Though all anions deserve love to the same equal extent, phosphate has risen to become exceptional in receiving attention in the form of an entire chapter.
The daily loss is about 800ml of "insensible water loss"; half is lost from the skin and half from the respiratory tract. Every gram of water evaporating loses 0.58 kcal of heat. Thus, with 800ml of water per day evaporating away, 464 kcal of heat are lost. That's 25% of basal heat production. The total osmolality of sweat is on average about 120mosm; sodium comprises 65mmol/L of this initially. With acclimatisation to heat stress, the sodium content of sweat decreases (down to a sodium concentration around 5mmol/L) and the volume of sweat increases. The maximum sweat volume is 1500-2000 ml/hr, or a maximum of 12 litres per day.
At the most basic level, its just interstitial fluid
Lymphatic vessels are not present in bone, cartilage or the central nervous system.
Terminal lymphatic capillaries are blind-ended tubes.
Total body glucose content
- Given the below concentrations in mmol/L, and knowing the total body fluid volume of a random 70kg guy, you can estimate that he will have a total of about 95mmol of glucose in the extracellular fluid. That comes to about 17 grams, rounded up to 20 according to G.F. Cahill.
- Glucose is neither acidic nor alkaline.
Chloride seems to be the forgotten electrolyte. Nobody cares about it enough to write a physiology book chapter about its secret life. I, for one, would like to see this change. I only hope that one day somebody smarter than me will do it justice with an appropriate erudition.
You have 60mmol/Kg of sodium on board. A 70kg male has about 4200mmol, or about 92g of sodium. Of this, 70% is “exchangeable” and the rest is locked up in bone crystal. The extracellular fluid contains 50% of the total body sodium; intracellular fluid contains 5% of the total body sodium.
The main stimulus for vasopressin release is an increase in plasma tonicity.
In the simplest way, vasopressin adjusts renal water excretion in response to changes in extracellular fluid tonicity.
The sensitivity threshold is a 1% increase in plasma tonicity.
Sensing the loss of tonicity
Water loss results in the increase of ECF tonicity.
This is sensed by hypothalamic osmoreceptors.
This mechanism is predominantly triggered by a rise in sodium concentration, as sodium contributes most to tonicity.
Water will move between compartments until their osmolality is the same
The cells will shrink because water will leave them to equilibrate the osmolality. Occasionally, this is useful.
The First Gibbs-Donnan Effect
The intracellular fluid colloids attract water into the cell.
This is partly because of the Gibbs-Donnan effect; the anionic colloid proteins attract cations (mainly sodium) into the cell.