrink) and water intoxication (Yuki: sodium 122, brain swelling, 3% saline slowly to avoid osmotic demyelination).
Prefer the full lecture? Water Management (original video on the site) · histology page: Renal Tubule
Explore
Set the ADH
Turn osmolality and blood volume and predict what ADH does to the collecting duct before it responds. Then run Yuki’s race, treat her, and run Stina.
Text description of this explore
Step 1: a collecting duct in cross-section, drawn as on slide 210: a ring of pale cuboidal cells with crisp borders and round dark nuclei around an open lumen, with blue dots for aquaporins, beside an ADH dial and a urine beaker. A slider sets plasma osmolality from 270 to 310 mOsm/kg and a menu sets blood volume (very low, a little low, normal, high); buttons load a hot tub, four litres of water, and a bleed. Before each run, predict ADH, the aquaporins and the urine: off with few aquaporins and pale plentiful urine; usual with some and straw-coloured urine; raised with many and darker, less urine; or high and packed, with dark scant urine. The readout lists ADH, the aquaporins at the lumen, the urine’s concentration and its volume. Step 2: a marathon course with eleven water stations, a brain in the skull and a body cell. Choose what Yuki drinks at each station (nothing, to thirst, or a litre of water) and predict her sodium, her cells and her symptoms at mile 23; the readout lists sodium, osmolality, the cells and the symptoms. Step 3: choose Yuki’s IV bag (3% NaCl, normal saline, ½NS or D5W) and how fast to run it. Step 4: run Stina, with a normal osmolality and a plasma tank that is a little low, and decide what ADH and the kidney do and whether it helps her ankles.
Think · not graded
Her plasma volume is a little low because fluid has leaked into her tissues; her osmolality is normal. Predict what her ADH and aldosteroneA hormone that increases sodium and water reabsorption in the kidneys, helping regulate blood pressu do about the low volume — and explain why the body’s correct response to a shrunken plasma tank makes an edemaExcess fluid in interstitial spaces. patient worse.
Spot-check your thinking: true or false?
Check · Drag the Words
Match each hormone to the salt or water it controlsVariables that remain constant to ensure a fair test..
Evidence card 5
Add it to your evidence board
The kidney answers a shrunken plasma tank by saving water and salt — correctly, and to her cost.
4
Your evidence board
Every scene gave you an evidence card, and the chart adds more. Sort each card into the column it supports: A boundary problem at the capillary — concentration unchanged, Neither on its own, or A concentration problem — too much salt or too much water. Some cards can honestly go in more than one place — that’s allowed, and the feedback tells you which cards decide the case.
5
Your verdict
Time to decide. Look back at your bet, then build your verdict from statements that hold up — no writing needed.
Look back at your prediction
Normal sodium and osmolality, three litres in the tissues — the water…
Find the one you chose at the top. Does the evidence support it, refute it, or revise it?
- Came from too much salt: sodium rose, water followed, the tissues filled
- Came from too much water: she is diluted, and her cells are swelling like the runner’s
- Shifted out of the plasma into the interstitial space with its osmolarity unchanged — a boundary problem, not a dilution problem
Build your verdict · no writing
Choose the statement that holds in each set. The ones you keep become your argument.
6
The finding
Finding · edema localized to a plasma → interstitium shift
The Right Tank, the Wrong Wall
Sodium 138, calculated osmolality 286, no thirst, pale urine, cells neither shrunken nor swollen — and three litres of water in her interstitial space. Not dehydration, not water intoxication, not salt following water into every tank: a shift across one wall, the capillary, with concentration unchanged on both sides. Chart entry: localize the edema to the capillary boundary. The one solute that differs across that wall is protein, and the next chapter spends it.
Next · Chapter 3
Hydrostatic vs Oncotic Pressure
Two pressures fight over every drop at every capillary — one pushing out, one pulling back. Her albuminA plasma protein that helps maintain osmotic pressure and transport substances. is the pull, and it is leaking into her urine.
Reliable information on rare diseases
NORD · NIH GARD · Orphanet · MedlinePlus Genetics: FMF · FMF & AID Global Association · Autoinflammatory Alliance · Global Genes · Amyloidosis Foundation
Stina has one rare disease. In the United States, about 1 in 10 people live with one of the more than 7,000 known rare diseases. These organizations are where patients, families and clinicians go for trustworthy information.
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All pages for Module 20 — Fluids, Electrolytes & Acid–Base Balance
20.0 Module Overview
20.1 The Swollen Ankles That Point Back to the Kidney
20.2 The Body’s Fluid Compartments & Water Movement
20.3 Hydrostatic vs Oncotic Pressure
20.4 The Major Electrolytes & the Albumin-Corrected Calcium
20.5 Acid-Base Balance & the Bicarbonate Buffer System
20.6 Metabolic Acidosis from a Failing Kidney
20.7 One Filter, Not Three Problems
20.8 Conclusion and Assessment
20.9 Evidence Behind the Case
All Modules
- Anatomical Language, Membranes & Homeostasis
- Just Enough Chemistry
- The Cell & Its Transport
- Making Cells & Proteins
- The Integumentary System
- The Skeletal System
- The Muscular System
- Nervous Tissue & the Senses
- The Spinal Cord
- The Brain & the Blood–Brain Barrier
- The Autonomic Nervous System
- Special Senses (in developmentThe process of growth and differentiation.)
- The Endocrine System
- Blood
- The Heart
- Blood Vessels
- The Digestive System
- The Respiratory System
- The Urinary System
- Fluids, Electrolytes & Acid–Base Balance
- The Reproductive System
- The Immune System
List of terms
- water
- osmolarity
- tonicity
- collecting duct
- urine
- potassium
- glucose
- specific gravity
- sodium
- plasma
- anatomy
- physiology
- cells
- interstitial fluid
- bicarbonate
- ATP
- solution
- hypertonic
- isotonic
- metabolism
- metabolic water
- skin
- feces
- osmoreceptors
- mouth
- hypothalamus
- extracellular fluid
- pressure
- movement
- respiration
- dehydration
- aldosterone
- edema
- controls
- albumin
- development