Body fluid compartments and their determination. The extracellular and intravascular fluid

Question 1

Bernard explained:

Answer 1

Milieu exterior: Physically surrounds whole organism

Milieu interior: where tissues and cells live

Question 2

Ionic compositions in ECF

Answer 2

Sodium : abt 140mM
Potassium: abt 4mM
Calcium: 2.1-2.8 mM
Chloride: abt 100 mM
HCO3-: 22-28 mM
Osmolality:290 mOsm
Ph: 7.38-7.42

Question 3

Ionic compositions in ICF

Answer 3

Sodium : 10-15mM
Potassium: 120-150mM
Calcium: 1.1-1.4mM free or 100nM free
Chloride: 20-30 mM
HCO3-: 12-16 mM
Osmolality:290 mOsm
Ph: 7.38-7.42

Question 4

Regulation of extracellular K+ concentration

Answer 4

1) Normal physiological range is abt 4 mM and set point is genetically encoded
2) Mechanism to monitor deviations from set point include glomerulosa cells of the adrenal gland- zone glomerulosa produces mineralocorticoids like aldosterone, doc and cortisol
3) Elevation of (K+)ec by aldosterone production
4) aldosterone acts on certain kidney cells and potassium concentration increases
5) decrease of potassium extracellular concentration by negative feedback

Question 5

Relationship between volumes of various Body fluid compartments

Answer 5

Total Body Water(42 L) or 60% of 70 kg man

-ECF(14 L) or 20%. -ICF(28L) or40%
;Interstitial fluid(10.5 L) or 15%
;plasma(3.5 L) or 5%
;transcellular fluid: 2.5%

side notes:

• interstitial fluid separated from plasma by capillary wall
• ECF and ICF separated by cell membrane
• Transcellular fluid makes up 2.5% of the interstitial fluid but it is separated from the interstitial fluid by epithelial cells. examples of Transcellular fluid is CSF, synovial fluid, pleural cavity, etc.

Question 6

Monitor, Effector and afterwards of regulation of extracellular K+ concentration

Answer 6

Monitor: glomerulosa cells of adrenal gland

Effector: If aldosterone increases, acts on kidney cells in collecting duct and K+ concentration decreases because more secreted because of romk1, but in the notes it said aldosterone increases ecf k+

afterwards: negative feedback lowers ECF K+ concentration

Question 7

Measuring volumes in body fluid compartments

Answer 7

Dilution Method: Principle is that a marker substance will be distributed to only the places that it can reach. For example radioactive albumin, deuterium, and Evans blue are frequently used to measure ECF. You can’t directly measure ICF but if you can measure total volume and ECF, just subtract them to get it.

Volume=mass/concentration

Question 8

what determines movement of water across fluid compartments?

Answer 8

Hydrostatic pressure: generated by pumping of heart and effect of gravity on blood in the vessels

Osmotic pressure: comes from solutes, such as plasma proteins and causes water to move